Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2021 Nov 17;11(58):36850-36858.
doi: 10.1039/d1ra07677a. eCollection 2021 Nov 10.

Revisiting salicylidene-based anion receptors

Sandeep Kumar Dey  1 , Sonam Kumari  1 , Sonal Mandrekar  1 , Shashank N Mhaldar  1 , Sarvesh S Harmalkar  1 , Christoph Janiak  2
Affiliations

Revisiting salicylidene-based anion receptors

Sandeep Kumar Dey et al. RSC Adv. .

Abstract

Several salicylidene-based colorimetric and fluorimetric anion sensors are known in the literature. However, our 1H-NMR experimental results (in DMSO-d6) showed hydrolysis of imine (-N[double bond, length as m-dash]CH-) bonds in salicylidene-based receptors (SL, CL1 and CL2) in the presence of quaternary ammonium salts (n-Bu4N+) of halides (Cl- and Br-) and oxo-anions (H2PO4 -, HSO4 - and CH3COO-). The mono-salicylidene compound CL1 showed the most extensive -N[double bond, length as m-dash]CH- bond hydrolysis in the presence of anions. In contrast, the di-salicylidene compound CL2 and the tris-salicylidene compound SL showed comparatively slow hydrolysis of -N[double bond, length as m-dash]CH- bonds in the presence of anions. Anion-induced imine bond cleavage in salicylidene compounds could easily be detected in 1H-NMR due to the appearance of the salicylaldehyde -CHO peak at 10.3 ppm which eventually became more intense over time, and the -N[double bond, length as m-dash]CH- peak at 8.9-9.0 ppm became considerably weaker. Furthermore, the formation of the salicylidene O-H⋯X- (X- = Cl-/Br-) hydrogen-bonded complex, peak broadening due to proton-exchange processes and keto-enol tautomerism have also been clearly observed in the 1H-NMR experiments. Control 1H-NMR experiments revealed that the presence of moisture in the organic solvents could result in gradual hydrolysis of the salicylidene compounds, and the rate of hydrolysis has further been enhanced significantly in the presence of an anion. Based on 1H-NMR results, we have proposed a general mechanism for the anion-induced hydrolysis of imine bonds in salicylidene-based receptors.

PubMed Disclaimer

Conflict of interest statement

There are no conflicts to declare.

