Methoxy supported, deep red emitting mono, bis and tris triphenylamine-isophorone based styryl colorants: Synthesis, photophysical properties, ICT, TICT emission and viscosity sensitivity

Abstract

A novel strategy for the synthesis of triphenylamine based and methoxy supported deep red emitting push-pull chromophores is developed. The methoxy groups though not in conjugation with the acceptor exhibited a red shifted absorption and emissions (670 nm) as compared to the unsubstituted analogues due to the improved donating ability of triphenylamine. The dyes show high molar extinction coefficients (1, 65,800 M−1 cm−1) and as the number of withdrawing groups increases the molar extinction coefficient and emission intensity increase. Positive solvatochromism (96 nm) was observed which is well supported by linear and multi-linear regression. The mono styryl dyes showed enhancement of fluorescence while the di and tri-styryl dyes show quenching of fluorescence in polar solvents, which is correlated with the intramolecular charge transfer and twisted intramolecular charge transfer. Viscosity induced emission enhancement has also been observed. The experimental findings were correlated theoretically by using Density Functional theory computations.