Three new binuclear cobalt (II) complexes with extended tetracarboxylato-bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA)(NO2phen)4 (3), where PMTA...Three new binuclear cobalt (II) complexes with extended tetracarboxylato-bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA)(NO2phen)4 (3), where PMTA represents the tetraanion of pyromellitic acid, and bpy, phen, NO2-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, ?=?2J ?1·?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.展开更多
基金Project supported by the Natural Science Foundation of Shandong Province(No. Q99B12) and the National Natural Science Foundation of China (No. 29873031).
文摘Three new binuclear cobalt (II) complexes with extended tetracarboxylato-bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA)(NO2phen)4 (3), where PMTA represents the tetraanion of pyromellitic acid, and bpy, phen, NO2-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, ?=?2J ?1·?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.
