A new one-dimensional coordination polymer and a new supramolecular dimer made of trinuclear copper(II) complexes: Crystal structure and magnetic properties

Two oxamato-bridged copper(II) complexes of formula [Cu₃(pbaOH)(tmen)₂(H₂O)(ClO₄)] _n[ClO₄]_n·nH₂O 1 and [Cu₃(opba)(tmen)₂(H₂O)₃][Cu ₃(opba)(tmen)₂(H₂O)₂][ClO ₄]₄·3H₂O 2 have been synthesized and characterized by IR, ESR, electronic spectra and X-ray crystallographic analyses, where pbaOH^4- = 2-hydroxyl-N,N′-trimethylenebis-(oxamate), opba^4- = N,N′-o-phenylenebis(oxamate), tmen = N,N,N′,N′-tetramethylethylenediamine. Both complexes consist of cationic trinuclear entities, in which copper atoms reside in square-planar (4) or square-pyramidal (4+1) environments. In complex 1 the hydroxyl group of one trinuclear entity coordinates to a terminal copper atom of another, thus forming an unusual one-dimensional chain. In 2 two neighboring trinuclear cations interact to form an interesting supramolecular (or "supracationic") dimer. The magnetic properties of the two complexes have been investigated, indicating that two copper(II) ions bridged by the oxamato bridge interact antiferromagnetically with J = -334.4 cm^-1 for 1 and -356.6 cm^-1 for 2 (based on Ĥ = -JŜ₁·Ŝ₂).