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A family of inherently chiral electroactive selectors based on the 2,2’‐biindole atropisomeric scaffold, of easy synthesis and modulable functional properties, is studied in cascade in two enantioselection contexts. They are at first investigated as probes in enantioselective HPLC, studying molecular structure and temperature effects, and achieving very efficient semipreparative enantioseparation. The enantiomers thus obtained, of remarkable chiroptical features (optical rotation as well as circular dichroism), are successfully applied as selectors in chiral voltammetry in different media for discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces by electrooligomerization on glassy carbon substrate (the two monomers with shorter alkyl chains), or as chiral additive in achiral ionic liquid (the monomer with longest alkyl chains). Discrimination is conveniently and reproducibly achieved in terms of significant potential differences for the two enantiomers, specularly inverting either probe or selector configuration. In one case successful discrimination is also observed with the two probe enantiomers concurrently present, either as racemate or with enantiomeric excesses, neatly accounted for by the peak current ratios., A series of inherently chiral electroactive selectors based on the 2,2’‐biindole atropisomeric scaffold is studied in two enantiodiscrimination contests: as probes in enantioselective HPLC and as selectors in chiral voltammetry for successful discrimination of the enantiomers of chiral electroactive probes, either by conversion into enantiopure electroactive electrode surfaces or as chiral additive in achiral ionic liquid.

A series of 2,2’-biindole-based inherently chiral electroactive monomers are comparatively investigated with their 3,3’ analogues as an excellent study case of two equivalent redox centres interacting through a torsional barrier. The twin peak potential splitting observed in voltammetry for the first oxidation of the biheteroaromatic core accounts for the energy barrier height: the lower the barrier, the larger the peak potential splitting, with modulation by solvent and temperature. The height of the energy barrier is determining for the electrochemical and spectroscopic features of the monomers as well as for their configurational stability and applicability for enantioselection purposes. The 3,3’ monomers, featuring large twin peak splittings in CV, are “trópos” systems with a low torsional barrier, so they cannot exist as stable enantiomers at room temperature. Instead their 2,2’ isomers, with much smaller twin peak splittings, are “átropos” systems and can be separated by enantioselective HPLC into stable enantiomers, providing powerful “inherently chiral” selectors with outstanding enantioselection properties in chiral electroanalysis and electrochemistry as well as in chiroptical spectroscopy, with fascinating reciprocal correlations.

A voltammetric comparative investigation on the electrochemical activity of substituted bromothiophenes vs bromobenzenes highlights the combined effects of the aromatic or heteroaromatic ring substituents and the sulphur atom on both the intrinsic reactivity (accounted for by experiments on a glassy carbon electrode, assumed to have negligible specific interactions) and the reactivity in the presence of electrocatalytic effects, working on Au or Ag electrodes. The two series of compounds share similarities concerning the dissociative electron transfer mechanism for the reductive cleavage of the C-Br bond, including substituent effects. However, the presence of the sulphur atom in the heteroaromatic series significantly promotes the process both in non-catalytic conditions, on account of electronic effects, and on catalytic electrodes, performing as adsorption auxiliary. The effect is particularly remarkable on Au, partially compensating for the effect of the very negative surface charge, and with significant modulation from the S position with respect to the Br leaving group. The nitrile group might act as an additional adsorption auxiliary besides the S atom. In dibromobithiophene systems Au and Ag catalytic surfaces can also induce a remarkable modification in molecular conformation in order to optimize Br and S interactions with the catalytic surface for both conjugated thiophene rings.

Configurationally stable 5-aza[6]helicene (1) was envisaged as a promising scaffold for non-conventional ionic liquids (IL)s. It was prepared, purified, and separated into enantiomers by preparative HPLC on a chiral stationary phase. Enantiomerically pure quaternary salts of 1 with appropriate counterions were prepared and fully characterized. N-octyl-5-aza[6]helicenium bis triflimidate (2) was tested in very small quantities as a selector in achiral IL media to perform preliminary electrochemical enantiodifferentiation experiments on the antipodes of two different chiral probes. The new organic salt exhibited outstanding enantioselection performance with respect to these probes, thus opening the way to applications in the enantioselective electroanalysis of relevant bioactive molecules.

Deep Eutectic Solvents (DESs) offer advantages similar to ionic liquid (IL) ones, with easier and more sustainable synthesis; moreover, bio-based DESs often include chiral components, surprisingly underexploited. A proof of concept is now offered of the impressive potential of enantiopure chiral DESs as chiral media for enantioselective electroanalysis. Three chiral DESs, consisting of a molecular salt with bio-based chiral cation [NopolMIm]+ combined with three natural and/or low-cost partners (levulinic acid, glycerol and urea), are introduced and investigated as chiral voltammetry media. Significant potential differences are observed for the enantiomers of a model chiral probe, with a dramatic tuning depending on the achiral DES component, reaching an impressive ~0.5 V in the levulinic acid case (while less efficient appears [NopolMIm]+ as chiral additive in IL). With the same medium good enantiodiscrimination is also observed for aminoacid tryptophan, a quite different probe and of applicative interest. These findings can be considered as a remarkable step further in chiral electroanalysis as well as in the development of task-specific enantioselective media.

