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A pair of enantiopure [6]‐azairidahelicenes incorporating chirality at the metal center and on the helicenic ligand were synthesized by dynamic kinetic resolution (dkr) of a configurationally labile [4]‐helicenic ligand (4‐(2‐pyridyl)‐benzo[g]phenanthrene, L1H) using bis‐cyclometalated chiral‐at‐metal only iridium(III) precursors as chiral inductors. The origin of the observed dkr is attributed to the different conformation and stability of diastereomeric reaction intermediates formed during the cyclometalation process. The isolated enantiomers exhibited circularly polarized phosphorescence (CPP), with |gphos| values of 1.8×10−3. [ABSTRACT FROM AUTHOR]

In this work a family of multidimensional (2‐(1H‐tetrazol‐5‐yl)ethyl) amino acid coordination compounds have been synthesized and thoroughly characterized. For this purpose, glycine, valine, phenylalanine and tyrosine have been selected as starting amino acids and Mn2+, Zn2+ and Cd2+ as metallic nodes. From one side, for Mn2+ based dimer magnetic resonance imaging studies have been conducted, prompted by the number and disposition of the coordinated water molecules and taking into consideration the promising future of manganese‐based coordination compounds as bio‐compatible substitutes to conventional Gd based contrast agents. From another side, d10 block metal‐based complexes allowed exploring photoluminescence properties derived by in situ synthesized ligands. Finally, amino acid preserved structural chirality allowed us to examine chiroptical properties, particularly focusing on circularly polarized luminescence. [ABSTRACT FROM AUTHOR]

Chiral metallo‐supramolecular fibres can be easily obtained by mixing a chloroform solution of a phenylacetylene monomer (PA) that bears a chiral sulfoxide group as pendant, with different equivalents of a methanolic solution of AgClO4. Thus, while the PA is found molecularly dissolved in chloroform, the addition of Ag+ ions induce its aggregation through the formation of an axially chiral metallo‐supramolecular aggregate with high thermal stable properties. In this case, the ability of the metal ion to coordinate the PA triple bond, combined with the argentophilicity of the metal ion and the planarity of the phenylacetylene drives to the formation of a helical coordination polymer, whose P or M axial chirality is determined by the chirality of the sulfoxide used as substituent of the PA. Depending on the PA/Ag+ (mol/mol) ratio, it is possible to tune the morphology of the metallo‐supramolecular aggregate from chiral fibers to chiral gel. [ABSTRACT FROM AUTHOR]

Lanthanides have unique photoluminescence (PL) emission properties, including very long PL lifetimes. This makes them ideal for biological imaging applications, especially using PL lifetime imaging microscopy (PLIM). PLIM is an inherently multidimensional technique with exceptional advantages for quantitative biological imaging. Unfortunately, due to the required prolonged acquisitions times, photobleaching of lanthanide PL emission currently constitutes one of the main drawbacks of PLIM. In this study, we report a small aqueous‐soluble, lanthanide antenna, 8‐methoxy‐2‐oxo‐1,2,4,5‐tetrahydrocyclopenta[de]quinoline‐3‐phosphonic acid, PAnt, specifically designed to dynamically interact with lanthanide ions, serving as exchangeable dye aimed at mitigating photobleaching in PLIM microscopy in cellulo. Thus, self‐assembled lanthanide complexes that may be photobleached during image acquisition are continuously replenished by intact lanthanide antennas from a large reservoir. Remarkably, our self‐assembled lanthanide complex clearly demonstrated a significant reduction of PL photobleaching when compared to well‐established lanthanide cryptates, used for bioimaging. This concept of exchangeable lanthanide antennas opens new possibilities for quantitative PLIM bioimaging. [ABSTRACT FROM AUTHOR]

The development of chiral compounds with enhanced chiroptical properties is an important challenge to improve device applications. To that end, an optimization of the electric and magnetic dipole transition moments of the molecule is necessary. Nevertheless, the relationship between chemical structure and such quantum mechanical properties is not always clear. That is the case of magnetic dipole transition moment (m) for which no general trends for its optimization have been suggested. In this work we propose a general rationalization for improving the magnitude of m in different families of chiral compounds. Performing a clustering analysis of hundreds of transitions, we have been able to identify a single group in which |m| value is maximized along the helix axis. More interestingly, we have found an accurate linear relationship (up to R2=0.994) between the maximum value of this parameter and the area of the inner cavity of the helix, thus resembling classical behavior of solenoids. This research provides a tool for the rationalized synthesis of compounds with improved chiroptical responses. [ABSTRACT FROM AUTHOR]

