Polyunsaturated Dicarboxylate Tethers Connecting Dimolybdenum Redox and Chromophoric Centers: Syntheses, Structures, and Electrochemistry
详细信息 查看全文
- 作者：F. Albert Cotton ; James P. Donahue ; and Carlos A. Murillo
- 刊名：Journal of the American Chemical Society
- 出版年：2003
- 出版时间：May 7, 2003
- 年：2003
- 卷：125
- 期：18
- 页码：5436 - 5450
- 全文大小：637K
- 年卷期：v.125,no.18(May 7, 2003)
- ISSN：1520-5126
文摘
Compounds with two quadruply bonded Mo24+ units, Mo2(DAniF)3 (DAniF = N,N '-di-p-anisylformamidinate), linked by unsaturated dicarboxylate dianions of various lengths have been preparedand their spectroscopic and electrochemical properties studied. As identified by the dicarboxylate linkers,these compounds are maleate (7), allene-1,3-dicarboxylate (10), cis,cis-muconate (11), trans,trans-muconate(12), octa-2,4,6-trans,trans,trans-hexatriene-1,8-dioate (tamuate, 13), and deca-2,4,6,8-trans,trans,trans,trans-octatetraene-1,10-dioate (texate, 14). The latter three molecules complete the five-membered (alltrans) series [Mo2(DAniF)3](O2C(CH=CH)nCO2)[Mo2(DAniF)3] (n = 0-4). Several unsymmetrical paddlewheel compounds of the type Mo2(DAniF)3(O2CX) (X = C
CH (3), CH=CH2 (4), (E)-CH=CH-CH=CH2(5)) have also been prepared for comparison to the molecules in which there are linked Mo2 units. Theprecursors [Mo2(DAniF)3(MeCN)2](BPh4), [1]BPh4, and Mo2(DAniF)3Cl(MeCN) (2) have also been isolatedand characterized. The structures of all new molecules have been established by X-ray crystallography,including the methyl esters of various carboxylates used as ligands. All of the linked molecules have beenexamined by cyclic and differential pulse voltammetry, and 
E1/2 values, the separation between successiveMo24+/Mo25+ oxidations, have been determined. Those compounds with highly unsaturated, fully conjugatedlinkers demonstrate electrochemical communication from end-to-end that is more persistent over distancethan is accounted for by an electrostatic interaction alone, implying that the 
system of these dicarboxylatelinkers is mediating communication. In the series [Mo2(DAniF)3](O2C(CH=CH)nCO2)[Mo2(DAniF)3] (n = 0-4),the first oxidation potential shifts progressively to less positive values due to an increasing contribution ofthe polyolefinic 
,
-dicarboxylate to the molecular orbital undergoing oxidation. This first oxidation potentialapproaches a limiting value of 63 mV (vs Ag/AgCl) as n becomes infinitely long. Compound 11 can bephotoisomerized to 12 in a process that is affected by the presence of the Mo24+ units, as the analogousrearrangement of dimethyl cis,cis-muconate is faster.
CH (3), CH=CH2 (4), (E)-CH=CH-CH=CH2(5)) have also been prepared for comparison to the molecules in which there are linked Mo2 units. Theprecursors [Mo2(DAniF)3(MeCN)2](BPh4), [1]BPh4, and Mo2(DAniF)3Cl(MeCN) (2) have also been isolatedand characterized. The structures of all new molecules have been established by X-ray crystallography,including the methyl esters of various carboxylates used as ligands. All of the linked molecules have beenexamined by cyclic and differential pulse voltammetry, and E1/2 values, the separation between successiveMo24+/Mo25+ oxidations, have been determined. Those compounds with highly unsaturated, fully conjugatedlinkers demonstrate electrochemical communication from end-to-end that is more persistent over distancethan is accounted for by an electrostatic interaction alone, implying that the system of these dicarboxylatelinkers is mediating communication. In the series [Mo2(DAniF)3](O2C(CH=CH)nCO2)[Mo2(DAniF)3] (n = 0-4),the first oxidation potential shifts progressively to less positive values due to an increasing contribution ofthe polyolefinic ,-dicarboxylate to the molecular orbital undergoing oxidation. This first oxidation potentialapproaches a limiting value of 63 mV (vs Ag/AgCl) as n becomes infinitely long. Compound 11 can bephotoisomerized to 12 in a process that is affected by the presence of the Mo24+ units, as the analogousrearrangement of dimethyl cis,cis-muconate is faster.