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

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 similar to 220 nm and similar to 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. (C) 2014 Elsevier B.V. All rights reserved.