The Rh(NN)33+-DQ2+ dyad, which contains a Rh(III) polypyridine moiety (Rh(NN)33+) and a N,N′-bridged diquaternarized 4,4′-dimethyl-2,2′-bipyridine (DQ2+) as covalently linked components, has been synthesized and used in the study of intramolecular electron transfer. The study, performed by laser flash photolysis, makes use of a relatively unconventional reaction scheme. First, bimolecular electron-transfer quenching of the Rh(NN)32+-localized excited state of the dyad (using 1,2,3-trimethoxybenzene as external reductant) is used to generate the reduced dyad in the thermodynamically unfavored Rh(NN)32+-DQ2+ form. Then, this species is observed to relax by a fast (k = (3 ± 1) × 107 s-1) intercomponent charge-shift process to the stable (ΔG°, ca. 0.2 eV) Rh(NN)33+-DQ+ form. A slower bimolecular back-electron-transfer reaction with the radical cation of the external quencher (k = 3.3 × 109 M-1 s-1) finally brings back the dyad to its original oxidation state. © 1991 American Chemical Society.
Intramolecular Charge Shift Following Bimolecular Reductive Quenching of a Rh(III)polypyridine-Diquat Dyad
INDELLI, Maria Teresa;POLO, Eleonora;BIGNOZZI, Carlo Alberto;SCANDOLA, Franco
1991
Abstract
The Rh(NN)33+-DQ2+ dyad, which contains a Rh(III) polypyridine moiety (Rh(NN)33+) and a N,N′-bridged diquaternarized 4,4′-dimethyl-2,2′-bipyridine (DQ2+) as covalently linked components, has been synthesized and used in the study of intramolecular electron transfer. The study, performed by laser flash photolysis, makes use of a relatively unconventional reaction scheme. First, bimolecular electron-transfer quenching of the Rh(NN)32+-localized excited state of the dyad (using 1,2,3-trimethoxybenzene as external reductant) is used to generate the reduced dyad in the thermodynamically unfavored Rh(NN)32+-DQ2+ form. Then, this species is observed to relax by a fast (k = (3 ± 1) × 107 s-1) intercomponent charge-shift process to the stable (ΔG°, ca. 0.2 eV) Rh(NN)33+-DQ+ form. A slower bimolecular back-electron-transfer reaction with the radical cation of the external quencher (k = 3.3 × 109 M-1 s-1) finally brings back the dyad to its original oxidation state. © 1991 American Chemical Society.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
