Photophysical study of 2-(4′-N,N-dimethylaminophenyl)oxazolo[4,5-b]pyridine in different solvents and at various pH

Abstract

The spectral characteristics of 2-(4′-N,N-dimethylaminophenyl)oxazolo[4,5-b]pyridine (DMAPOP) have been investigated in solvents of different polarity and hydrogen bonding capacity. Unlike its imidazole analogue, DMAPOP emits single emission in both aprotic and protic solvents and the hydrogen-bond induced TICT emission is not observed in any protic solvents. The solvent effect on both absorption and the emission spectral data are analyzed by multiple parametric regression analysis. The prototropic studies reveal that two kinds of monocations are formed by protonation of pyridine nitrogen (MC1) and the dimethylamino nitrogen (MC3) in both ground and excited states. However three kinds of dications are formed by protonation of pyridine and oxazole nitrogens (DC1), pyridine and dimethylamino nitrogens (DC2), and dimethylamino and oxazole nitrogens (DC3).