Viscosity-active D-π-A chromophores derived from benzo[b]thiophen-3(2H)-one 1,1-dioxide (BTD): Synthesis, photophysical, and NLO properties

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2018-10, Vol.203, p.244-257
• Main Authors: Bhagwat, Archana A., Mohbiya, Dhanraj R., Avhad, Kiran C., Sekar, Nagaiyan
• Format: Article
• Language: English
• Subjects: AIEE; Benzo[b]thiophen-3(2H)-one 1,1-dioxide (BTD); DFT and TD-DFT; Solid-state fluorescence; Two-photon absorption; Viscosity induced emission enhancement
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2018.05.101

Donor-π-Acceptor (D-π-A) compounds comprising of benzo[b]thiophen-3(2H)-one 1,1-dioxide (BTD) as acceptor with dibenzofuran, carbazole, triphenylamine, and N-methyl diphenylamine moieties as donors were synthesized for aggregation, viscosity induced emission enhancement and nonlinear optical studies. Compounds 3a–3d exhibited solid state emission. The compounds 3a–3d are viscosity sensitive in a solution of MeOH: PEG-400 and showed 10, 23, 14, and 25 fold viscosity induced enhanced emission. The compounds 3a, 3c, and 3d are aggregation-induced emission enhancement (AIEE) active while 3b quenches the fluorescence on aggregation. The quantum yield of 3a, 3c, and 3d in acetonitrile are 0.041, 0.002 and 0.002 which are enhanced in the aggregate state to 0.31, 0.009, and 0.22 respectively. Solvent-dependent parameters like dipole moment (μ), static polarizability (α), and hyperpolarizability (β and γ) were determined spectroscopically and using Density Functional Theory (DFT) calculations. First and second order hyperpolarizability increase as donor strength increases and the trend is found as 3a