Detection of Metal Ions and Protons with a New Blue Fluorescent Bis(1,8-Naphthalimide)

The synthesis of a new blue fluorescent bis(1,8-naphthalimide) has been described and its basic photophysical characteristics have been investigated in organic solvents of different polarity. The detection of protons and different metal cations (Ag+, Cu2+, Co2+, Ni2+, Fe3+ and Zn2+) with the new compound has been investigated by the use fluorescence spectroscopy. 1. Introduction Metal ions pollution in the environment has received significant attention because of its toxicity and adverse biological effects. In this respect, environmental monitoring is important to ensure ecosystem health and humanity. Of particular interest are the optical fluorosensors, which are molecular devices able to detect the presence of environmental pollutants via the changes in their fluorescence intensity [1, 2]. In this sense, sensors are of great importance to chemistry, biology, and medicine because they allow rapid detection of different compounds in the living organisms and environment. Most of the known fluorescent sensors are based on the photoinduced electron transfer (PET) [3, 4]. The fluorescent PET sensors are of great interest because of their various applications. Under appropriated conditions, the fluorophore emission is quenched by the distal amino group by means of electron transfer from the substituent to the fluorophore ring. If the PET process is “switched off” by, for example, protonation of the amino group or complexation with metal ions, the emission of the fluorophores is restored. Due to their excellent photophysical properties, 1,8-napthalimide derivatives are unsurpassed as a signal fragment in the design of fluorescent chemosensors [5–10]. Various other mechanisms and fluorophores are used in the design of molecular devices with sensory properties [11–14]. In this work, the study is focused on the synthesis and photophysical investigation of a blue fluorescent compound (Bis2) having N,N-dimethylaminoethyl group in C-4 position at the 1,8-naphthalimide structure as a receptor for metal ions and protons. The functional properties of Bis2 have been investigated in organic solvents of different polarity. Its photophysical and supramolecular properties have been also studied in the presence of some metal cations. 2. Experimental 2.1. Materials and Methods UV-Vis spectrophotometric investigations were performed using “Thermo Spectronic Unicam UV 500” spectrophotometer. Emission spectra were taken on a “Cary Eclipse” spectrofluorometer. All spectra were recorded using 1？cm pathlength synthetic quartz glass cells (Hellma, Germany). All organic solvents