Syntheses, structures and magnetic properties of three Co(II) coordination architectures based on a flexible multidentate carboxylate ligand and different N-donor ligands

Abstract

Three new cobalt complexes, {[Co5(tci)2(bimb)3(µ3-O)2(H2O)2]·3DMF·4H2O}n (1), {[Co3(tci)2(bib)]·2DMF·2H2O}n (2) and {[Co(Htci)(bpea)0.5]·H2O}n (3) (H3tci = tris(2-carboxyethyl)isocyanurate, bimb = 4,4′-bis(imidazol-1-yl)biphenyl, bib = 1,4-bis(imidazol-1-yl)benzene, bpea = 1,2-bis(4-pyridyl)ethane, DMF = N,N′-dimethylformamide), have been successfully synthesized through the assembly of Co(II) ions, H3tci and different N-donor ligands, respectively. All complexes were structurally characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric (TG) analyses and X-ray powder diffraction (XRPD). Complex 1 exhibits a 3D three-fold parallel interpenetrated 3D → 3D structure with (65·8) CdSO4 topology. Complex 2 is built from [Co3(µ2-Ocarboxyl)2(CO2)4] clusters and linear bib ligands, displaying a two-fold parallel interpenetrated (3,8)-connected (43)2(46·618·84) topology, while complex 3 is a 3D pillar-layered structure involving an infinite -Co-(µ2-Ocarboxyl)(CO2)-Co-chain. The diverse structures of the three complexes indicate that the skeletons of different N-donor ligands play an important role in the assembly of such different frameworks. In addition, magnetic investigation indicates that besides spin-orbit coupling of Co(II) ions, there exist antiferromagnetic exchange interactions in Co5 and Co3 clusters of 1 and 2, respectively.