FUNCTIONALIZED ACYCLIC SCHIFF-BASES AND RELATED COMPLEXES WITH D-METAL AND F-METAL IONS

The condensation reaction in acetonitrile of 2,6-diformyl-4-chlorophen ol with tris-(2-aminoethyl)amine forms the [3 + 1] macroacyclic Schiff base H-3-I which reacts with LnCl(3) . nH(2)O (Ln = La3+, Dy3+, Gd3+) in the presence of NEt3 giving rise to Ln(I). nS (S = H2O, dmf, CH3CN ; n = 0-1.5). Crystals of La(I) (dmf), grown from a dimethylformamide/ acetonitrile solution, are monoclinic, space group P2(1)/c with a = 12 .590(4), b = 14.277(5), c = 19.710(5) Angstrom, beta = 95.45 degrees a nd Z = 2. This complex is a dimeric entity and shows an inversion cent er in between the two lanthanum(III) ions. The organic ligand coordina tes to one lanthanum ion through the four nitrogen and the three pheno xide oxygen atoms while it links the second lanthanum ion through one aldehydic oxygen atom; the other two aldehydic oxygens are not involve d in the coordination and do not form significative interactions with neighboring molecules. Thus each dinuclear complex behaves as an isola ted entity. The nonacoordination around each metal ion is reached thro ugh the additional coordination of the oxygen atom of a dimethylformam ide molecule. The three La-N (iminic) bond distances fall between 2.70 and 2.79 Angstrom, while the La-N (aminic) bond is longer (2.86 Angst rom). Similarly the La-O (phenolic) bonds distances are in the range 2 .41-2.47 Angstrom, considerably shorter than the La-O (aldehydic) whic h is 2.72 Angstrom, while the La-O (dimethylformamide) is 2.55 Angstro m. Finally the two lanthanum atoms are 8.24 Angstrom apart. 2,6-Diform yl-4-chlorophenol reacts in CH3CN with H2N-R-NH2 to give the [2 + 1] a cyclic Schiff bases H-2-II. The corresponding complexes containing a d (nickel(II) Ni(II), or manganese(III) Mn(II)(OH), an f (lanthanum(III ), gadolinium(III), dysprosium(III)) Ln(H-2-II)(NO3)(3) or the uranyl( VI) ion, UO2(II)(MeOH), UO2(H-II)(NO3) and UO2(H-2-II)(NO3)(2) have al so been prepared by reaction of these ligands with the appropriate met al salts or by template procedure, the different content of the nitrat e in the uranyl(VI) complexes depending on the amount of base used. Th ese complexes may be converted into the acetal analogues in alcoholic solution. Similarly the condensation of 3-methoxy-2-hydroxybenzaldehyd e or 3-ethoxy-2-hydroxybenzaldehyde with tris-(2-aminoethyl)amine in a 1:3 molar ratio afforded the [3 + 1] Schiff bases H-3-IV and H-3-V wh ich react with lanthanide(III) salt to give rise, respectively, in the presence or in the absence of the appropriate amount of base, to Ln(I V). nH(2)O and Ln(V). nH(2)O and Ln(H-3-IV)(X)(3) . nH(2)O or Ln(H-3-V )(X)(3) . nH(2)O (Ln = La3+, Gd3+; X = Cl-, NO36-; n = 1-5). These com plexes are no longer stable in solution and hydrolyzed especially when redissolved in alcohol. H-3-I, H-2-II and/or the related complexes ha ve been engaged in further condensation reactions with 2-aminomethyl-1 2-crown-4 or 2-aminomethyl-15-crown-5 to give rise to the functionaliz ed Schiff bases (H-3-III and H-2-VII) and related d- or f-complexes. M oreover the functionalized ligands H-3-VI, H-2-VIII, H-2-X and H-2-XI and/or the related d- or f-complexes have been synthesized by condensa tion of the appropriate formyl and amine precursors. The ligands and t he complexes have been characterized by physico-chemical measurements, especially by IR and NMR spectroscopy, SEM and EDX investigation, and FAB mass spectrometry. (C) 1998 Elsevier Science S.A. All rights rese rved.