We report on the chemical design of chiral molecular junctions with stress‐dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau‐length distributions, attributed to different conformations of the helical structures. The large chiro‐optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state‐of‐the‐art Density Functional Theory (DFT) calculations, including a fully ab‐initio estimation of the CISS‐originating spin polarization which is done, for the first time, for a realistic molecular system. [ABSTRACT FROM AUTHOR]

We report on the preparation and characterization of two dimensional (2D) films of (S,S,P)-1 and (R,R,M)-1ortho-oligophenylene ethylene (o-OPE) enantiomers presenting high values of circularly polarized luminescence (CPL). The amphiphilic character of these two molecules allows a precise 2D self-assembly at the air/water interface and an efficient transfer onto a glass solid support. The morphological and chiroptical characterization of the solid supports after the transfer of 1, 8, 16 and 32 Langmuir films of (S,S,P)-1 and (R,R,M)-1 has been carried out. The strong chiroptical values of these monomers allow reliable ECD measurements to be obtained after a single transfer, with ECD values increasing as the number of transferred films increases. The semi-liquid behavior of the monomers on the solid substrate allows CPL measurements free of photoselection artifacts that show values similar to those obtained in solution and independent of monomer concentration. All these properties have allowed us to develop the first simple organic molecule (SOM)-based chiroptical barcoding presenting positive and negative regions as a proof of concept. [ABSTRACT FROM AUTHOR]

The present work reports on a detailed discussion about the synthesis, characterization, and luminescence properties of three pairs of enantiopure 3D metal–organic frameworks (MOFs) with general formula {[Ln2(L/D-tart)3(H2O)2]·3H2O}n (3D_Ln-L/D, where Ln = Sm(III), Eu(III) or Gd(III), and L/D-tart = L- or D-tartrate), and ten pairs of enantiopure 2D coordination polymers (CPs) with general formula [Ln(L/D-Htart)2(OH)(H2O)2]n (2D_Ln-L/D, where Ln = Y(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III) or Yb(III), and L/D-Htart = hydrogen L- or D-tartrate) based on single-crystal X-ray structures. Enantiopure nature of the samples has been further corroborated by Root Mean Square Deviation (RMSD) as well as by circular dichroism (CD) spectra. Solid-state emission spectra of Eu(III), Tb(III), and Dy(III)-based compounds confirm the occurrence of ligand-to-metal charge transfers in view of the characteristic emissions for these lanthanide ions, and emission decay curves were also recorded to estimate the emission lifetimes for the reported compounds. A complete theoretical study was accomplished to better understand the energy transfers occurring in the Eu-based counterparts, which allows for explaining the different performances of 3D-MOFs and 2D-layered compounds. As inferred from the colorimetric diagrams, emission characteristics of Eu-based 2D CPs depend on the temperature, so their luminescent thermometry has been determined on the basis of a ratiometric analysis between the ligand-centered and Eu-centered emission. Finally, a detailed study of the polarized luminescence intensity emitted by the samples is also accomplished to support the occurrence of chiro-optical activity. [ABSTRACT FROM AUTHOR]

Copyright of Acta Odontologica Latinoamericana: AOL is the property of Acta Odontologica Latinoamericana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A direct, efficient and versatile strategy for the modulation of optoelectronic and magnetic properties of indeno[1,2-b]fluorene has been developed. 4-Substituted-2,6-dimethylphenyl acetylene groups placed in the apical carbon of the five-membered rings lead to redshifted absorption maxima (λmax ranging from 600–700 nm) and considerable narrowing of the HOMO–LUMO energy gap (down to 1.5 eV). Experimental and theoretical data show an increase in the diradical character (y) and a decrease of the singlet-triplet energy gap. Moreover, we have investigated the single-molecule conductance of the antiaromatic indeno[1,2-b]fluorene for the first time by including thiomethyl (-SMe) anchor groups on the phenylacetylene moiety. Conductance values one order of magnitude higher than those of a reference linear 3-ring para-phenylene ethylene have been found, despite the longer length of the S-to-S molecular junction. First principles transport calculations support this high conductance value. [ABSTRACT FROM AUTHOR]

