Magnetic coupling constants and spin density maps for heterobinuclear complexes GdCu(OTf)(3)(bdmap)(2)(H2O)center dot THF, [Gd(C4H7ON)(4)(H2O)(3)][Fe(CN)(6)]center dot 2H(2)O, and [Gd(C4H7ON)(4)(H2O)(3)][Cr(CN)(6)]center dot2H(2)O: A density functional study

Magnetic coupling constants J for the complete structures of heterobinuclea r compounds GdCu(OTf)(3)(bdmap)(2)-(H2O). THF (1, (GdCuII)-Cu-III), [Gd(C4H 7ON)(4)(H2O)(3)][Fe(CN)(6)]. 2H(2)O (2, (GdFeIII)-Fe-III), and [Gd(C4H7ON)( 4)(H2O)(3)]- [Cr(CN)(6)]. 2H(2)O (3, (GdCrIII)-Cr-III) have been calculated by the combination of the broken-symmetry approach with the spin project m ethod under the DFT framework. The calculated J values (3.6 (1), 8.1 (2), a nd 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 absolut e value. The compounds 1-3, whose J values are all positive, show ferromagn etic couplings between two metal centers; thus, their ground states are all in high-spin states. The spin density distributions are discussed in detai l on the basis of Mulliken population analysis, taking into account the coe xistence of spin delocalization and spin polarization mechanisms. For 1, th e spin distribution in the ground state may be understood as a result of th e competition between two mechanisms: a spin delocalization from Cu(II) and a spin polarization of Gd-III, and the former is dominant. In the cases of 2 and 3, both transition metal (Fe-III or Cr-III) and rare earth Gd-III di splay a spin polarization effect on the surrounding atoms, where a countera ction of the opposite polarization effects leads a low spin density on the bridging ligand C1N1. In the ground state of 3, the stronger polarization e ffect of Cr(III) even causes the positive spin density on the adjacent brid ging atom N1, different from the situation in 2.