129 results on '"Sergio Abbate"'
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2. Fluorescence detected circular dichroism (FDCD) of a stereodynamic probe
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Roberto Penasa, Federico Begato, Giulia Licini, Klaus Wurst, Sergio Abbate, Giovanna Longhi, and Cristiano Zonta
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Materials Chemistry ,Metals and Alloys ,Ceramics and Composites ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials - Abstract
Fluorescence detected circular dichroism (FDCD) has been used to determine e.e. of carboxylic acids at sensor concentrations down to 0.1 μM also in the presence of chiroptical active contaminants.
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- 2023
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3. Inherently chiral helicene-substituted thioalkyl porphyrazine complexes: synthesis and electronic and chiroptical properties
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Roberta Franzini, Giulia Marsico, Giovanna LONGHI, Sergio ABBATE, Claudio Villani, and Sandra Belviso
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Inorganic Chemistry - Abstract
The chiral Ni(II) and Pd(II) complexes of [6]helicene thioethyl porphyrazine have been synthesized and their spectroscopic, electrochemical, and chiroptical properties have been investigated by experimental and computational analyses. In these compounds, the tetrapyrrole macrocycle is β-substituted with an inherently chiral extended aromatic moiety potentially suitable to establish attractive π-π interactions with nanocarbons and endowed with helical chirality, both features providing interesting properties for optoelectronic applications. Experimental and density functional theory computational analyses highlight the presence of HOMO-LUMO charge-transfer transitions between the helicene moiety and the porphyrazine macrocycle. These compounds behave as mono-substituted push-pull systems without any typical electron-withdrawing or electron-donating groups and thus appear promising for optoelectronics. The enantiomers of the Ni(II) complex have been separated by chiral HPLC and their absolute configuration has been established by density functional theory computational analysis of electronic circular dichroism spectra. The magnetic circular dichroism spectrum of this complex has also been recorded providing better insight into its electronic structure.
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- 2022
4. Anharmonic Aspects in Vibrational Circular Dichroism Spectra from 900 to 9000 cm
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Marco, Fusè, Giovanna, Longhi, Giuseppe, Mazzeo, Stefano, Stranges, Francesca, Leonelli, Giorgia, Aquila, Enrico, Bodo, Bruno, Brunetti, Carlo, Bicchi, Cecilia, Cagliero, Julien, Bloino, and Sergio, Abbate
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Vibrational circular dichroism (VCD) spectra and the corresponding IR spectra of the chiral isomers of methyloxirane and of methylthiirane have been reinvestigated, both experimentally and theoretically, with particular attention to accounting for anharmonic corrections, as calculated by the GVPT2 approach. De novo recorded VCD spectra in the near IR (NIR) range regarding CH-stretching overtone transitions, together with the corresponding NIR absorption spectra, were also considered and accounted for, both with the GVPT2 and with the local mode approaches. Comparison of the two methods has permitted us to better describe the nature of active "anharmonic" modes in the two molecules and the role of mechanical and electrical anharmonicity in determining the intensities of VCD and IR/NIR data. Finally, two nonstandard IR/NIR regions have been investigated: the first one about ≈2000 cm
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- 2022
5. Chiral bis(benzo[1,2-b:4,3-b′]dithiophene) atropisomers: experimental and theoretical investigations of the stereochemical and chiroptical properties
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Roberta Franzini, Valentina Pelliccioli, Claudio Villani, Sergio Abbate, Silvia Cauteruccio, Giuseppe Mazzeo, Emanuela Licandro, and Giovanna Longhi
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Atropisomer ,Chemistry ,Computational chemistry ,Materials Chemistry ,Absolute configuration ,Enantioselective synthesis ,Single bond ,General Chemistry ,Enantiomer ,Chirality (chemistry) ,Racemization ,Catalysis ,Stereocenter - Abstract
Conformational chirality is a feature that may arise from the presence of a hindered rotation around a single bond that corresponds to a stereogenic axis. Atropisomers that feature such an element show interesting characteristics suitable for developing chiral systems with applicability in asymmetric synthesis, catalysis and materials chemistry. Here, we report the investigation of the stereochemical and chiroptical properties of a series of axially chiral intermediates useful in the synthesis of helicenes. Racemates of the four studied atropisomeric bisbenzodithiophenes were resolved by enantioselective HPLC and the single enantiomers were investigated by HPLC, ECD, VCD and CPL. Configurational stability was successfully established by dynamic HPLC or by monitoring thermal racemization, allowing the measurement of the free activation energy values for the stereomutation process. Moreover, the absolute configuration was assigned, thanks to a combination of TD-DFT and DFT calculations and experimental data derived by ECD and VCD, and the emissive chiral properties were measured by recording the CPL spectrum. Attention was paid to the importance of considering also aliphatic pendant groups in order to obtain a good calculation–experiment correspondence for both the ECD and VCD spectra. Considering the significant interest for axially chiral biaryl derivatives, this novel class of bisbenzodithiophenes are expected to have broad applications, not only in asymmetric synthesis, but also as potential chiral ligands or CPL emitters.
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- 2021
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6. Extended enantiopure ortho-phenylene ethylene (o-OPE)-based helical systems as scaffolds for supramolecular architectures: a study of chiroptical response and its connection to the CISS effect
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Jose M. Paredes, Ana M. Ortuño, Sandra Resa, Delia Miguel, Giuseppe Mazzeo, Luis Álvarez de Cienfuegos, Juan M. Cuerva, Víctor Blanco, Sergio Abbate, Giovanna Longhi, Jesus M. Ugalde, Pablo Reiné, Vladimiro Mujica, and Antonio J. Mota
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010405 organic chemistry ,Chemistry ,Organic Chemistry ,Supramolecular chemistry ,Foldamer ,Conjugated system ,Metallacycle ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Crystallography ,chemistry.chemical_compound ,Enantiopure drug ,Phenylene ,Molecule ,Bifunctional - Abstract
We thank the Ministerio de Economia y Competitividad (CTQ2017-85454-C2-1-P), Ministerio de Ciencia en Innovacion (PID2020-113059GB-C21) and Junta de Andalucia (P20_00162) (Spain) for funding and P. R. and A. O. G. also for FPU contracts. We also thank the UGR CSIRC for access to computational facilities. We also thank Big&Open Data Innovation Laboratory (BODaI-Lab), University of Brescia, granted by Fondazione Cariplo and Regione Lombardia, for access to resources of Computing Center CINECA (Bologna), Italy. Support from the Italian MIUR (grant N. 2017A4XRCA) is also acknowledged. VM acknowledges a Fellowship from Ikerbasque, the Basque Foundation for Science., A novel synthetic strategy based on a bifunctional stapled chiral nucleus from which segments of different lengths can be added to both ends of o-phenylene ethynylenes (o-OPEs) has been developed to obtain a new type of foldamer and a novel chiral Pd2L2 metallacycle. For the first time, an enantiopure fully conjugated helical foldamer having 14 phenyl rings and 13 alkynes is reported. The folded structure has four complete loops and is able to host three Ag(I) cations in their cavity with high binding constants. The complete photophysical and chiroptical (ECD, CPL and VCD) characterization of these foldamers has shown that these molecules show intense chiroptical responses with dissymmetry ratios in the range of 10−2. Theoretical modeling of these systems reveals the origin of these remarkable responses and points out a potential connection with the chiral induced spin selectivity (CISS) effect. The magnetic dipole moment is proposed as a key physical variable connecting the chiroptical properties and CISS-based spin filtering properties observed in chiral compounds., Ministerio de Economia y Competitividad (Spain) CTQ2017-85454-C2-1-P, Ministerio de Ciencia en Innovacion (Spain) PID2020-113059GB-C21, Junta de Andalucia European Commission P20_00162, Ministry of Education, Universities and Research (MIUR) 2017A4XRCA, Ikerbasque, the Basque Foundation for Science
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- 2021
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7. Insights into the Structures of Bilirubin and Biliverdin from Vibrational and Electronic Circular Dichroism: History and Perspectives
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Giovanna Longhi, Simone Ghidinelli, Sergio Abbate, Giuseppe Mazzeo, Marco Fusè, Stefan E. Boiadjiev, and David A. Lightner
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Organic Chemistry ,Pharmaceutical Science ,deracemization ,biliverdin ,anesthetics ,bilirubin ,circular dichroism ,structural and configurational aspects ,Analytical Chemistry ,Chemistry (miscellaneous) ,Drug Discovery ,Molecular Medicine ,Physical and Theoretical Chemistry - Abstract
In this work we review research activities on a few of the most relevant structural aspects of bilirubin (BR) and biliverdin (BV). Special attention is paid to the exocyclic C=C bonds being in mostly Z rather than E configurations, and to the overall conformation being essentially different for BR and BV due to the presence or absence of the double C=C bond at C-10. In both cases, racemic mixtures of each compound of either M or P configuration are present in achiral solutions; however, imbalance between the two configurations may be easily achieved. In particular, results based on chiroptical spectroscopies, both electronic and vibrational circular dichroism (ECD and VCD) methods, are presented for chirally derivatized BR and BV molecules. Finally, we review deracemization experiments monitored with ECD data from our lab for BR in the presence of serum albumin and anesthetic compounds.