Figures

Scheme 1
Scheme 1. Molecular structures of salicylidene Schiff bases studied here (synthesis details are provided in the ESI†).
Fig. 1
Fig. 1. Aromatic region of 1H-NMR (DMSO-d6) spectra of SL in the presence of 10 equivalents of (n-Bu4N+)Cl−, recorded after 24 hours (D2), 48 hours (D3), and after 72 hours (D4). Signals labelled with red and black dots indicate –OH peaks of salicylaldehyde (red) and SL (black) respectively. Signals labelled with blue and green dots indicate –NH and –NH2 peaks of SL (blue) and AL (green) respectively. Signals labelled with red and blue asterisk indicate –CHO and –NCH– protons of salicylaldehyde (red) and SL (blue) respectively (additional spectra are provided in the ESI†).
Scheme 2
Scheme 2. Plausible mechanism for the anion-induced hydrolysis of imine bond in salicylidene Schiff bases widely studied as anion sensors (A− = Cl−, Br−, H2PO4−, HSO4− or CH3COO−). Hydrogen bonds are shown in green dotted lines.
Fig. 2
Fig. 2. Aromatic region of 1H-NMR (DMSO-d6) spectra of SL in the presence of 10 equivalents of (n-Bu4N+)H2PO4−, recorded after 1 hour (D1), 24 hours (D2) and after 72 hours (D4). Signals labelled with red and blue asterisk indicate –CHO and –NCH– protons of salicylaldehyde (red) and SL (blue) respectively. Signal labelled with black dot represent –OH proton of SL (additional spectra are provided in the ESI†).
Fig. 3
Fig. 3. Aromatic region of 1H-NMR (DMSO-d6) spectra of SL in the presence of 10 equivalents of (n-Bu4N+)CH3COO−, recorded after 1 hour (D1), 24 hours (D2) and after 48 hours (D3). Signals labelled with red and blue asterisk indicate –CHO and –NCH– protons of salicylaldehyde (red) and SL (blue) respectively. Signals labelled with black and blue dots indicate –OH and –NH peaks of SL (additional spectra are provided in the ESI†).
Fig. 4
Fig. 4. Aromatic region of 1H-NMR (DMSO-d6) spectra of CL1 in the presence of 5 equivalents of (n-Bu4N+)Cl− and (n-Bu4N+)H2PO4− recorded after 1 hour (D1) and after 24 hours (D2). Signals labelled with red and blue asterisk indicate –CHO and –NCH– protons of salicylaldehyde (red) and CL1 (blue) respectively. Signals labelled with red and black dots indicate –OH peaks of salicylaldehyde (red) and CL1 (black) respectively (additional spectra are provided in the ESI†).
Fig. 5
Fig. 5. Aromatic region of 1H-NMR spectra (DMSO-d6) of CL2 in the presence of 5 equivalents of (n-Bu4N+)Cl−, recorded after 24 hours (D2) and after 72 hours (D4). Signals labelled with e and k indicate the enol and keto forms of CL2 respectively. Signals labelled with red and blue asterisk indicate –CHO and –NCH– protons of salicylaldehyde (red) and CL2 (blue) respectively. Signals labelled with blue hexagons represent –OH signals for O–H⋯Cl− hydrogen bonded complexes and the corresponding keto–enol peaks for the H-bond complexes. Signals labelled with red and black dots indicates –OH peaks of salicylaldehyde (red) and CL2 (black) respectively (additional spectra are provided in the ESI†).
Fig. 6
Fig. 6. Aromatic region of 1H-NMR spectra (DMSO-d6) of CL2 in the presence of 5 equivalents of (n-Bu4N+)H2PO4−, recorded after 24 hours (D2), 48 hours (D3) and after 72 hours (D4). Signals labelled with e and k indicate the enol and keto forms of CL2 respectively. Signals labelled with red and blue asterisk indicate –CHO and –NCH– peaks of salicylaldehyde (red) and CL2 (blue) respectively. Signals labelled with black and green dots indicate –OH and –NH2 peaks of CL2 (black) and amine product (green) respectively (additional spectra are provided in the ESI†).
Fig. 7
Fig. 7. Aromatic region of 1H-NMR spectra (DMSO-d6) of CL2 in the presence of 15 equivalents of H2O, recorded after 1 hour (D1), 24 hours (D2), 48 hours (D3) and after 72 hours (D4). Signals labelled with e and k indicate the enol and keto forms of CL2 respectively. Signals labelled with red and blue asterisk indicate –CHO and –NCH– peaks of salicylaldehyde (red) and CL2 (blue) respectively.
Fig. 8
Fig. 8. Aromatic region of 1H-NMR spectra (DMSO-d6) of CL2 in the presence of 15 equivalents of H2O and 1 equivalent of (n-Bu4N+)Cl−, recorded after 1 hour (D1), 24 hours (D2), 48 hours (D3) and after 72 hours (D4). Signals labelled with e and k indicate the enol and keto forms of CL2 respectively. Signals labelled with red and blue asterisk indicate –CHO and –NCH– peaks of salicylaldehyde (red) and CL2 (blue) respectively. Signals labelled with black and green dots indicate –OH and –NH2 peaks of CL2 (black) and amine product (green) respectively.
See this image and copyright information in PMC

