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Review
. 2021 Oct 21;11(54):34206-34234.
doi: 10.1039/d1ra06567j. eCollection 2021 Oct 18.

Chemosensors based on N-heterocyclic dyes: advances in sensing highly toxic ions such as CN- and Hg2

María-Camila Ríos  1 , Néstor-Fabián Bravo  1 , Christian-Camilo Sánchez  1 , Jaime Portilla  1
Affiliations
Review

Chemosensors based on N-heterocyclic dyes: advances in sensing highly toxic ions such as CN- and Hg2

María-Camila Ríos et al. RSC Adv. .

Abstract

CN- and Hg2+ ions are harmful to both the environment and human health, even at trace levels. Thus, alternative methods for their detection and quantification are highly desirable given that the traditional monitoring systems are expensive and require qualified personnel. Optical chemosensors (probes) have revolutionized the sensing of different species due to their high specificity and sensitivity, corresponding with their modular design. They have also been used in aqueous media and different pH ranges, facilitating their applications in various samples. The design of molecular probes is based on organic dyes, where the key species are N-heterocyclic compounds (NHCs) due to their proven photophysical properties, biocompatibility, and synthetic versatility, which favor diverse applications. Accordingly, this review aims to provide an overview of the reports from 2016 to 2021, in which fluorescent probes based on five- and six-membered N-heterocycles are used for the detection of CN- and Hg2+ ions.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Fig. 1
Fig. 1. Structure of (a) five- and six-membered N-heterocycles and (b) some representative examples.
Fig. 2
Fig. 2. Probes based on thiazoles for CN− sensing in (a) DMSO : H2O and (b) in HEPES solution (1% MeCN as a co-solvent), and (c) for Hg2+ recognition.
Fig. 3
Fig. 3. Structure of (a) ligand IPr 7 and (b) Cu(i) complex 8.
Fig. 4
Fig. 4. (a) Jablonski diagram and (b) photophysical process.
Fig. 5
Fig. 5. Structures of the hybrid system 9, hydrazone 10, and pyrazoline 11.
Fig. 6
Fig. 6. Conventional configuration and optical response of a chemosensor.
Fig. 7
Fig. 7. Probes for CN− sensing. (a) Type I, (b) Type II, and (c) Type III.
Fig. 8
Fig. 8. (a) Probes based on (a) pyrrole units 12 and (b) DPP unit 13.
Fig. 9
Fig. 9. Probes based on indoles with (a) thiazolium salt 14/15, (b) pyridinium salt 16/17, and (c) spirochromene moiety 18.
Fig. 10
Fig. 10. Probes based on carbazoles bearing (a) benzothiazole 19 and (b) barbituric acid 20 moieties.
Fig. 11
Fig. 11. BODIPY derivates (a) 21, (b) 22 and (c) 23 for cyanide sensing.
Fig. 12
Fig. 12. Probes based on functionalized pyrazoles (a) 24, (b) 25 and (c) 26.
Fig. 13
Fig. 13. Probes having fused pyrazoles (a) 27, (b) 28, (c) 29/30, and (d) 31.
Fig. 14
Fig. 14. Probes based on fused NH-imidazoles (a) 32, (b) 33, and (c) 34.
Fig. 15
Fig. 15. Chemosensors bearing fused imidazoles (a) 35, (b) 36, and (c) 37.
Fig. 16
Fig. 16. Probes having a pyridine ring (a) 38–41, (b) 42, (c) 43, and (d) 44.
Fig. 17
Fig. 17. Probes for cyanide based on quinoline derivates (a) 45 and (b) 46.
Fig. 18
Fig. 18. Tautomers of pyridin-2-ol 47/48 and isoquiolin-1-ol 49/50.
Fig. 19
Fig. 19. Probes based on fused pyridines (a) 51, (b) 52, and (c) 53.
Fig. 20
Fig. 20. Probes for sensing CN− based on coordination compounds bearing (a) ruthenium, (b) copper, and (c) iridium.
Fig. 21
Fig. 21. Probes for CN− based on iridium complexes (a) 58 and (b) 59.
Fig. 22
Fig. 22. Indole-based chemosensors (a) 60, (b) 61/62/63, and (c) 64.
Fig. 23
Fig. 23. Carbazole-based probes for Hg2+ sensing (a) 65, (b) 66, and (c) 67.
Fig. 24
Fig. 24. Probes having a BODIPY fluorophore (a) 68, (b) 69, and (c) 70.
Fig. 25
Fig. 25. Chemosensors having imidazole (a) 71, (b) 72, (c) 73, and (d) 74.
Fig. 26
Fig. 26. Chemosensors for sensing Hg2+ having pyrazol (a) 75 and (b) 76.
Fig. 27
Fig. 27. Probes for Hg2+ sensing having pyrazole (a) 77, (b) 78, and (c) 79.
Fig. 28
Fig. 28. Probes for Hg2+ sensing having pyridine (a) 80, (b) 81, and (c) 82.
Fig. 29
Fig. 29. Quinoline-based probes (a) 83, (b) 84, (c) 85, (d) 86, and (e) 87.
Fig. 30
Fig. 30. Probes bearing (a) naphthalimide 88/89 and (b) julolidine 90.
Fig. 31
Fig. 31. Probes for Hg2+ based on polycyclic systems (a) 91a/91b and (c) 92.
Fig. 32
Fig. 32. Pt(II) metallomesogens for Hg2+ sensing (a) 93 and (b) 94.
Fig. 33
Fig. 33. Porphyrins for the detection of CN and Hg (a) 95, (b) 96, and (b) 97.
None
María-Camila Ríos
None
Néstor-Fabián Bravo
None
Christian-Camilo Sánchez
None
Jaime Portilla
See this image and copyright information in PMC

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