Spectroscopic and photophysical studies of a naphthalene-based emissive probe for metal cations

Abstract

A comprehensive photophysical characterization of a bis-naphthalene derivative, L, was carried out in acetonitrile, using UV–Vis absorption, steady-state and time-resolved emission spectroscopy. It was found that in the 250–400 nm region, the absorption spectra showed two bands with maxima at ~ 220 nm and ~ 292 nm whereas the emission spectrum showed a band settled between 300 and 550 nm. A detailed time-resolved investigation (in the ps and ns time domain) showed that the fluorescence decay of L in dichloromethane was bi-exponential indicative of the presence of a ground-state equilibrium involving two species: monomeric (absorption of a single naphthalene unit) and dimeric. Upon addition of Cu2 +, Zn2 +, Cd2 + or Hg2 + metal cations in acetonitrile a quenching of the fluorescence emission was observed. From time-resolved data, it is shown that the fluorescence contribution of the species with the longest decay time was sensitive to the explored metal ions.