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Influence of decreasing solvent polarity (1,4-dioxane/water mixtures) on the stability and structure of complexes formed by copper(II), 2,2`-bipyridine or 1,10-phenanthroline and guanosine 5`-diphosphate : evaluation of isomeric equilibria

Operschall, Bert P. and Bianchi, Emanuela M. and Griesser, Rolf and Sigel, Helmut. (2009) Influence of decreasing solvent polarity (1,4-dioxane/water mixtures) on the stability and structure of complexes formed by copper(II), 2,2`-bipyridine or 1,10-phenanthroline and guanosine 5`-diphosphate : evaluation of isomeric equilibria. Journal of coordination chemistry, Vol. 62. pp. 23-39.

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Official URL: http://edoc.unibas.ch/dok/A5248794

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Abstract

The stability constants of the 1 : 1 complexes formed between Cu(Arm)2+, where Arm = 2,2`-bipyridine or 1,10-phenanthroline, and guanosine 5`-diphosphate (GDP)3- or its monoprotonated form H(GDP)2- were determined by potentiometric pH titrations in water and in water containing 30 or 50 stability of the binary Cu(GDP)- complex is enhanced due to macrochelate formation of the diphosphate-coordinated Cu2+ with N7 of the guanine residue as previously shown. In Cu(Arm)(GDP)- the N7 is released from Cu2+ and the stability enhancement of more than one log unit in aqueous solution is clearly attributable to intramolecular stack formation between the aromatic rings of Arm and the guanine moiety. Indeed, stacked isomers occur to more than 90 with open unstacked forms. Surprisingly, the same formation degrees of the stacks are observed for Cu(Arm)(dGMP) complexes, where dGMP2- = 2`-deoxyguanosine 5`-monophosphate, despite the fact that the overall stability of the latter species is by about 2.7 log units lower. In 1,4-dioxane-water mixtures stack formation is drastically reduced, probably due to hydrophobic solvation of the aromatic rings by the ethylene bridges of 1,4-dioxane. The relevance of these results regarding biological systems is indicated.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie
UniBasel Contributors:Operschall, Bert P. and Griesser, Rolf and Sigel, Helmut
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
ISSN:0095-8972
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:22 Mar 2012 14:29
Deposited On:22 Mar 2012 14:07

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