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RESEARCH PRODUCT

Synthesis, Structural, Magnetic and Thermal Characterization of {[Cu(bipy)] 2 (μ‐HP 2 O 7 )(μ‐Cl)}·H 2 O

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Copper(II) hydroxide reacts with 2,2′-bipyridine (bipy) and sodium pyrophosphate in a 2:2:1 stoichiometric ratio under ambient conditions at pH 1.6 in water. The resulting neutral dinuclear CuII complex features a bridging set containing bridging monoprotonated pyrophosphate and a monoatomic chloro bridge (making this the first pyrophosphate bridged coordination complex containing an alternate, additional halide bridge between the metal centers). Single-crystal X-ray diffraction studies revealed the complex to be {[Cu(bipy)]2(μ-HP2O7)(μ-Cl)}·H2O. The structure consists of a dimeric copper(II) system with each metal ion in a square pyramidal geometry. The asymmetric [Cu(bipy)]2+ units are bridged by bis-bidentate pyrophosphate and an axially bridging chlorine atom. The incorporation of an additional bridge (halide) and the presence of protonated pyrophosphate (HP2O73–) in the structure are both rare for this family of structures. Intermolecular π–π interactions between the bipy ligands from adjacent dinuclear complexes and hydrogen bonding between the lattice water molecule and the bridging chloro atom create a 1D network. Variable-temperature magnetic susceptibility measurements show the occurrence of a weak antiferromagnetic interaction with a maximum at 3.0 K. The analysis of the magnetic data in the whole temperature range (1.9–300 K) allows the determination of the value of the intramolecular magnetic coupling (J = –3.19 cm–1, the Hamiltonian being defined as Ĥ = –JŜA. ŜB). This value of J is significantly lower than that observed for the analogous dicopper(II) system devoid of the bridging chloro group. Reasons for this difference and its importance are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)