ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

A Molecular Swan: Naphthalene-hydrazone-based π···hole-coupled electron-deficient naked-eye selective colorimetric cyanide sensor

Vanthana Jeyasingh, Senthilkumaran Rajakumar, Murugesan Kumaresan, Sudha Lakshminarayanan, Narayanan Selvapalam, Geetha Dass, and Lakshminarayanan Piramuthu

Department of Chemistry, International Research Centre, Centre for Supramolecular Chemistry, Kalasalingam Academy of Research and Education (KARE), Srivilliputtur, India

E-mail: lakshmi16narayanan@gmail.com

Received: 2 June 2021  Accepted: 29 August 2021

Abstract:

We are reporting a naphthalene-hydrazone-coupled, π···hole-assisted selective colorimetric cyanide receptor L, (E)-2-((naphthalen-1-yl)methylene)-1-(perfluorophenyl)hydrazine. This colorimetric receptor L shows high selectivity toward cyanide anion through ICT mechanism. The binding strength and sensitivity of the chemo-sensor L toward cyanide is found to be 2.813 × 10⁴ and 6 × 10^–6 M, respectively. This preferential cyanide binding is mainly attributed due to the presence of pentafluoro-substituted electron-deficient phenyl moiety which is subsequently supported with UV–Vis and ¹H-NMR spectroscopic studies. The detailed naked-eye colorimetric experiment, UV–Vis spectrometric titration, ¹H-NMR analysis, IR spectroscopic investigation and molecular electrostatic potential (MEP) studies support the proposed binding mechanism. The reference receptor L¹ does not show any response with tested anions including cyanide and fluoride. The receptor L acts as “Molecular Swan.” Swans are birds of the family Anatidae; the swan if offered a mixture of milk and water is said to be able to drink the milk alone. Similar way, if we offer mixture of various anions, the receptor L is able to take only cyanide anion.

Graphic abstract

Keywords: Cyanide sensor; Naphthalene derivative; Colorimetric sensors; Fluorescent spectroscopy and molecular electrostatic surface

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01845-y

Chemical Papers 76 (1) 323–327 (2022)