Effect of methoxy group on NLOphoric properties of fluorescent 7-arylstyryl-2-methoxyphenylimidazo[1,2-a]pyridine - Solvatochromic and computational method

Abstract

Extensively conjugated donor-π-acceptor-donor (D-π-A-π-D) type fluorescent styryl dyes bearing imidazo[1,2-a]pyridine units have been investigated for their nonlinear optical properties (NLO). Enhanced Stokes shift (2486–2843 cm−1) brought about by replacing methoxy group by diethyl, dimethyl, cyclohexylamino substituents at C-2 and C-7 positions of imidazo[1,2-a]pyridine core in styryl dyes have been understood in elucidating the electronic structures. The position of methoxy group acting as auxiliary donor largely influences the nonlinear optical (NLO) properties of imidazo[1,2-a]pyridine derivatives. Polarizabilities and hyperpolarizabilies were estimated by solvatochromic and DFT method using BHandHLYP and CAM-B3LYP functionals with the 6-311 + G(d,p) basis set. Imidazo[1,2-a]pyridine derivatives showed minimum ten-fold higher NLO parameters compared to reminiscent of charge transfer contribution of donor groups. The dyes have two-photon cross-section values 66–189 GM and comparable with commercial two photon absorbing styryl dyes.