LASER FLASH-PHOTOLYSIS OF 2,2'-BIPYRIDINE IN AQUEOUS-SOLUTION

The transient species produced on laser flash photolysis (248 nm) of an aqueous solution of 2,2′-bipyridine (Bpy) have been identified as the excited triplet (3Bpy*), radical (BpyH{radical dot} and radical cation (Bpy+{radical dot}). BpyH{radical dot} and Bpy+{radical dot} are formed via a biphotonic ionization reaction; 3Bpy* is produced predominantly via monophotonic absorption. The transient absorption maximum at 340 nm is assigned to Bpy+{radical dot}; since it is also observed on pulse radiolysis of Bpy in 1,2-dichloroethane. The molar absorbance of Bpy+{radical dot} at 340 nm in aqueous solution is 2.33 × 104 M-1 cm-1. The decay of Bpy+{radical dot} follows first-order kinetics independent of pH with a rate constant k of 1.6 × 105 s-1. 3Bpy* and BpyH{radical dot} have absorption maxima in the region 350-370 nm, and their decay kinetics are complex. © 1990.