Dynamic Electrochemistry of Anthanthrone.

In this investigation, we present a “nanographene” based on the low-cost commercially available 4,10-dibromoanthanthrone building block, where the anthanthrone core can be viewed as a fusion of two anthracene moieties with lateral functionalization. The chemical and physical properties of this molecule stand in sharp contrast with the present anthracene subunit. We have studied the dynamic electrochemistry from two derivates of anthanthrone where the research depends on the radical of peripheral phenyl groups. In this case, we compared the changes that produce a donor group and acceptor group respectively. In both cases, the neutral molecule has a butterfly shape due to the steric congestion between the protons at the peri position of the quinoidal anthanthrone core, which possess a nonplanar folded geometry, and the protons from the peripheral phenyl groups. However, when two electrons are subtracted, exist a core aromatization and planarization, this provides a stable flat shape. We show the existence of two conformational states through cyclic voltammetry, electrochemistry and variable temperature chemistry oxidation. We demonstrate the fast or slow equilibrium between both geometries depending on the radical of peripheral phenyl groups (donor or acceptor).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cross-conjugated isothianaphthene quinoids: a versatile strategy for controlling electronic structures

The elucidation of new structure–property relationships in π-conjugated molecules bearing quinoidal moieties is of relevance because of their use in organic electronics applications and their traditional assimilation as models of doped conducting polymers. Quinoidal oligothiophenes are ground state electronic hybrids between closed-shell Kekulé quinoidal and open-shell aromatic diradicaloid forms. The prominent contribution of the diradical character in longer oligomers beyond thiophene 4-mers results in a low stability, thereby limiting the ability to tune their properties. Thus, the control of these quinoidal/aromatic contributions is an important prerequisite to develop long quinoidal oligothiophenes. To address this problem, a series of quinoidal pentathiophenes with benzene-annelated isothianaphthene units were designed and successfully synthesized as stable structures. Combined molecular spectroscopies and theoretical modelling indicated that cross-conjugation appears upon the introduction of multiple benzene-annelated units, and that the number and position of the benzene-annelated units have a significant influence on the quinoidal/aromatic/cross-conjugated electronic structures. The newly developed quinoidal pentathiophenes functioned as organic semiconducting materials in transistor and near infrared phototransistor devices. This study demonstrates that modification of the cross-conjugated quinoidal structure is a promising strategy for fine-tuning electronic structures in π-extended quinoidal systems, which could help us to understand unique π-electronic features and to develop novel organic electronic materials.This work was supported by JSPS KAKENHI (20H02814, 20K21224, 20H05841, 20KK0123, 19K15505, 20H04639, 20K15352, 21K05213, 20H00379, 20H05833, and 20K15261), CREST (J205101030), NEDO (21500248-0), and “Dynamic Alliance for Open Innovation Bridging Human, Environmental and Materials” from The Ministry of Education, Culture, Sports, Science and Technology, Japan. We are grateful to Prof. Toshihiro Ohnishi for helpful discussion. The authors thank the Spanish Ministry of Science, Innovation and Universities MCIU and MINECO/FEDER of the Spanish Government (project PGC2018-098533-B-100), the Ministry of Science and Technology of the Spanish Government (project RED2018-102626-T) and the Junta de Andalucía, Spain (UMA18FEDERJA057). We also thank the Research Central Services (SCAI) of the University of Málaga. // Funding for open access charge: Universidad de Málag

[All]-S,S-dioxide Oligo-Thienylenevinylenes: Synthesis and Structural/Electronic Shapes from Their Molecular Force Fields

Oligo-S,S-dioxothienylenevinylenes have been prepared by transferring oxygen atoms to the sulfur atoms using the HOF·CH3CN complex. Their photophysical properties are presented in comparison with their thio phenevinylene congeners. Together with their vibrational properties and molecular force fields, this study allows for the interpretation of the alteration of aromaticity and inter-ring exocyclic p-conjugation in this series