A voltammetric and scanning electrochemical microscopy (SECM) investigation was performed on an inherently chiral oligomer-coated gold electrode to establish its general properties (i.e., conductivity and topography), as well as its ability to discriminate chiral electroactive probe molecules. The electroactive monomer (S)-2,2&prime, bis(2,2&prime, bithiophene-5-yl)-3,3&prime, bibenzothiophene ((S)-BT2T4) was employed as reagent to electrodeposit, by cyclic voltammetry, the inherently chiral oligomer film of (S)-BT2T4 (oligo-(S)-BT2T4) onto the Au electrode surface (resulting in oligo-(S)-BT2T4-Au). SECM measurements, performed in either feedback or competition mode, using the redox mediators [Fe(CN)6]4&minus, and [Fe(CN)6]3&minus, in aqueous solutions, and ferrocene (Fc), (S)-FcEA, (R)-FcEA and rac-FcEA (FcEA is N,N-dimethyl-1-ferrocenylethylamine) in CH3CN solutions, indicated that the oligomer film, as produced, was uncharged. The use of [Fe(CN)6]3&minus, allowed establishing that the oligomer film behaved as a porous insulating membrane, presenting a rather rough surface. This was inferred from both the approach curves and linear and bidimensional SECM scans, which displayed negative feedback effects. The oligomer film acquired semiconducting or fully conducting properties when the Au electrode was biased at potential more positive than 0.6 V vs. Ag|AgCl|KCl. Under the latter conditions, the approach curves displayed positive feedback effects. SECM measurements, performed in competition mode, allowed verifying the discriminating ability of the oligo-(S)-BT2T4 film towards the (S)-FcEA and (R)-FcEA redox mediators, which confirmed the results obtained by cyclic voltammetry. SECM linear scans indicated that the enantiomeric discriminating ability of the oligo-(S)-BT2T4 was even across its entire surface.

Redox potential modulation of achiral probes on chirally modified electrode surfaces with spin filter features under an applied magnetic field., Impressive spin-related effects are observed in cyclic voltammetry (CV) experiments performed under an applied magnetic field on a non-ferromagnetic electrode modified with a thin electroactive oligothiophene film, either “inherently chiral” or featuring chiral pendants with stereogenic centres. When flipping the magnet’s north/south orientation, the CV peaks of two achiral, chemically reversible Fe(iii)/Fe(ii) redox couples in aqueous or organic solution undergo impressive potential shifts (up to nearly 0.5 V depending on protocol conditions), specularly by changing the film’s (R)- or (S)-configuration. The magnitude of the potential shift decreases upon increasing both the polymer film thickness and the distance between the permanent magnet and the electrode surface. Such unprecedented spin-related redox potential modulation, obtained in the absence of a magnetic electrode acting as a spin injector, provides striking evidence (as well as an attractive evaluation criterion) of the spin selectivity properties of chiral thin films.

Chiral electroanalysis could be regarded as the highest recognition degree in electrochemical sensing, implying the ability to discriminate between specular images of an electroactive molecule, particularly in terms of significant peak potential difference. A groundbreaking strategy was recently proposed, based on the use of "inherently chiral" molecular selectors, with chirality and key functional properties originating from the same structural element. Large differences in peak potentials have been observed for the enantiomers of different chiral molecules, also of applicative interest, using different selectors, all of them based on atropisomeric biheteroaromatic scaffolds of axial stereogenicity. However, helicene systems also provide inherently chiral building blocks with attractive features. In this paper the enantiodiscrimination performances of enantiopure inherently chiral films obtained by electrooxidation of a thiahelicene monomer with helicoidal stereogenicity are presented for the first time. The outstanding potentialities of this novel approach are evaluated towards chiral probes with different chemical nature and bulkiness, in comparison with a representative case of the so far exploited class of inherently chiral selectors with axial stereogenicity. It is also verified that the high enantiodiscrimination ability holds as well for electron spins, as for atropisomeric selectors.

