title: Formation and stability of pyrophosphate complexes with aliphatic amines in aqueous solution.
abstract: The complex formation between pyrophosphate (P(2)O(7)(4-)) and protonated methylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine, has been studied potentiometrically, in aqueous solution, at 25 degrees C. It was found that the species ALH(q)(A = amine, L = P(2)O(7)(4-)) are formed with q = 1 ... n(n = 3, 5, 6, 7, 7 and 8 for the above amines respectively). Mono- and di-amines form species A(p)LH(q) too. The stability of these species is quite high [e.g. H(4)A(4+) + HL(3-)ALH(5)(+): log K = 8.1 (A = pentaethylenehexamine)] and depends strictly on the charges involved in the formation reaction. Charges of reactants being equal, the stability trend is penten > tetren > trien > dien > en > meta and cationic mixed species are more stable than anionic ones. These results are discussed in relation to speciation problems in natural and biological fluids.
authors.affiliation: Dpt. Chimica Inorganica, Analitica e Struttura Molecolare dell'Università, Salita Sperone 31, Villa S. Agata, Messina, Italy
authors.forename: C
authors.initials: C
authors.lastname: De Stefano
authors.forename: C
authors.initials: C
authors.lastname: Foti
authors.forename: O
authors.initials: O
authors.lastname: Giuffrè
authors.forename: S
authors.initials: S
authors.lastname: Sammartano