Quantum-chemical modeling of exchange coupling in the magnetic sublattice of bifunctional compounds containing heterometallic complexes of 3d and 4d metals with oxalate and dithiooxamide ligands

To find components of the magnetic sub-lattice of bi-functional compounds with maximum ferromagnetic exchange coupling, quantum-chemical calculations of complexes [(L)(2)M1(III)(L)M2(II)(L)(2)](5-) are performed (M1(III) and M2(II) are tri- and divalent atoms of 3d and 4d transition metals M1(III) (Cr, Mo) and M2(II) (Ni, Co, Tc, Ru, Rh, Pd), L is dithiooxamide or oxalate). Calculations of the geometric structure of the complex are performed at the B3LYP/LANL2DZ level and calculations of J constants are performed at the B3LYP/TZV level. The replacement of a divalent atom of 3d metal by a divalent atom of 4d metal leads to an increase of J, whereas the replacement of a trivalent atom of 3d metal by a trivalent atom of 4d metal does not change the value of J. It is concluded that there is a correlation of J with a total change in the spin density on the M1(III) and M2(II) metals in the complexes compared to the M1(3+) and M2(2+) isolated cations.