Enantioselective electroanalysis, which aims to discriminate the enantiomers of electroactive chiral probes in terms of potential difference, is a very attractive goal. To achieve this, its implementation is being studied for various "inherently chiral" selectors, either at the electrode surface or in the medium, yielding outstanding performance. In this context, the new inherently chiral monomer Naph2T4 is introduced, based on a biaromatic atropisomeric core, which is advantageously obtainable in enantiopure form without HPLC separation steps by a synthetic route hinging on enantiopure 2,2&rsquo, dibromo-1,1&rsquo, binaphthalenes. The antipodes of the new inherently chiral monomer can be easily electrooligomerized, yielding inherently chiral electrode surfaces that perform well in both cyclic voltammetry (CV) enantiodiscrimination tests with pharmaceutically interesting molecules and in magnetoelectrochemistry experiments.

beta-Diketones are an important class of bidentate cyclometalating compounds, used in organometallic chemistry as ancillary ligands because of their wide commercial availability and easy synthesis. They are employed to finely tune the electronic, spectroscopic and physical properties of metal complexes. Heteroleptic iridium complexes often benefit from the use of -diketonate ligands, their properties being similar to those of the corresponding homoleptic tris-cyclometalated ones. Nevertheless, in some cases, their use results in a complete quenching of the phosphorescence. Aiming to understand the origin of this drawback, we designed a suitable class of heteroleptic complexes and studied their thermal stability (DSC/TGA). We explored the effect of the ancillary ligand in a series of Ir(iii) complexes bearing 2-phenylpyridine (ppy) as a cyclometalated ligand and acac (acetylacetonate), tta (2-thienoyltrifluoroacetonate), dtdk (1,3-di(thiophen-2-yl)propane-1,3-dionate) and BPhen (4,7-diphenyl-1,10-phenanthroline) as ancillary ligands. Through photochemical and electrochemical investigations, whose results agree with and support our density functional theory calculations, we demonstrate that -diketonate ligands with low triplet energy generate dark triplet excited states with negligible coupling to the ground state which indeed promote non-radiative relaxation through population of higher states.

In the present paper, the synthesis and characterization of 2,2′-bis{bi[2,2’-(3,4-ethylenedioxy)thiophen-5-yl]}-3,3′-bithianaphthene, nicknamed BT2E4, is reported. We show that electrooligomerization of BT2E4 leads to electroactive films which are evaluated by cyclic voltammetry (CV), UV/vis spectroelectrochemistry and CV coupled with in-situ conductance measurements. Direct comparisons to the properties of the oligomers obtained from the atropisomeric all-thiophene analogue BT2T4 show that the introduction of EDOT leads to a strong reduction of the band-gap, an overall red-shifted absorption spectrum and a rigidification of the structure. Finally, DFT and TD-DFT calculations were performed in parallel to investigate and to compare the electronic and molecular structures of neutral and charged monomer and oligomer species.

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.

A dialkyl-1,1′-bibenzimidazolium salt, consisting of an atropisomeric dication (i.e. featuring a stereogenic axis and thus “inherently chiral”) and an achiral counteranion, is employed as a chiral additive in three commercial ionic liquids, providing successful enantiodiscrimination in voltammetry experiments on screen-printed electrodes (SPEs) with the enantiomers of N,N′-dimethyl-1-ferrocenyl-ethylamine as model chiral probes. Significant differences in redox potentials are observed for the probe enantiomers despite the low concentration (0.01 M) of the chiral additive. The nature of the achiral ionic liquid in which the additive is employed significantly affects the peak potentials and potential differences, but does not alter the enantiomer sequence. Keywords: Chiral electrochemistry and electroanalysis, Ionic liquids, Chiral additives, Inherent chirality, Enantiorecognition

Summary The ability to select among different electroactive molecules, or among different redox centers on a single molecule, in both analytical and synthetic applications, is a typical asset of electrochemistry, based on fine control of the electrode potential, possibly enhanced by the choice of appropriate electrode surfaces and media. An attractive step further, of great fundamental and applicative interest, is represented by enantioselective electrochemistry, implying the ability to discriminate the enantiomers of chiral molecules (in electroanalysis), or to selectively activate or achieve a given enantiomer of a chiral molecule controlling the electrode potential (in electrosynthesis). Since the enantiomers of a chiral molecule have identical scalar physico-chemical properties and therefore the same electrochemical behavior except when interacting with some other chiral entity, enantioselective electrochemistry necessarily implies the electron transfer process to take place in asymmetric conditions. This can be achieved by the use of a chiral electrode surface or a chiral medium. Artificial selectors are particularly interesting on account of the virtually unlimited range of tailored structures possible as well as the possibility to have both enantiomers of a given selector equally available. Among the many approaches so far proposed for this ambitious target along either of the two above ways, outstanding results have been recently obtained, based on the use of "inherently chiral molecular materials" (either as electrode surfaces or as media) in which the same structural element endows the molecule with both its key functional property and with chirality.

