| Abstract
| - Step-scan FTIR time-resolved spectroscopy in acetonitrile-d3 has been applied to the determination of excited-state dipole orientation for the metal-to-ligand charge transfer (MLCT) excited states of two monomeric RuII polypyridyl complexes and analogues bound in 20-mer metallopolymers. Changes in ν(CO) for amide substituents between the ground and excited states confirm that the excited-state dipole orientation can be directed toward or away from the chemical link to the polymer by exploiting substituent effects.
- Step-scan FTIR time-resolved spectroscopy (S2FTIR TRS) in acetonitrile-d3 has been used to probe the acceptorligand in metal-to-ligand charge transfer (MLCT) excited states of amide-substituted polypyridyl complexes ofRuII and in analogues appended to polystyrene. On the basis of ground-to-excited state shifts in ν(CO) of −31cm-1 for the amide group in [RuII(bpy)2(bpyCONHEt‘)]2+ (bpyCONHEt‘ = 4‘-methyl-2,2‘-bipyridine-4-carboxamide-Et‘; Et‘ = −CH2CH2BzCH2CH3) (1) and in the derivatized polystyrene abbreviated {PS−[CH2CH2NHCObpy−RuII(bpy)2]20}40+ (3), the excited-state dipole is directed toward the amide-containing pyridylgroup in the polymer side chain. Smaller shifts in ν(CO) of −17 cm-1 in [RuII(4,4‘-(CONEt2)2bpy)2(bpyCONHEt‘)]2+ (2) and in the derivatized polystyrene abbreviated {PS−[CH2CH2NHCObpy−RuII(4,4‘-(CONEt2)2bpy)2]20}40+ (4) indicate that the excited-state dipole is directed toward one of the diamide bpy ligands.The nearly identical results for 1 and 3 and for 2 and 4 show that the molecular and electronic structures of themonomer excited states are largely retained in the polymer samples. These conclusions about dipole orientationin the polymers are potentially of importance in understanding intrastrand energy transfer dynamics. The excited-state dipole in 3 is oriented in the direction of the covalent link to the polymer backbone, and toward nearestneighbors. In 4, it is oriented away from the backbone.
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