Cu2+ and AMP complexation of enlarged tripodal polyamines

Abstract

The synthesis, characterization, Cu²⁺ coordination and interaction with AMP of three tripodal polyamines are reported. The polyamines are based on the structure of the tetraamine (tren) which has been enlarged with three propylamino functionalities (TAL), with a further anthrylmethyl fragment at one of its terminal primary nitrogens (ATAL) or with naphthylmethyl fragments at its three ends (N3TAL). The protonation constants of all three polyamines show that at pH 6, all six primary and secondary nitrogen atoms in the arms are protonated. The interaction with Cu²⁺ and AMP (adenosine-5′-monophosphate) has been studied by potentiometric, UV-Vis, ESI-MS spectroscopy and NMR techniques. pH-Metric, NMR and ESI/MS techniques indicate that TAL and ATAL form with AMP adducts of 1 : 1, 2 : 1 and 3 : 1 AMP : L stoichiometries in water. This is one of the first examples for the formation of such complexes in aqueous solution. Formation of ternary complexes between TAL, ATAL, N3TAL, Cu²⁺ and AMP is observed. Paramagnetic NMR techniques have been used to obtain structural information on the binding mode of AMP to the Cu²⁺–TAL binuclear complexes.