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Trabajo presentado a la XXXIst European Congress on Molecular Spectroscopy, Cluj-Napoca, Romania, August 26–31,2012.-- et al., The infrared and Raman spectra of a donor (dithiole)–acceptor (dicyano) compound having a quinoidal thiazole bridge connecting the two electro-active groups have been recorded and the vibrational properties described on the basis of MP2 and DFT theoretical approaches. The spectroscopic data have been interpreted accounting for: (i) charge polarization or donor–acceptor charge separation in the S0 ground electronic state from the infrared spectrum; (ii) π-conjugation on the donor-(π-spacer)–acceptor sequence from the non-resonant Raman spectrum; and (iii) intramolecular donor-to-acceptor charge transfer character of the S0 → S1 excitation from the resonant Raman spectrum; and (iv) dependence of the non-resonant and resonant Raman spectra varying the spacer and the donor group. This paper highlights the interesting combination of vibrational spectroscopy and theoretical modeling in order to get insight on the relevant electro-optical and molecular properties on these compounds which are items of interest to develop organic molecules for non-linear optical applications., Financial support from the Ministerio de Economía y Competitividad (MINECO) of Spain (Projects CTQ2009-08790 and CTQ2011-22727) and Junta de Andalucía (Grant FQM-0159, Project P09-4708) and Gobierno de Aragón-Fondo Social Europeo (E39) are gratefully acknowledged. A predoctoral fellowship to EG (CSIC, JAE 2008) is also acknowledged. JLZP thanks the MINECO for a FPI grant.

A simple synthesis of dipolar one- and two-dimensional chromophores bearing two or three 4H-pyran-4-ylidene moieties is reported. Whereas the pyranylidene fragments acting as donors are proaromatic, the spacer one is not. In the linear derivatives, chain elongation gives rise to a sharp increase in the second order nonlinear optical responses, but some V-shaped derivatives display first hyperpolarizabilities (β) lower than those of their linear analogues. This uncommon feature lends experimental support to previous theoretical studies on the relative contribution and sign of the β-tensor components., Financial support from MICINNFEDER (CTQ2008-02942 and MAT2008-06522C02-02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. Predoctoral fellowships to E. Galán (CSIC, JAE 2008) and R. Alicante (FPI BES 2006- 12104) are also acknowledged.

The formal [2 + 2] cycloaddition-cycloreversion (CA-CR) between 4-ethynyl-N,N-dimethylaniline and polyenic Donor-π-Acceptor (D-π-A) systems takes place to yield compounds bearing two donors and one acceptor. Structural, linear and second-order nonlinear optical (NLO) properties of the new molecules reveal the stronger polarization of these systems when compared to analogous merocyanines lacking the dimethylaminophenyl (DMA) ring. © 2012 The Royal Society of Chemistry., Financial support from MICINN-FEDER (CTQ2011-22727 and MAT2011-27978-C02-02) and Gobierno de Aragón-Fondo Social Europeo (E39) and a predoctoral fellowship to E. Galán (CSIC, JAE 2008) are gratefully acknowledged.

Two series of matched and mismatched donor-thiazole-acceptor chromophores have been synthesized to disclose the role that the orientation of the thiazole ring plays on their second-order nonlinear optical (NLO) properties. Whereas previous theoretical studies predict that the matched systems show markedly higher NLO responses, our experimental results do not parallel this trend, showing differences between regioisomers much lower than those predicted. © 2012 Elsevier Ltd. All rights reserved., Financial support from MICINN-FEDER (CTQ2008-02942, CTQ2011-22727, MAT2008-06522-C02-02 and MAT2011-27978-C02-02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. A predoctoral fellowship to E.G. (CSIC, JAE 2008) is also acknowledged.

Push-pull compounds, in which a proaromatic electron donor is conjugated to a 2-dicyanomethylenethiazole acceptor, have been prepared, and their properties compared to those of model compounds featuring an aromatic donor. A combined experimental (X-ray diffraction, 1HNMR, IR, Raman, UV/Vis, nonlinear optical (NLO) measurements) and theoretical study reveals that structural and solvent effects determine the ground-state polarisation of these merocyanines: whereas 4H-pyran-4-ylidene- and 4-pyridylidene-containing compounds are zwitterionic and 1,3-dithiol-2-ylidene derivatives are close to the cyanine limit, anilino-derived merocyanines are essentially neutral. This very large range of intramolecular charge transfer (ICT) gives rise to efficient second-order NLO chromophores with μβ values ranging from strongly negative to strongly positive. In particular, pyranylidene derivatives are unusual in that they show an increase in the degree of ICT on lengthening the π-spacer, a feature that lies behind the very large negative μβ values they display. The linking of the formally quinoidal 2- dicyanomethylenethiazole moiety to proaromatic donors seems a promising approach towards the optimisation of zwitterionic NLO chromophores., Financial support from MICINN-FEDER (CTQ2008-02942, MAT2008-06522C02-02 and CTQ2009-10098), Gobierno de Aragón- Fondo Social Europeo (E39) and Junta de Andalucía (Proyecto de Excelencia P09-4708) is gratefully acknowledged. The predoctoral fellowships for E. Galán (CSIC, JAE 2008) and R. Alicante (FPI BES2006-12104) are also acknowledged.

A series of merocyanines containingisophorone or pyran rings in the spacer have been synthesized. For a given pair of donor and acceptor groups, the isophorone derivatives show higher second-order optical nonlinearities, but lower thermal stabilities. The first NLO-chromophores endowed with a dihydropyran fragment in the spacer have also been prepared and studied., Financial support from MICINN-FEDER (CTQ2008-02942 and MAT2008-06522C02-02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. Predoctoral fellowships to E.G. (CSIC, JAE 2008), N.M.de B. (Departamento de Educación, Gobierno de Navarra) and R. Alicante (FPI BES 2006-12104) are also acknowledged.

A series of merocyanines with a benzothiazolylidene donor and a quinoidal thiazole moiety have been synthesized. Experimental results and theoretical calculations show that these compounds have zwitterionic ground states and negative second-order optical nonlinearities. Unlike most merocyanines, the degree of charge transfer does not decrease on increasing the separation between the donor and the acceptor groups, an unexpected feature related to the presence of the proaromatic thiazole fragment., Financial support from MICINN-FEDER (CTQ2008-02942 and MAT2008-06522C02-02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. Predoctoral fellowships to E.G. (CSIC, JAE 2008) and R. Alicante (FPI BES 2006- 12104) are also acknowledged.