Helical polymers such as poly(phenylacetylene)s (PPAs) are interesting materials due to the possibility of tuning their helical scaffold (sense and elongation) once they have been prepared and by the presence of external stimuli. The main limitation in the application of PPAs is their poor photostability. These polymers degrade under visible light exposure through a photochemical electrocyclization process. In this work, it was demonstrated, through a selected example, how the photochemical degradation in PPAs is directly related to their dynamic helical behavior. Thus, while PPAs with dynamic helical structures show poor photostability under UV/Vis light exposure, poly‐(R)‐1, bearing an enantiopure sulfoxide group as pendant group and designed to have a quasi‐static helical behavior, shows a large photostability due to the restricted conformational composition at the polyene backbone, needed to orient the conjugated double bonds prior to the photochemical electrocyclization process and the subsequent degradation of the material. [ABSTRACT FROM AUTHOR]

A novel convergent procedure that has proved useful in the synthesis of a wide range of meroterpenoid-related structures containing a mono-, sesqui, or diterpenoid moiety linked to a nonfused aromatic subunit with various substitution patterns is discussed. The coupling reaction is perfectly compatible with preformed epoxides, while the sequential cyclixation provide exocyclic alkenes.

This document is a summary of various articles published in the journal Angewandte Chemie International Edition. The articles cover a range of topics including the synthesis of enantiopure irida[6]helicenes, the use of CF3 groups in palladium chemistry, the engineering of oxygen vacancies in αMoO3 for energy storage in aluminum-ion batteries, and a proposal for a unified set of priorities in sustainable chemistry. The articles are authored by various researchers and provide valuable insights into these areas of study. [Extracted from the article]

This document, published in the journal Angewandte Chemie, highlights several research findings in the field of chemistry. One study discusses the synthesis of enantiopure irida[6]helicenes, which exhibit mirrored electronic circular dichroism and circularly polarized phosphorescence signals. Another study explores the use of the CF3 group as a synthon in palladium chemistry. Additionally, researchers demonstrate a selective shift in energy storage mechanism in aqueous aluminum-ion batteries through the engineering of oxygen vacancies in the α-MoO3 structure. Lastly, a scientific perspective proposes a unified set of triple E priorities (environment, economy, equity) to guide efforts in sustainable chemistry. [Extracted from the article]

Research has been conducted on eudesmanolides which are the sequiterpene lactones' main skeletal types. The results of the straightforward synthesis of such eudesmanolides as (+)-3alpha-hydroxyreynosin and (+)-8beta-hydroxyasterolide carried out via different solvents and additives and containing exocyclic double bond are reported.

Research has been conducted on the oxabicyclic compounds. The application of a technique that involves the homolytic opening of epoxides with Ti(III) complexes to acyclic epoxypolyenes is discussed.

In this paper, we describe the optical and chiroptical properties of an enantiopure multipodal ortho‐oligophenylethynylene (S,S,S,S)‐1 presenting four chiral sulfoxide groups at the extremes. The presence of these groups together with alkynes allows the coordination with carbophilic Ag(I), and/or oxophilic Zn(II) cations, yielding double helical structures in an enantiopure way. In this sense, different behaviors in absorption, fluorescence, ECD and CPL spectra have been found depending on the stoichiometry and nature of the metal. We have observed that Zn(II) coordination favors an intensity increase of the electronic circular dichroism (ECD) spectra of compound (S,S,S,S)‐1 yielding an M‐helicity in the ortho‐oligophenylene ethynylene (o‐OPE) backbone. On the other hand, ECD spectra of final Ag(I) complex shows two different bands with an opposite sign to the free ligand, thus giving the P‐helical isomer. In addition, circularly polarized luminescence (CPL) exhibit an enhanced intensity and negative sign in both complexes. Computational studies were also carried out, supporting the experimental results. [ABSTRACT FROM AUTHOR]

We report on the synthesis and single-molecule conductance of a para-oligo(phenylene)ethynylene (p-OPE) derivative with three well-defined conductance states. Employing theoretical models and comparing to reference compounds we show that this effect is due to the presence of the internal non-symmetrically placed pyrimidine ring, acting as an in-backbone anchor group. This is the first example in which the non-symmetric positioning of an internal binding site opens up two new conduction channels, giving rise, in a simple way, to a system that displays three conduction pathways which differ distinctively in both conductance and length. [ABSTRACT FROM AUTHOR]

The ruthenium complex RuH2(PPh3)4 is an excellent catalyst for the Michael addition of active methylene compounds lacking cyano groups when the reactions are performed in acetonitrile instead of THF. The reaction proceeds satisfactorily in acetonitrile under mild and neutral conditions with malonates, beta-ketoesters, 1,3-diketones, 1,1-disulfones, nitro compounds, Meldrum acid and anthrone as the Michael donors. Cyano acetates can also be ideal substrates for this reaction.

