Copper(II) complexes derived from tripodal tris[(2-ethyl-(1-pyrazolyl)]amine

Three mono-nuclear copper(II) complexes [Cu(tepza)X]ClO4 (X = Cl, 1; X = NCS, 2; X = dca, 3) and two dinuclear bridging complexes [Cu2(tepza)2(μ-C4O4)](ClO4)2·H2O(4) and [Cu2(tepza)2(μ-C5O5)](ClO4)2(5) where tepza = tris[2-ethyl(1-pyrazolyl)]amine, dca = dicyanamide, C4O42− = 3,4-dihydroxycyclobut-3-ene-1,2-dionate (squarate dianion) and C5O52− = 4,5-dihydroxycyclopent-4-ene-1,2,3-trionate (croconate dianion) were synthesized and structurally characterized by IR and UV–Vis spectroscopy as well as by single X-ray crystallography. In the solid state, the geometry of copper(II) centers in these complexes are as follows: close to SP in 2, distorted TBP in 3, predominant SP in 4, and distorted octahedral in 5, whereas in solution distorted SP geometry was generally found. The squarato and the croconato dianions in complexes 4 and 5 are bridging the two copper(II) centers in cis-bis-monodentate and bis-bidentate bonding modes, respectively. Magnetic susceptibility measurements at variable temperatures (2–300 K) reveal the weak antiferromagnetic coupling in the two bridging dinuclear complexes 4 (J = −24.9 cm−1) and 5 (J = −3.1 cm−1).