Temperature-Independent Rate of Electron-Transfer between a Cobalt(II) and a Ruthenium(III) of Doublet Electronic Configuration

A study of laser kinetic spectroscopy on [RuII(tpy)(BL)CoIII(tpy)]5+ (BL:  1,4-bis[2,2‘:6‘,2‘ ‘-terpyridine-4‘-yl]benzene (btbz) and 6‘,6‘ ‘-bis(2-pyridyl)- 2,2‘:4‘,4‘ ‘:2‘ ‘,2‘ ‘‘-quarter-pyridine (bpqp)) revealed rise-and-decay of a triplet Ru-to-ligand charge-transfer state, 3CT(Ru), and an elect...

Full description

Saved in:
Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2002-11, Vol.106 (46), p.11034-11044
Main Authors: Torieda, Hiroaki, Yoshimura, Akio, Nozaki, Koichi, Sakai, Satomi, Ohno, Takeshi
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A study of laser kinetic spectroscopy on [RuII(tpy)(BL)CoIII(tpy)]5+ (BL:  1,4-bis[2,2‘:6‘,2‘ ‘-terpyridine-4‘-yl]benzene (btbz) and 6‘,6‘ ‘-bis(2-pyridyl)- 2,2‘:4‘,4‘ ‘:2‘ ‘,2‘ ‘‘-quarter-pyridine (bpqp)) revealed rise-and-decay of a triplet Ru-to-ligand charge-transfer state, 3CT(Ru), and an electron-transfer product of [(tpy)RuIII(BL)CoII(tpy)]5+. 3CT(Ru) underwent electron-transfer with a rate constant of 0.3 × 1012 and 1 × 1012 s-1 to produce [(tpy)RuIII(BL)CoII(tpy)]5+ with a doublet electronic configuration d π 6d σ * of cobalt(II). The return electron transfer (RET) of [RuIII(tpy)(BL)CoII(tpy)]5+ (BL:btbz and bpqp) in acetonitrile occurred with a rate constant of 1 × 1010 and 6 × 1010 s-1 at 298 K, respectively, which are much faster than intramolecular RET of [(bpy)2Ru(BL)Co(bpy)2]5+ from cobalt(II) with a quartet electronic configuration of d π 5d σ * 2. The magnitude of reorganization energy (0.95 ± 0.15 eV) and electronic coupling matrix element (0.8 and 2 meV) are evaluated from the independence of RET rate on the temperature by using a small entropy change of RET. The small intramolecular reorganization energy (0−0.3 eV) for 2Co(II)/Co(III) redox process of [(tpy)RuII(BL)CoIII(tpy)]5+ (BL: btbz and bpqp) are responsible for the fast RET. The magnitude of the intramolecular reorganization energy is in agreement with those (0.27−0.29 eV) calculated by using a density functional theory.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp021257h