Macrocyclic heterodinuclear NiMn and CuMn complexes: Crystal structure and electrochemical behaviour

Dinuclear Ni(II)Mn(II) and Cu(II)Mn(II) complexes of the general formula [MMn(L^m,n)](ClO₄)₂ ((L^2,3)^2-, (L^2,3)^2-, (L^2,4)^2-, (L^3,3)^2-; M = Ni, Cu) are obtained as solvates, using the dinucleating macrocycles (L^m,n)^2- (derived from the [2:1:1] condensation of 2,6-diformyl-4-methylphenol, NH₂(CH₂)_mNH₂ (m = 2-3) and NH₂(CH₂)_nNH₂ (n = 2-4). [NiMn(L^2,3)](ClO₄)₂·2DMF crystallizes in the orthorhombic space group Pbca with a = 22.186(4), b = 22.855(3), c = 13.951(2) Å, V = 7074(2) ų, and Z = 8. [NiMn(L^2,4)](ClO₄)₂·2DMF crystallizes in the monoclinic space group P2₁/n with a = 15.330(4), b = 11.739(3), c = 20.829(5) Å, β = 101.05(2)°, V = 3678(1) ų, and Z = 4. In both complexes the Ni(II) and Mn(II) ions are bridged by two endogenous phenolic oxygens of the macrocycle, with the Ni-Mn intermetallic separation of 3.145(2) Å for the former and 3.111(3) Å for the latter. In each complex the Ni(II) resides at the N₂O₂ site with the ethylene lateral chain and assumes a planar geometry. The Mn(II) at the N₂O₂ site with the trimethylene or tetramethylene lateral chain assumes a distorted six-coordinate geometry together with two DMF molecules. The M(II)Mn(II) (M = Ni, Cu) complexes are electrochemically converted to M(I)Mn(II) and M(II)Mn(III) complexes which are characterized by visible spectroscopy.