Photoinduced electron-transfer reactions of ruthenium(II) complexes. 1. Reductive quenching of excited tris(2,2'-bipyridine)ruthenium(2+) by aromatic amines
Photoinduced electron-transfer reactions of ruthenium(II) complexes. 1. Reductive quenching of excited tris(2,2'-bipyridine)ruthenium(2+) by aromatic amines
复制标题
钌(II)配合物的光诱导电子转移反应。
DOI：
10.1021/j100352a021
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
S. Tazuke
中科院分区：
文献类型：
--
作者：
N. Kitamura;Haeng;Sumio Okano;S. Tazuke
The rate constants (k{sub q}) and activation parameters for reductive quenching of *Ru(bpy){sub 3}{sup 2+} (bpy = 2,2{prime}-bipyridine) by 19 aromatic amines were determined in acetonitrile. The activation enthalpies ({Delta}H{sub 23}{double dagger}) increased from +1 to +6 kcal/mol with decreasing k{sub q} while the activation entropies were almost constant around {minus}15 eu for all quenchers except for those of highly exoergic reactions. The mechanism of the reductive quenching is discussed on the basis of k{sub q} as well as of the activation parameters. The quenching was shown to depend on the nature of the aromatic amine; the quenching by tertiary amines was always faster than that by primary and secondary amines when k{sub q} are compared at the same free energy change. The results are explained by the variation of outer-sphere reorganization energy with the nature of a quencher. For the quenching by tertiary and primary/secondary amines, the radii of the quenchers (r{sub Q}{sup ex}) were estimated to be 3 and 2.4 {angstrom}, respectively, by analyzing free energy relationships of the activation free energy of the quenching. The difference in r{sub Q}{sup ex} between tertiary and primary or secondary amines (0.5-0.6 {angstrom}) was in good agreement with that between N,N-dimethylaminomore » and anilino groups estimated by the space-filling model (0.7 {angstrom}). The solvent reorganization around the amino group is more relevant than that around an aromatic ring or a whole molecule to the actual outer-sphere reorganization energy.« less
The rate constants (k{sub q}) and activation parameters for reductive quenching of *Ru(bpy){sub 3}{sup 2+} (bpy = 2,2{prime}-bipyridine) by 19 aromatic amines were determined in acetonitrile. The activation enthalpies ({Delta}H{sub 23}{double dagger}) increased from +1 to +6 kcal/mol with decreasing k{sub q} while the activation entropies were almost constant around {minus}15 eu for all quenchers except for those of highly exoergic reactions. The mechanism of the reductive quenching is discussed on the basis of k{sub q} as well as of the activation parameters. The quenching was shown to depend on the nature of the aromatic amine; the quenching by tertiary amines was always faster than that by primary and secondary amines when k{sub q} are compared at the same free energy change. The results are explained by the variation of outer-sphere reorganization energy with the nature of a quencher. For the quenching by tertiary and primary/secondary amines, the radii of the quenchers (r{sub Q}{sup ex}) were estimated to be 3 and 2.4 {angstrom}, respectively, by analyzing free energy relationships of the activation free energy of the quenching. The difference in r{sub Q}{sup ex} between tertiary and primary or secondary amines (0.5-0.6 {angstrom}) was in good agreement with that between N,N-dimethylaminomore » and anilino groups estimated by the space-filling model (0.7 {angstrom}). The solvent reorganization around the amino group is more relevant than that around an aromatic ring or a whole molecule to the actual outer-sphere reorganization energy.« less