A new phenothiazine-based selective visual and fluorescent sensor for cyanide

Fatimah A M Al-Zahrani; Reda M El-Shishtawy; Abdullah M Asiri; Amerah M Al-Soliemy; Khloud Abu Mellah; Nahed S E Ahmed; Abdesslem Jedidi

doi:10.1186/s13065-019-0656-x

A new phenothiazine-based selective visual and fluorescent sensor for cyanide

BMC Chem. 2020 Jan 7;14(1):2. doi: 10.1186/s13065-019-0656-x. eCollection 2020 Dec.

Authors

Fatimah A M Al-Zahrani¹, Reda M El-Shishtawy^{2

3}, Abdullah M Asiri^{2

4}, Amerah M Al-Soliemy⁵, Khloud Abu Mellah¹, Nahed S E Ahmed³, Abdesslem Jedidi²

Affiliations

¹ 1Chemistry Department, Faculty of Science, King Khalid University, P.O.Box 9004, Abha, 61413 Saudi Arabia.
² 2Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah, 21589 Saudi Arabia.
³ 3Dyeing, Printing and Textile Auxiliaries Department, Textile Research Division, National Research Centre, Dokki, Cairo 12622 Egypt.
⁴ 4Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, 21589 Saudi Arabia.
⁵ 5Chemistry Department, Faculty of Science, Umm Al-Qura University, Mecca, Saudi Arabia.

Abstract

A new donor-π-acceptor derived from phenothiazine, namely 2-(2-((10-hexyl-10H-phenothiazin-3-yl)methylene)-3-oxo-2,3-dihydroinden-1-ylidene) malononitrile (PTZON) was synthesized and fully characterized, and its potential as a fluorescent sensor for cyanide anion was investigated. The PTZON showed a visible absorption band at 564 nm corresponds to an intramolecular charge transfer (ICT) and an emission band at 589 nm in CH₃CN/H₂O. The results of cyanide anion titration revealed ratiometric changes in both absorption and fluorescence spectra as a result of the nucleophilic addition of cyanide anion via Michael addition. The optical studies, FT-IR spectra, NMR, high-resolution mass, and DFT calculations confirmed the sensing mechanism. The selectivity of PTZON as a cyanide anion fluorescent sensor was proved in mixed solvent solutions, and the sensitivity was as low as 0.011 µM, which is far lower than the value allowed by the United States Environmental Protection Agency for drinking water (1.9 µM). Also, the detection limit of PTZON was assessed to be 3.39 μM by the spectrophotometric method. The binding stoichiometry between PTZON and cyanide anion was found to be 1:1 as evidenced by mass spectra. TLC silica-coated plates test strips demonstrated the fluorescent detection of cyanide anion.

Keywords: Cyanide; Detection limit; Intramolecular charge transfer; Nucleophilic addition; Phenothiazine; Visual and fluorescent sensor.