Design and one-pot synthesis of a novel pyrene based fluorescent sensor for selective turn on, naked eye detection of Ni2+ ions, and live cell imaging

A novel pyrene based fluorescent probe, 4-phenyl-2-(pyren-l-y1)-1,8-naphthyridine (Pyr-1), was designed and synthesized through tandem cyclization of pyrenealdehyde, amine and alkyne in the presence of quinolinium modified beta-CD (Qun-beta-CD) in water. Pyr-1 was characterized by H-1 NMR, C-13 NMR and ESI-MS spectra and was used as a selective turn-on and naked eye sensor for Ni2+ ion over other cations. The localized frontier molecular orbitals (DFT studies) and the solvent polarity dependent photoluminescence characteristics strongly validate the presence of photo induced electron transfer from pyrene to 1,8-naphthyridine unit in Pyr-1. Upon Ni2+ addition, the fluorescence was shifted to 450 nm due to the formation of a square planar 2:1 complex of pyr-1 with Ni2+ at room temperature even in the presence of other interfering ions such as Cd2+ and Hg2+. The resultant excimer emission and conquest of photoinduced electron transfer (PET) from pyrene moiety to the 1,8-naphthyridine part is supported by DFT studies. The sensor also exhibited very low cytotoxicity and strong fluorescence emission in living cells, indicating its potential applicability as a novel chemosensor for selective detection of Ni2+ ions in biological environment also. (C) 2018 Elsevier B.V. All rights reserved.