These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Syntheses, crystal structures and magnetic properties of three novel cobalt(II) complexes containing imidazole derivative groups.
    Author: Yang H, Chen JM, Sun JJ, Yang SP, Yu J, Tan H, Li W.
    Journal: Dalton Trans; 2009 Apr 14; (14):2540-51. PubMed ID: 19319399.
    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 cis-trans 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 pi-pi 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 theta = -12.3, and -9.8 K and a Curie constants C = 5.31 and 5.32 cm3 K 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.
    [Abstract] [Full Text] [Related] [New Search]