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

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 = −7.09 cm−1 for 1 and J = −17.00 cm−1 for 2) whereas 3 and 4 show ferromagnetic interaction (J = 7.44 cm−1 for 3 and J = 10.45 cm−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.

Graphical abstractSyntheses of azide bridged dicopper(II), dicobalt(II) complexes and a rare double μ-chloride bridged ferromagnetic dicobalt(II) complex of a pyrazolyl-pyrimidine ligand have been reported along with their crystal structures, magnetic and DFT.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Crystal structure of azide bridged Cu(II), Co(II) and chloride bridged Co(II) complexes. ► Magnetic properties. ► DFT.