The effect of anchoring group position and, in consequence, the orientation of the ruthenium dye molecule on titania surface on the performance of dye-sensitized solar cells has been studied intensively. Three model ruthenium sensitizing dyes bearing carboxylic anchoring group in ortho , meta or para position were synthesized and well characterized by spectroscopic, electrochemical, photophysical and photochemical measurements. The results were confronted with the quantum-mechanical calculations and discussed. The para derivative has been found as the most effective sensitizer with the cells efficiency twice higher than the meta and four times higher than the ortho derivatives.

An increasing number of strategies and tools have been proposed to endow the electrochemical interphase with chirality, to achieve enantiodiscrimination in analytical and/or preparative applications. So far, chirality has mostly been implemented not only at the electrode surface side but also on the medium one. Recently, the attractiveness of the latter approach has remarkably increased on account of the increasing availability of advanced chiral molecular media with intrinsic attractive features for electrochemistry applications, such as chiral ionic liquids, chiral ionic liquid crystals, and chiral deep eutectic solvents. With respect to solid layer/fixed chiral networks, advanced chiral media can still offer a reasonably high degree of local structuring, while being less demanding concerning preparation and management protocols, as well as less sensitive to fouling/regeneration issues. Different ways to implement chirality in advanced molecular media, including cases of powerful ‘inherent chirality,’ will be presented and discussed, particularly focusing on recent applications in the electrochemical field.

Summary Electronically conducting polymer (ECP) and oligomer films are one of the most popular classes of artificial materials for electrode surface modification and nanostructured electroactive film preparation for use as active layers in advanced sensing electrochemical devices. They can act as both receptors and transducers on account of their electroactivity and easy derivatization in a virtually unlimited structure range, and typically have low cost and easy processability. The tailoring possibilities of ECP films also make them attractive selector candidates to achieve the superior level of molecular recognition represented by enantioselective electroanalysis, implying to discriminate between specular images of a chiral molecule. This superior recognition level requires to endow them with chirality and to employ them as enantiopure films, which can be made along different strategies, with different implications in terms of enantioselectivity, kind of transduction of the recognition event, specificity vs general applicability, preparation difficulty, robustness, etc. In this context an outstanding tool is provided by the “inherent chirality” strategy.

a detailed electrochemical and photophysical comparative study of three parallel series of phenyl, thienyl and furyl substituted ethylenes has been carried out, implemented by the computational calculation of selected terms. Relationships have been highlighted between molecular structure (number and type of aromatic rings) and important functional properties (in particular, electronic features and oligomerization ability). Interestingly, some of the studied heteroaryl-ethylenes show emission in the solid state displaying an aggregation-induced emission behavior.

The new configurationally stable, unsymmetrical 2,12-diaza[6]helicene was synthesized as a racemate and the enantiomers were separated in an enantiopure state by semi-preparative HPLC on chiral stationary phase. Under selected alkylation conditions it was possible to obtain both the enantiopure 2-N-mono- and di-N-ethyl quaternary iodides. Metathesis with bis(trifluoromethanesulfonyl)imide anion gave low-melting salts which were tested as inherently chiral additives to achiral ionic liquids for the electrochemical enantiodiscrimination of chiral organic probes in voltammetric experiments. Remarkable differences in the oxidation potentials of the enantiomers of two probes, a chiral ferrocenyl amine and an aminoacid, were achieved, the differences increase with increasing additive concentration and number of alkylated nitrogen atoms.

FeCl3 oxidation of the racemate of C2 symmetric, inherently chiral, sexithiophene monomer 1 (2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene) affords a mixture of cyclic oligomers, from the prevailing dimer to traces of the pentamer. The oligomers are constituted by mixtures of stereoisomers which are two for dimer 2, four for trimer 3 and six for tetramer 4. Cyclooligomers 2 and 3 could be separated by chromatography, while 4 was synthesized by ring closure of open chain dimer 2a, prepared in turn by controlled coupling of the anion of racemic 1. The optical properties of open-chain stereoisomer 2a and tetramer 4 have been compared with those of 2 and 3 respectively. The macrocyclic oligomers have been tested as donor materials in bulk heterojunction solar cell prototypes both as a crude mixture resulting from oxidation of 1 and as a single oligomer. Theoretical calculations support the photophysical properties of these new materials.

The racemate of an inherently chiral "spider-like" octathiophene monomer T83 , in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T83 racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross-linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer-based chemosensor selective for a thymine-adenine oligonucleotide.