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- 2023
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8. Resolution of a Configurationally Stable Hetero[4]helicene
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Michela Lupi, Martina Onori, Stefano Menichetti, Sergio Abbate, Giovanna Longhi, and Caterina Viglianisi
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Chemistry (miscellaneous) ,Organic Chemistry ,Drug Discovery ,Molecular Medicine ,Pharmaceutical Science ,Physical and Theoretical Chemistry ,heterohelicene ,chirality ,resolution ,enantiomers ,chiroptical ,screw-shaped compounds ,Analytical Chemistry - Abstract
We have developed an efficient chemical resolution of racemic hydroxy substituted dithia-aza[4]helicenes (DTA[4]H) 1(OH) using enantiopure acids as resolving agents. The better diastereomeric separation was achieved on esters prepared with (1S)-(−)-camphanic acid. Subsequent simple manipulations produced highly optically pure (≥ 99% enantiomeric excess) (P) and (M)-1(OH) in good yields. The role of the position where the chiral auxiliary is inserted (cape- vs. bay-zone) and the structure of the enantiopure acid used on successful resolution are discussed.
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- 2021
9. The Assignment of the Absolute Configuration of Non-Cyclic Sesquiterpenes by Vibrational and Electronic Circular Dichroism: The Example of
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Giuseppe, Mazzeo, Alessio, Cimmino, Giovanna, Longhi, Marco, Masi, Antonio, Evidente, and Sergio, Abbate
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Molecular Structure ,Plant Extracts ,Circular Dichroism ,Stereoisomerism ,VCD ,Asteraceae ,DFT calculations ,Vibration ,Article ,Chiliadenus lopadusanus ,absolute configuration ,farnesane-type sesquiterpenes ,9-hydroxynerolidol ,ECD ,9-oxonerolidol and chiliadenol B ,Sesquiterpenes ,Density Functional Theory - Abstract
9-Hydroxynerolidol, 9-oxonerolidol, and chiliadenol B are three farnesane-type sesquiterpenoids isolated from Chiliadenus lopadusanus that have shown an interesting activity against human pathogens as Gram+ and Gram− bacteria resistant to antibiotics. However, the absolute configuration (AC) of these interesting sesquiterpenes has not been assigned so far. Vibrational and electronic circular dichroism spectra have been recorded and correlations are pointed out for the three compounds. Density functional theory (DFT) calculations are used in conjunction with Mosher’s method of investigation to assign AC. Statistical analysis is considered to quantitatively define the choice of AC from VCD spectra.
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- 2021
10. Biliverdin chiral derivatives as chiroptical switches for pH and metal cation sensing
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Simone, Ghidinelli, Sergio, Abbate, Giuseppe, Mazzeo, Stefan E, Boiadjiev, David A, Lightner, and Giovanna, Longhi
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A series of six optically active derivatives of the bile pigment biliverdin, namely (β
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- 2021
11. Four-Fold Alkyne Benzannulation: Synthesis, Properties, and Structure of Pyreno[a]pyrene-Based Helicene Hybrids
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Vincent J. Catalano, Sergio Abbate, Roberta Franzini, Matteo Tommasini, Radha Bam, Wesley A. Chalifoux, Claudio Villani, Giovanna Longhi, Marilyn M. Olmstead, Andrea Lucotti, and Wenlong Yang
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chemistry.chemical_classification ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Alkyne ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Medicinal chemistry ,0104 chemical sciences ,chemistry.chemical_compound ,Helicene ,Pyrene ,Molecule ,helicene ,circular dichroism ,alkyne benzannulation ,Physical and Theoretical Chemistry ,Brønsted–Lowry acid–base theory - Abstract
The synthesis of pyreno[a]pyrene-based helicene hybrids was achieved in good yield via a four-fold alkyne benzannulation reaction that was promoted by Bronsted acid. The molecules are configuration...
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- 2019
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12. Characterization of 'Free Base' and Metal Complex Thioalkyl Porphyrazines by Magnetic Circular Dichroism and TDDFT Calculations
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Sergio Abbate, Giovanna Longhi, Simone Ghidinelli, Sandra Belviso, and Ernesto Santoro
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010304 chemical physics ,Spin states ,Magnetic circular dichroism ,Free base ,Porphyrazine ,Time-dependent density functional theory ,010402 general chemistry ,01 natural sciences ,Article ,0104 chemical sciences ,Surfaces, Coatings and Films ,Metal ,chemistry.chemical_compound ,Crystallography ,chemistry ,visual_art ,0103 physical sciences ,Materials Chemistry ,visual_art.visual_art_medium ,Molecular orbital ,Density functional theory ,Physical and Theoretical Chemistry - Abstract
UV-vis absorption and magnetic circular dichroism (MCD) spectra of octakis thioethyl "free base" porphyrazine H2OESPz and its metal complexes MOESPz (M = Mg, Zn, Ni, Pd, Cu), as well as of [MnOESPz(SH)] were recorded. In the last case, MCD proved to have quite good sensitivity to the coordination of this complex with 1-methylimidazole (1-mim) in benzene. Time-dependent density functional theory (TDDFT) calculations were carried out for the considered porphyrazine complexes and showed good performance on comparing with MCD and UV-vis experimental spectra, even in the open-shell Cu and Mn cases. Calculations accounted for the red shift observed in the thioalkyl compounds and allowed us to reveal the role of sulfur atoms in spectroscopically relevant molecular orbitals and to highlight the importance of the conformations of the thioethyl external groups. Calculated MCD spectra of [MnOESPz(SH)] confirm the Mn(III) → Mn(II) redox process, which leads to the [Mn(OESPz)(1-mim)2] species, and the relevance of the spin state for MCD is revealed.
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- 2020
13. Magnetic Circular Dichroism of Naphthalene Derivatives: A Coupled Cluster Singles and Approximate Doubles and Time-Dependent Density Functional Theory Study
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Giovanna Longhi, Simone Ghidinelli, Christof Hättig, Sonia Coriani, and Sergio Abbate
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Physics ,Coupled cluster ,Chemistry ,Magnetic dipole transition ,Atomic electron transition ,Magnetic circular dichroism ,Excited state ,Density functional theory ,Time-dependent density functional theory ,Physical and Theoretical Chemistry ,Physics::Chemical Physics ,Electric dipole transition ,Molecular physics - Abstract
The UV-Vis absorption and Magnetic Circular Dichroism spectra of naphthalene and some of its derivatives have been simulated at the Coupled Cluster Singles andApproximate Doubles (CC2) level of theory, and at the Time-Dependent Density Functional Theory level (TD-DFT) using the B3LYP and CAM-B3LYP functionals. DFT and CC2 predict in general opposite energetic ordering of the Lb and La transitions (in gas phase), as previously observed in adenine. The CC2 simulations of UV and MCD spectra show the best agreement with the experimental data. Analysis of the Cartesiancomponents of the electric dipole transition strengths and the magnetic dipole transition moment between the excited states have been considered in the interpretationof the electronic transitions and the Faraday B term inversion among the naphthalenederivatives.
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- 2020
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14. Spectroscopic investigation on 1,2-substituted ferrocenes with only planar chirality: How chiroptical data are related to absolute configuration and to substituents
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Giuseppe, Mazzeo, Sonia, Pedotti, Giovanna, Longhi, Angela, Patti, and Sergio, Abbate
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Magnetic Resonance Spectroscopy ,Metallocenes ,Circular Dichroism ,Molecular Conformation ,Stereoisomerism ,VCD and ECD spectroscopies ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry ,Planar Chirality ,Lipase-catalyzed resolution ,Hydrogen Bonding (HB) ,Ferrocenes ,Density Functional Theory (DFT) calculations ,Instrumentation ,Spectroscopy - Abstract
Single enantiomers of three 1,2-substituted ferrocene derivatives, i.e. 1-methoxymethyl-2-hydroxymethylferrocene (1), 1-formyl-2-hydroxymethylferrocene (2) and 1-iodo-2-hydroxymethylferrocene (3), sharing the common hydroxymethyl substituent and the presence of planar chirality only, were investigated for their spectroscopic (IR and UV) and chiroptical (VCD and ECD) properties. Both enantiomers of 1 were obtained for the first time in optically pure form by lipase-catalyzed kinetic resolution of the corresponding racemate (±)-1 and separately converted into formyl derivatives (+)-2 and (-)-2. The experimental spectroscopic and chiroptical data were compared with DFT calculated spectra and excellent correspondence was found for all compounds, allowing one to confirm the previously assigned absolute configurations. The common features in the VCD spectra of a doublet between 940 and 965 cm and the short-wavelength (about 200 nm) doublet and the longest wavelength band in the ECD spectra were analyzed to test whether they may be taken as markers of the absolute configuration (AC). The predominance of conformers with intramolecular hydrogen bond for the first two investigated compounds is predicted by conformational analysis and also confirmed by NMR.
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- 2022
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15. l-Stercobilin-HCl and d-Urobilin-HCl. Analysis of Their Chiroptical and Conformational Properties by VCD, ECD, and CPL Experiments and MD and DFT Calculations
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Simone Ghidinelli, David A. Lightner, Giovanna Longhi, Sergio Abbate, and Stefan E. Boiadjiev
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Materials Chemistry2506 Metals and Alloys ,Materials science ,Chloroform ,010405 organic chemistry ,Infrared spectroscopy ,010402 general chemistry ,01 natural sciences ,Spectral line ,0104 chemical sciences ,Surfaces, Coatings and Films ,Surfaces ,Coatings and Films ,Molecular dynamics ,chemistry.chemical_compound ,chemistry ,Vibrational circular dichroism ,Materials Chemistry ,Physical chemistry ,Molecule ,Density functional theory ,Physical and Theoretical Chemistry ,Cotton effect - Abstract
Vibrational circular dichroism (CD) and IR spectra of dichloromethane solutions of l-stercobilin and d-urobilin hydrochlorides have been recorded in the mid-IR region. The spectra are best interpreted by combining molecular dynamics calculations and density functional theory (DFT) calculations within the quantum mechanics/molecular mechanics ONIOM-type framework, and the combined predicted results are better and more informative than the more standard analysis provided by DFT calculations. The same approach also sheds light on the Cotton effect sign inversion of room temperature versus low-temperature electronic CD spectra of the same compounds in methanol-glycerol solution. Finally, circularly polarized luminescence spectra for l-stercobilin in chloroform solution provide information on the excited-state geometry of this molecule.
