One-dimensional compounds containing copper(II) ions symmetrically bridgedby 2-oxo-pyrimidinate. Crystal structure and magnetic behaviour

Reaction of Cu(ClO4)(2) with 4,6-dimethyl-2-hydroxypyrimidine (Hdmpymo) in aqueous amine solution gives rise to compounds of formula [L2Cu(dmpymo)](Cl O4) (L = NH3, 1a; MeNH2, 1b). An X-ray crystallographic study on 1a reveale d a 1-D polymeric structure in which dmpymo entities symmetrically bridge s quare planar copper(II) centres. The copper environment is made up of two a mmonia and two nitrogen donor atoms from the pyrimidine ligands disposed in a trans configuration. Spectroscopic data (electronic spectra, EPR, IR) fo r la and Ib are very similar revealing their related nature. The magnetic p roperties of la have been investigated in the temperature range 2-300 K. A significant antiferromagnetic coupling with J = -23.0 cm(-1), through the p yrimidine bridges, is observed by analysing the susceptibility data with th e Hamiltonian H = -2J SigmaS(i)S(i+1). Crystal data: orthorhombic, space gr oup Pnma, a = 13.676(3), b = 10.804(2), c = 9.528(2) Angstrom, V= 1407.8(5) A(3), Z = 4, D-calc = 1.681 g cm(-3) R = 0.037 for 999 reflections. (C) 20 01 Published by Elsevier Science B.V.