Highly fluorescent blue-green emitting phenanthroimidazole derivatives: Detail experimental and DFT study of structural and donating group effects on fluorescence properties

A series of highly fluorescent blue-green emitting phenanthrene and 3,6-diphenylphenanthrene based compounds have been synthesized to study the effect of different electron donating groups on photophysical properties. A very unique and different fluorescence properties are observed in the case of N-phenyl carbazole donor based compounds as compared to the other electron donating groups. Observed intramolecular charge transfer and highly polar excited states of these compounds are elucidated by Lipert-Mataga correlations. The positive and negative solvatochromism observed from non-polar to polar solvents is also supported using Kamlet-Taft and Catalan multilinear regression analysis. Comparative study of photophysical properties between benzil, phenanthrene and 3,6-diphenylphenanthrene based hydroxyl imidazole derivatives is presented to study the effect of rigidity and extended conjugation. Observed experimental results are also correlated theoretically using Density Functional theory computations.