On the elusive, non-emissive yet reactive, upper excited states of [(4,4′-bpy)ReI(CO)3(dppz)]PF6 (dppz = dipyridil[3,2-a:2′3′-c]phenazine)

Abstract

Gradual solvation of [(4,40 -bpy)ReI (CO)3(dppz)]+ (dppz = dipyridil[3,2-a:20 30 -c]phenazine) by water molecules causes a quenching of the emission in accordance with Perrin’s model of spheres. The calculated radius of the sphere, r = 2.6 ± 0.2 ÅA0 , is therefore very close to the distance from the Re center to the oxygen atom of the CO ligands, i.e., l = 2.73 ÅA0 . In addition, excited state reactions with TEA produce [(4,40 - bpyÆ)ReI (CO)3(dppz)] and [(4,40 -bpy)ReI (CO)3(dppzÆ)]. This experimental observation is inconsistent with the formation of the products in the lowest lying and emissive dppz-centered 3 pp* excited state. Jablonski schemes based on the participation of excited states other than the lowest 3 pp* excited state are proposed.