Zinc(II) complexes of 4,7-diazadecane-1,10-diamine, 4,8-diazaundecane-1,11-diamine, and tetraethylenepentamine: a carbon-13 nuclear magnetic resonance study

Abstract

Carbon- 13 n.m.r. spectra are reported as a function of pH for mixtures of zinc and 4,7-diazadecane-1,10 diamine (dad), 4,8-diazaundecane-1,11-diamine (daud), or tetraethylenepentamine (tetren), of zinc and dadd or daud with 1,2-diaminoethane (en), 1,3-diamionpropane (pn), or glycine (gly), and of zinc and tetren with en or pn; supporting data have also been obtained from potentiometric titrations. The pH profiles have been analysed and chemical shifts determined for the following species: [Zn(dadd)]²⁺, [Zn(dadd)(en)]²⁺, [Zn(dadd)(glyO)]⁺, [Zn(daud)]²⁺, [Zn(daud)(OH)]⁺, [Zn(daud)(en)]²⁺, [Zn(daud)(pn)]²⁺, [Zn(daud)(glyO)]⁺, and [Zn(tetren)]²⁺. Stability constants have been determined for the ternary complexes. The results support the proposals that [Zn(dadd)]²⁺ and [Zn(daud)]²⁺ contain ionizable water but [Zn(tetren)]²⁺ does not.