Self-assembly of the cyclic dimer [Cu(hfac)2(bpmu)]2 (bpmu = N,N′-bis(3-pyridylmethyl)urea; hfac = hexafluoroacetylacetonate ion) using coordination chemistry and predictable O=C(N-H)2•••O=C hydrogen bonds

A novel binuclear metallacyclic complex, [Cu(hfa)(2)(bpmu)](2), was isolated by reacting copper(II) hexafluoroacetylacetonate with the bpmu ligand. The crystal structure reveals the presence of dimetal units with the Cu(II) centers in a six-coordinate environment and bridged by the bpmu spacers. The crystal consists of a racemate with the two copper(II) ions of one dimer molecule carrying either a Delta Delta or Lambda Lambda configuration. The pyridyl-urea-based spacers are connected intramolecularly by the expected strong urea-based hydrogen bonds O=C(N-H)(2)center dot center dot center dot O=C. The same type of H-bonds allows the molecular units of the same chirality to assemble forming supramolecular columns. This conformationally defined array and hydrogen-bonding network, together with the bulky properties of the fragment {Cu(hfa)(2)}, were used as a pre-programmed supramolecular information for controlling the formation of discrete species. (C) 2005 Elsevier B.V. All rights reserved.