MONONUCLEAR, HOMOPOLYNUCLEAR AND HETEROPOLYNUCLEAR COMPLEXES WITH ACYCLIC COMPARTMENTAL SCHIFF-BASES

Acyclic compartmental Schiff bases (H4L) have been synthesized by condensation of 2,3-dihydroxybenzaldehyde with the diamines NH2-R-NH2 (R = - (CH2)2-, H4L(A); -C(CH3)2-CH2-, H4L(B); -CH2-C(CH3)2-CH2-, H4L(C); -C6H4-, H4L(D)). Mononuclear complexes have been obtained by reaction of these hexadentate ligands with the appropriate metal(II) ions (copper(II), nickel(II), uranyl(VI) or lanthanium(III)) or by template procedure. The d metal ions coordinate into the inner N2O2 Compartment, while uranyl(VI) or lanthanium(III) occupy the outer O2O2 site of the ligands. Crystals of Ni(H2L(C)), grown from a methanol/diethyl ether solution are triclinic, space group P1BAR with a = 11.040(5), b = 13.645(5), c = 14.877(6) angstrom; alpha = 71.93(4), beta = 84.62(5), gamma = 66.56(5)-degrees for Z = 2. The two chemically identical molecules of the nickel complex, present in the asymmetric portion of the cell, contain a methanol or a water molecule, respectively, linked by hydrogen bonds in the O2O2 outer site. The coordination around nickel ions, placed in the N2O2 sites, is not strictly planar, all atoms being tetrahedrally displaced from the mean coordination planes by about 0.047 and 0.093 angstrom (mean) for the two molecules A and B, respectively. The metal ion is displaced by 0.026 and 0.015 angstrom from the same planes. The average bond lengths for Ni-O and Ni-N are 1.84 angstrom. In the heteropolynuclear complexes MLn(H2L)(X)3, [MLn(L)(NO3)(S)]2 and MUO2(L)(S), (M = Cu2+, Ni2+; Ln = La, Gd; S = H2O, MeOH, dmso), obtained by a step by step procedure, the smaller d ion always occupies the inner N2O2 chamber, while the larger f ion occupies the outer O2O2 chamber. The ligands and the complexes have been characterized by IR, H-1 and C-13 NMR, X-ray, mass spectrometric and magnetic susceptibility studies. The temperature dependence of the magnetic susceptibility of heterodinuclear and heterotetranuclear complexes containing copper(II) and gadolinium(III) ions, in the temperature range 4.2-300 K, shows a ferromagnetic-interaction between the d and f metal ions (J(CuGd) = 1.59(3) and -3.76(4) cm-1 for CuGd(H2LA)(NO3)3 and [CuGd(LA)(NO3)(H2O)]2, respectively.