Synthesis, Crystal Structures and Magnetic Properties of a Linear Trinuclear Cu(II) Complex [Cu < inf > 3 < /inf > (ClCH < inf > 2 < /inf > COO) < inf > 6 < /inf > (bpy) < inf > 2 < /inf > ] and a Dinuclear Complex [Cu < inf > 2 < /inf > (bpy) < inf > 2 < /inf > (μ-OH)(μ-OH < inf > 2 < /inf > ) (μ-ClCH < inf > 2 < /inf > COO)](ClO < inf > 4 < /inf > ) < inf > 2 < /inf >

Abstract

Two new triply bridged Cu(II) compounds [Cu 3 (bpy) 2 (μ-ClCH 2 COO) 6 ] (1) and [Cu 2 (bpy) 2 (μ-OH)(μ-OH 2 )(μ-ClCH 2 COO)](ClO 4 ) 2 (2) (where, bpy=2,2’-bipyridine) have been synthesized and their magnetic properties have been measured and correlated with structure. Compound 1 is a novel centrosymmetric tricopper compound with only carboxylate bridges. The terminal Cu 2+ ions have [5 + 1] coordination while the central ion has [4 + 2] coordination. The three centres are antiferromagnetically coupled, the exchange parameters for the neighbouring and distant pairs of Cu(II) atoms being 2 J=–28.6 cm –1 and 2 J'=–1.0 cm –1 , respectively. In compound 2 three types bridging modes are observed, viz., hydroxo, aquo and carboxylato. The two Cu(II) centers are ferromagnetically coupled (2 J=73.8 cm –1 ) as previously observed for several di-copper complexes with the same bridges. DFT calculations are in reasonable agreement with the magnetic exchange parameters for both dinuclear and trinuclear compounds.