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- 2018
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16. Absolute configuration assignment to anticancer Amaryllidaceae alkaloid jonquailine
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Stefania Vergura, Sergio Abbate, Patrizia Scafato, Giuseppe Mazzeo, Ernesto Santoro, Marco Masi, Giovanna Longhi, Stefano Superchi, Antonio Evidente, Vergura, Stefania, Santoro, Ernesto, Masi, Marco, Evidente, Antonio, Scafato, Patrizia, Superchi, Stefano, Mazzeo, Giuseppe, Longhi, Giovanna, and Abbate, Sergio
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Circular dichroism ,Amaryllidaceae Alkaloid ,Stereochemistry ,Narcissus jonquilla quail ,Plant Roots ,01 natural sciences ,Stereocenter ,Alkaloids ,Alkaloid ,Drug Discovery ,Absolute configuration ,Optical rotation ,Amaryllidaceae Alkaloids ,Optical rotatory dispersion ,Pharmacology ,Molecular Structure ,010405 organic chemistry ,Chemistry ,Drug Discovery3003 Pharmaceutical Science ,Circular Dichroism ,Amaryllidaceae ,Electronic circular dichroism ,Plant Root ,Jonquailine ,Vibrational circular dichroism ,Optical Rotatory Dispersion ,General Medicine ,0104 chemical sciences ,010404 medicinal & biomolecular chemistry ,Density functional theory - Abstract
Jonquailine, a new alkaloid recently isolated from Narcissus jonquilla quail, an Amaryllidaceae species cultivated for its flowers fragrance in Europe and USA, shows very significant anti-proliferative activity against several , malignant cancer cell types. Although it was reported that this activity is related to the functionalities and to its stereochemistry at C-8 of B ring, the absolute configuration at this stereocenter was not known. Density functional theory (DFT) calculations of chiroptical properties, namely electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) are employed here to complete assignment of absolute configuration of jonquailine, and then, by extension, to its analogues pretazettine and 8-Omethylpretazettine. While ECD is not discriminating and ORD is of limited use, VCD reveals decisive in the task of absolute configuration assignment.
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- 2018
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17. Searching for Models Exhibiting High Circularly Polarized Luminescence: Electroactive Inherently Chiral Oligothiophenes
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Giuseppe Mazzeo, Roberto Cirilli, Elsa Quartapelle Procopio, Monica Panigati, Patrizia R. Mussini, Giovanna Longhi, Serena Arnaboldi, Sergio Abbate, Giulio Appoloni, and Tiziana Benincori
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Models, Molecular ,Circular dichroism ,Molecular Conformation ,Stereoisomerism ,Thiophenes ,010402 general chemistry ,01 natural sciences ,Catalysis ,circularly polarized luminescence (CPL) ,density functional calculations ,electronic circular dichroism (ECD) ,inherent chirality ,vibrational circular dichroism (VCD) ,Chromatography, High Pressure Liquid ,Circular Dichroism ,Electrochemical Techniques ,Quantum Theory ,Spectrophotometry, Ultraviolet ,Organic Chemistry ,chemistry.chemical_compound ,Models ,Ultraviolet ,Pyrrole ,Chromatography ,010405 organic chemistry ,Chemistry ,Absolute configuration ,Molecular ,General Chemistry ,Inherent chirality ,0104 chemical sciences ,Crystallography ,Spectrophotometry ,High Pressure Liquid ,Vibrational circular dichroism ,Enantiomer ,Luminescence - Abstract
Two new inherently chiral oligothiophenes characterized by the atropisomeric 3,3'-bithianaphtene scaffold functionalized with fused ring bithiophene derivatives, namely 4H-cyclopenta[2,1-b3:4b']dithiophene (CPDT) and dithieno[3,3-b:2',3'-d]pyrrole (DTP), were synthesized. The racemates were fully characterized and resolved into antipodes by enantioselective HPLC. The enantiomers were analyzed through different chiroptical techniques: electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) were employed to attribute the absolute configuration (AC). Comparison of experimental and calculated VCD spectra confirmed the DFT calculated conformational characteristics. The compound functionalized with two CPDT units was oxidized with FeCl3 , and ECD and CPL of the resulting material were measured. Circularly polarized luminescence (CPL) was measured to verify if inherently chiral oligothiophenes could be promising systems for chiral photonics applications.
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- 2018
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18. Pyrene-Containing ortho-Oligo(phenylene)ethynylene Foldamer as a Ratiometric Probe Based on Circularly Polarized Luminescence
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Luis Álvarez de Cienfuegos, Juan M. Cuerva, María Ribagorda, Araceli G. Campaña, Giovanna Longhi, Sergio Abbate, Pablo Reiné, Angel Orte, José Justicia, Sara P. Morcillo, Delia Miguel, and Belén Vaz
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010405 organic chemistry ,Organic Chemistry ,Foldamer ,010402 general chemistry ,Photochemistry ,01 natural sciences ,3. Good health ,0104 chemical sciences ,chemistry.chemical_compound ,Oligo(phenylene-ethynylene) ,Enantiopure drug ,chemistry ,Phenylene ,Pyrene ,Luminescence - Abstract
In this manuscript, we report the first synthesis of an organic monomolecular emitter, which behaves as a circularly polarized luminescence (CPL)-based ratiometric probe. The enantiopure helical ortho-oligo(phenylene)ethynylene ( o-OPE) core has been prepared by a new and efficient macrocyclization reaction. The combination of such o-OPE helical skeleton and a pyrene couple leads to two different CPL emission features in a single structure whose ratio linearly responds to silver(I) concentration.
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- 2018
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19. Mannich-type addition of 1,3-dicarbonyl compounds to chiral tert-butanesulfinyltrifluoroacetaldimines. Mechanistic aspects and chiroptical studies
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Claudio Santi, Luca Melensi, Jianlin Han, Giovanna Longhi, Vadim A. Soloshonok, Francesca Mangiavacchi, Giuseppe Mazzeo, Renzo Ruzziconi, and Sergio Abbate
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Circular dichroism ,010405 organic chemistry ,Organic Chemistry ,010402 general chemistry ,Biochemistry ,Physical and Theoretical Chemistry ,01 natural sciences ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Computational chemistry ,Optical rotatory dispersion ,Dichloromethane - Abstract
Mannich-type addition of 1,3-dicarbonyl compounds to (SS)-N-tert-butanesulfinyltrifluoroacetaldimine has been carried out under dramatically different conditions. The stereochemical outcome was quite different when the reaction was carried out under solvent-free conditions, at high temperature and without any catalyst or additive, compared with the DBU catalyzed reaction in dichloromethane solution at low temperature. Mechanistic aspects of the reaction under both the conditions are discussed. In this respect, vibrational (VCD) and electronic circular dichroism (ECD) and optical rotatory dispersion (ORD) experiments proved to be valuable tools for determining the absolute configurations of the reaction products.
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- 2018
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20. On the aggregation of bilirubinoids in solution as evidenced by VCD and ECD spectroscopy and DFT calculations
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David A. Lightner, Stefan E. Boiadjiev, Giuseppe Mazzeo, Sergio Abbate, Giovanna Longhi, and Simone Ghidinelli
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Circular dichroism ,Stereochemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,Analytical Chemistry ,dimers ,chemistry.chemical_compound ,density functional theory (DFT) ,Drug Discovery ,Molecule ,Spectroscopy ,Pharmacology ,hydrogen bond ,Chloroform ,010405 organic chemistry ,Hydrogen bond ,aggregation ,bilirubin ,vibrational circular dichroism (VCD) ,Drug Discovery3003 Pharmaceutical Science ,Organic Chemistry ,0104 chemical sciences ,Crystallography ,Monomer ,chemistry ,Intramolecular force ,Lactam ,Density functional theory - Abstract
Vibrational and electronic circular dichroism (VCD and ECD) spectra of 3 optically active bilirubin analogs with propionic acid groups replaced by (1) 1-(S)-methylpropyl groups, (2) 3-acetoxy-1-(S)-methylpropyl groups, and (3) 1-(S)-2-(R)-dimethyl-2-(methoxycarbonyl)ethyl groups have been recorded at different concentrations in chloroform. The aliphatic chains attached to C-8 and C-12 of the 3 chosen mesobilirubins were modified so as to possess no OH group. The variation of the VCD spectra with concentration is consistent with the formation of dimers at high concentration. Density functional theory and time-dependent density functional theory calculations on monomeric and dimeric forms support such a conclusion. Comparing with previous VCD (ECD) and IR (UV) studies of other mesobilirubin molecules, it is concluded that here, the key feature for aggregation is the missing OH groups on the propionic acid chains. The latter, in synergy with the polar groups of lactam moieties, appear to be involved in intramolecular phenomena and thus favor monomeric forms. Investigation of ECD and UV spectra of the same compounds in mixed DMSO/chloroform solutions provide further clues to the proposed picture.
