Versatile binding behaviour of 4,6-dimethyl-1,2,3-triazolo[4,5-d]-pyrimidin-5,7-dionato in the presence of bipyrimidine. Supramolecular H-bond architectures.

Complexes with the ligand 4,6-dimethyl-1,2,3-triazolo-[4,5-d]-pyrimidin-5,7-dionato (dmax(-)) and the auxiliary chelating-bridging ligand bipyrimidine (bpym) have been synthesized and structurally characterized for the divalent cations of Zn, Cd and Cu. For Zn and Cd, dinuclear complexes with the formulae [Zn(2)(dmax)(4)(H(2)O)(2)(bpym)].2H(2)O and [Cd(2)(dmax)(4)(H(2)O)(4)(bpym)].6H(2)O have been isolated whereas for Cu, the one-dimensional polymer {[Cu(2)(dmax)(4)(bpym)].5H(2)O}(n) has been obtained. Bpym acts as a chelating-bridging ligand in the three compounds, joining couples of metal ions. Two crystallographically and chemically different dmax(-) ligands are present in each of these complexes, one monodentately linked via the triazole N atom furthest from the pyrimidine ring (N2) and the other either monodentately linked via the triazole N atom closer to a carbonyl group (N1, Zn and Cd compounds) or in bridging N1-N2 mode (Cu compound), in the latter case generating an one-dimensional polymer with alternating bpym and (dmax)(2) bridges. The magnetic interaction across the bpym bridge gives rise to a strong antiferromagnetic interaction (2J = -201 cm(-1)), whereas that across the (dmax)(2) bridge is negligible and cannot be reliably determined (obscured by the strong one). The hydrogen bonds between water molecules and the triazolopyrimidine derivative build the 3-D structure of the compounds.