NOVEL NITROAROMATIC SENSORS FROM NAPHTHALENE BENZIMIDAZOLE

Abstract

New fluorescent compounds based on naphthalenebenzimidazole and pyrenes were designed and synthesized in via Suzuki-coupling. These compounds, which are different in the substitution positions of the pyrene unit, are fully characterized by NMR spectroscopy and MALDI-TOF mass spectrometry. For the photophysical properties, these compounds exhibit large Stokes shift (>100 nm) indicating significant geometry differences between ground and excited states. The maximum emission peaks are ranging between 580-585 nm with fluorescence quantum efficiencies (Φf) of 0.006-0.17. Most interestingly, these structurally related compounds show difference photophysical behaviors in aqueous/THF solution. The compound 3 exhibits simple aggregation and precipitation in high aqueous-content media. Meanwhile, the compounds 2 and 4, which show very low quantum yields in pure THF, exhibit interesting Aggregation-Induced Emission Enhancement (AIEE) when aqueous content is increased. These compounds also exhibit selective fluorescent quenching by photo-induced electron transfer mechanism towards trinitrotoluene (TNT) with high quenching efficiencies (Ksv = 96,300 and 60,000 M-1) and detection limits of 127 and 252 ppb, respectively.