The new inherently chiral material shows outstanding chirality manifestations with chiral probes, as well as with circularly polarized light components and electron spins., Chiral oligothiophene monomers with C2 symmetry, based on 3,3′-bithiophene atropisomeric cores with high racemization barriers, have recently been shown to provide excellent chiral starting materials with high electroactivity for the easy preparation of enantiopure electroactive films endowed with powerful chirality manifestations. We now introduce an inherently chiral monomer based on a 2,2′-biindole core, as the prototype of a new inherently chiral monomer family, whose properties could be modulable through functionalization of the pyrrolic N atoms. By fast, regular electrooligomerization the new monomer yields inherently chiral films with high, reversible electroactivity and, above all, impressive enantioselectivity towards very different chiral probes, some of pharmaceutical interest, as general-scope electrode surfaces. Such results, while opening the way to a new, attractive inherently chiral selector class, nicely confirm the general validity of the inherent chirality strategy for chiral electrochemistry. Furthermore, the enantioselectivity of the new selectors not only holds with electroactive chiral probes, but also with circularly polarized light components as well as electron spins, resulting in good chiroptical and spin filter performances, which suggests fascinating correlations between the three contexts.

The synthesis, photophysical and electrochemical characterization, theoretical calculations and photovoltaic studies of a push-pull dye with an unconventional nonplanar tetrathiahelicene π−spacer between the donor-acceptor groups, are reported. The molecule exhibits suitable HOMO LUMO levels to be used in DSSC. The presence of the donor-acceptor helical architecture allows the internal charge transfer and subsequent electron injection to the conduction band of TiO2 leading to the good photocurrent value of 4.6 mA cm−2.

In spite of the increasing fundamental and practical interest of electrochemistry in ionic liquids (ILs), exploration of chiral ionic liquids (CILs) in view of enantioselective electrochemistry and electroanalysis is surprisingly overdue. In this study a family of chiral ionic liquids (CILs) based on natural chiral building blocks, of easy synthesis, is detailedly characterized in terms of thermal and electrochemical properties, achieving valuable information about structure−property relationships on account of the systematicity of available family terms. Moreover, they are submitted to a series of chiral electroanalysis tests. Cyclic voltammetry in bulk CILs or with CIL as additives in a bulk achiral ionic liquid IL, shows small but statistically significant potential differences for the enantiomers of two quite different chiral probes, an interesting result since enantiodiscrimination in terms of potential differences in chiral voltammetry (more desirable respect to current differences) has been only seldom obtained so far. The present first example of enantioselective voltammetry in CIL media with stereocenters as localized chirality sources also offers an important and so far missing confirmation of the intrinsically superior level of the inherent chirality strategy, recently resulting in larger potential differences with the same protocols implemented in "inherently chiral" ionic liquid media. Furthermore, an alternative transduction mode, based on electrochemical impedance spectroscopy EIS, is proposed to effectively highlight the enantiodiscrimination ability of CIL media in analytical experiments.

Combined experimental and theoretical study on the electronic characteristics of tetrathiahelicene (7-TH) alkyl and aryl phosphorus derivatives, including phosphanes, phosphine–borane complexes, phosphine oxides, and phosphine–selenides, is described. The collected data give useful information on the σ-donor ability of the phosphorus atoms, which mainly depends on the aryl or alkyl nature of the substituents at the phosphorus atom. Electrochemical investigations provide the relationships between the electronic and structural properties, and quantum chemical calculations show a clear dominance of the 7-TH scaffold on the electronic properties of all investigated molecules. Finally, different electronic and steric properties of 7-TH phosphanes strongly influenced their catalytic behavior, for example, as Lewis base organocatalysts in typical [3+2] annulation reactions.

A detailed electrochemical study has been carried out on 1,1’-bibenzo[d]imidazoles and the corresponding mono- and bibenzimidazolium salts, and compared to benzimidazole and benzimidazolium moiety models, and to 2,2’-bibenzo[d]imidazole constitutional isomers. The voltammetric experiments, supported by theoretical calculations and structural diffractometric characterizations, evidence how both electrochemical and chiral properties of bibenzimidazole systems depend on the torsional barrier between the two moieties, which determines at the same time the effective conjugation and communication between symmetrical redox centres, and the possibility of obtaining the molecule in two inherently chiral enantiomers that are configurationally stable at room temperature. In particular, the 1,1’-bibenzimidazole scaffold appears very promising for perspective development of inherently chiral substrates that may be used as additives, or supporting electrolytes, or ionic liquids. In fact, the high torsional angle granted by the 1,1’ connectivity results both in an energy barrier high enough to yield permanently stable enantiomers at room temperature, and in low effective conjugation between the two moieties, affording a very large operating window. The effect of single and double alkylation has also been considered. A preliminary enantiorecognition test, achieved performing the electrooligomerization of enantiopure 2,2’-bi[2-(5,2’-bithienyl)]3,3’-bithianaphthene in the presence of either the (R)- or the (S)- enantiomer of a 1,1’-bibenzimidazolium salt, has shown interesting results.

