Structure determination and magnetic studies of triazole chelated Co(II) coordination polymers

Abstract Two cobalt(II) halide complexes with 1,2,4‐triazole as a ligand were synthesized. Their structures were determined by extended x‐ray absorption fine structure (EXAFS) and powder x‐ray diffraction (XRD). Both complexes [Co(Htrz)Cl 2 ] n ( 1 ) and {[Co(Htrz) 2 (trz)]BF 4 } n ( 2 ) form one‐dimensional polymeric chain and the distances of Co⋯Co are 3.3521(2) Å and 3.8629(2) Å, respectively. The Htrz and Cl − are bridging ligands to connect two Co(II) ions in 1 , and the local environment of Co site is in a distorted octahedron with {CoN 2 Cl 4 } core. In complex 2 , two Htrz and one trz are bridging ligands to connect two Co(II) ions, and the local geometry of Co is in a pseudo octahedron with {CoN 6 } core. The analysis of Co L II,III ‐edge XAS indicates that the Co(II) of both complexes are at high spin state with t 2g 5 e g 2 configuration and the crystal field strength (10Dq) is about 1.2 eV. The broken‐symmetry DFT calculations indicate that antiferromagnetic coupling state of Co⋯Co is the most stable state in both complexes; and the coupling constants of 1 and 2 are −0.32 cm −1 and −3.70 cm −1 , respectively. Based on the distances of Co⋯Co and coupling constants, such antiferromagnetic interaction is achieved through triazole ligands.