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Cyclic conjugation and Biradical formation in charged cycloparaphenylenes are described by Raman spectroscopy and DFT., Radical cations and dications of [n]CPP from n = 5 to n = 12 have been studied by Raman spectroscopy and density functional theory. Small [n]CPP dications owe their stability to the closed-shell electronic structure imposed by cyclic conjugation surpassing the destabilizing effect of ring strain and of the electron deficiency of the charged states. Large [n]CPP dications mitigate cyclic strain by forming diradicals. The Raman spectra reflect the balance among cyclic conjugation, cyclic strain and biradicaloid stabilization by finding an unexpected turning point in the frequency behavior of the G vibrational modes as a function of size. These Raman data represent the vibrational fingerprint of this rare form of conjugation which is central to stabilize both cations and dications of [n]CPP macrocycles.

Pro-aromatic Thn-TIPS exhibits distinctly different physical properties from anti-aromatic Sn-TIPS., Open-shell singlet diradicaloids have recently received much attention due to their unique optical, electronic and magnetic properties and promising applications in materials science. Among various diradicaloids, quinoidal π-conjugated molecules have become the prevailing design. However, the need for a fundamental understanding on how the fusion mode and pro-aromaticity/anti-aromaticity affect their diradical character and physical properties remains unaddressed. In this work, a series of pro-aromatic benzo-thia-fused [n]thienoacenequinodimethanes (Thn-TIPS (n = 1–3) and BDTh-TIPS) were synthesized and compared with the previously reported anti-aromatic bisindeno-[n]thienoacenes (Sn-TIPS, n = 1–4). The ground-state geometric and electronic structures of these new quinoidal molecules were systematically investigated by X-ray crystallographic analysis, variable temperature NMR, ESR, SQUID, Raman, and electronic absorption spectroscopy, assisted by DFT calculations. It was found that the diradical character index (y0) increased from nearly zero for Th1-TIPS to 2.4% for Th2-TIPS, 18.2% for Th3-TIPS, and 38.2% for BDTh-TIPS, due to the enhanced aromatic stabilization. Consequently, with the extension of molecular size, the one-photon absorption spectra are gradually red-shifted, the two-photon absorption (TPA) cross section values increase, and the singlet excited state lifetimes decrease. By comparison with the corresponding anti-aromatic analogues Sn-TIPS (n = 1–3), the pro-aromatic Thn-TIPS (n = 1–3) exhibit larger diradical character, longer singlet excited state lifetime and larger TPA cross section value. At the same time, they display distinctively different electronic absorption spectra and improved electrochemical amphotericity. Spectroelectrochemical studies revealed a good linear relationship between the optical energy gaps and the molecular length in the neutral, radical cationic and dicationic forms. Our research work discloses a significant difference between the pro-aromatic and anti-aromatic quinoidal compounds and provides guidance for the design of new diradicaloids with desirable properties.

In the last years, conjugated oligothiophene macrocycles have attracted increasing scientific interest due to some peculiar properties related to their cyclic structure [1-3]. T. Benincori et al. synthesized the 2,2′-bis(2,2′-bithiophene-5-yl)-3,3′-bithianaphthene nicknamed BT2T4 (Figure 1) that represents the first member of a new class of chiral oligothiophenes in which chirality results from a tailored torsion produced in the polyconjugated backbone and not from the presence of stereogenic centres, external to it. Interestingly, the FeCl3 oxidation of the enantiopure BT2T4 produce a mixture of chiral macrocycles, like dimers and trimers. [4] Recently, also thanks to DFT and TD-DFT calculations, we have studied the new monomer BT2E4 in order to investigate the role of the insertion of 3,4-ethylenedioxythiophene (EDOT) units on the electronic and molecular properties of neutral and charged monomer and oligomer species. Furthermore, the electroactive films were evaluated by cyclic voltammetry (CV), UV/vis spectroelectrochemistry and CV coupled with in-situ conductance measurements. [5] Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

