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Recent efforts in the field of surface-enhanced spectroscopies have focused on the paradigm of superchirality, entailing the engineering of the local electromagnetic fields to boost the enantiospecific interaction between light and chiral molecules. In this framework, approaches based on both metallic and dielectric nanostructures have been proposed and have also recently been extended to vibrational circular dichroism in the mid-infrared. In this work, we design, fabricate and characterize arrays of chiral plasmonic slits featuring enhanced chiral fields in the mid-infrared. We exploit collective lattice resonances to further enhance the local intensity and to generate sharp features in the circular dichroism spectra of the platform. Such features are ideally suited to test the superchiral coupling with the vibrational resonances of chiral molecules.

The luminescent square-planar Pt(II) complexes of the type [Pt(C^N)(N^N)] + X - , where (C^N) is the cyclometallated 2-phenylpyridine ligand, (N^N) a chiral diamine and BF 4 − or CH 3 COO − as counterion (X − ) have been synthesized. The chiral diamine Campy has been used, resulting in a mixture of regioisomers. The complexes were characterized and their structures in solution were determined by a combination of different spectroscopic and chiroptical techniques (NMR, UV–Vis, ECD, IR, VCD and CPL) associated with electrochemical, DFT and TDDFT studies. Remarkably, the acetate derivatives proved to be soluble and stable in water for at least a month. The electrochemical behaviour of the [Pt(C^N)(N^N)]BF 4 was investigated and the LUMO energies estimated. The photophysical properties of the new compounds were deeply investigated in water or dimethyl sulfoxide solution by UV–Vis, steady state emission and time-correlated single-photon counting spectroscopy.

Chiral stapled o-OPEs show excellent circular polarized luminescence responses (glum of 1.1 × 10–2) which can be modulated by carbophilic interactions., ortho-Oligo(phenylene)ethynylenes (o-OPEs) stapled with enantiopure 2,3-dihydroxybutane diethers have highly intense circular dichroism (CD) spectra and excellent circular polarized luminescence (CPL) responses (glum values up to 1.1 × 10–2), which are consistent with homochiral helically folded structures. In the presence of Ag(i), a change in the CPL emission is observed, representing the first example of CPL active small organic molecular emitters, which can be modulated by carbophilic interactions in a reversible manner.

We extend a recently proposed mixed quantum/classical method for computing the vibronic electronic circular dichroism (ECD) spectrum of molecules with different conformers, to cases where more than one hindered rotation is present. The method generalizes the standard procedure, based on the simple Boltzmann average of the vibronic spectra of the stable conformers, and includes the contribution of structures that sample all the accessible conformational space. It is applied to the simulation of the ECD spectrum of (S)-2,2,2-trifluoroanthrylethanol, a molecule with easily interconvertible conformers, whose spectrum exhibits a pattern of alternating positive and negative vibronic peaks. Results are in very good agreement with experiment and show that spectra averaged over all the sampled conformational space can deviate significantly from the simple average of the contributions of the stable conformers. The present mixed quantum/classical method is able to capture the effect of the nonlinear dependence of the rotatory strength on the molecular structure and of the anharmonic couplings among the modes responsible for molecular flexibility. Despite its computational cost, the procedure is still affordable and promises to be useful in all cases where the ECD shape arises from a subtle balance between vibronic effects and conformational variety.

"This is the peer reviewed version of the following article: Resa, S.; et al. Sulfoxide-Induced Homochiral Folding of o-OPEs by AgI Templating: Structure and Chiroptical Properties. Chemistry a European Journal, 2018, which has been published in final form at http://dx.doi.org/10.1002/chem.201704897 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.", A new family of homochiral silver complexes based on carbophilic interactions with ortho-phenyleneethynylene (o-OPE) scaffolds containing up to two silver atoms is 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 an efficient transfer of chirality to the helically folded o-OPE, leading to CPL and VCD active compounds. In the presence of AgI cation carbophilic interactions dominate, promoting 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 using different chiroptical techniques including CD, CPL and VCD, also representing one of the few CPL switches described in literature., We thank MINECO (FEDER funded grant CTQ2014-53598-R). Computing Center CINECA, Bologna, Italy, Regione Lombardia for the LISA Grant No. “ChiPhyto: HPL13POZE1” and the “Centro de Supercomputación de la UGR” (UGRGRID) are acknowledged for access to computational facilities. Sandra Resa thanks the MECD for a FPU fellowship.

