Supramolecular self-assembly of cytidine monophosphate-di-copper building blocks

Abstract

We report the synthesis and characterization of three di-copper compounds, [Cu2phen2CMP(µ-OH)(µ-X)]·3H2O (with X = Cl− (1) and Br− (2)) and [Cu2phen2CMP(µ-OH)(µ-NO3)]·[Cu2phen2CMP(µ-OH)(NO3)]·7H2O (3). 1 and 3 present a dinuclear core assembled by an unusual bis-monodentate phosphate and µ2-hydroxo double bridge, further supported by bridging anions. The spontaneous self-assembly of an extended coordination structure of higher dimensionality, although possible in principle, has been hindered by the use of strongly coordinating counterions (Cl−, Br−) and, unexpectedly, even by the less coordinating nitrate ions. The neutral complexes feature unsaturated coordination sites, having both the N(3) and O(2) of the cytosine moieties of the CMP ligands still available for coordination. π···π Stacking and hydrogen bonding interactions established between the discrete chiral entities mainly drive the self-assembling of a 3D supramolecular network. Small hydrophilic voids are defined within the 3D net, which are filled by solvent water molecules. These small nuclearity complexes with coordinatively unsaturated CMP ligands are likely to act as tectons. They could be used as complex-as-ligands for further binding additional metal ions in a predictable manner, favoring a more rational synthetic approach aimed to a stricter structural and chemical control of the resulting material.