Synthesis, Crystal Structure, Magnetic Properties, and EPR of Cu(bp3ca)Br < inf > 2 < /inf > ·H < inf > 2 < /inf > O (bp3ca = 2,2′-Bipyridine-3,3′-dicarboxylic Acid). Ferromagnetic Interactions via Unsymmetrical Bromide Bridges

Abstract

Cu(bp3ca)Br2·H2O crystallizes in the triclinic space group PI with a = 10.622(2) Å, b = 10.832(2) Å, c = 14.684(2) Å, α = 106.13(1)°, β = 105.91(1)°, γ = 102.74(1)°, and Z = 2. The asymmetric unit consists of a bis μ-bromo unsymmetrically dibridged dimer which is further linked to its inversion-related partner to form a dimer of dimers. Weak intertetramer contacts are also observed. The magnetic data for this compound were fit to a linear tetramer model to give J1 = J3 = -8.69 x 10-3 cm-1, J2 = 91.52 cm-1, and the intertetramer interaction J = -1.187 cm-1 with g = 1.93. EPR data are consistent with the magnetic data. This system is compared to its previously reported chloro counterpart, which differs markedly in both structure and magnetic properties.