Cyclic and acyclic compartmental Schiff bases, their reduced analogues and related mononuclear and heterodinuclear complexes

Abstract

[1+1] macrocyclic and [1+2] macroacyclic compartmental ligands (H 2L), containing one N 2O 2, N 3O 2, N 2O 3, N 4O 2 or O 2N 2O 2 Schiff base site and one O 2O n ( 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 Na 2(L) or Na(HL) · nH 2O. When reacted with the appropriate transition metal acetate hydrate, H 2L form M(L) · nH 2O, M(HL)(CH 3COO) · nH 2O, M(H 2L)(X) 2 · nH 2O (M=Cu 2+, Co 2+, Ni 2+; X=CH 3COO −, Cl −) or Mn(L)(CH 3COO) · nH 2O 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 NaBH 4 to the related polyamine derivatives H 2R, which form, when reacted with the appropriate metal ions, M(H 2R)(X) 2 (M= Co 2+, Ni 2+; X=CH 3COO −, Cl −), Cu(R) · nH 2O and Mn(R)(CH 3COO) · nH 2O. 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 N 3O 2 Schiff base and one O 2O 3 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 H 2L or H 2R 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)(CH 3COO) x ] (M=Cu 2+, Co 2+, Ni 2, x=1; M=Mn 3+, x=2) have been synthesised by reacting the appropriate formyl and amine precursors in the presence of M(CH 3COO) n · nH 2O and NaOH in a 1:1:1:2 molar ratio. The reaction of the mononuclear transition metal complexes with Na(CH 3COO) · nH 2O gives rise to the same heterodinuclear complexes. Similarly [MNa(R)(CH 3COO) x ] have been prepared by reaction of the appropriate polyamine ligand H 2R with the desired metal acetate hydrate and NaOH in 1:1:2 molar ratio.