The data presented in this article are related to the research article entitled “An unconventional helical push-pull system for solar cells” (Dova et al., 2019). This article provides: a) the cyclic voltammogram plots in solution of helical push-pull sensitizers and the corresponding precursors; b) the visualization of the leading natural transition orbital (NTO) pairs obtained by theoretical calculation of frontiers orbitals; c) J/V curves of dye-sensitized solar cells (DSSC) sensitized by the dyes, without 3a,7a-dihydroxy-5b-cholic acid (CDCA) as co-adsorbent agent; d) 1H and 13C NMR spectra of dyes.

The novel [Re2(μ-H)(μ-OOC-CPDT)(CO)6(μ-3-Me-pydz)] complex (1; OOC-CPDT = 4H-cyclopenta[2,1-b:3,4-b']dithiophene-4-carboxylate, 3-Me-pydz = 3-methylpyridazine) has been prepared and characterized by single-crystal X-ray diffraction, density functional theory (DFT), and time-dependent DFT computations, UV-vis absorption and emission spectroscopy, and cyclic voltammetry (CV). The measured properties indicate the lack of electronic communication in the ground state between the CPDT and the rhenium diazine moieties. Oxidative electropolymerization of 1, achieved by repeated potential cycling (-0.4 to +1.0 V vs Fc(+)/Fc, in acetonitrile) with different supporting electrolytes, on different electrodes, afforded an electroactive and stable metallopolymer (poly-1). In situ measurements of the mass of the growing film (on a gold electrode, with an electrochemical quartz microbalance) confirmed the regularity of the polymerization process. The polymer exhibits two reversible oxidation peaks of the thiophene chain and a broad irreversible reduction peak (-1.4 V, quite close to that observed for the reduction of monomer 1), associated with a remarkably delayed sharp return peak, of comparable associated charge, appearing in close proximity (+0.3 V) to the first oxidation peak of the neutral polythiophene chain. This charge-trapping effect can be observed upon repeated cycles of p and n doping, and the negative charge is maintained even if the charged electrode is removed from the solution for many hours. Electrochemical impedance spectroscopy showed that the main CV oxidation peak corresponds to facile charge transfer, combined with very fast diffusion of both electrons and ions within the polymer. In summary, poly-1 provides a new example of a metallopolymer, in which the conductive properties of the π-conjugated system are added to the redox behavior of the pendant-isolated complexes.

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...

Three novel dyes based on ZnII porphyrinates combined, in β-pyrrolic position, with the π unit dithienylethylene (DTE) have been synthesized and investigated for application in DSSCs. The panchromatic effect due to elongation of the π-delocalized system through a bridge between the porphyrinic ring and the DTE unit such as the 4-ethynylstyryl (1), ethynyl (2), and ethenyl (3) bonds have been investigated by computational, electrochemical, and photoelectrochemical methods. For all three dyes the π conjugated substituents in the β position produced the expected panchromatic effect with broadened electronic absorption spectra over a wide range of wavelengths and IPCE spectra featuring a broad plateau in the region 430-650 nm. In addition both DFT computational and electrochemical data have shown a smaller HOMO-LUMO energy gap for dye 3, when compared to dye 2 suggesting a slightly more facile conjugation between the porphyrinic core and the DTE unit through the ethenylic bond. Conversely the photoelectrochemical investigation showed improved DSSC performances from 3 to 1. These results have been rationalized by an in-depth DFT computational study of dyes 2 and 3 interacting with a cluster of 82 TiO2 units. The small energetic overlap between the LUMO and the TiO2 conduction band characterizing the more structurally distorted dye 3 would suggest low quantum yield of electron injection, while dye 2 shows a greater interaction between the LUMO of the dye and the semiconductor. Consequently the increased linearity and planarity of the structure of dye 1 seems to be the origin of its best performance in DSSC. Therefore it appears that the nature of the bridge between the DTE unit and the porphyrinic ring is quite relevant for the efficiency of these dyes for DSSC, due to distortion from the planarity and linearity of the structure of the dye and the consequent changes on the dye π conjugation. © 2014 American Chemical Society.

The typical design of chiral electroactive materials involves attaching chiral pendants to an electroactive polyconjugated backbone and generally results in modest chirality manifestations. Discussed herein are electroactive chiral poly-heterocycles, where chirality is not external to the electroactive backbone but inherent to it, and results from a torsion generated by the periodic presence of atropisomeric, conjugatively active biheteroaromatic scaffolds, (3,3′-bithianaphthene). As the stereogenic element coincides with the electroactive one, films of impressive chiroptical activity and outstanding enantiodiscrimination properties are obtained. Moreover, chirality manifestations can be finely and reversibly tuned by the electric potential, as progressive injection of holes forces the two thianaphthene rings to co-planarize to favor delocalization. Such deformations, revealed by CD spectroelectrochemistry, are elastic and reversible, thus suggesting a breathing system.

