Acidochromism of amino-substituted indolizine chromophores: Towards white light emission

Abstract

There is a continuous interest in the development of advanced materials with tunable photophysical properties, among which white light emission represents a major challenge. Indolizines are a kind of azaheterocycles that have gained a great deal of attention in the recent past due to their intriguing photophysical behavior. We report herein on the synthesis of new push–pull indolizines bearing amino and electron-withdrawing groups at positions 1 and 7, respectively, and on their optical response in acidic medium. Exclusive protonation on the amino group has led to a hypsochromic shift in the emission spectra. Interestingly, white photoluminescence can be attained by adjusting the amount of acid as a result of color complementarity between neutral and charged species. Moreover, Density Functional Theory (DFT) calculations on the molecular structure and photophysical properties of these compounds are in agreement with the experimental results, providing very useful information about the main electronic transitions and the influence of protonation on the optical transitions.