Yellow-red emitting, methoxy substituted triphenylamine-based styryl derivatives: Synthesis, photophysical properties, viscosity sensitivity, aggregation induced emission, NLO properties, and DFT study

Three novel triphenylamine based fluorescent molecular rotors (FMRs) are designed and synthesized to study the effect of auxiliary methoxy substituent on aggregation induced emission (AIE) and viscosity sensitivity. Instead of elongated, short conjugated dicyanovinyl derivatives are preferred for the improved AIE and viscosity sensitivity properties. The sensitivity study of fluorescence emission towards viscosity and polarity of organic solvents was investigated by UV visible solvatochromism study, while AIE study was performed in DMF-water mixture of solvents. All the compounds were well characterized by H-1 and C-13 NMR, mass spectra IR as well as elemental analysis. They exhibited very good solid state emission between 544-620 nm. High values for their first and second order hyperpolarizability (378-1755 x10(boolean AND)-36 e.s.u) are observed. 'Two photon absorption cross sections' are in the range of 168-229 GM for 3. Effective charge transfer is elucidated using Mulliken Hush analysis.