Issue 14, 2009

Syntheses, crystal structures and magnetic properties of three novel cobalt(ii) complexes containing imidazole derivative groups

Abstract

Three Co(II) complexes with the formulas: {[Co2(Bib)3Cl2]Cl(CH3COO)}·CH3OH·H2O (1), [Co2(Bib)3Cl2]Cl2·(CH3OH)2·H2O, (2) and [Co3K1(Tib)2(CH3COO)6]PF6 (3), were obtained by self-assembly of a cobalt(II) salt with Bib and Tib (Bib = 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene; Tib = 1,3,5-tris(4,5-dihydro-1H-imidazol-2-yl)benzene) and were structurally and magnetically characterized. X-Ray single-crystal diffraction showed that each Co(II) ion was in a highly distorted tetrahedral coordination geometry with a cistrans ratio of 1 : 2 from the Bib ligand, which functioned in a bidentate fashion in the binuclear triple-helical [Co2(Bib)3Cl2]2+ cations in 1 and 2. In the [Co3K1(Tib)2(CH3COO)6] anions in 3, each Co(II) ion was also in a highly distorted tetrahedral coordination geometry and the Tib ligands acted in an offset fashion in C, C, C and A, A, A coordination to the Co(II) ions with π–π stacking interactions between two benzene rings from the Tib ligand in the cluster cation. Each Tib ligand in a cluster unit acted as a tridentate entity to coordinate three Co(II) ions resulting in a cylinder-like cluster structure. The intermolecular hydrogen bonds in the solid-state resulted in the well-shaped 2D layer network which formed a honeycomb in 1, the 3D supramolecular architecture which was connected to the 2D sheet into 3D in 2 and the 3D supramolecular architecture, which was extended into a well-shaped 2D honeycomb layer network in 3. The results from magnetic data, in the high-temperature region, showed that 1 and 2 obeyed the Curie–Weiss law with a Weiss constants θ = −12.3, and −9.8 K and a Curie constants C = 5.31 and 5.32 cm3K mo1−1, respectively, indicating antiferromagnetic interactions between adjacent cobalt(II) ions. Both complex 1 and 2 showed magnetic ordering at low temperature due to the canting effect. The zero-field AC magnetic susceptibility measurements for 1 and 2 displayed a maximum which was frequency dependent owing to a slow relaxation process, which could be caused by either domain wall movements or spin-glass behaviours.

Graphical abstract: Syntheses, crystal structures and magnetic properties of three novel cobalt(ii) complexes containing imidazole derivative groups

Supplementary files

Article information

Article type
Paper
Submitted
19 May 2008
Accepted
23 Jan 2009
First published
23 Feb 2009

Dalton Trans., 2009, 2540-2551

Syntheses, crystal structures and magnetic properties of three novel cobalt(II) complexes containing imidazole derivative groups

H. Yang, J. Chen, J. Sun, S. Yang, J. Yu, H. Tan and W. Li, Dalton Trans., 2009, 2540 DOI: 10.1039/B808385A

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