Unusual Polynuclear Copper(II) Complexes with a Schiff-Base Ligand Containing Pyridyl and 1,2,4-Triazolyl Rings

The reaction between Cu(NO3)2 and Schiff-base ligand 4-(pyridin-2-yl)methyleneamino-1,2,4-triazole (L) in water due to hydrolysis process results in the formation of new ligand 4-[bis(pyridin-2-yl-methanol)]amino-1,2,4-triazole (H2L1) and 4-amino-4H-1,2,4-triazole (L2). Slow diffusion of methanol or ethanol vapors into the reaction solution leads to the growth of single crystals of the 12-nuclear complex [Cu12(L1)4(L2)6(NO3)6(MeOH)2(H2O)6](NO3)10·3MeOH·11H2O (1) with an unusual cyclic metal core or 1D coordination polymer {[Cu3L1(L2)2(NO3)2(H2O)2](NO3)2·1.5H2O}n (2), respectively. According to the X-ray diffraction data, both structures are constructed from similarly formed units, where three copper atoms are linked by one [L1]2− ligand and two amino-1,2,4-triazolyl fragments. Magnetic behaviour of compound 2 indicates the presence of antiferromagnetic-type exchange coupling between CuII ions in the trinuclear unit {Cu1–Cu2–Cu3} (J12 = − 149 cm−1, J23 = –175 cm−1, zJ = − 0.7 cm−1).