A very rare hydrogen-bridged hexanuclear Cu^II complex containing a triangular Cu₃O core capped by an unusual triply coordinated perchlorate anion

Abstract

An unusual hexanuclear Cu^II complex, [{[Cu(NHDEPO)]₃(μ ₃-O)(O₃ClO)}₂(μ-H)]•7ClO₄•4H₂O (1) was prepared starting from Cu(ClO₄)₂•6H₂O and the oxime-based Schiff base ligand NHDEPO (= 3-[3-(diethylamino)propylimino]butan-2-one oxime). Structural characterization of the complex reveals that it consists of two triangular Cu₃O units, the copper ions being at the corners of an equilateral triangle, separated by an O•••O distance of 2.447(5) Å, held together solely by a proton. In each triangle, the copper atoms are in square-pyramid environments. The equatorial plane consists of the bridging oxygen of the central OH^– (O^2–) group together with three atoms (N, N, O) of the Schiff base. An unusual triply coordinated perchlorate ion (μ ₃-κO:κO′:κO″) interacts in axial position with the three copper ions. Variable-temperature (2–300 K) magnetic susceptibility measurements show that complex 1 is antiferromagnetically coupled (J = –148 cm^–1). The EPR data at low temperature clearly indicates the presence of spin frustration phenomenon in the complex.