On the molecular structure that produces the phosphorescence of 7‐azaindole

Abstract

AbstractThe structured phosphorescence with a 0–0 component at ∼430 nm exhibited by 7‐azaindole is not due to its monomer, its normal or tautomeric C2h dimer, or its oligomeric forms consisting of five monomers, but rather to a molecular structure resulting from the interaction of the C2h dimer with a polar molecule (7‐azaindole itself, another solute or the solvent). Such an interaction breaks the C2h symmetry of 7‐azaindole dimer, thereby facilitating the localization of the electronic excitation on one of the dimer molecules and resulting in the presence of dimers of C1 symmetry. Based on the results, the structure that produces this phosphorescence is a normal dimer exhibiting a double hydrogen bond but no symmetry constraint. Surprisingly, its first triplet state, T(DC1), is ∼20 kcal/mol below the first triplet state for the system of C2h symmetry. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005