Synthesis, photophysical, viscosity and DFT study of solid state fluorescent molecular rotors

Abstract

Four novel Fluorescent Molecular Rotors (FMR) (1, 2, 3, 4) comprising carbazole, triphenylamine, phenothiazine, diethylaniline as donating groups and cyanoformyl vinylene as an accepting group are synthesized and characterized by NMR. They show emission in the solid state in the range of 581–651 nm. The viscosity sensitivity of emission was investigated 3.1–3.4 fold increase in emission intensity was observed in a mixture of polar protic ethanol and polyethyleneglycol 400 mixture. The experimental results are well in correlation with those of Density Functional Theory (DFT) computations. Compounds show higher values of dipole moment, linear polarizability values ranging from 49 to 59 × 10^−24 e.s.u., first order hyperpolarizability ranging from 77 to 250 × 10^-30 e.s.u. and second order hyperpolarizability ranging between 105–695 × 10^-30 e.s.u. suggest that the compounds show good Nonlinear Optical (NLO) property. The two photon absorption cross sections are found in the range 50–150 GM, which is further elucidated using Mulliken Hush analysis for analyzing effective charge transfer in the present compounds.