Structural and Kinetic Study of Reversible CO2 Fixation by Dicopper Macrocyclic Complexes. From Intramolecular Binding to Self-Assembly of Molecular Boxes
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- 作者：Anna Company ; Joo-Eun Jee ; Xavi Ribas ; Josep Maria Lopez-Valbuena ; Laura Gó ; mez ; Montserrat Corbella ; Antoni Llobet ; José ; Mahí ; a ; Jordi Benet-Buchholz ; Miquel Costas ; Rudi van Eldik
- 刊名：Inorganic Chemistry
- 出版年：2007
- 出版时间：October 29, 2007
- 年：2007
- 卷：46
- 期：22
- 页码：9098 - 9110
- 全文大小：374K
- 年卷期：v.46,no.22(October 29, 2007)
- ISSN：1520-510X
文摘
A study of the reversible CO2 fixation by a series of macrocyclic dicopper complexes is described. The dicoppermacrocyclic complexes [Cu2(OH)2(Me2p)](CF3SO3)2, 1(CF3SO3)2, and [Cu2(-OH)2(Me2m)](CF3SO3)2, 2(CF3SO3)2,(Scheme 1) containing terminally bound and bridging hydroxide ligands, respectively, promote reversible inter- andintramolecular CO2 fixation that results in the formation of the carbonate complexes [{Cu2(Me2p)}2(-CO3)2](CF3SO3)4, 4(CF3SO3)4, and [Cu2(-CO3)(Me2m)](CF3SO3)2, 5(CF3SO3)2. Under a N2 atmosphere the complexes evolveCO2 and revert to the starting hydroxo complexes 1(CF3SO3)2 and 2(CF3SO3)2, a reaction the rate of which linearlydepends on [H2O]. In the presence of water, attempts to crystallize 5(CF3SO3)2 afford [{Cu2(Me2m)(H2O)}2(-CO3)2](CF3SO3)4, 6(CF3SO3)4, which appears to rapidly convert to 5(CF3SO3)2 in acetonitrile solution. [Cu2(OH)2(H3m)]2+, 7, which contains a larger macrocyclic ligand, irreversibly reacts with atmospheric CO2 to generate cagelike[{Cu2(H3m)}2(-CO3)2](ClO4)4, 8(ClO4)4. However, addition of 1 equiv of HClO4 per Cu generates [Cu2(H3m)(CH3CN)4]4+ (3), and subsequent addition of Et3N under air reassembles 8. The carbonate complexes 4(CF3SO3)4,5(CF3SO3)2, 6(CF3SO3)4, and 8(ClO4)4 have been characterized in the solid state by X-ray crystallography. Thisanalysis reveals that 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 consist of self-assembled molecular boxes containingtwo macrocyclic dicopper complexes, bridged by CO32- ligands. The bridging mode of the carbonate ligand isanti-anti--1:1 in 4(CF3SO3)4, anti-anti--2:1 in 6(CF3SO3)4 and anti-anti--2:2 in 5(CF3SO3)2 and 8(ClO4)4.Magnetic susceptibility measurements on 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 indicate that the carbonate ligandsmediate antiferromagnetic coupling between each pair of bridged CuII ions (J = -23.1, -108.3, and -163.4 cm-1,respectively, H = -JS1S2). Detailed kinetic analyses of the reaction between carbon dioxide and the macrocycliccomplexes 1(CF3SO3)2 and 2(CF3SO3)2 suggest that it is actually hydrogen carbonate formed in aqueous solutionon dissolving CO2 that is responsible for the observed formation of the different carbonate complexes controlled bythe binding mode of the hydroxy ligands. This study shows that CO2 fixation can be used as an on/off switch forthe reversible self-assembly of supramolecular structures based on macrocyclic dicopper complexes.