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- 2017
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21. Vibrational Circular Dichroism Unveils Chiroptical, Electrical, and Magnetic Properties of Borylated Isocyanides and Aldehydes
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Giuseppe Mazzeo, Adam Zajdlik, Giovanna Longhi, Sergio Abbate, Victoria B. Corless, and Andrei K. Yudin
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Circular dichroism ,Ir absorption ,010405 organic chemistry ,Chemistry ,Ligand ,Organic Chemistry ,Analytical chemistry ,Absolute configuration ,Infrared spectroscopy ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,01 natural sciences ,Spectral line ,0104 chemical sciences ,Crystallography ,Vibrational circular dichroism ,Physical and Theoretical Chemistry - Abstract
The absolute configurations of two novel chiral borylated compounds bearing the (S)-proline-derived N-carboxymethylproline ligand have been studied by vibrational circular dichroism (VCD) in conjunction with IR absorption, UV absorption, and electronic circular dichroism (ECD). DFT and time-dependent DFT calculations allowed us to interpret the observed spectra and gave credibility to the VCD data. The VCD data in the CH stretching region were also considered. The experimental and computational data are consistent with those obtained by NMR spectroscopy. The investigation of the C=O stretching region should assist in the future assignment of the absolute configuration of chiral borylated compounds bearing carbonyl groups.
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- 2017
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22. Synthesis of Intrinsically Blue-Colored bis-Nitronyl Nitroxide Peptidomimetic Templates and Their Conformational Preferences as Revealed by a Combined Spectroscopic Analysis
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Marta De Zotti, Giovanna Longhi, Giuseppe Mazzeo, Edouard d'Aboville, Fernando Formaggio, Sergio Abbate, Karen Wright, Claudio Toniolo, and Antonio Toffoletti
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Nitroxide mediated radical polymerization ,010405 organic chemistry ,Peptidomimetic ,Chemistry ,Stereochemistry ,Organic Chemistry ,vibrational circular dichroism ,010402 general chemistry ,01 natural sciences ,spin-label ,0104 chemical sciences ,law.invention ,nitronyl nitroxide ,non natural amino acids ,Blue colored ,law ,Intramolecular force ,Helix ,Vibrational circular dichroism ,peptides ,Spin label ,Electron paramagnetic resonance - Abstract
The intrinsically blue-colored Ullman imidazolinyl nitronyl nitroxide (NN) mono-radicals have found various applications, in particular as spin probes and organic magnetic materials. Here, we present the solution-phase synthesis, extensive characterization, and conformational analysis of the first peptidomimetics with two pendant, chiral nitronyl nitroxide free radical units. Two (R)-Aic(NN) residues, where Aic(NN) is 2-amino-5-nitronylnitroxide-indan-2-carboxylic acid, have been inserted at positions i and i+3 of the pentapeptide Boc-(R)-Aic(NN)-(Ala)2-(R)-Aic(NN)-Ala-OMe and the hexapeptide Boc-[Ala-(R)-Aic(NN)-Ala]2-OMe as well. The two compounds were obtained in good yields and high purities. Thanks to a combination of several spectroscopic techniques (IR absorption, NMR, VCD, and EPR) we gained clear evidence that both compounds adopt a right-handed 310-helical conformation with both nitronyl nitroxide pendants positioned on the same side of the helix. This peptidomimetic/free radical system is a potentially excellent template for the preparation of a set of appropriate analogs with exciting applications in the area of host-guest organic chemistry, or to spectroscopically evaluate in-depth the intramolecular exchange interactions in this type of probe.
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- 2017
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23. Importance and Difficulties in the Use of Chiroptical Methods to Assign the Absolute Configuration of Natural Products: The Case of Phytotoxic Pyrones and Furanones Produced by Diplodia corticola
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Maurizio Memo, Giovanna Longhi, Lucia Maddau, Marco Masi, Alessio Cimmino, Antonio Evidente, Sergio Abbate, Giuseppe Mazzeo, Mazzeo, Giuseppe, Cimmino, Alessio, Masi, Marco, Longhi, Giovanna, Maddau, Lucia, Memo, Maurizio, Evidente, Antonio, and Abbate, Sergio
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Circular dichroism ,Stereochemistry ,Pharmaceutical Science ,Stereoisomerism ,Alkenes ,Ascomycota ,Biological Products ,Circular Dichroism ,Furans ,Lactones ,Molecular Structure ,Optical Rotatory Dispersion ,Pyrones ,Quercus ,Analytical Chemistry ,Molecular Medicine ,Pharmacology ,3003 ,Drug Discovery3003 Pharmaceutical Science ,Complementary and Alternative Medicine2708 Dermatology ,Organic Chemistry ,010402 general chemistry ,01 natural sciences ,Stereocenter ,Drug Discovery ,Optical rotatory dispersion ,010405 organic chemistry ,Chemistry ,Enantioselective synthesis ,Absolute configuration ,Total synthesis ,0104 chemical sciences ,Complementary and alternative medicine ,Vibrational circular dichroism - Abstract
α-Pyrones and furanones are metabolites produced by Diplodia corticola, a pathogen of cork oak. Previously, the absolute configuration (AC) of diplopyrone was defined by chiroptical methods and Mosher's method. Using X-ray and chiroptical methods, the AC of sapinofuranone C was assigned, while that of the (4S,5S)-enantiomer of sapinofuranone B was established by enantioselective total synthesis. Diplofuranone A and diplobifuranylones A-C ACs are still unassigned. Here electronic and vibrational circular dichroism (ECD and VCD) and optical rotatory dispersion (ORD) spectra are reported and compared with density functional theory computations. The AC of the (4S,5S)-enantiomer of sapinofuranone B and sapinofuranone C is checked for completeness. The AC of diplobifuranylones A-C is assigned as (2S,2'S,5'S,6'S), (2S,2'R,5'S,6'R), and (2S,2'S,5'R,6'R), respectively, with the Mosher's method applied to define the absolute configuration of the carbinol stereogenic carbon. The AC assignment of sapinofuranones is problematic: while diplofuranone A is (4S,9R), sapinofuranones B and C are (4S,5S) according to ORD and VCD, but not to ECD. To eliminate these ambiguities, ECD and VCD spectra of a di-p-bromobenzoate derivative of sapinofuranone C are measured and calculated. For phytotoxicity studies, it is relevant that all six compounds share the S configuration for the stereogenic carbon atom of the lactone moiety.
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- 2017
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24. The role of chirality in a set of key intermediates of pharmaceutical interest, 3-aryl-substituted-γ-butyrolactones, evidenced by chiral HPLC separation and by chiroptical spectroscopies
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Sergio Abbate, Giuseppe Mazzeo, Giovanna Longhi, Simone Ghidinelli, Rita Nasti, Simona Collina, Maurizio Memo, and Daniela Rossi
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Circular dichroism ,γ-Butyrolactones ,Stereochemistry ,VCD (vibrational circular dichroism) ,Clinical Biochemistry ,Pharmaceutical Science ,010402 general chemistry ,01 natural sciences ,Analytical Chemistry ,4-Butyrolactone ,Computational chemistry ,Chiral HPLC ,Lactone chirality rule ,Molecular docking calculations ,ORD (optical rotatory dispersion) and ECD (electronic circular dichroism) ,3003 ,Drug Discovery3003 Pharmaceutical Science ,Spectroscopy ,Drug Discovery ,Optical rotatory dispersion ,Chromatography, High Pressure Liquid ,010405 organic chemistry ,Chemistry ,Circular Dichroism ,Absolute configuration ,Enantioselective synthesis ,Stereoisomerism ,0104 chemical sciences ,Molecular Docking Simulation ,Chiral column chromatography ,Optical Rotatory Dispersion ,Pharmaceutical Preparations ,Vibrational circular dichroism ,Enantiomer ,Chirality (chemistry) - Abstract
The enantiomers of four chiral 3-aryl-substituted-γ-butyrolactones, key intermediates for the preparation of compounds of pharmaceutical interest, were successfully isolated by enantioselective chromatography, employing the Chiralpak AD-H chiral stationary phase. For all compounds the same elution order was observed, as monitored by a full set of chiroptical methods that we employed, namely ORD (optical rotatory dispersion), ECD (electronic circular dichroism, or CD in the UV range), and VCD (vibrational circular dichroism, or CD in the IR range). By density functional theory (DFT) calculations we were able to determine that the first eluted enantiomer has (S) absolute configuration in all four cases. We were able to justify the elution order by molecular docking calculations for all four enantiomeric pairs and suitable modeling of the stationary and mobile phases of the employed columns. The optimal performance of the chiroptical spectroscopies and of the DFT calculations allows us to formulate a lactone chirality rule out of the CO stretching region of the VCD spectra.
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- 2017
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25. Chiral-at-Metal Phosphorescent Square-Planar Pt(II)-Complexes from an Achiral Organometallic Ligand
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Eri Sakuda, Dietmar Stalke, Lennard Krause, Giovanna Longhi, Reent Michel, Keisuke Umakoshi, Guido H. Clever, Julian J. Holstein, Thorben R. Schulte, and Sergio Abbate
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Circular dichroism ,010405 organic chemistry ,Ligand ,Chemistry ,Absolute configuration ,Quantum yield ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Biochemistry ,Catalysis ,0104 chemical sciences ,Crystallography ,Colloid and Surface Chemistry ,Enantiomer ,Phosphorescence ,Group 2 organometallic chemistry - Abstract
The synthesis and characterization of a new kind of cis- and trans-cyclometalated square-planar platinum(II) complexes is reported. Uncharged organometallic compounds carrying one or two of the C∧N-donor ligand LCN were prepared. Due to the heterobidentate coordination of the achiral chelate ligand, the formed [PtLCNCl(SEt2)], cis- and trans-[PtLCN2] complexes are chiral with the metal serving as the stereo center. The enantiomers of complex trans-[PtLCN2] could be separated and their absolute configuration was determined by anomalous X-ray diffraction, in accordance with CD spectroscopic results and TD-DFT calculations. All compounds were fully characterized by NMR spectroscopy, mass spectrometry and X-ray structure determination. The photophysical properties of trans-[PtLCN2] have been investigated showing phosphorescence in solution and in the solid state with a moderate quantum yield. For the enantiomers, strong circular dichroism (CD) and circularly polarized luminescence (CPL) effects were observed,...
