Energy transfer between Ru II and Os II polypyridyl complexes covalently attached to polystyrene has been in studied in CH 3 CN. The polymer is a 1:1 styrene- p -aminomethylstyrene copolymer derivatized by amide coupling with the acid-functionalized metal complexes [M II (bpy) 2 (bpy-COOH)](PF 6 ) 2 (M II = Ru II, Os II; bpy is 2,2‘-bipyridine and bpy-COOH is 4‘-methyl-2,2‘-bipyridine-4-carboxylic acid). In the resulting polymer [ co -PS−CH 2 NHCO−(Ru II 11 Os II 5 )](PF 6 ) 32, 11 of, on the average, 16 polymer sites are derivatized by Ru II and five by Os II . Photophysical properties compared to the homopolymers [ co -PS−CH 2 NHCO−(Ru II 16 )](PF 6 ) 32 and [ co -PS−CH 2 NHCO−(Os II 16 )](PF 6 ) 32 reveal that excitation at Ru II is followed by efficient energy transfer to the lower energy Os II sites with near unit efficiency (95%). Time-correlated single photon counting measurements with picosecond time resolution reveal that quenching of Ru II* produced adjacent to an Os II trap site is quenched with an average rate constant 〈 k en 〉 = 4.2 × 10 8 s -1 . Ru II* decay and Os II* sensitization kinetics are complex because the polymer sample consists of a distribution of individual strands varying in chain length, loading pattern, and number of styryl spacers. The kinetics are further complicated by a contribution from random walk energy migration. An average energy transfer matrix element of 〈 V en 〉 ∼ 2 cm -1 for Ru II* → Os II energy transfer has been estimated by using emission spectral fitting parameters to calculate the energy transfer barrier.
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Fleming et al. (2002) studied this question.
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