Effect of amino and amido group on fluorescent, viscosity sensitive, thermally stable, NLOphoric thiophene fused acenaphthene derivatives

Thiophene fused acenaphthene derivatives based on the D-π-A framework were synthesized to study the effect of amino and amido groups on geometrical, thermal, spectral, linear, and non-linear optical properties. These molecules exhibit absorption ⁓ 300–520 nm and emission ⁓ 450–620 nm range in toluene, CHCl₃, EA, THF, MeOH, and DMSO. Moreover, these molecules exhibit ⁓ 1.20–5.67 fold increased emission intensity in the toluene-paraffin and EtOH-PEG-400 system. DFT study at B3LYP/6–311++G(d,p) revealed that these molecules are electron-rich systems with a planar geometry. TD-DFT results show a reasonable agreement with the experimental absorption maxima. Thiophene fused acenaphthene derivatives are thermal stable (⁓ 220–250 °C) and display relatively higher static polarizability and hyperpolarizability in comparison to p-nitroaniline.