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- 2017
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26. Structural and Electronic Information Drawn from the Circularly Polarized Luminescence Spectra: Many Questions and Some Answers for Simple Organic Molecules, Polymers, and Molecular Aggregates
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Giovanna Longhi and Sergio Abbate
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chemistry.chemical_classification ,Circular dichroism ,Materials science ,chemistry ,Chemical physics ,Metal ions in aqueous solution ,Molecule ,Luminescence spectra ,Electronic information ,Polymer ,Chromophore ,Luminescence - Abstract
In the last ten years, circularly polarized luminescence (CPL) has greatly advanced: lots of data have been collected and many compounds have been synthesized with the aim of enhancing this chiroptical response. We review here a few aspects with illustrative examples. After examination of the relation of circular dichroism (CD) and CPL signals, we investigate how CPL can be used to probe environment: aggregation phenomena or the presence of metal ions or pH variations. We also study the CPL of inherently dissymmetric chromophores and of metal complexes. We finally touch upon whether CPL originates from molecules or from aggregated inhomogeneous systems.
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- 2020
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27. Four-Fold Alkyne Benzannulation: Synthesis, Properties, and Structure of Pyreno[
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Radha, Bam, Wenlong, Yang, Giovanna, Longhi, Sergio, Abbate, Andrea, Lucotti, Matteo, Tommasini, Roberta, Franzini, Claudio, Villani, Vincent J, Catalano, Marilyn M, Olmstead, and Wesley A, Chalifoux
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The synthesis of pyreno[
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- 2019
28. Optically active Ag(i): o-OPE helicates using a single homochiral sulfoxide as chiral inducer
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Pablo Reiné, Juan M. Cuerva, Luis Álvarez de Cienfuegos, Sergio Abbate, Santiago Guisán-Ceinos, Giuseppe Mazzeo, Sandra Resa, María Ribagorda, Giovanna Longhi, Delia Miguel, and Antonio J. Mota
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010405 organic chemistry ,Organic Chemistry ,Sulfoxide ,Optically active ,010402 general chemistry ,Triple bond ,01 natural sciences ,Biochemistry ,0104 chemical sciences ,Folding (chemistry) ,chemistry.chemical_compound ,Crystallography ,Enantiopure drug ,chemistry ,Inducer ,Physical and Theoretical Chemistry - Abstract
In this work we describe the ability of a simple enantiopure sulfoxide group to promote folding of oligo ortho-phenylene ethynylenes (o-OPEs) with one helical sense. A family of foldamers with up to seven triple bonds was synthesized and fully characterized. Moreover, changes in structure and chiroptical properties caused by Ag(I) coordination have been studied by NMR, UV, VCD and ECD measurements. Quantum mechanical DFT calculations support experimental results.
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- 2019
29. Assignment Through Chiroptical Methods of The Absolute Configuration of Fungal Dihydropyranpyran-4-5-Diones Phytotoxins, Potential Herbicides for Buffelgrass (
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Ernesto, Santoro, Giuseppe, Mazzeo, Giulia, Marsico, Marco, Masi, Giovanna, Longhi, Stefano, Superchi, Antonio, Evidente, and Sergio, Abbate
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buffelgrass ,Molecular Structure ,Electronic Circular Dichroism (ECD) ,Herbicides ,Circular Dichroism ,Cenchrus ,Stereoisomerism ,Article ,Cochliobolus australiensis ,phytotoxins ,absolute configuration ,Optical Rotatory Dispersion (ORD) ,Optical Rotatory Dispersion ,Vibrational Circular Dichroism (VCD) ,DFT (Density Functional Theory) calculations - Abstract
Radicinin and cochliotoxin (1 and 2) two phytotoxic pyranpyran-4,5-diones were isolated together with their close metabolites 3-epi-radicinin, radicinol, and its 3-epimer (3–5), from the culture filtrates of Cochliobolus australiensis, a fungus proposed as mycoherbcide for biocontrol of buffelgrass, a very noxious and dangerous weed. The absolute configuration of cochliotoxin was determined by chiroptical Optical Rotatory Dispersion (ORD), Electronic Circular Dichroism (ECD), and Vibrational Circular Dichroism (VCD)) and computational methods. The same methods were used to confirm that of radicinin, radicinol and their 3-epimers, previously determined with chemical, spectroscopic and ECD methods.
- Published
- 2019
30. Vibrational Optical Activity of BODIPY Dimers: The Role of Magnetic–Electric Coupling in Vibrational Excitons
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Giovanna Longhi, Torsten Bruhn, Gennaro Pescitelli, and Sergio Abbate
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Physics ,Magnetic moment ,010405 organic chemistry ,Exciton ,Aryl ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Spectral line ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Vibrational circular dichroism ,Organic chemistry ,Physical and Theoretical Chemistry ,BODIPY ,Electric coupling ,Boron - Abstract
The vibrational exciton (VE) interpretation of intense bisignated couplets in vibrational circular dichroism (VCD) spectra of a pair of atropisomeric BODIPY (boron dipyrrin) dimers is discussed. The role of intrinsic magnetic moments is crucial to reproduce the different behaviors of quasi-isomeric BODIPY dimers with different aryl junction.
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- 2016
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31. Discrimination of Axial and Central Stereogenic Elements in Chiral Bis(oxazolines) Based on Atropisomeric 3,3′-Bithiophene Scaffolds Through Chiroptical Spectroscopies
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Giuseppe Mazzeo, Giovanna Longhi, Tiziana Benincori, Sara Gabrieli, and Sergio Abbate
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Pharmacology ,Atropisomer ,Circular dichroism ,010405 organic chemistry ,Chemistry ,Stereochemistry ,Organic Chemistry ,Diastereomer ,Absolute configuration ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Analytical Chemistry ,Stereocenter ,Drug Discovery ,Vibrational circular dichroism ,Density functional theory ,Chirality (chemistry) ,Spectroscopy - Abstract
Two diastereoisomeric pairs of bis-oxazolines, provided with a stereogenic center at carbon 4 and based on the 3,3′-bithiophene atropisomeric scaffold, were synthesized and structurally characterized. They differ in the substituents at positions 2 and 5 of the thiophene rings, which are functionalized with methyl (1) or phenyl (2) groups, respectively. In vibrational circular dichroism (VCD) spectra, recorded in CCl4 solutions, it is possible to distinctly recognize the characteristic features of axial and central stereogenic elements. In tandem with Density Functional Theory (DFT) calculations, the absolute configuration (AC) of the diastereoisomers was safely established. In this case, VCD was shown to be superior to ECD (electronic circular dichroism) in the assignment of AC. The normal modes, evaluated from DFT calculations, show that the VCD signals in correspondence with the stereogenic axis of the bithiophene unit are different for 1 and 2. The VCD spectra of a molecular analog of 1, the (S)-2,2′,5,5′-tetramethyl-4,4′-bis-(diphenylphosphino)-3,3′-bithiophene oxide (3), characterized by the same 3,3′-bithiophene scaffold, but devoid of stereogenic centers, exhibits signals similar to those observed in the case of diastereoisomer (aS,R,R)-1a, associated with almost identical normal modes. Chirality 28:686–695, 2016. © 2016 Wiley Periodicals, Inc.
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- 2016
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32. Circularly Polarized Luminescence: A Review of Experimental and Theoretical Aspects
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Giovanna Longhi, Sergio Abbate, Giuseppe Mazzeo, Ettore Castiglioni, and Jun Koshoubu
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Pharmacology ,010405 organic chemistry ,Chemistry ,Organic Chemistry ,Nanotechnology ,Limiting ,010402 general chemistry ,01 natural sciences ,Chirality (electromagnetism) ,Catalysis ,Spectral line ,0104 chemical sciences ,Analytical Chemistry ,Computational physics ,Organic molecules ,Drug Discovery ,Density functional theory ,Luminescence ,Spectroscopy - Abstract
We review the present status of experiments and calculations for circularly polarized luminescence (CPL) of simple organic molecules and of stimuli-responsive organic molecules. Together with the historical report of the main instrumental approaches, a few crucial points about experiments are tackled, with the aim of defining measurement protocols, in view of the wide availability of commercial apparatuses in the near future. The calculations aimed at interpreting the CPL spectra, mostly based on time-dependent Density Functional Theory (TD-DFT) calculations, which started around 2010, are reviewed, limiting the discussion to small to mid-sized molecules. Some applications of CPL spectra of organic molecules-based systems are presented, with a focus especially on two fields: material science and biology. Chirality 28:696–707, 2016. © 2016 Wiley Periodicals, Inc.
