Heterodinuclear MIICuII complexes of a constrained macrocyclic compartmental ligand.: EPR studies of spin-coupled MnIICuII (ST=2) and NiIICuII (ST=1/2)

A phenol-based macrocyclic compartmental ligand (L)(2-), having an N(amine)(2)O-2 metal-binding site with 1,3-trimethylene chain between the two aminic nitrogen atoms and an N(imine)(2)O-2 site with 1,8-naphthalene chain between the two iminic nitrogen atoms, has afforded the following heterodinuclear (MCuII)-Cu-II complexes, [MCu(L)(dmf)(2)](ClO4)(2) (M = Mn (1), Co (2), Ni (3), Zn (4)). X-ray crystallographic studies for 1-4 demonstrate that the M-II resides in the N(amine)(2)O-2 site and the Cu-II in the N(imine)(2)O-2 site of the constrained macrocyclic ligand. The M-II has a six-coordinate geometry together with two dmf molecules at the axial site and the Cull has a square-pyramidal geometry with a perchlorate oxygen atom at the apical site. Magnetic, visible spectral and electrochemical properties of the complexes are examined. A frozen dmf solution of 1 at liquid nitrogen temperature shows an EPR signal with a Mn hyperfine structure (A(Mn) = 103 x 10(-4) cm(-1)) at similar to 2400 Ga, which is attributed to the S-T = 2 ground state of the spin-coupled Mn-II (S = 5/2)-Cu-II (S = 1/2). A qualitative analysis is made for the EPR of I in comparison with the EPR of the S-T = 1/2 state of spin-coupled Ni-II (S = 1)-Cu-II (S = 1/2) of 3. (C) 2002 Elsevier Science B.V. All rights reserved.