Structure of the anion radical of 2,2′-bipyridine in solution

Abstract

The vibrational properties of the anion radical of 2,2′-bipyridine produced in solution upon laser photolysis in the presence of 1,4-diazabicyclo[2.2.2]octane (DABCO) as electron donor are studied by time-resolved Raman measurements in resonance with two different electronic transitions. Four isotopomers are analyzed in addition to the parent h₈ species. In parallel, the density functional theory approach at the B3-LYP level with the 6-31G(+*) basis set is applied to determine the geometrical, energetic and vibrational characteristics of the anion radical. The theoretical harmonic frequencies derived from the optimized geometry are compared to the experimental Raman data. The very good agreement between theory and experiment, concerning not only the absolute frequencies, but also the isotopic shifts, and the frequency shifts on going from the parent neutral molecule to its reduced form for each isotopomer, allows us to validate the calculated structure of the anion radical.