N-aryl-4-amino-1,8-naphthalimide Tröger's bases-based internal charge transfer (ICT) fluorescence ‘turn-on’ chemosensors for volatile organic amines

Abstract

The design of reliable sensor systems for quick sensing and monitoring the trace concentrations of volatile organic compounds (VOCs) has been a topical area of research in recent years due to their serious menace to living systems and environmental hazardousness. In this article, we report two unique ‘cleft-shaped’ N-aryl-4-amino-1,8-naphthalimide derived Tröger's bases (TBNap-Ph and TBNap-Es) as efficient, fast fluorescence sensors for discriminative sensing of volatile organic amines (VOAs). The fluorescence titration studies using TBNap-Ph and TBNap-Es demonstrated discriminative fluorescence sensing responses for VOAs with high selectivity for benzylamine detection. The initial emission intensity of TBNap-Ph and TBNap-Es was enhanced drastically upon the addition of benzylamine. However, similar titration studies using other VOAs such as n-propylamine, n-butylamine, diethylamine, isopropylamine, 3-dimethylamino-1-propylamine, triethylamine, and ethanolamine elicited poor to negligible changes in the fluorescence emission intensity. The selective ‘turn-on’ fluorescence sensing of benzylamine was also reflected by sharp color changes and these sensors can be used to detect benzylamine at the parts-per-millions (ppm) level of sensitivity. Furthermore, the experimentally observed discriminative fluorescence sensing property of TBNap-Ph and TBNap-Es towards VOAs was supported by computational calculations.