Funding text This work was partly supported by Fondazione Cariplo through the project INDIXI (Grant no. Ref.2011/0368 ). P.E.K. acknowledges the financial support of an Intra European Marie Curie Fellowship ( FP7-PEOPLE-2011-IEF project DELUMOPV) G.T. and G.C. acknowledge Fondazione Cariplo (projects 2009-2550 and 2010-1351 ) and project 5×1000 Junior 2011 for financial support. The authors would like to cordially thank Dr. M. R. Antognazza for offering access to her cw-PIA experimental set-up. Herein we present a methodology for improving the power conversion efficiency of organic solar cells made by photoactive layers of poly(3-hexylthiophene) (P3HT) and phenyl-C61 butyric acid methyl ester (PCBM) of non-optimized microstructure. In our study we achieve a 47% improvement in the power conversion efficiency (PCE) of the device by utilizing a thiophene-based quinoid (QBT) moiety as the third component in the P3HT:PCBM:QBT photoactive layers. Based on a set of independent characterization experiments we address the QBT composition dependent photophysical, electrical, thermal, structural and morphology-related properties of the ternary photovoltaic P3HT:PCBM:QBT system for elucidating the origin of the PCE improvement. In small amounts (0.3-0.6 wt%), QBT serves as a nucleation agent, it enlarges the size of the P3HT crystallites by 15% and it increases the fraction of well-ordered P3HT chains in the P3HT:PCBM:QBT layer. The improved microstructure of the photoactive layer in combination with the QBT-assisted photo-induced hole transfer step from PCBM to P3HT, lead to an increase of the charge photogeneration yield in the P3HT:PCBM:QBT triple bulk heterojunction. The relatively small optical gap of QBT facilitates a resonant energy transfer step from the photoexcited PCBM to the QBT followed by a charge transfer process between QBT and the P3HT matrix. Based on these findings we propose general guidelines for the design of next generation functional additives to be used in organic photovoltaics. © 2013 Elsevier B.V.

Unknown 1H-2,7-dihydro-1-phenylphosphepine, containing a 2,2′,5,5′-tetramethyl-3,3′-bithiophene atropisomeric scaffold (Ph-tetraMe-Bithienine), and its oxide have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. The most evident structural feature is the very small dihedral angle. The electronic properties of the phosphane were quantitatively evaluated by cyclic voltammetry and compared with three other 2,7-dihydro-1-phenylphosphepines differing in the nature of the biaromatic scaffold (biphenyl, 1,1′-binaphthyl and 2,2′-dimethoxybiphenyl). The racemate of the phosphane oxide was resolved into antipodes, which were reduced to the enantiopure phosphanes and employed as ligands in Rh and Pt complexes in homogeneous stereoselective catalytic reactions. The enantioselective ability and catalytic activity of the new mediators were found to be quite modest in the hydrogenation reactions of olefinic double bonds, whereas good performances were achieved in specific C–C bond-forming reactions. The results are interpreted on the basis of the steric and electronic properties of the ligand.

We have synthesized a series of tetra(2-thienyl)ethylene (TTE) derivatives, selectively functionalized at the thiophene α positions, either by a coupling procedure or by direct electrophilic substitution of the TTE system. Optical spectroscopy revealed that TTE shows orange emission (470 nm) in a diluted 2-MeTHF matrix at 77 K and blue (420 nm) aggregation-induced emission (AIE) in the solid state. An exhaustive electrochemical study afforded a full rationalization of the electronic properties in terms of the HOMO and LUMO energy levels and gaps, as well as localization and features of the redox centers with respect to TTE functionalization.

In the present work, we report a convenient synthesis with a microwave reactor of [Ru(quo)(dcbpy)2]+Cl (quo = 8-hydroxyquinolinate, dcbpy = 2,2′-bipyridinyl-4,4′-dicarboxyl acid) and of the parental complex [Ru(Me2-quo)(dcbpy)2] +Cl (Me2-quo = 5,7-dimethyl-8-hydroxyquinolinate) along with their electrochemical and photovoltaic characterization. © 2013 Elsevier B.V. All rights reserved.