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- 2016
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33. Vibronic Coupling Explains the Different Shape of Electronic Circular Dichroism and of Circularly Polarized Luminescence Spectra of Hexahelicenes
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Sergio Abbate, Giuseppe Mazzeo, Fabrizio Santoro, Xian Zhao, Javier Cerezo, Na Lin, Yanli Liu, and Giovanna Longhi
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Circular dichroism ,010405 organic chemistry ,Chemistry ,Vibronic Coupling ,Electronic Circular Dichroism ,Circularly Polarized Luminescence ,Computer Science Applications1707 Computer Vision and Pattern Recognition ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Molecular electronic transition ,Spectral line ,0104 chemical sciences ,Computer Science Applications ,Vibronic coupling ,Excited state ,Atomic physics ,Luminescence ,Absorption (electromagnetic radiation) ,Line (formation) - Abstract
We present the simulation of the absorption (ABS), electronic circular dichroism (ECD), emission (EMI), and circularly polarized luminescence (CPL) spectra for the weak electronic transition between the ground (S0) and the lowest excited state (S1) of hexahelicene, 2-methylhexahelicene, 2-bromohexahelicene, and 5-azahexahelicene. Vibronic contributions have been computed at zero Kelvin and at room temperature in harmonic approximation including Duschinsky effects and accounting for both Franck-Condon and Herzberg-Teller contributions. Our results nicely capture the effects of the different substituents on the experimental spectra. They also show that HT effects dominate the shape of ECD and CPL spectra where they even induce changes of signs; HT effects are also relevant in ABS and EMI, tuning the relative intensities of the different vibronic bands. HT effects are the main reason for the differences in the line shapes of ABS and ECD and of EMI and CPL spectra and for the mirror-symmetry breaking between ABS and EMI and between ECD and CPL spectra. In order to check the robustness of our results, given also that few examples of calculations of vibronic CPL spectra exist, we adopted both adiabatic and vertical approaches to define the model potential energy surfaces of the (S0) and the (S1) states; moreover we expanded the electric and magnetic dipole transition moments around both the S0 and S1 equilibrium geometries.
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- 2016
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34. Enantiomeric 4-Acylamino-6-alkyloxy-2 Alkylthiopyrimidines As Potential A3Adenosine Receptor Antagonists: HPLC Chiral Resolution and Absolute Configuration Assignment by a Full Set of Chiroptical Spectroscopy
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Sabrina Taliani, Federico Da Settimo, Barbara Cosimelli, Claudia Martini, Silvia Meneghini, Daniela Rossi, Ettore Novellino, Maurizio Memo, Giuseppe Mazzeo, Simona Collina, Annamaria Marra, Giovanni Greco, Giovanna Longhi, Rita Nasti, and Sergio Abbate
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Pharmacology ,Circular dichroism ,010405 organic chemistry ,Stereochemistry ,Chemistry ,Organic Chemistry ,Absolute configuration ,010402 general chemistry ,01 natural sciences ,Catalysis ,Chiral resolution ,0104 chemical sciences ,Analytical Chemistry ,Chiral column chromatography ,chemistry.chemical_compound ,Drug Discovery ,Vibrational circular dichroism ,Enantiomer ,Optical rotatory dispersion ,Spectroscopy ,Acetamide - Abstract
The chiral separation of enantiomeric couples of three potential A3 adenosine receptor antagonists: (R/S)-N-(6-(1-phenylethoxy)-2-(propylthio)pyrimidin-4-yl)acetamide (), (R/S)-N-(2-(1-phenylethylthio)-6-propoxypyrimidin-4-yl)acetamide (), and (R/S)-N-(2-(benzylthio)-6-sec-butoxypyrimidin-4-yl)acetamide () was achieved by high-performance liquid chromatography (HPLC). Three types of chiroptical spectroscopies, namely, optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD), were applied to enantiomeric compounds. Through comparison with Density Functional Theory (DFT) calculations, encompassing extensive conformational analysis, full assignment of the absolute configuration (AC) for the three sets of compounds was obtained. Chirality 28:434-440, 2016. © 2016 Wiley Periodicals, Inc.
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- 2016
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35. CF
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Sergio, Abbate, Giovanna, Longhi, Giuseppe, Mazzeo, Claudio, Villani, Silvija, Petković, and Renzo, Ruzziconi
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The VCD spectra of several chiral compounds containing the CF
- Published
- 2019
36. OFF/ON switching of circularly polarized luminescence by oxophilic interaction of homochiral sulfoxide-containing o-OPEs with metal cations
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Juan M. Cuerva, Giuseppe Mazzeo, Sandra Resa, Pablo Reiné, Andrea Lucotti, Luis Álvarez de Cienfuegos, Víctor Blanco, Matteo Tommasini, Santiago Guisán-Ceinos, Delia Miguel, Antonio J. Mota, Ana M. Ortuño, María Ribagorda, M. José Ruedas-Rama, Sergio Abbate, Araceli G. Campaña, and Giovanna Longhi
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Materials Chemistry2506 Metals and Alloys ,010402 general chemistry ,Photochemistry ,01 natural sciences ,Catalysis ,Metal ,Coatings and Films ,chemistry.chemical_compound ,Materials Chemistry ,Electronic ,Optical and Magnetic Materials ,Quantum ,010405 organic chemistry ,Chemistry ,Chemistry (all) ,Metals and Alloys ,Cationic polymerization ,Sulfoxide ,General Chemistry ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Surfaces ,visual_art ,visual_art.visual_art_medium ,Ceramics and Composites ,Luminescence ,2506 - Abstract
Here we describe a new class of CPL switches based on oxophilic interactions between chiral sulfoxide-containing ortho-phenylene ethynylene (o-OPE) foldamers and cationic metals. These systems represent a unique case combining high glum values (up to 0.7 × 10-2) and high quantum yields in both folded ON and unfolded OFF CPL states.
- Published
- 2018
37. Azabora[5]helicene Charge-Transfer Dyes Show Efficient and Spectrally Variable Circularly Polarized Luminescence
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Rocío López-Rodríguez, Uwe Pischel, Giovanna Longhi, Zoe Domínguez, Eleuterio Álvarez, Abel Ros, Sergio Abbate, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), European Commission, Junta de Andalucía, and Fondazione Banca del Monte di Lombardia
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Circular dichroism ,boron ,circular dichroism ,circularly polarized luminescence ,helicene ,push-pull chromophores ,Catalysis ,Organic Chemistry ,010402 general chemistry ,Photochemistry ,01 natural sciences ,chemistry.chemical_compound ,symbols.namesake ,Stokes shift ,Boron ,Helicene ,010405 organic chemistry ,General Chemistry ,Push-pull chromophores ,Toluene ,0104 chemical sciences ,Wavelength ,Enantiopure drug ,Circularly polarized luminescence ,chemistry ,symbols ,Luminescence ,Derivative (chemistry) - Abstract
Three helicenes based on a borylated arylisoquinoline skeleton have been prepared in their enantiopure forms and characterized with respect to their photophysical properties, including the use of chiroptical spectroscopies. The dyes show varying charge-transfer characteristics and efficient emission (quantum yields between 0.13 and 0.30, in toluene), which is governed by the electron-donor substitution (p-MeO-phenyl, p-MeN-phenyl) at the helicene. Marked differences in the emission wavelength and Stokes shift are observed, with the dimethylamino-substituted derivative emitting most red-shifted (maximum at ca. 590 nm) and displaying the highest Stokes shift (ca. 6000 cm) in toluene. The helicenes show electronic circular dichroism (ECD) and significant circularly polarized luminescence (CPL) with dissymmetry factors of up to 3.5×10. The sign of the ECD band corresponding to the first transition and of the CPL spectrum depend sensibly on the electron-donor substitution., This work was financially supported by the Spanish Ministry of Economy, Industry, and Competitiveness (CTQ2014‐54729‐C2‐1‐P and CTQ2017‐89832‐P for U.P., CTQ2013‐48164‐C2‐1‐P and CTQ2013‐48164‐C2‐2‐P for A.R., Ramon y Cajal contract RYC‐2013‐12585 for A.R., Ph.D. fellowship BES‐2015‐074458 for Z.D.), the ERDF, the Junta de Andalucía (2012/FQM‐2140 for U.P. and 2012/FQM‐1078 for A.R.), Fondazione Cariplo and Regione Lombardia (Big&Open Data Innovation Laboratory, BODaI‐Lab, University of Brescia).
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- 2018
38. Absolute Configuration Assignment of a Paraconic Acid Derivative via Vibrational Circular Dichroism Spectroscopy and Density Functional Theory Calculation
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Giovanna Longhi, Riccardo Zanasi, Paola Rizzo, Alessandra Lattanzi, Giuseppe Mazzeo, Sergio Abbate, Guglielmo Monaco, and Sara Meninno
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Pharmacology ,Quantitative Biology::Biomolecules ,Circular dichroism ,Tandem ,010405 organic chemistry ,Stereochemistry ,Organic Chemistry ,Absolute configuration ,010402 general chemistry ,01 natural sciences ,Catalysis ,0104 chemical sciences ,Analytical Chemistry ,Crystallography ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Vibrational circular dichroism ,Density functional theory ,Spectroscopy ,Conformational isomerism ,Derivative (chemistry) - Abstract
Density functional theory calculation of the vibrational circular dichroism spectrum was used to assign the absolute configuration of an all-carbon quaternary β-stereocenter of a γ-butyrolactone recently synthesized through an asymmetric organocatalytic tandem aldol/lactonization sequence. Comparison with the experimental spectrum is satisfactory, on account of the fact that spectroscopic features are weak due to the presence of multiple conformers. As a result, the (R) absolute configuration was assigned to the (+) optical isomer.
