Cu(C2N4H4)(2)Br-2 center dot 2H(2)O: an antiferromagnetic cyanoguanidine coordination compound and its characterization

Phase-pure copper(II) cyanoguanidine bromide hydrate, Cu(C2N4H4)(2)Br-2 center dot 2H(2)O (1), was precipitated from aqueous solution and its structure was solved and refined from single-crystal X-ray diffraction data at 100 K. 1 crystallizes in space group P2(1)/n with a = 12.09(3) angstrom, b = 3.925(9) angstrom, c = 13.79(3) angstrom, beta = 96.62(6)degrees, Z = 2, and V = 650(2) angstrom(3). The copper(II) cation is coordinated by two cyanoguanidine molecules adopting the cyanoimine shape and four bromide anions in a Jahn-Teller-distorted motif, forming infinite chains of edge-sharing octahedra along the crystallographic b axis. IR spectroscopic and magnetic susceptibility measurements were carried out in addition to density-functional electronic-structure calculations performed to assess both the magnetic ground state and the exchange interactions. Experiment and theory agree as regards antiferromagnetism and weak magnetic exchange.