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.

The octahedral ionic Ir(iii) complex with a dual stereogenic centre of general formula Δ,Λ-(R,S)-[(ppy)2Ir(Me-Campy)]X, where ppy = 2-phenylpyridine and Me-Campy = 2-methyl-5,6,7,8-tetrahydroquinolin-8-amine, and the complex Λ-(R,S)-[(ppy)2Ir(H-Campy)]X, where ppy = 2-phenylpyridine, H-Campy = 8-amino-5,6,7,8-tetrahydroquinolines and X(-) = Cl(-) as a counterion in both cases, have been characterized by vibrational circular dichroism (VCD), which turns out to be efficacious in diastereomeric discrimination. Moreover, the single crystal X-ray structure of the complex Δ-(R)-[(ppy)2Ir(Me-Campy)]Cl is reported here. Density functional theory (DFT) calculations allow us to conclude that the most important doublet feature in the VCD spectra is associated with a clear vibrational exciton structure located on the two dissymmetrically disposed phenylpyridine ligands. The features in the VCD spectra associated with the (R) or (S)-central chirality configuration are identified and commented on. DFT calculations provide also the interpretation of electronic circular dichroism (ECD) spectra. Finally, circularly polarized luminescence (CPL) spectra are presented as an additional chiroptical characterization of these luminescent iridium complexes.

In this paper we have studied the chiroptical properties of a family of o-OPE derivatives with different steric hindrance. Experimental results show high dissymmetry factors (gabs and glum up to 1.1x10-2) and very similar ECD and CPL for all the derivatives, that makes this basic o-OPE scaffold a robust pure organic emitter. VCD spectra are used to characterize conformational properties in solution. DFT and TD-DFT calculations support experimental results also proving that ECD and CPL are almost exclusively linked to helical moiety and not to size or conformation of substituents. As chiroptical properties of these emitters are independent of substituents, this OPE scaffold can be used as basic skeleton for the design of sensing probes with high CPL efficiencies., We thank MICINN (CTQ2014-53598-R) and Junta de Andalucía (FQM1484) for financial support. Computing Center CINECA Via Magnanelli 6/3 40033 – Casalecchio di Reno (Bologna) Italy and Regione Lombardia for the LISA Grant No. “ChiPhyto: HPL13POZE1” is acknowledged for access to computational facilities. P. Reiné thanks MICINN for a FPU fellowship.

Leishmaniosis is a neglected tropical disease which affects several millions of people worldwide. The current drug therapies are expensive and often lack efficacy, mainly due to the development of parasite resistance. Hence, there is an urgent need for new drugs effective against Leishmania infections. As a part of our ongoing study on the phytochemical characterization and biological investigation of plants used in the traditional medicine of western and central Asia, in the present study, we focused on Eremurus persicus root extract in order to evaluate its potential in the treatment of leishmaniosis. As a result of our study, aloesaponol III 8-methyl ether (ASME) was isolated for the first time from Eremurus persicus root extract, its chemical structure elucidated by means of IR and NMR experiments and the (R) configuration assigned by optical activity measurements: chiroptical aspects were investigated with vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopies and DFT (density functional theory) quantum mechanical calculations. Concerning biological investigations, our results clearly proved that (R)-ASME inhibits Leishmania infantum promastigotes viability (IC50 73 µg/mL), inducing morphological alterations and mitochondrial potential deregulation. Moreover, it is not toxic on macrophages at the concentration tested, thus representing a promising molecule against Leishmania infections.

Vibrational circular dichroism, VCD, gives evidence that the carbon monoxide chromophore in a heteroleptic cyclopentadienyl Ru(II)-carbonyl complex is very sensitive to the chirality of the metal centre and becomes an excellent probe to define the configuration of chiral metal complexes.

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.

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.

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.

Ultraviolet (UV), Circular Dichroism (CD), Fluorescence, and Circularly Polarized Luminescence (CPL) spectra were recorded for mixed chloroform/methanol and chloroform/butanol solutions of regioregular poly[3-((S)-2-methylbutyl)-thiophene]. An evaluation of the chiral and nonchiral components in solution is proposed on the basis of the UV and CD spectra. The fluorescence and CPL spectra are observed in a wavelength range where some UV and CD activity still appears. For this reason, the observed CPL features are strongly influenced by CD. A general procedure for evaluating true CPL spectra is proposed, when absorption and emission coexist.