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)
摘要:
Gradual solvation of [(4,4'-bpy)Re-I(CO)(3)(dppz)](+) (dppz = dipyridil[3,2-a:2'3'-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 angstrom' , is therefore very close to the distance from the Re center to the oxygen atom of the CO ligands, i. e., l = 2.73 angstrom'. In addition, excited state reactions with TEA produce [(4,4'-bpy)Re-I(CO)(3)(dppz)] and [(4,4'-bpy)Re-I(CO)(3)(dppz)]. This experimental observation is inconsistent with the formation of the products in the lowest lying and emissive dppz-centered (3)pi pi* excited state. Jablonski schemes based on the participation of excited states other than the lowest (3)pi pi* excited state are proposed. (C) 2010 Elsevier B.V. All rights reserved.