Influence of Copper(II) and Nickel(II) Ions in the Topology of Systems Based on a Flexible Bis-Oxamate and Bipyridine Building Blocks

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Single crystals of the mononuclear bis-oxamate nickel(II) complex [Ni(bipy)(H 2 edpba)]·dmso ( 1 ) are obtained by reacting [Ni(bipy)Cl 2 ]·H 2 O and the flexible K 2 (H 2 edpba) ligand [bipy = 2,2′ - bipyridine; H 4 edpba = N, N ′-2,2′-ethylenediphenylenebis(oxamic acid)]. The reaction of 1 with copper(II) ions resulted in two products in which the replacement of the nickel(II) ion by copper(II) took place: the chain compound [Cu(bipy)(H 2 edpba)] n ·3 n H 2 O· n dmso [dmso = dimethyl sulfoxide] ( 2 ) and the analogous chain compound without dmso crystallization molecules [Cu(bipy)(H 2 edpba)] n ·1.5 n H 2 O ( 3a ) in its polycrystalline form. The reaction of [Cu(bipy)Cl 2 ] and K 2 (H 2 edpba) yielded single crystals of [Cu(bipy)(H 2 edpba)] n ·1.5 n H 2 O ( 3b ). The H 2 edpba 2– ligand exhibits the anti conformation in 1, 2, and 3b, but it adopts different coordination modes: terminal bis-bidentate ( 1 ) and bridging bis-bidentate ( 2 and 3b ) through the two pairs of carbonyl-oxygen atoms of the two oxamate arms. Magnetic susceptibility measurements carried out on a polycrystalline sample of 3b in the temperature range 1.9–295 K showed the occurrence of very weak intrachain antiferromagnetic interactions [ J = −0.40 cm –1, the Hamiltonian being defined as H = − J ∑ i S i · S i +1 ], in agreement with the large values of the copper–copper separation [8.308(3) Å].