References

    1. Liu X. Hamon J.-R. Coord. Chem. Rev. 2019;389:94–118. doi: 10.1016/j.ccr.2019.03.010. - DOI
    2. Karmakar M. Chattopadhyay S. J. Mol. Struct. 2019;1186:155–186. doi: 10.1016/j.molstruc.2019.02.091. - DOI
    3. Zhang J. Xu L. Wong W.-Y. Coord. Chem. Rev. 2018;355:180–198. doi: 10.1016/j.ccr.2017.08.007. - DOI
    4. da Silva C. M. da Silva D. L. Modolo L. V. Alves R. B. de Resende M. A. Martins C. V. B. de Fátima A. J. Adv. Res. 2011;2:1–8. doi: 10.1016/j.jare.2010.05.004. - DOI
    5. Nath M. Saini P. K. Dalton Trans. 2011;40:7077–7121. doi: 10.1039/C0DT01426E. - DOI - PubMed
    6. Zoubi W. A. Mohamed S. G. Al-Hamdani A. A. S. Mahendradhany A. P. Ko Y. G. RSC Adv. 2018;8:23294–23318. doi: 10.1039/C8RA01890A. - DOI - PMC - PubMed
    1. Cozzi P. G. Chem. Soc. Rev. 2004;33:410–421. doi: 10.1039/B307853C. - DOI - PubMed

    2. , and references therein;

    3. Gupta K. C. Sutar A. C. Coord. Chem. Rev. 2008;252:1420–1450. doi: 10.1016/j.ccr.2007.09.005. - DOI
    4. Drozdzak R. Allaert B. Ledoux N. Dragutan I. Dragutan V. Verpoort F. Adv. Synth. Catal. 2005;347:1721–1743. doi: 10.1002/adsc.200404389. - DOI
    5. Adaeo P. Kuznetsov M. L. Barroso S. Martins A. M. Avecilla F. Pessoa J. C. Inorg. Chem. 2012;51:11430–11449. doi: 10.1021/ic301153p. - DOI - PubMed
    6. Das P. Linert W. Coord. Chem. Rev. 2016;311:1–23. doi: 10.1016/j.ccr.2015.11.010. - DOI
    7. Gong D. Wang B. Jia X. Zhang X. Dalton Trans. 2014;43:4169–4178. doi: 10.1039/C3DT52708E. - DOI - PubMed
    1. Che C. M. Chan S. C. Xiang H. F. Chan M. C. Liu Y. Wang Y. Chem. Commun. 2004:1484–1485. doi: 10.1039/B402318H. - DOI - PubMed
    2. Sano T. Nishio Y. Hamada Y. Takahashi H. Usuki T. Shibata K. J. Mater. Chem. 2000;10:157–161. doi: 10.1039/A903239H. - DOI
    3. Li S. H. Chen F. R. Zhou Y. F. Wang J. N. Zhang H. Xu J. G. Chem. Commun. 2009:4179–4181. doi: 10.1039/B906467B. - DOI - PubMed
    4. Lee S. A. You G. R. Choi Y. W. Jo H. Y. Kim A. R. Noh I. Kim S. J. Kim Y. Kim C. Dalton Trans. 2014;43:6650–6659. doi: 10.1039/C4DT00361F. - DOI - PubMed
    1. Sun Y. Lu Y. Bian M. Yang Z. Ma X. Liu W. Eur. J. Med. Chem. 2021;211:113098. doi: 10.1016/j.ejmech.2020.113098. - DOI - PubMed
    2. Parveen S. Appl. Organomet. Chem. 2020;34:e5687. doi: 10.1002/aoc.5687. - DOI - PubMed
    3. More M. S. Joshi P. G. Mishra Y. K. Khanna P. K. Mater. Today Chem. 2019;14:100195. doi: 10.1016/j.mtchem.2019.100195. - DOI - PMC - PubMed
    4. Kaczmarek M. T. Zabiszak M. Nowak M. Jastrzab R. Coord. Chem. Rev. 2018;370:42–54. doi: 10.1016/j.ccr.2018.05.012. - DOI
    5. Hajrezaie M. Paydar M. Looi C. Y. Moghadamtousi S. Z. Hassandarvish P. Salga M. S. Karimian H. Shams K. Zahedifard M. Majid N. A. Ali H. M. Abdulla M. A. Sci. Rep. 2015;5:9097–9104. doi: 10.1038/srep09097. - DOI - PMC - PubMed
    1. Bowman-James K., Bianchi A. and Garcia-Espana E., Anion Coordination Chemistry, Wiley-VCH, 1st edn, 2011