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- 2015
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39. Vibrational Circular Dichroism (VCD) Reveals Subtle Conformational Aspects and Intermolecular Interactions in the Carnitine Family
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Sergio Abbate, Giuseppe Mazzeo, Giovanna Longhi, Ettore Castiglioni, and Claudio Villani
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Pharmacology ,endocrine system ,Circular dichroism ,Stereochemistry ,Chemistry ,Organic Chemistry ,Intermolecular force ,Absolute configuration ,Catalysis ,Analytical Chemistry ,chemistry.chemical_compound ,Drug Discovery ,Vibrational circular dichroism ,Molecule ,Moiety ,Density functional theory ,Deuterated methanol ,Spectroscopy - Abstract
Vibrational circular dichroism spectra (VCD) in the mid-IR region and electronic circular dichroism (ECD) spectra for three carnitine derivatives in the form of hydrochloride salts were recorded in deuterated methanol solutions. Density Functional Theory calculations help one to understand the significance of the observed VCD bands. VCD and ECD spectra are informative about the absolute configuration of the molecule, but VCD data reveal also some conformational aspects in the N,N,N-trimethyl moiety and inform us about intermolecular interactions gained from the carbonyl stretching region for the acyl substituted carnitines.
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- 2015
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40. The connection between robustness angles and dissymmetry factors in vibrational circular dichroism spectra
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Prasad L. Polavarapu, Giovanna Longhi, Matteo Tommasini, and Sergio Abbate
- Subjects
Physics ,Physical and Theoretical Chemistry ,Physics and Astronomy (all) ,business.industry ,Magnetic dipole transition ,Coordinate system ,Dissymmetry Factor ,General Physics and Astronomy ,Density Functional Theory (DFT) Calculations ,Vibrational Circular Dichroism (VCD) ,Normal Mode Robustness, Dissymmetry Factor ,Molecular physics ,Spectral line ,Optics ,Normal Mode Robustness ,Normal mode ,Robustness (computer science) ,Vibrational circular dichroism ,business - Abstract
To analyze vibrational circular dichroism (VCD) spectra the angle between the electric and magnetic dipole transition moments was introduced as robustness index. We demonstrate that VCD for each normal mode can be made robust by a suitable translation of the coordinate system origin to a robust point . Normal modes differ in how VCD band robustness varies under translations from these respective robust points . It is shown that variation in robustness of a VCD band depends on a parameter inversely proportional to the dissymmetry factor g . Thus, robustness varies slowly for VCD bands with large dissymmetry factors and vice versa.
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- 2015
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41. Sulfoxide-Induced Homochiral Folding of ortho-Phenylene Ethynylenes (o-OPEs) by Silver(I) Templating: Structure and Chiroptical Properties
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Giovanna Longhi, Juan M. Cuerva, M. Carmen Carreño, Diego J. Cárdenas, Santiago Guisán-Ceinos, María Ribagorda, Sergio Abbate, Luis Crovetto, Sandra Resa, Antonio J. Mota, Giuseppe Mazzeo, Delia Miguel, Luis Álvarez de Cienfuegos, and Duane Choquesillo-Lazarte
- Subjects
Circular dichroism ,Supramolecular chemistry ,010402 general chemistry ,01 natural sciences ,Catalysis ,supramolecular chemistry ,host-guest systems ,chemistry.chemical_compound ,Phenylene ,nanostructures ,Helical structures ,010405 organic chemistry ,Organic Chemistry ,Chemistry (all) ,chiroptical properties ,Sulfoxide ,General Chemistry ,0104 chemical sciences ,Nanostructures ,Folding (chemistry) ,Chiroptical properties ,Host-guest systems ,Crystallography ,chemistry ,helical structures ,Vibrational circular dichroism ,Luminescence ,Chirality (chemistry) - Abstract
A new family of homochiral silver complexes based on carbophilic interactions with ortho-phenylene ethynylene (o-OPE) scaffolds containing up to two silver atoms are described. These compounds represent a unique class of complexes with chirality at the metal. Chiral induction is based on the inclusion of chiral sulfoxides, which allow efficient transfer of chirality to the helically folded o-OPE, leading to circularly polarized luminescence (CPL)- and vibrational circular dichroism (VCD)-active compounds. In the presence of silver(I) cations, carbophilic interactions dominate, which promote helical structures with a defined helicity. This is one of the very scarce examples of the use of such interactions in the attractive field of abiotic foldamers. The switching event has been extensively studied by using different chiroptical techniques, including circular dichroism, CPL, and VCD, and represents one of the few CPL switches described in the literature.
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- 2017
42. Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives
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Giovanna Longhi, Renzo Ruzziconi, Sergio Abbate, Federica Buonerba, and Giuseppe Mazzeo
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Crystallography ,Circular dichroism ,Chemistry ,Asymmetric carbon ,Computational chemistry ,Axial chirality ,Organic Chemistry ,Vibrational circular dichroism ,Density functional theory ,Physical and Theoretical Chemistry ,Planar chirality ,Optical rotation ,Chirality (chemistry) - Abstract
Electronic and vibrational circular dichroism (ECD and VCD) spectra and specific optical rotation measurements at the sodium D-line (OR) have been taken for thirteen chiral [2]paracyclo[2](5,8)quinolinophane derivatives and calculated by density functional theory. Besides the planar chirality from the paracyclophane moiety in all molecules, some of the investigated compounds also exhibit central chirality due to an asymmetric carbon atom in the side-chain bound at C-2 of the heterocyclic ring. Characteristic bands for each type of chirality were clearly identified in the VCD spectra in the CH-stretching and mid-IR regions, allowing assignment of absolute and relative configurations. ECD was found to be sensitive mostly, if not exclusively, to planar chirality, whereas OR was also very sensitive to central chirality. Configurational assignment of the different diastereomers by the present method provided results that are in agreement with those inferred from NOE-NMR experiments.
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- 2014
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43. Structural and Optical Properties of Inherently Chiral Polythiophenes: A Combined CD-Electrochemistry, Circularly Polarized Luminescence, and TD-DFT Investigation
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Rocco Martinazzo, Giuseppe Mazzeo, Francesco Sannicolò, Ettore Castiglioni, Tiziana Benincori, Sergio Abbate, Giovanna Longhi, and Patrizia R. Mussini
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Circular dichroism ,Materials science ,Electrochemical polymerization ,business.industry ,Ultraviolet absorption ,Photochemistry ,Electrochemistry ,Spectral line ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Surfaces ,Coatings and Films ,Physical and Theoretical Chemistry ,Energy (all) ,General Energy ,Electronic ,Optoelectronics ,Optical and Magnetic Materials ,Luminescence ,business - Abstract
Circular dichroism (CD) and ultraviolet absorption (UV) spectra of films obtained by electrochemical polymerization of inherently chiral 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene (T4-BT2...
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- 2014
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44. Importance of C*–H Based Modes and Large Amplitude Motion Effects in Vibrational Circular Dichroism Spectra: The Case of the Chiral Adduct of Dimethyl Fumarate and Anthracene
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Giovanna Longhi, Marco Passarello, Renzo Ruzziconi, Susan Lepri, Sergio Abbate, and Valentin Paul Nicu
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Circular dichroism ,Anthracene adducts ,Dimethyl Fumarate ,chirality ,Photochemistry ,Vibration ,Isotopomers ,Motion ,chemistry.chemical_compound ,Fumarates ,Absolute configuration ,Physical and Theoretical Chemistry ,Optical rotation ,Conformational isomerism ,Anthracenes ,Anthracene ,Circular Dichroism ,Water ,Stereoisomerism ,vibrational circular dichroism ,Deuterium ,Crystallography ,chemistry ,Asymmetric carbon ,Vibrational circular dichroism ,Quantum Theory ,Thermodynamics - Abstract
The role played by the C*-H based modes (C* being the chiral carbon atom) and the large amplitude motions in the vibrational absorption (VA) and vibrational circular dichroism (VCD) spectra is investigated. The example of an adduct of dimethyl fumarate and anthracene, i.e., dimethyl-(+)-(11R,12R)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate, and two deuterated isotopomers thereof specially synthesized for this goal, are considered. By comparing the experimental and DFT calculated spectra of the undeuterated and deuterated species, we demonstrate that the C*-H bending, rocking, and stretching modes in the VA and VCD spectra are clearly identified in well defined spectroscopic features. Further, significant information about the conformer distribution is gathered by analyzing the VA and VCD data of both the fingerprint and the C-H stretching regions, with particular attention paid to the band shape data. Effects related to the large amplitude motions of the two methoxy moieties have been simulated by performing linear transit (LT) calculations, which consists of varying systematically the relative positions of the two methoxy moieties and calculating VCD spectra for the partially optimized structures obtained in this way. The LT method allows one to improve the quality of calculated spectra, as compared to experimental results, especially in regard to relative intensities and bandwidths.
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- 2014
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45. Chiroptical Phenomena in Reverse Micelles: The Case of (1R,2S)-Dodecyl (2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium Bromide (DMEB)
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Franca Castiglione, Daniele Mendola, Angela Ruggirello, Vincenzo Turco Liveri, Giovanna Longhi, Marco Passarello, Fiorenza Viani, Andrea Mele, and Sergio Abbate
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Pharmacology ,Hydrogen bond ,Organic Chemistry ,Supramolecular chemistry ,Photochemistry ,Micelle ,Catalysis ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Bromide ,Drug Discovery ,Vibrational circular dichroism ,Proton NMR ,Molecule ,Organic chemistry ,Chirality (chemistry) ,Spectroscopy - Abstract
(1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) aggregates dispersed in carbon tetrachloride have been investigated by Fourier transform infrared (FT-IR), vibrational circular dichroism (VCD) and 1H nuclear magnetic resonance (NMR) spectroscopy at various surfactant concentration and water-to-surfactant molar ratio. Experimental data indicate that, even at the lowest investigated concentration and in absence of added water, DMEB molecules associate in supramolecular assemblies. At higher DMEB concentration the aggregates can confine water molecules, making it plausible to think that DMEB form reverse micelles and that water molecules are quite uniformly distributed among them and mainly located in the proximity of surfactant head groups. Moreover, the water state in DMEB reverse micelles has been found to be different from that in pure water, due to system-specific water/surfactant head group interactions. 1H NMR diffusion measurements of both water and DMEB emphasize their joined translational motion characterized by a diffusion rate one order of magnitude lower than that of free molecules. Finally, VCD allowed us to show some characteristics of the association of optically active DMEB molecules as reverse micelles and water confinement inside; namely, we monitored the vibrational optical activity of deuterated hydroxyl bonds of the self-assembled DMEB molecules and their interaction with D2O molecules. Chirality 26:532–538, 2014.© 2014 Wiley Periodicals, Inc.
