Nonlinear Optical Chromophores with Aggregation Induced Emission Enhancement Based on 2-N,N-Dibutylamino-4-Phenyl Thiazole with FMR Characteristics

Abstract

The synthesis, photophysical, linear and nonlinear optical (NLO) properties of novel fluorescent styryls based on 2-N,N-dibutylamino-4-phenyl thiazole as donor attached to different acceptor groups via conjugated π-bridge were studied with the help of solvatochromic model. The NLO properties of extended styryls based on benzylidene malononitrile and isophorone were more enhanced than the simple styryls based on malononitile and ethylcyano acetate which was attributed to the longer conjugation path. The benzylidene based extended styryl dye showed maximum value of two-photon absorption cross section σ_2PA 98.85GM in dichloromethane. The 2-amino thiazole derivatives were responsive towards the viscosity of the medium hence investigated for the fluorescent molecular rotor (FMR) properties wherein almost 2.07 to 3.65 fold increase in emission intensity was observed. Also, the aggregates of these dyes in N,N-dimethyl formamide-water mixture showed enhancement in emission on aggregates formation like 3.73 fold increase in emission intensity was observed for benzylidene based extended styryl dye. Thus NLOphoric AIEgens with FMR properties emitting in the red region of the electromagnetic radiation were developed.

Keywords: 2-N,N-dibutylamino-4-phenyl thiazole; Aggregation induced emission (AIE); Florescent molecular rotors (FMR); Two-photon absorption.