N-SALICYLIDENEGLYCINATO COMPLEXES - A COMPARISON WITH PYRIDOXAL

The compositions and stabilities of the soluble ternary complexes formed between salicylaldehyde, glycinate and M(II) [where M(ll) = Mn(ll), Ni(ll), Cu(ll) and Zn(ll)] have been determined in aqueous solutions. Species of the type M(Sal)(Gly), M(Sal)(Gly)2 and M(Sal)2-(Gly)22 have been found. Cu(ll) forms only Cu(Sal)(Gly). The greatly enhanced stabilities of the complexes which contain salicylaldehyde anion and glycinate ion in equimolar ratios indicate that the ligands are condensed as Schiff bases. UV-spectral data further support this line of evidence. The n-salicylideneglycinato complexes arem ore stable than those of pyridoxal, the difference increasing in the order Ni ≤ Cu < Zn. This effect seems to arise from the different influences of the pyridine nitrogen on the Schiff base imine and phenolate groups combined with the differences in the metal ion coordination to these groups. © 1968, American Chemical Society. All rights reserved.