Copyright of Acta Odontologica Latinoamericana: AOL is the property of Acta Odontologica Latinoamericana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Palladium catalyzes coupling reactions between acid chlorides and E-(1,2)-bis(tri-n-butylstannyl)ethene or beta-stannyl enones to produce butane-1,4-diones. The reaction involves reduction of an enedicarbonyl intermediate. Coupling reactions at low temperatures yield alpha, beta-unsaturated 1,4-diketones, and involve palladium hydride-promoted reduction. This method facilitates synthesis of two 1,4-diketone ipomeanines.

The article discusses a significant advancement in quantitative PLIM bioimaging called PAnt (phosphonic acid antenna). PAnt is a small water-soluble lanthanide antenna that can self-assemble with lanthanide ions, serving as an exchangeable probe to overcome photobleaching in PLIM microscopy in cellulo. This allows for continuous replenishment of lanthanide complexes that may be photobleached during acquisition, resulting in remarkable photostability compared to traditional lanthanide cryptates. The research was conducted by Angel Orte, Juan A. González-Vera, and their team, and the article includes artwork by M. Eugenio Vázquez from the University of Santiago de Compostela. [Extracted from the article]

The article discusses a significant advancement in quantitative PLIM bioimaging called PAnt (phosphonic acid antenna). PAnt is a small water-soluble lanthanide antenna that can self-assemble with lanthanide ions, serving as an exchangeable probe to overcome photobleaching in PLIM microscopy in cellulo. The use of PAnt allows for continuous replenishment of lanthanide complexes that may be photobleached during acquisition, resulting in remarkable photostability compared to traditional lanthanide cryptates. The research was conducted by Angel Orte, Juan A. González-Vera, and their colleagues. [Extracted from the article]

This work reports on the synthesis and characterization of an enantiomeric pair of 3D coordination polymers (CPs) based on heavy alkaline-earth metal ions and cyclic aliphatic chiral linkers, i.e. [Ba2(μ- L -pyro)2(μ4-NO3)(μ3-form)]n (1-L) and [Ba2(μ- D -pyro)2(μ4-NO3)(μ3-form)]n (1-D) [where pyro = pyroglutamate and form = formate]. These materials present a dense framework built up from the junction of barium(II) ions by means of three bridging ligands showing different connectivity, which affords robustness and, in turn, large stability to the crystal building. L - or D -pyro ligands are formed in situ during the solvothermal synthesis through the cyclization of the corresponding chiral glutamine species, which does not affect the chirality of the resulting ligand such that the structures preserve an enantiopure nature. A deep study of the photophysical properties reveals that these CPs display intriguing photoluminescence (PL) properties involving intense fluorescence and long-lasting phosphorescence, even at room temperature, which have been deeply characterized by diffuse reflectance, variable-temperature emission analysis and time-resolved emission spectra (TRES). The experimental results are sustained by DFT calculations that decipher the PL mechanism. Moreover, these materials exhibit intense pyro-based circularly polarized luminescence in agreement with their chiral nature, which constitutes the first example of an AE-based CP able to display CPL signals. [ABSTRACT FROM AUTHOR]

A series of highly emissive inert and chiral CrIII complexes displaying dual circularly polarized luminescence (CPL) within the NIR region have been prepared and characterized. The helical [Cr(dqpR)2]3+ (dqp=2,6‐di(quinolin‐8‐yl)pyridine; R=OCH3, Br or C≡CH) complexes were synthesized as racemic mixtures and resolved into their respective PP and MM enantiomers by chiral stationary phase HPLC. The corresponding enantiomers show large glum≈0.2 and high quantum yield of up to 17 %, which afford important CPL brightness of up to 170 m−1 cm−1, a key point for applications as chiral luminescent probes. Moreover, the long‐lived CP‐NIR emission provided by these chromophores (ms range) in aqueous solution opens the way toward the quantification of chiral targets in biological systems with time‐gated detection. Thus, such chiral chromophores based on earth abundant and inert 3d metals open new perspectives in the field of CPL and represent an alternative to precious 4d, 5d and to labile 4f metal‐based complexes. [ABSTRACT FROM AUTHOR]

