Hydrogen bonding in diruthenium(II,III) tetraacetate complexes with biologically relevant axial ligands

Bland, Brendan R.A.;Gilfoy, Heather J.;Vamvounis, George;Robertson, Kathy N.;Cameron, T. Stanley;Aquino, Manuel A.A.

Abstract

Three diadduct complexes of the mixed-valent form of diruthenium tetraacetate, [Ru-2(mu-O2CCH3)(4)L-2](PF6), where L are the biologically relevant ligands imidazole, 1, 7-azaindole, 2, and caffeine, 3, were synthesized and characterized by elemental analysis, IR and UV-Vis spectroscopy and X-ray crystallography. In order to further elucidate the potential interactions of these dimers with DNA, the nature of the ligand coordination and the secondary inter- and intramolecular hydrogen-bonding interactions in all three complexes were assessed. Complex 1 center dot CH2Cl2 shows, exclusively, intermolecular interactions with the PF6-counterion whereas complexes 2 center dot ClCH2CH2Cl and 3 center dot OC(CH3)(2) center dot H2O, in addition to extensive intermolecular interactions, show intramolecular hydrogen bonding from the axial ligand to the bridging acetate oxygens, locking the ligand mean planes in place between the bridging acetate mean planes. In addition, all three complexes display pi-pi stacking of axial ligand rings on adjacent diadduct units.

Journal

Inorganica Chimica Acta

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358

ISBN/ISSN

1873-3255

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Publisher

Elsevier

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DOI

10.1016/j.ica.2005.06.023