Syntheses, Crystal Structures, and Magneto−Structural Correlations of Novel Cu^II Complexes Containing a Planar [Cu(μ-L¹)]₂ (HL¹ = 3-(2-Pyridyl)pyrazole) Unit: From Dinuclear to Tetranuclear and Then to One-Dimensional Compounds

Seven new CuII complexes based on a binuclear planar unit [Cu(μ-L1)]2, {[Cu(μ-L1)(NO3)(H2O)]2 (1), [Cu(μ-L1)(HL1)(ClO4)]2 (2), [Cu4(μ-L1)6(NO3)2] (3), [Cu4(μ-L1)6(L1)2] (4), [Cu4(μ-L1)6(μ-L2)]n (5), [Cu4(μ-L1)6(μ-L3)]n (6), {[Cu4(μ-L1)4(μ-L4)2](H2O)3}n (7) (HL1 = 3-(2-pyridyl)pyrazole, L2 = 1,8-naphthalenedicarboxylate, L3 = terephthalate, L4 = 2,6-pyridinedicarboxylate)}, have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. In 1 and 2, the CuII centers are linked by deprotonated pyrazolyl groups to form dinuclear structures. 3 and 4 have similar gridlike tetranuclear structures in which two additional deprotonated L1 ligands bridge two [Cu(μ-L1)]2 units perpendicularly. 5 and 6 consist of similar one-dimensional (1-D) chains in which gridlike tetranuclear copper(II) units similar to that of 3 are further linked by L2 or L3 ligands, respectively. And, in 7, L4 ligands link [Cu(μ-L1)]2 binuclear units to form a tetranuclear gridlike structure in chelating/bridging mode and simultaneously bridge the tetranuclear units to form a 1-D chain. The magnetic properties of all complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements. The obtained parameters of J range from −33.1 to −211 cm-1, indicating very strong antiferromagnetic coupling between CuII ions. The main factor that affects the |J| parameter is the geometry of the Cu(N2)2Cu entity. From the magnetic point of view, 1 and 2 feature “pure” dinuclear, 3 and 5 tetranuclear, and 4, 6, and 7 pseudodinuclear moieties.