Potentiometric, NMR, and fluorescence-emission studies on the binding of adenosine 5′-triphosphate (ATP) by open-chain polyamine receptors containing naphthylmethyl and/or anthrylmethyl groups

The interaction in aqueous solution of adenosine 5'-triphosphate (ATP) with a series of open-chain polyamines linked at one or both ends to anthrylmethyl or naphthylmethyl fragments was followed by potentiometric titration, H-1-, C-13-, and P-31-NMR spectroscopy, and by steady-state fluorescence measurements. The results revealed greater stabilities for the compounds containing one anthracene moiety than for those with one naphthalene moiety, the stabilities of the compounds with both ends N-substituted with naphthylmethyl groups being close to those containing just one anthrylmethyl unit. The H-1-NMR spectra showed that in all systems, there is involvement of pi-pi stacking interactions in the stabilization of the adduct species. The competitive effect of the anions afforded by the supporting electrolyte was checked in some of the studied systems working at two different ionic strenghts (0.15m and 1.0m NaCl). The joint analysis of the spectrofluorimetric titrations and pH-metric species-distribution curves showed that for all the ATP-receptor systems, a quenching of the fluorescence occurred upon protonation of the adenine N(1)atom. Steady-state fluorescence and time-correlated single-photon-counting analysis of a system made up of ATP and a bischromophoric polyamine receptor containing anthracene and naphthalene fluorophores established that the energy-transfer process between the naphthalene and anthracene moieties is still operative despite the presence of ATP.