This work reports on a quinodimethane-type molecule, 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole (1), one of the shortest π-conjugated biradicaloids reported to be stable in solution under ambient conditions. This carbazole-based quinoidal precursor is able to form a macrocyclic σ-bonded tetramer (2). The resolved single-crystal X-ray structure of tetramer 2 shows that four molecules of 1 are linked together through four long (CN)2C−C(CN)2 bonds (1.631 Å) resulting from coupling of the unpaired electrons in biradicaloid 1. Dynamic interconversion between monomer 1 and cyclophane tetramer 2 is achieved by reversible cleavage and recovery of the four (CN)2C−C(CN)2 bonds upon soft external stimuli (light absorption, temperature and pressure), which is accompanied by significant color changes. These novel photo-, thermo-, and mechanochromic properties expand the versatility of π-conjugated biradicaloid compounds as novel functional materials that, in combination with spin chemistry and dynamic covalent chemistry, can be relevant in molecular machines, sensors, and switches.

New stilbenoid and thiophenic compounds terminally functionalized with donor-donor, acceptor-acceptor and donoracceptor moieties and substituting a central [2,2]paracyclophane unit have been prepared and their properties interpreted in terms of through-bond and through space conjugations. A description of the excited state properties based on photophysical data and with focus on the participation of the central [2,2]paracyclophane, or “phane” state, in competition with through-bond conjugation in the arms has been conducted. To this end, one-photon absorption and emission spectroscopy, as a function of temperature, of solvent polarity in solution and of pressure in solid state have been carried out. Furthermore, the analysis of charge delocalization in the face-toface [2,2]paracyclophane part in the neutral state and in the oxidized species (dications and trications) has been assessed allowing to elucidate the vibrational Raman fingerprint of charge delocalization in these systems. Thus, a complementary approach to “intermolecular” excitation and charge delocalization has been presented in [2,2]paracyclophane model systems by means of the pertinent spectroscopic techniques.

After the feasibility of the 1,3-dipolar cycloaddition reaction between nitrile imines and exfoliated graphene by density functional theory calculations was proved, very few-layer graphene was effectively functionalized using this procedure. Hydrazones with different electronic properties were used as precursors for the 1,3-dipoles, and microwave irradiation as an energy source enabled the reaction to be performed in a few minutes. The anchoring of organic addends on the graphene surface was confirmed by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis. Ultraviolet photoelectron spectroscopy (UPS) was used to measure the work function and band gap of these new hybrids. Our results demonstrate that it is possible to modulate these important electronic valence band parameters by tailoring the electron richness of the organic addends and/or the degree of functionalization.

200 páginas.-- Libro de Actas del Congreso: Estudio y Conservación del Patrimonio Cultural. Celebrado del16-19 de noviembre 2015, Málaga, Estudio y Conservación del Patrimonio Cultural recoge cuarenta y nueve ponencias presentadas al Congreso Nacional “Estudio y Conservación del Patrimonio Cultural”, celebrado en Málaga entre los días 16 y 19 de noviembre de 2015. El congreso, organizado por el Nodo “Arqueometría- Raman-UMA” (U38) dentro del marco de la iniciativa TechnoHeritage, continúa la labor de los tres congresos ya celebrados hasta ahora por TechnoHeritage: Congreso Nacional sobre Ciencia y Tecnología para la Conservación del Patrimonio Cultural, Madrid, 2011; International Congress Science and Technology for the Conservation of Cultural Heritage, Santiago de Compostela, 2012; y Second International Congress on Science and Technology for the Conservation of Cultural Heritage, Sevilla, 2014. El congreso se organizó en torno a cinco temas: (1) Monitorización y evaluación ambiental del Patrimonio Cultural; (2) Gestión del Patrimonio Cultural; (3) Desarrollo de nuevos instrumentos, tecnologías no invasivas y protocolos para el análisis, protección y conservación del Patrimonio Cultural; (4) Nuevos productos y materiales para la conservación del Patrimonio Cultural; y (5) Agentes y mecanismos de deterioro del Patrimonio Cultural