Iridium complexes bearing cyclometalated (CN) ligands are the current emitters of choice for efficient phosphorescent organic light emitting diodes (OLEDs). Homoleptic iridium complexes Ir(CN)(3) and the analogous heteroleptic ones carrying a beta-diketonate ancillary ligand (CN)(2)Ir(OO) often exhibit similar photophysical properties and device performances; the choice among them usually depends both on the yield/ease of the respective synthetic preparations as well as on the device fabrication methods (i.e. vacuum-deposition or solution-process). In our recent study we found a significant spectral red shift on going from the homoleptic to the beta-diketonate Ir(III) derivatives. The NIR emitting complex Ir(iqbt)(2)dpm (lambda(max) = 710 nm) has almost 20 nm red shifted emission compared to the homologue Ir(iqbt) 3 making only the former a real NIR emitter. For comparison, we studied the Pt(iqbt) dpm complex as the suitable example to investigate metal ligand interactions. Noteworthily the Pt(iqbt) dpm emission perfectly overlaps that of the Ir(iqbt) 2dpm. In this paper we provide an in-depth investigation of these systems by electro-chemical and spectroscopic analyses and corroborate the results with DFT and TDDFT calculations to investigate whether the Pt(II) complex can be used as a model system to predict how far the emission can be pushed in a Ir(III) heteroleptic derivative bearing the same CN ligand.

Square planar platinum complexes are an important class of compounds used in (nano)technology, optoelectronics, medicinal chemistry and catalysis. The major research interests in cyclometalated Pt(ii) complexes focus on the selective modulation of their electronic properties and the control of the (cis/trans) geometry. For the first time, we unveil and demonstrate that cis-trans isomers of Pt(ii) complexes can be obtained in a derivative carrying the 1-phenyl-pirazolate (Hppz) and 2-hydroxy-1-naphtyl-(N-phenyl)imine ligands. The two isomers display significant differences in both optical and electronic properties. While luminescence is quenched in solution, they are brightly emissive in the PMMA matrix at room temperature and in the 2MeTHF rigid matrix at 77 K. The phosphorescent emission of the cis isomer, blue-shifted compared to that of the trans one, results from the significantly different trans influence of the ppz ligand. Theoretical investigation highlights the almost isoenergetic potential energy of the two isomers therefore explaining their formation and evidences a large geometry distortion of their triplet state, which should be responsible for the observed luminescence efficiency.

Dissociative electron transfers (DETs) involving aryl halides in the presence of supporting electrolytes with tetraalkylammonium cations TAA+ of different diameters provide a first model case of rationalized relationship between supporting electrolyte bulkiness effect and DET mechanism. In non-catalytic conditions, with the molecule reacting at the OHP, increasingly bulkier TAA+ cations result in increasing double layer (DL) thickness and consequently in increasingly hindered electron tunnelling, and the reduction peak potentials Ep,DET linearly shift in the negative direction with increasing cation diameter dTAA+. The linear variation of Ep,DET with dTAA+ is consistent with the distance dependence of kET for reagents held at fixed distances from the electrode (ln k = ln k0 − βx). The ∂Ep,DET/∂dTAA+ slope is not constant in the investigated model series, but linearly increases with decreasing κ parameter, accounting for the heterogeneous ET step becoming increasingly more determining with respect to the following C X bond cleavage step (as a consequence of decreasing stability of the π* orbital corresponding to the radical anion). Thus the β parameter in the electron tunnelling equation appears to be strictly related to the ET activation barrier (in particular, to its relative weight in the overall DET kinetics). On catalytic Ag electrodes, with the molecule reacting at the IHP, the supporting electrolyte effect is assumed to depend on the increasingly smaller effective potential difference available to the molecule, reacting close to the electrode, with increasing double layer thickness. It appears more conspicuous than in non-catalytic conditions, in spite of the less extreme operating potentials, but consistently with the increased relative importance of the ET activation barrier at a catalytic electrode.

"Inherently chiral" thiophene-based electroactive oligomer films have recently been shown to exhibit outstanding chirality manifestations. One of the most exciting among them is an unprecedented enantioselection ability as electrode surfaces. In fact, in preliminary chiral voltammetry experiments, the new electrodes have been shown to both discriminate the enantiomers of chiral probes (either enantiopure or in a mixture, in terms of large differences in peak potentials) and quantify them (in terms of linear dynamic ranges in peak currents), without the need for preliminary separation steps. Such ability has now been tested on a series of chiral DOPA-related molecules, from phenolic amino acid tyrosine (together with its methyl ester) to catecholic amino acid DOPA (together with its methyl ester), to catecholamine epinephrine (adrenaline). The wide-range enantioselectivity of the new inherently chiral electrode surfaces is fully confirmed, as large peak potential differences are obtained for probe enantiomers of the whole series working in common aqueous buffers. Moreover, interesting modulating effects on enantiodiscrimination can be observed as a function of both molecular structure and pH. Graphical abstract Inherently chiral thiophene-based electrodes at work with pharmaceutically relevant probes.