Orbital Nature of Carboionic Monoradicals Made from Diradicals

The electronic, optical, and solid state properties of a series of monoradicals, anions and cations obtained from starting neutral diradicals have been studied. Diradicals based on s-indacene and indenoacenes, with benzothiophenes fused and in different orientations, feature a varying degree of diradical character in the neutral state, which is here related with the properties of the radical redox forms. The analysis of their optical features in the polymethine monoradicals has been carried out in the framework of the molecular orbital and valence bond theories. Electronic UVVis-NIR absorption, X-ray solid-state diffraction and quantum chemical calculations have been carried out. Studies of the different positive-/negative-charged species, both residing in the same skeletal π-conjugated backbone, are rare for organic molecules. The key factor for the dual stabilization is the presence of the starting diradical character that enables to indistinctively accommodate a pseudo-hole and a pseudoelectron defect with certainly small reorganization energies for ambipolar charge transport.The authors thank the Spanish Ministry of Science and Innovation (projects MINECO/FEDER PGC2018-098533-B-100 and PID2021-127127NB-I00) and the Junta de Andalucía, Spain (UMA18FEDERJA057 and Proyecto de Excelencia PROYEXCEL- 00328). We also thank the Research Central Services (SCAI) of the University of Málaga and the US National Science Foundation (CHE-1954389 to M.M.H., CHE-2003411 to M.A. P.). F.N and Y.D. acknowledge support from “Valutazione della Ricerca di Ateneo” (VRA)-University of Bologna. Y.D. acknowledges Ministero dell’Università e della Ricerca (MUR) for her Ph.D. fellowship. Funding for open access charge: Universidad de Málaga / CBU

Operative Mechanism of Hole-Assisted Negative Charge Motion in Ground States of Radical-Anion Molecular Wires

Charge transfer/transport in molecular wires over varying distances is a subject of great interest. The feasible transport mechanisms have been generally accounted for on the basis of tunneling or superexchange charge transfer operating over small distances which progressively gives way to hopping transport over larger distances. The underlying molecular sequential steps that likely take place during hopping and the operative mechanism occurring at inter mediate distances have received much less attention given the difficulty in assessing detailed molecular-level information. We describe here the operating mechanisms for unimolecular electron transfer/transport in the ground state of radical-anion mixed-valence derivatives occurring between their terminal perchlorotriphenylmethyl/ide groups through thiophene−vinylene oligomers that act as conjugated wires of increasing length up to 53 Å. The unique finding here is that the net transport of the electron in the larger molecular wires is initiated by an electron− hole dissociation intermediated by hole delocalization (conformationally assisted and thermally dependent) forming transient mobile polaronic states in the bridge that terminate by an electron−hole recombination at the other wire extreme. On the contrary, for the shorter radical-anions our results suggest that a flickering resonance mechanism which is intermediate between hopping and superexchange is the operative one. We support these mechanistic interpretations by applying the pertinent biased kinetic models of the charge/spin exchange rates determined by electron paramagnetic resonance and by molecular structural level information obtained from UV−vis and Raman spectroscopies and by quantum chemical modeling

The heteroatom effect in ambipolar diradicals.

Contribución tipo Póster con Flash oralThe ability to efficiently transport both holes and electrons makes ambipolar organic materials appealing architectures in organic electronics for the development of p- and n-channel devices. However, most of the organic semiconductors do not exhibit ambipolar behaviour mainly due to their intrinsic electronic properties (energetic mismatch between their frontier molecular orbitals and the Fermi levels of the metals used as drain and source electrodes) and to charge trapping at OFET–gate dielectric interfaces. The search of new ambipolar materials is closely related to the examination of the redox amphoterism in π-conjugated structures, i.e., the capacity to equally accommodate positive and negative charges. In this context, the small HOMO-LUMO gap of π-conjugated molecules showing an incipient or medium diradical character makes them good candidates to display p–n balanced mobilities. Several open-shell molecules, such as a diindeno[b,i]anthracene derivative, zethrenes and diindenoperylenes, have been reported as efficient ambipolar materials indeed. In this communication we present a series of four difluorenoheteroles (DFX) with identical chemical structure except for the role of the heteroatom which is played by Oxygen, Nitrogen, Sulphur and Sulphur dioxide. The entire DFX series exhibit a medium diradical character as consequence of the combination of electronic affinity, captodative effect and aromatic stabilization. Addressing the electronic properties of the neutral, reduced and oxidized species of the DFX family we demonstrate their ambipolar electrical behaviour and elucidate the connection between their diradical character and the balance between the electron and hole transport.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Oligomers of cyclopentadithiophene-vinylene in aromatic and quinoidal versions and redox species with intermediate forms

