First Investigation at Elevated Pressures To Confirm the Exact Nature of the Gated Electron-Transfer Systems: Volume Profiles of the Gated Reduction Reaction and Nongated Reverse Oxidation Reaction In
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- 作者：Sumitaka Itoh ; Kyoko Noda ; Ryouhei Yamane ; Nobuyuki Kishikawa ; Hideo D. Takagi
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：February 19, 2007
- 年：2007
- 卷：46
- 期：4
- 页码：1419 - 1425
- 全文大小：195K
- 年卷期：v.46,no.4(February 19, 2007)
- ISSN：1520-510X
文摘
Redox reactions involving the [Cu(dmp)2]2+/+ couple (dmp = 2,9-dimethyl-1,10-phenanthroline) in acetonitrile wereexamined at elevated pressures up to 200 MPa. Activation volumes were determined as -8.8 and -6.3 cm3 mol-1for the reduction cross-reaction by [Co(bipy)3]2+ (bipy = 2,2'-bipyridine) and for the oxidation cross-reaction by[Ni(tacn)2]3+ (tacn = 1,4,7-triazacyclononane), respectively. The activation volume for the hypothetical gated modeof the self-exchange reaction estimated from the reduction cross-reaction was -13.9 cm3 mol-1, indicating extensiveelectrostrictive rearrangement of solvent molecules around the CuII complex during the change in the coordinationgeometry before the electron-transfer step. On the other hand, the activation volume for the self-exchange reactionestimated from the oxidation cross-reaction was -2.7 ± 1.5 cm3 mol-1. Although this value was within the rangethat can be interpreted by the concept of the ordinary concerted process, from theoretical considerations it wasconcluded that the reverse (oxidation) cross-reaction of the gated reduction reaction of the [Cu(dmp)2(CH3CN)]2+/[Cu(dmp)2]+ couple proceeds through the product excited state while the direct self-exchange reaction between[Cu(dmp)2(CH3CN)]2+ and [Cu(dmp)2]+ proceeds through an ordinary concerted process.