Design and Synthesis of Ruthenium Oligothienylacetylide Complexes. New Materials for Acoustically Induced Nonlinear Optics

A series of new donor−π-acceptor ruthenium acetylide systems built around thiophene-based π-conjugating spacers of different lengths have been developed. Comparison of the linear and third-order nonlinear optical properties of these donor−π-acceptor chromophores shows that the elongation of the oligothiophene-based spacer or further introduction of a double bond leading to a dithienylethylene spacer produces a considerable bathochromic shift of the absorption maximum together with a dramatic enhancement of the molecular cubic hyperpolarizability. Furthermore acoustically induced second-harmonic generation (AISHG) has been observed for film composites of these complexes incorporated in PMMA matrixes and reaches values among the highest reported so far.