Magnetic coupling constants J for the complete structures of heterobinuclear compounds GdCu (OTf) 3 (bdmap)2-(H2O)‚THF (1,GdIIICuII),[Gd(C4H7ON)4(H2O)3][Fe(CN)6]‚ 2H2O (2,GdIIIFeIII), and [Gd(C4H7ON) 4 (H2O)3]-[Cr(CN)6]‚2H2O (3,GdIIICrIII) have been calculated by the combination of the broken-symmetry approach with the spin project method under the DFT framework. The calculated J values (3.6 (1), 8.1 (2), and 20.3 cm-1 (3)) conform well to that of experimental findings (2.9 (2)(1), 0.74 (3)(2), and 0.40(2)cm-1 (3)) with a small difference in absolute value. The compounds 1-3, whose J values are all positive, show ferromagnetic couplings between two metal centers; thus, their ground states are all in high-spin states. The spin density distributions are discussed in detail on the basis of Mulliken population analysis, taking into account the coexistence of spin delocalization and spin polarization mechanisms. For 1, the spin distribution in the ground state may be understood as a result of the competition between two mechanisms: a spin delocalization from Cu (II) and a spin polarization of GdIII, and the former is dominant. In the cases of 2 and 3, both transition metal (FeIII or CrIII) and rare earth GdIII display a spin polarization effect on the surrounding atoms, where a counteraction of the opposite polarization effects leads a low spin density on the bridging ligand C1N1. In the ground state of 3, the stronger polarization effect of Cr (III) even causes the positive spin density on the adjacent bridging atom N1, different from the situation in 2.

The synthesis, structures, and magnetic properties of four cyano-bridged MIIRuIII 2 compounds prepared from the paramagnetic RuIII building blocks, trans-[Ru(salen)(CN)2]- 1 [H2salen) N, N¢-ethylenebis(salicylideneimine)] and trans-[Ru(acac)2(CN)2]-(Hacac) acetylacetone), are described. Compound 2, {Mn(CH3OH)4[Ru(salen)(CN)2]2}‚ 6CH3OH‚2H2O, is a trinuclear complex that exhibits antiferromagnetic coupling between MnII and RuIII centers. Compound 3,{Mn(H2O)2[Ru(salen)(CN)2]2 H2O}n, has a 2-D sheetlike structure that exhibits antiferromagnetic coupling between Mn and Ru, leading to ferrimagnetic-like behavior. Compound 4,{Ni(cyclam)[Ru(acac)2(CN)2]2}‚ 2CH3OH‚2H2O (cyclam ) 1,4,8,11-tetraazacyclotetradecane), is a trinuclear complex that exhibits ferromagnetic coupling. Compound 5,{Co[Ru(acac)2(CN)2]2}n, has a 3-D diamond-like interpenetrating network that exhibits ferromagnetic ordering below 4.6 K. The density functional theory (DFT) method was used to calculate the molecular magnetic orbitals and the magnetic exchange interaction between RuIII and MII (MnII, NiII) ions.

First published as an Advance Article on the web 25th October 2002 A novel 1D-coordination polymeric Co (II) complex [Co(btp)2(NCS)2]n [1, btp ¼ 1,3-bis(1,2,4-triazol-1-yl)propane] was synthesized and characterized. The coordination geometry of the cobalt ions is distorted octahedral, with the equatorial plane formed by the four nitrogen atoms of the four triazole groups and the axial sites occupied by two terminal trans thiocyanato ligands. The Co (II) ions are linked by the btp ligands, building up coordination polymers of infinite 1D-neutral chains.

Two new complexes, 1 and 2, with halo acetate ligands have been prepared from the reaction of ClCH2CO2H or BrCH2CO2H with the precursor Mn12Ac, and their structures and magnetic properties studied. The structures of complexes 1 and 2 consist of a central cubane-like [Mn4O4]8 unit held within a non-planar ring of eight Mn4 by eight µ3-O ions, sixteen XCH2CO2 units and four terminal water molecules, as well as included CH2Cl2 and H2O. Dierent arrangements of the four Mn4 relative to the eight Mn4 comparable complexes could play a role in the observed magnetic properties. Five and three periodic steps in the magnetic hysteresis loops are observed for both 1 and 2 at 2.2 and 2.6K, respectively.χmT values for complexes 1 and 2, where χm is the in-phase component of the AC magnetic susceptibility, exhibit a plateau in the 6-20K region, below which there is an abrupt decrease in χmT. Their χm signals measured at different frequencies are observed in the region 2-10 K, and exhibit a frequency dependency on the χm AC peaks, with a predominant peak in the 4-10K region. For these complexes, there is a difference between the zero-field-cooled (ZFC) and the field-cooled (FC) magnetization due to slow relaxation of the magnetization.

The magnetic exchange interaction behavior and energy spectrum of low-lying spin states are investigated by using ab initio multireference configuration-interaction method for the representative binuclear transition-metal complexes fsNH3d5Crs m-OHdCrsNH3d5g5+ and fCl3FeOFeCl3g2−. Our calculations for the nonmodeling real title complexes found that under the appropriate basis sets and active space, ab initio method at multireference configuration-interaction level of theory is able to give accurate energy spectrum of low-lying spin states within reachable computation demand nowadays and the deviation of magnetic exchange interaction to Lande interval rule can be described by the biquadratic correction in terms of Heisenberg spin Hamiltonian. As a methodology comparison, density-functional theory combined with broken-symmetry approach provides an alternative yet efficient approach to produce accurate numerical results, but there are dependences on the particular chosen exchange-correlation functionals and system dependent. The spin population analyses at complete active space self-consistent-field level of the theory provide an instructively understanding and prediction for the magnetic interaction mechanism.