Journal of Photochemistry & Photobiology, A: Chemistry 406 (2021) 113021 Available online 2 November 2020 1010-6030/© 2020 Elsevier B.V. All rights reserved. A simple imine as a dual-channel chemosensor for detection of CN  and HS  ions via different mechanisms in organic and aquo-organic media G. Mahalakshmi , P. Saravana Kumar , G. Sivaraman , M. Seenivasa Perumal , Kuppanagounder P. Elango * Department of Chemistry, Gandhigram Rural Institute (Deemed to be University), Gandhigram 624302, India A R T I C L E INFO Keywords: Chemosensor Cyanide Hydrogen sulfde Nucleophilic addition Imine ABSTRACT An imine based easy to make receptor (R) has been synthesized and characterized, which senses CN ¡ and HS ¡ ions selectively and sensitively in neat DMSO and H 2 O:DMSO (60:40 v/v) media. Upon treatment with these ions, the receptor exhibited instantaneous colour change from yellow to colourless and a fuorescence enhancement and these optical changes are easily detected by direct visualization. Further, other competitive anions didn’t display any observable colour and fuorescence changes, indicating the receptor’s high selectivity towards CN  and HS  ions. The nucleophilic addition of cyanide ion to the imine bond induces an increase in fuorescence, while HS  ion triggered cleavage of the imine bond, producing enhancement in fuorescence in both the media. The limits of detection for CN  and HS  ions were calculated to be 0.9 and 0.7 μM, respectively, which are lower than the permissible limit of these ions in drinking water set by the World Health Organization (WHO). The receptor has fruitfully been applied for the detection of these ions in live HeLa cells. 1. Introduction Over the last three decades, signifcant attention has been paid to developing small molecule anion sensors. This is because anions play essential roles in biology, environment and industrial processes. A re- view of the literature revealed that three main approaches such as binding site-signaling approach, displacement approach and reaction- based approach have widely been used to detect anions in environ- mental and biological samples [1–5]. In these entire strategies, imine moiety was found to be one of the major functional groups tested to a large extent. This may be because it can be synthesized easily and can serve as a reaction centre for anions and H-bonding sites for anions. It is well-known that cyanide ion can bind to cytochrome oxidase’s active site and inhibit cellular respiration and thus leads to deadly ef- fects on human beings [6,7]. Despite its lethal toxicity, several industries like metal plating, herbicidal, textile, dye, mining, leather industries use cyanide to a greater extent [8–16]. The World Health Organization (WHO) has recommended the permissible limit of cyanide ion in drinking water to be 1.9 μM. Likewise, hydrogen sulfde molecule plays an essential role in many physiological processes and any disorder of this messenger molecule in vivo can lead to many diseases. Therefore, it is recognized as the third important gasotransmitter after NO and CO molecules [17–19]. Thus, it is highly desirable to develop effective methods for detecting these two anions in environmental and biological samples. A review of the literature revealed that the sensing of cyanide and hydrogen sulfde ions by chemosensors occurs via various mechanisms. Over the years, optical sensors for cyanide ion detection have been studied actively. Generally, three different approaches viz. chemosensor bearing a signaling subunit/binding site, displacement approach and chemodosimeter, have been employed to design optical sensors for cy- anide ions. Chemodosimeter approach relies on specifc and often irre- versible chemical reactions between the probe and cyanide ions, leading to colour and/or fuorescence changes [20]. Recently Li et al. [21] have made a comprehensive review of chromogenic and fuorogenic chemo- sensors for hydrogen sulfde and their detection mechanisms. According to their detection mechanisms, the receptors were classifed into several types, such as H-bonding and reaction-based receptors. The reaction-based mechanisms of detection of hydrogen sulfde ion re- ported so far include cleavage of R–O and S–O bonds, reduction of azide and nitro groups, double addition reaction and copper complex replacement. In all these cases the reactions are complemented with colour and/or fuorescence changes, making the visual detection of the analyte easier. * Corresponding author. E-mail address: drkpelango@rediffmail.com (K.P. Elango). Contents lists available at ScienceDirect Journal of Photochemistry & Photobiology, A: Chemistry journal homepage: www.elsevier.com/locate/jphotochem https://doi.org/10.1016/j.jphotochem.2020.113021 Received 18 August 2020; Received in revised form 9 October 2020; Accepted 29 October 2020