Synthesis, structure and magnetic properties of a singly carboxylate-bridged dinuclear manganese(II) complex

Abstract

A novel dinuclear manganese(II) complex bridged by a single carboxylate ligand [{Mn(bipy)₂-(H₂O)}₂(Me₃NCH₂CO₂)][ClO₄]₄·2H₂O (bipy = 2,2′-bipyridine) has been prepared and structurally characterized by X-ray crystallography. It crystallizes in the monoclinic space group C2, with a= 16.321(5), b= 13.354(5), c= 13.298(2)Å, β= 96.55(2)°. Refinement converged to R= 0.066 for 1975 observed reflections with I 2σ(I). The crystal structure comprises a dinuclear cation, perchlorate anions and lattice water molecules. The pair of metal ions separated at 5.67 Å in the cation is bridged by a single syn-anti carboxylate ligand. Each metal ion is co-ordinated in a distorted octahedral N₄O₂ geometry by two chelate bipy ligands [Mn–N 2.238(8)–2.257(7)Å], one aqua ligand [2.173(7)Å] and one µ-carboxylate oxygen atom [Mn–O = 2.081 (10), 2.193(10)Å]. The powder EPR spectrum at 77 K shows a broad absorption at g= 1.970. The temperature-dependent magnetic susceptibility data (4.4-95.0 K) were fitted based on H=–2JS₁·S₂, yielding the intramolecular coupling constant J value of –0.193 cm^–1.