Mononuclear, homo- and heteropolynuclear complexes with acyclic compartmental Schiff bases

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Acyclic compartmental Schiff bases (H 4L) have been synthesized by condensation of 2, 3-dihydroxybenzaldehyde with the diamines NH 2RNH 2 (R- (CH 2) 2, H 4L A; C(CH 3) 2CH 2, H 4L B; CH 2C(CH 3) 2CH 2, H 4L C; C 6H 4, H 4L 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 N 2O 2 compartment, while uranyl(VI) or lanthanium(III) occupy the outer O 2O 2 site of the ligands. Crystals of Ni(H 2L C), grown from a methanol/diethyl ether solution are triclinic, space group P 1 with a=11.040(5), b=13.645(5), c=14.877(6) Å; α=71.93(4), β=84.62(5), γ=66.56(5)° 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 O 2O 2 outer site. The coordination around nickel ions, placed in the N 2O 2 sites, is not strictly planar, all atoms being tetrahedrally displaced from the mean coordination planes by about 0.047 and 0.093 Å (mean) for the two molecules A and B, respectively. The metal ion is displaced by 0.026 and 0.015 Å from the same planes. The average bond lengths for NiO and NiN are 1.84 Å. In the heteropolynuclear complexes MLn(H 2L)(X) 3, [MLn(L)(NO 3)(S)] 2 and MUO 2(L)(S), (MCu 2+, Ni 2+; LnLa, Gd; SH 2O, MeOH, dmso), obtained by a step by step procedure, the smaller d ion always occupies the inner N 2O 2 chamber, while the larger f ion occupies the outer O 2O 2 chamber. The ligands and the complexes have been characterized by IR, 1H and 13C 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(H 2L A)(NO 3) 3 and [CuGd(L A)(NO 3)(H 2O)] 2, respectively.