Complex formation between 4,9-diazadodecane-1,12-diamine (spermine) and copper(II) ions and protons in aqueous solution

Abstract

Equilibrium constants are reported for protonation of the linear tetra-amine 4,9-diazadodecane-1,12-diamine (4,9NH-ddd) and for formation of the complexes [CuL]²⁺ and [Cu(HL)]³⁺(L = 4,9NH-ddd) at I= 0·1M-NaCl and 25 °C. The bis(propane-1,3-diamine) complex, [Cu(prd)₂]²⁺, and that formed by the title ligand are of similar stability; in this respect 4,9NH-ddd contrasts with the lower members of the homologous series of tetra-amines (3,6-diazaoctane-1,8-diamine and 3,7-diazanonane-1,9-diamine with respect to ethylenediamine, and 4,7-diazadecane-1,10-diamine and 4,8-diazaundecane-1,11-diamine with respect to prd) and displays a much reduced ‘chelate effect.’