Variation in nonadiabaticity and dual fluorescence causality by extension with aromatic rings in tropolone

Abstract

Photophysical aspects of tropolone upon extension with aromatic rings are studied theoretically. Tropolone possesses three energetically close lying singlet excited states (S 1 (1 π π ∗ ), S 2 (2 π π ∗ ) and S 3 (1 n π ∗ )), resulting in a rapid internal conversion among these states upon photoexcitation. The excited-state energetics and decay dynamics of benzotropolone are similar to the tropolone molecule. On the other hand, upon extending the tropolone with naphthalene moiety (naphthatropolone), the molecule exhibits relatively well-separated electronic states, thus displaying significantly slower photorelaxation compared to the tropolone molecule. Both benzotropolone and naphthatropolone exhibit the dual emission feature, which is absent in the parent tropolone due to the symmetrical double-well potential of S 1 . • Loss of near-degeneracy upon ring extension in tropolone. • Competing nonadiabatic relaxation and ESIPT. • O-H vibrations facilitates rapid internal conversion. • Dual emission features in extended tropolones.