Searching the factual factor in emission tweaking of a reported bisindole based self aggregation sensitive organic emitter: The missing link

Abstract

A bis-indole derivative, 3,3′-bisindolyl(phenyl)methane (BIPM), is studied by using steady-state and time-resolved optical spectroscopy in several pure and mixed solvents to investigate its solvent sensitive photophysical behavior. The micro-environments possess diverse and captivating influences on the photophysical properties of luminophores. Therefore, the comprehensive understanding of the interplay between the micro-solvent parameters and the spectroscopic properties of various probes is a must before developing advanced photo-functional materials. Previously, BIPM exhibited a unique bell-patterned emission yield modulation with changing the composition of DiOx-H2O binary mixture where all the primary micro-parameters (polarity, proticity and viscosity) of the solvent system varied simultaneously. Therefore, here we intend to unveil the independent and specific effects of the solvent microparameters on the overall spectroscopic behaviour of BIPM. The probe reveals very attractive and complex photophysics and expresses high sensitivity towards the micro-polarity, proticity, and viscosity. The radiationless transitions are majorly affected by the local solvent parameters resulting significant changes in the emission efficiency of BIPM. The microparameters individually direct the QY of BIPM in three different ways, increasing, decreasing and increasing-then-decreasing patterns, that are rather uncommon. Besides the opportunity of optical sensing the liquid micro-environment based on the solvent-sensitivity of the probe, BIPM also demonstrates its wide applicability considering the easy-modulation of its emission efficiency in any way through controlling the solvent microparameters only.

Keywords

• Fluorescence efficiency
• Binary solvents
• Micropolarity
• Microproticity
• Microviscosity
• Bis(indolyl)methane