A new fluorescent “turn-on” chemodosimeter for cyanide based on dual reversible and irreversible deprotonation of NH and CH groups

Abstract

A new fluorescent ''turn-on'' cyanide chemodosimeter 5 was developed for the first time based on the irreversible deprotonation/oxidation of the CH group followed by the reversible deprotonation of the NH group, with high selectivity and dramatic red-shifted absorption (E263 nm). The photoinduced electron transfer (PET) is prevented by the irreversible process, which results in coplanar geometry between indole and naphthalimide causing enhancement of fluorescence. Fig. 1 Promoted strategy for sensing anions.

Benzoquinone–imidazole hybrids as selective colorimetric sensors for cyanide in aqueous, solid and gas phases

“…Here again majority of the receptors can tolerate only <75% of water in the medium. 35,39,40,57,58 But in the present case the receptors developed sense CN À ion in a medium containing 90% water. The most interesting result of the present investigation is that one of the receptor R5 selectively senses CN À ions colorimetrically in solid, aqueous and gas phases i.e.…”

“…The test strips were utilized to sense CNions of different concentrations in water. 35,39,40,57,58 But in the present case the receptors developed sense CNion in a medium containing 90% water. Development of such test strips approach is extremely attractive for 'in-the field' qualitative identification of toxic CNions as it doesn't require any additional equipment.…”

“…40 Here again, in the case of receptors having urea (III), thiourea (IV) and guanidine (V) as H-bond donor moieties, as the two N-H groups are close to each other, they can make H-bonds with anions like acetate and phosphate in a bidentate manner leading to lack of selectivity. 40 Here again, in the case of receptors having urea (III), thiourea (IV) and guanidine (V) as H-bond donor moieties, as the two N-H groups are close to each other, they can make H-bonds with anions like acetate and phosphate in a bidentate manner leading to lack of selectivity.…”

“…Also, in the case of receptors that works via the formation of H-bond with the anions, compared to the single H-bond donor moiety (like N-H), the receptors with multiple H-bond donor moieties can both signicantly increase the anion affinity and allow the receptors to tolerate a substantial amount of water from the solvent. 40 Here again, in the case of receptors having urea (III), thiourea (IV) and guanidine (V) as H-bond donor moieties, as the two N-H groups are close to each other, they can make H-bonds with anions like acetate and phosphate in a bidentate manner leading to lack of selectivity.…”

A highly selective colorimetric and “turn-on” fluorimetric chemosensor for detecting CN − based on unsymmetrical azine derivatives in aqueous media

“…Chemosensor S1 could form a fine conjugate structure with azine moiety, as a result, the chemosensor has an excellent optical property to achieve nakedeye colorimetric and fluorimetric recognition. Meanwhile, salicylicaldehyde hydrazone provided an active hydrogen atom, which easily combined with strong alkaline ion CN − and allowed the receptors to tolerate a substantial amount of water from the solvent [20]. When CN − was added to the sensor solution, solution color changes from colorless to yellow and shows strong yellow fluorescence.…”