Synthesis of Conjugated Tetrathiafulvalene (TTF)-π-Acceptor Molecules − Intramolecular Charge Transfer and Nonlinear Optical Properties

We have synthesised new conjugated donor-π-acceptor (D-π-A) chromophores 7, 9, and 12−15 in which monosubstituted tetrathiafulvalene (TTF) and trimethyl-TTF units are the donor moieties, connected by ethylenic bridges to electron-deficient benzene derivatives as the acceptor moieties. These compounds display a broad intramolecular charge transfer (ICT) band in their solution UV/Vis spectra at λmax = ca. 500 nm. The second order nonlinear optical (NLO) properties of these derivatives have been studied using the EFISH technique and calculated by semiempirical and ab initio theoretical methods. The effect of methyl substituents in the TTF moiety and the nature of the conjugated bridge are discussed. Analysis of the bond lengths obtained by an X-ray diffraction study of compound 9 reveal ICT in the solid state.