The single‐molecule conductance of a series of BN‐acene‐like derivatives has been measured by using scanning tunneling break‐junction techniques. A strategic design of the target molecules has allowed us to include azaborine units in positions that unambiguously ensure electron transport through both heteroatoms, which is relevant for the development of customized BN‐doped nanographenes. We show that the conductance of the anthracene azaborine derivative is comparable to that of the pristine all‐carbon anthracene compound. Notably, this heteroatom substitution has also allowed us to perform similar measurements on the corresponding pentacene‐like compound, which is found to have a similar conductance, thus evidencing that B–N doping could also be used to stabilize and characterize larger acenes for molecular electronics applications. Our conclusions are supported by state‐of‐the‐art transport calculations. [ABSTRACT FROM AUTHOR]

Thiele (Th) and tetrabenzo-Chichibabin (TBC) derivatives with terminal dibenzocycloheptatriene (DBHept) units were prepared. A clear correlation between their electronic and molecular structures was stablished. Insights into their closed- or open-shell ground states were gained, where particular contribution of the heptagonal carbocycles as end-groups was proved. Remarkably, a thermally accessible triplet diradical configuration was confirmed for the DBHept-TBC compound. [ABSTRACT FROM AUTHOR]

A cyclophane is reported incorporating two units of a heptagon‐containing extended polycyclic aromatic hydrocarbon (PAH) analogue of the hexa‐peri‐hexabenzocoronene (HBC) moiety (hept‐HBC). This cyclophane represents a new class of macrocyclic structures that incorporate for the first time seven‐membered rings within extended PAH frameworks. The saddle curvature of the hept‐HBC macrocycle units induced by the presence of the nonhexagonal ring along with the flexible alkyl linkers generate a cavity with shape complementarity and appropriate size to enable π interactions with fullerenes. Therefore, the cyclophane forms host–guest complexes with C60 and C70 with estimated binding constants of Ka=420±2 m−1 and Ka=(6.49±0.23)×103 m−1, respectively. As a result, the macrocycle can selectively bind C70 in the presence of an excess of a mixture of C60 and C70. [ABSTRACT FROM AUTHOR]

This work reports on the synthesis and characterization of five enantiomeric pairs of isostructural 3D metal–organic frameworks (MOFs) with the general formula {[Ln2(μ4-tar)2(μ-tar)(H2O)2]·xH2O}n [where Ln(III) = Tb (Tb-L and Tb-D), Dy (Dy-L and Dy-D), Ho (Ho-L and Ho-D), Er (Er-L and Er-D) and Tm (Tm-L and Tm-D); tar = tartrate (D - or L -) and x = 3 or 4 depending on the counterpart], which possess interesting luminescence and magnetic properties. These MOFs undergo progressive and reversible dehydration processes upon controlled heating yielding three crystalline phases (Ln-L′, Ln-L′′ and Ln-L′′′). Alternating current magnetic measurements on Tb, Dy and Er-based compounds exhibit field induced single-molecule magnet behavior dominated by QTM, which is partially suppressed when diluted on a Y-based matrix. Tartrate ligands show poor room temperature sensitization of Tb and Dy centers that is enhanced at low temperature (10 K), even enabling weak Tm-based emission. More interestingly, the dehydration modulates both magnetic and photoluminescence properties on the basis of both the distortions occurring in the coordination shells and a decrease of water molecules acting as quenchers, respectively, endowing these materials with potential humidity sensing capacity. Remarkably, the Tb-based MOF shows circularly polarized luminescence (CPL), being one of the examples of this very scarce family of CPL emitters reported so far. [ABSTRACT FROM AUTHOR]

A new family of distorted ribbon‐shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two‐photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven‐membered‐ring‐containing nanographene presenting a tropone moiety at the edge, its full‐carbon analogue, and a purely hexagonal one. We have found that the TPA cross‐sections and the electrochemical band gaps of the seven‐membered‐ring‐containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non‐linear optical properties of those ribbons. [ABSTRACT FROM AUTHOR]

A mild, simple, safe, chemoselective reduction of different kinds of aldehydes to the corresponding alcohols mediated by the Mn dust/water system is described. An efficient, inexpensive alternative for the preparation of the same type of compounds through the synthesis of [alpha]-deuterated alcohols in presence of [D.sub.2]O is also described.

A study was conducted to demonstrate the efficiency of titanocene(III) aqua complexes as a unique class of hydrogen-atom donor (HAT) reagents based on two key features such as excellent binding capabilities of water toward titanocene(III) complexes and a low activation energy for the HAT step. The results provide insight into the remarkable hydrogen-atom donor characteristics of water in [Ti.sup.III]-mediated free-radical chemistry.