824426-12-2Relevant academic research and scientific papers
Cyclic and acyclic compartmental Schiff bases, their reduced analogues and related mononuclear and heterodinuclear complexes
Casellato,Tamburini,Tomasin,Vigato
, p. 4191 - 4207 (2004)
[1+1] macrocyclic and [1+2] macroacyclic compartmental ligands (H 2L), containing one N2O2, N3O 2, N2O3, N4O2 or O 2N2O2 Schiff base site and one O 2On (n=3, 4) crown-ether like site, have been prepared by self-condensation of the appropriate formyl- and amine precursors. The template procedure in the presence of sodium ion afforded Na2(L) or Na(HL)·nH2O. When reacted with the appropriate transition metal acetate hydrate, H2L form M(L)·nH2O, M(HL)(CH3COO)·nH2O, M(H2L)(X) 2·nH2O (M=Cu2+, Co2+, Ni 2+; X=CH3COO-, Cl-) or Mn(L)(CH 3COO)·nH2O according to the experimental conditions used. The same complexes have been prepared by condensation of the appropriate precursors in the presence of the desired metal ion. The Schiff bases H 2L have been reduced by NaBH4 to the related polyamine derivatives H2R, which form, when reacted with the appropriate metal ions, M(H2R)(X)2 (M= Co2+, Ni2+; X=CH3COO-, Cl-), Cu(R)·nH2O and Mn(R)(CH3COO)·nH2O. The prepared ligands and related complexes have been characterized by IR, NMR and mass spectrometry. The [1+1] cyclic nature of the macrocyclic polyamine systems and the site occupancy of sodium ion have been ascertained, at least for the sodium (I) complex with the macrocyclic ligand containing one N3O2 Schiff base and one O2O3 crown-ether like coordination chamber, by an X-ray structural determination. In this complex the asymmetric unit consists of one cyclic molecule of the ligand coordinated to a sodium ion by the five oxygen atoms of the ligand. The coordination geometry of the sodium ion can be described as a pentagonal pyramid with the metal ion occupying the vertex. In the mononuclear complexes with H2L or H2R the transition metal ion invariantly occupies the Schiff base site; the sodium ion, on the contrary, prefers the crown-ether like site. Accordingly, the heterodinuclear complexes [MNa(L)(CH3COO)x] (M=Cu2+, Co 2+, Ni2, x=1; M=Mn3+, x=2) have been synthesised by reacting the appropriate formyl and amine precursors in the presence of M(CH3COO)n·nH2O and NaOH in a 1:1:1:2 molar ratio. The reaction of the mononuclear transition metal complexes with Na(CH3COO)·nH2O gives rise to the same heterodinuclear complexes. Similarly [MNa(R)(CH3COO) x] have been prepared by reaction of the appropriate polyamine ligand H2R with the desired metal acetate hydrate and NaOH in 1:1:2 molar ratio.
