Synthesis and spectroscopic characterization of an alkoxysilane dye containing azo-benzothiazole chromophore for nonlinear optical applications

To form covalent linking between organic and inorganic hybrid materials for nonlinear optical (NLO) applications, an alkoxysilane dye (ICTES–EHNBT) which can be copolymerized via sol–gel process was synthesized from 3-isocyanatopropyl triethoxysilane (ICTES) and an NLO-active chromophore 2-[4′-(N-ethyl-N-2-hydroxyethyl)-amino-phenylazo]-6-nitrobenzothiazole (EHNBT) by a nucleophilic addition reaction. The azo-benzothiazole chromophore is formed by a donor–π-acceptor system, based on a nitro group connected with benzothiazole as the acceptor and a hydroxyl-functional amino group as the donor. EHNBT and ICTES–EHNBT were characterized by elemental analysis, 1H NMR, FTIR, UV–visible spectra, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Comparing to C.I. Dispersed 1 (DR1), the replacement of benzene ring by a less aromatic heterocycle determines a significant bathochromic shift of the visible absorption band and an increase in molecular hyperpolarizability.