Thermochemical study of the stepwise protonation of 3-azaheptane-1,7-diamine and 4-azaoctane-1,8-diamine, and of complex formation between copper(II) and 3-azaheptane-1,7-diamine and 4,9-diazadodecane-1,12-diamine

Abstract

Calorimetric enthalpy data [at 25 °C and I= 0.1 mol dm^–3(NaCl)] are reported for stepwise protonation of the tribasic ligands 3-azaheptane-1,7-diamine (3NH-hd) and 4-azaoctane-1,8-diamine (4NH-od, spermidine) and for the formation of the copper complexes [CuL]²⁺, [Cu(HL)]³⁺, and [Cu(OH)L]⁺(L = 3NH-hd) and [CuL]²⁺ and [Cu(HL)]³⁺[L = the tetrabasic ligand 4,9-diazadodecane-1,12-diamine (4,9NH-ddd, spermine)]. By comparison with data for homologous linear triamines and tetra-amines, the relative importance of enthalpy and entropy terms in stabilising large chelate rings is assessed.