The reaction of trinuclear manganese complex [Mn₃O(ClCH₂COO)₆(py)₂]•(H₂O) with 2,2′-bipyridine in CH₃CN led to the new mixed valence tetranuclear Mn₃^IIIMn^II complex of formulation [Mn₄O₂(ClCH₂COO)₇(bipy)₂]•H₂O. The structure and chemical composition of title complex were determined by elemental analysis, IR spectrum, thermal analysis and X-ray diffraction analysis. The crystal structure belongs to triclinic system with space group P-1 and a＝0.89854(13) nm, b＝1.4027(2) nm, c＝1.9037(3) nm, α＝93.518(3)°, β＝96.736(3)°, γ＝94.875(3)°, V＝2.3680(6) nm³, Z＝2, D_c＝1.734 g/cm³, F(000)＝1238, GOF＝1.036, R₁＝0.0592, wR₂＝0.1162 [I＞2σ(I)]. The analysis of the crystal structure indicates that the title complex has a butterfly [Mn₄(μ₃-O)₂]^7＋core, which consists of two Mn₃(μ₃-O) units, with approximate C₂ symmetric axis. The four manganese atoms are all six-coordinated with seven chloroacetate acid anions and two 2,2′-bipyridine molecules, forming distorted octahedron configuration. Variable temperature magnetic susceptibility of the title complex showed the existence of intramolecular antiferromagnetic interaction, and it was intricate at relatively low temperature.

Key words: mixed-valence complex, tetranuclear manganese complex, crystal structure, magnetic property, thermal decomposition