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- 2014
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46. Confinement of chiral molecules in reverse micelles: FT-IR, polarimetric and VCD investigation on the state of dimethyl tartrate in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles dispersed in carbon tetrachloride
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Vincenzo Turco Liveri, Sergio Abbate, Giovanna Longhi, Angela Ruggirello, SERGIO ABBATE, GIOVANNA LONGHI, ANGELA RUGGIRELLO, and TURCO LIVERI V
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Circular dichroism ,Inorganic chemistry ,Infrared spectroscopy ,Tartrate ,Micelle ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Monomer ,chemistry ,Pulmonary surfactant ,Vibrational circular dichroism ,Physical chemistry ,Enantiomer ,Dimethyl tartrate Sodium bis(2-ethylhexyl) sulfosuccinate Reverse micelles Chiral nanostructures FT-IR spectroscopy Vibrational circular dichroism Optical rotation - Abstract
The state of d and l -dimethyl tartrate confined within dry sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles dispersed in CCl 4 has been investigated by FT-IR spectroscopy, polarimetry, and vibrational circular dichroism (VCD). Measurements have been performed at 25 °C as a function of the solubilizate-to-surfactant molar ratio ( R ) at a fixed AOT concentration (0.158 M). The analysis of experimental data is consistent with the hypothesis that both enantiomers of dimethyl tartrate are mainly entrapped in the reverse micelles and located in proximity to the surfactant head-group region. The formation of this interesting self-organized chiral nanostructure involves some changes of the typical H-bonding of dimethyl tartrates in the pure solid state or as monomers dispersed in CCl 4 attributable to the establishment of specific solubilizate/surfactant head-group interactions and confinement effects.
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- 2008
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47. Theoretical investigation and computational evaluation of overtone and combination features in resonance Raman spectra of polyenes and carotenoids
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Giuseppe Zerbi, Sergio Abbate, Matteo Tommasini, and Giovanna Longhi
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Basis (linear algebra) ,Chemistry ,Overtone ,Resonance Raman spectroscopy ,Resonance (particle physics) ,Quantum chemistry ,symbols.namesake ,Computational chemistry ,symbols ,General Materials Science ,Density functional theory ,Atomic physics ,Raman spectroscopy ,Spectroscopy - Abstract
We review the theory for overtones and combinations in resonant Raman spectroscopy introduced by Nafie, Stein and Peticolas in 1971 on the basis of time-ordered diagrams, and we apply it to β-carotene with the support of density functional theory calculations. Comparison with experimental results obtained by Tasumi's group in 1994 is provided. The theory here presented allows a prompt evaluation of resonant Raman intensities with presently available quantum chemistry tools. Copyright © 2014 John Wiley & Sons, Ltd.
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- 2014
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48. Combined use of three forms of chiroptical spectroscopies in the study of the absolute configuration and conformational properties of 3-phenylcyclopentanone, 3-phenylcyclohexanone, and 3-phenylcycloheptanone
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Patrizia Scafato, Francesca Caprioli, Laura Pisani, Daniele Padula, Fabrizio Santoro, Giuseppe Mazzeo, Sergio Abbate, France Lebon, and Giovanna Longhi
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Circular dichroism ,Chemistry ,Absolute configuration ,Conformations ,ECD ,ORD ,Phenyl hindered rotation ,VCD ,Vibronic features ,Organic Chemistry ,Ring (chemistry) ,Biochemistry ,ORD, ECD, VCD, Vibronic features, Absolute configuration, Conformations, Phenyl hindered rotation ,Spectral line ,Vibronic coupling ,Computational chemistry ,Drug Discovery ,Vibrational circular dichroism ,Molecule ,Optical rotatory dispersion - Abstract
Three forms of chiroptical spectroscopies, electronic circular dichroism (ECD), vibrational circular dichroism (VCD), and optical rotatory dispersion (ORD) have been employed to study the configuration and conformational properties of the three molecules: (S)-3-phenylcyclopentanone, (S)-3-phenylcyclohexanone, and (S)-3-phenylcycloheptanone (including (S)-3-phenylcyclopentanone-2,2,5,5-d4 and (S)-3-phenylcyclohexanone-2,2,6,6-d4). ECD and VCD spectra in the mid-IR for the three molecular systems are marginally dependent on fine conformational details, as interpreted in terms of standard DFT computational methods, with common spectroscopic features to the three systems clearly identified. Accounting for vibronic coupling mechanisms reproduces the structuring of ECD n→π∗ band. The ORD curves are quite similar for the three types of molecules, but their interpretation highlights a crucial role played by conformations of the cycloalkanone ring in the case of (S)-3-phenylcycloheptanone. The same conclusions are reached by considering the VCD spectra in the CH-stretching region.
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- 2013
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49. Experimental and Calculated CPL Spectra and Related Spectroscopic Data of Camphor and Other Simple Chiral Bicyclic Ketones
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Giovanna Longhi, Ettore Castiglioni, Sergio Abbate, France Lebon, and David A. Lightner
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Pharmacology ,Diketone ,Circular dichroism ,Bicyclic molecule ,Chemistry ,Stereochemistry ,Organic Chemistry ,Fluorescence ,Catalysis ,Analytical Chemistry ,Excited state ,Drug Discovery ,Vibrational circular dichroism ,Physical chemistry ,Luminescence ,Chirality (chemistry) ,Spectroscopy - Abstract
UV, circular dichroism (CD), fluorescence and circularly polarized luminescence (CPL) spectra were recorded for a set of four related [2.2.1] bicyclic compounds ((1S,4S)-and (1R,4R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one, namely (1S)- and (1R)-camphor (1), (1S,4R)-4,7,7-trimethylbicyclo[2.2.1]hept-5-en-2-one, (1S)-dehydro-epicamphor (2), (1S,4S)-1,7,7-trimethylbicyclo[2.2.1]heptane-2,5-dione, (1S)-5-oxocamphor (3), (1S,4R)- and (1R,4S)-1,7,7-trimethylbicyclo[2.2.1]heptane-2,3-dione, (1S)- and (1R)-camphorquinone (4)) and a set of three related [2.2.2] bicyclic compounds (1S,4S)-bicyclo[2.2.2]octan-2,5-dione (saturated diketone (5)), (1R,4R)-bicyclo[2.2.2]oct-7-en-2,5-dione (unsaturated diketone (6)), ((1S,4S)-bicyclo[2.2.2]oct-7-en-5(S)-ol-2-one (which we refer to as unsaturated hydroxy-ketone (7)). For the latter three compounds also mid-IR vibrational circular dichroism (VCD) spectra were recorded and are presented. Time-Dependent Density Functional (TD-DFT) calculations provide a satisfactory interpretation of both absorption and emission chiroptical spectra and permit insight into ground and excited state electronic properties. We discuss the applicability of the octant rule or of other approximated models to rationalize the observed sign of the CPL. Chirality 25:589–599, 2013. © 2013 Wiley Periodicals, Inc.
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- 2013
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50. Molecular dynamics of electrosprayed water nanodroplets containing sodium bis(2-ethylhexyl)sulfosuccinate
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Giovanna Longhi, Alberto Ceselli, Leopoldo Ceraulo, Vincenzo Turco Liveri, Sergio Abbate, and Sandro L. Fornili
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chemistry.chemical_classification ,Aqueous solution ,Chemistry ,Electrospray ionization ,Sodium ,Analytical chemistry ,Anhydrous ,Molecule ,chemistry.chemical_element ,Micelle ,Spectroscopy ,Alkyl ,Ion - Abstract
The behavior of aqueous solutions of sodium bis(2-ethylhexyl)sulfosuccinate (AOTNa) subject to electrospray ionization (ESI) has been investigated by molecular dynamics (MD) simulations at three temperatures (350, 500 and 800 K). We consider several types of water nanodroplets containing AOTNa molecules and composed of a fixed number of water molecules (1000), N(AOT)(0) AOT(-) anions (N(AOT)(0) = 0, 5, 10) and N(Na)(0) sodium ions (N(Na)(0) = 0, 5, 10, 15, 20): in a short time scale (less than 1 ns), the AOTNa molecules, initially forming direct micelles in the interior of the water nanodroplets, are observed in all cases to diffuse nearby the nanodroplet surface, so that the hydrophilic heads and sodium ions become surrounded by water molecules, whereas the alkyl chains lay at the droplet surface. Meanwhile, evaporation of water molecules and of solvated sodium ions occurs, leading to a decrease of the droplet size and charge. At 350 K, no ejection of neutral or charged surfactant molecules is observed, whereas at 500 K, some fragmentation occurs, and at 800 K, this event becomes more frequent. The interplay of all these processes, which depend on the values of temperature, N(AOT)(0) and N(Na)(0) eventually leads to anhydrous charged surfactant aggregates with prevalence of monocharged ones, in agreement with experimental results of ESI mass spectrometry. The quantitative analysis of the MD trajectories allows to evidence molecular details potentially useful in designing future ESI experimental conditions.
- Published
- 2013
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