Contrasting tunability of quinizarin fluorescence with p-sulfonatocalix[4,6]arene hosts

Abstract

This study reveals the intriguing modulations in the photophysics of quinizarin (QZ) on its interaction with p-sulfonatocalix[4]arene (SCX4) and p-sulfonatocalix[6]arene (SCX6) hosts. While the SCX6–QZ system shows the usual reduction in both fluorescence intensity and lifetime, the SCX4–QZ system shows a contrasting effect of enhancement in the fluorescence intensity and reduction in the fluorescence lifetime. Such a contrasting effect is not only unusual but also observed for the first time for any host–guest system. The observed results are justifiably correlated with the changes in both radiative and nonradiative decay rate constants for the SCX4–QZ system.