Azide bridged dicopper(II), dicobalt(II) complexes and a rare double μ-chloride bridged ferromagnetic dicobalt(II) complex of a pyrazolyl-pyrimidine ligand: Synthesis, crystal structures, magnetic and DFT studies

Abstract

Two new dinuclear copper(II) complexes [Cu2(PymPz)2(N3)2Cl2] (1), [Cu2(PymPz)2(N3)4] (2) and two new dinuclear cobalt(II) complexes [Co2(PymPz)2Cl4] (3), [Co2(PymPz)2(N3)4] (4) [PymPz=2-(3,5-dimethyl-1H-pyrazol-1-yl)-4,6-dimethylpyrimidine] have been synthesized and characterized crystallographically and spectroscopically. In each of the complexes 1, 2 and 4 the two adjacent metal centers are bridged by a pair of μ-1,1 azide groups whereas in 3 the metal centers are bridged by a pair of chloride ions. In the complexes, all the metal centers are pentacoordinated. In 1 and 2 the copper(II) centers have distorted square pyramidal geometry (τ=0.18 for 1 and 0.091 for 2) but in 3 and 4 cobalt(II) centers have distorted trigonal bipyramidal geometry (τ=0.619 for 3 and 0.557 for 4). Complexes 1 and 2 show antiferromagnetic interaction (J=−7.09cm−1 for 1 and J=−17.00cm−1 for 2) whereas 3 and 4 show ferromagnetic interaction (J=7.44cm−1 for 3 and J=10.45cm−1 for 4). Complex 3 displays an unprecedented ferromagnetic interaction over double μ-chloro bridges in the observed angle range (94.87°). The exchange pathways parameters for all the complexes have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings.