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Synthesis, characterization and magnetism of binuclear cobalt (II) complexes bridged by tetracarboxylato groups
Author(s) -
CuiWei Yan,
YanTuan Li,
DaiZheng Liao
Publication year - 2000
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.20000180317
Subject(s) - chemistry , antiferromagnetism , molar conductivity , cobalt , magnetism , crystallography , octahedron , molecule , magnetic susceptibility , stereochemistry , inorganic chemistry , elemental analysis , crystal structure , organic chemistry , condensed matter physics , physics
Three new binuclear cobalt (II) complexes with extended tetracarboxylato‐bridge have been synthesized and characterized, namely [Co 2 (PMTA) (bpy) 4 ] (1), [Co 2 (PMTA)‐(phen) 4 ] (2) and [Co2(PMTA)(NO 2 phen) 4 (3), where PMTA represents the tetraanion of pyromellitic acid, and bpy, phen, NO 2 ‐phen denote 2,2‐bipyridine, 1,10‐phenanthroline; 5‐nitro‐1, 10‐phenanthroline, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have PMTA‐bridged structures and consist of two cobalt(II) ions, each in a distorted octahedral environment. These complexes were further characterized by variable temperature magnetic susceptibility measurements (4–300 K) and the observed data were successfully simulated by th e equation based on the spin Hamiltonian operator, Ĥ =−2 J Ŝ 1 ·Ŝ 2 , giving the exchange integral J = −1.02 cm −1 for 1, J = −1.21 cm −1 for 2 and J = −1.18 cm −1 for 3, respectively. These results revealed the operation of antiferromagnetic spin‐exchange interaction between the two Co(II) ions within each molecule.