An indanone-based alkoxysilane dye with second order nonlinear optical properties

An azo-chromophore containing 2-methylidene-3-(dicyano-methylidene)-1-indanone as electronic acceptor group was synthesized via the Knoevenagel condensation between an aldehyde and indanedione derivative, followed by reaction with 3-isocyanatopropyltriethoxysilane. The structures of the chromophore and the synthesized alkoxysilane dye were confirmed by means of elemental analysis, NMR and FTIR analyses. Thermal analysis revealed that both had distinct melting points and thermal stability up to 240 °C. The chromophore and alkoxysilane dye are readily soluble in common solvents such as DMF, THF and DMSO. Compared with the traditional dye C.I. Disperse Red 1, the indanone-based chromophore exhibited larger molecular hyperpolarizability owing to its stronger electron-withdrawing ability.