A new series of p-conjugated oligomers based on the 4,4 dihexyl-4H-cyclopenta[2,1-b:3,4-b0 ]dithiophene vinylene repeating unit has been prepared and characterized by X-ray, electrochemical, spectroscopic (UVVis absorption, emission and Raman) and density functional theory methods. The oligomers in their neutral, oxidized and reduced forms have been investigated. The neutral compounds show a longer mean conjugation length than oligothiophenes and oligothiophene-vinylenes and display very rich redox chemistry with the stabilization of polycationic states of which the radical cations and dications are strong NIR absorbers, the latter displaying singlet diradicaloid character. An interesting complementarity between the sequence of aromatic-quinoidal structural segments in the radical cations and dications has been described and interpreted. Two derivatives with the 4,4 dihexyl-4H-cyclopenta[2,1-b:3,4-b0 ] dithiophene vinylene unit, disubstituted either with electron donor, bis(triaryl amino) groups, or acceptors bis(dicyano-methylene) caps enforcing a quinoidal structure in the dithiophene-vinylene bridge, have been also synthesized and characterized. The radical cation of the triarylamine compound and the radical anion of the tetracyano compound similarly display hole and electron charge localization, or confinement, in the nitrogen and dicyano surrounding parts, or class II mixed valence systems, while their dication and dianion species, conversely, are open-shell diradical (i.e., polaron pair) and closed-shell (i.e., bipolaron), respectively. The preparation of these new p-conjugated oligomers gives way to the realization of compounds with new electronic properties and unique structures potentially exploitable in organic electronic

Synthesis and electronic properties of pyridine end capped cyclopentadithiophene-vinylene oligomers

A series of four oligomers of cyclopentadithiophene-vinylenes end capped with pyridine groups was prepared and their optical and electronic properties studied. Treatment with trifluoroacetic acid (TFA) leads to the bisprotonation of the nitrogens of the pyridine, which has an important impact on the optical properties. Excess treatment with TFA provokes the oxidation of the conjugated core, generating radical cations and dications. The ease of the TFA treatment in solution was extended to protonation in the solid-state where further characterization of the neutral and TFA-treated samples was carried out in electrically active substrates in organic field-effect transistors. Finally, the new molecules were found to be excellent conductors in single-molecule junctions thanks to strong electron delocalization and resonance orbital mediated transport. These studies show the opening of a spectrum of possibilities by suitable terminal substitution of π-cores

Patterns of Antiretroviral Therapy Use and Immunologic Profiles at Enrollment in the REPRIEVE Trial

BackgroundPatterns of antiretroviral therapy (ART) use and immunologic correlates vary globally, and contemporary trends are not well described.MethodsThe REPRIEVE trial (Randomized Trial to Prevent Vascular Events in HIV) enrolled persons with human immunodeficiency virus (HIV) who were aged 40-75 years, receiving ART, and had low-to-moderate cardiovascular disease risk. ART use was summarized within Global Burden of Disease (GBD) super-regions, with adjusted linear and logistic regression analyses examining associations with immune parameters and key demographics.ResultsA total of 7770 participants were enrolled, with a median age of 50 years (interquartile range, 45-55 years); 31% were female, 43% were black or African American, 15% were Asian, 56% had a body mass index >25 (calculated as weight in kilograms divided by height in meters squared), and 49% were current or former smokers. The median CD4 T-cell count was 620/µL (interquartile range, 447-826/ µ L), and the median duration of prior ART use, 9.5 years (5.3-14.8) years. The most common ART regimens were nucleoside/nucleotide reverse-transcriptase inhibitor (NRTI) plus nonnucleoside reverse-transcriptase inhibitor (43%), NRTI plus integrase strand transfer inhibitor (25%), and NRTI plus protease inhibitor (19%). Entry ART varied by GBD region, with shifts during the trial enrollment period. In adjusted analyses, entry CD4 cell count and CD4/CD8 ratio were associated with GBD region, sex, entry regimen, duration of ART, and nadir CD4 cell count; CD4 and CD8 cell counts were also associated with body mass index and smoking status.ConclusionsThere were substantial variations in ART use by geographic region and over time, likely reflecting the local availability of specific medications, changes in treatment guidelines and provider/patient preferences. The analyses of CD4 cell counts and CD4/CD8 ratios may provide valuable insights regarding immune correlates and outcomes in people living with HIV.Clinical trials registrationNCT02344290