Carbon-13 nuclear magnetic resonance study of ternary complexes involving zinc(II) and triethylenetetramine

Abstract

The ¹³C n.m.r. spectra are reported as a function of pH for mixtures of triethylenetetramine (trien) and zinc nitrate with acetic acid, glycine (gly), L-alanine (ala), 1,2-diaminoethane (en), and 1,3-diaminopropane (pn) and for pn alone. The pH profiles for these rapidly-exchanging systems have been analysed by computer, and the chemical shifts of the methyl, methylene, and methine carbon atoms and the stability constants determined for the following species: [Zn(trien)(MeCO₂)]⁺, [Zn(trien)(gly)]²⁺, [Zn(trien)(ala)]²⁺, [Zn(trien)(Hen)]³⁺, [Zn(trien)(Hpn)]³⁺, [Zn(trien)(glyO)]⁺, [Zn(trien)(alaO)]⁺, [Zn(trien)(en)]²⁺, and [Zn(trien)(pn)]²⁺[glyO = glycinate(1–), alaO =L-alaninate(1–)]. The implications of the results as to the co-ordination geometry of zinc in these complexes and the extent of transmission of inductive effects through the metal are discussed.