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

Colorimetric and selective turn-on fluorescent sensor for cyanide via aggregation-induced enhanced emission (AIEE)

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

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

E-mail: geethadchem2016@gmail.com

Received: 31 August 2021  Accepted: 13 November 2021

Abstract:

We have prepared and reported a new cyanide colorimetric and turn-on fluorescent chemo sensor L. Naked-eye colorimetric studies show the prepared receptor is selectively sensing cyanide ion in acetonitrile medium. The sensor L shows very weak fluorescence in acetonitrile medium. The emission intensity of L gets reduced (quenching of fluorescence) upon addition of one equivalent of cyanide. Meanwhile, further gradual addition of more than one equivalents of cyanide onto 1:1 cyanide complex of L shows remarkable fluorescence enhancement. We have tested the absorbance and emission intensity of cyanide ion in the presence of other interfering anions such as fluoride, chloride, bromide, iodide, acetate, dihydrogen phosphate, azide, bifluoride, thio cyanate, and nitrate. The experimental results show none of the anions interfered the binding/sensing of cyanide by receptor L which clearly depicts the selectivity of cyanide by L. The weakly emissive receptor L shows drastic enhancement in fluorescence intensity upon addition of excessive cyanide ion (CN⁻) which is mainly attributed due to the restriction of intramolecular rotation of 1:1 L·CN⁻ complex and intermolecular aggregation of host:guest complex. This enhanced fluorescence emission is attributed due to the aggregation-induced enhanced emission (AIEE) subsequently supported with ultraviolet–visible (UV–Vis), emission and proton nuclear magnetic resonance (¹H-NMR) spectroscopic studies. The preferential binding of cyanide by electron-deficient receptor L through hydrogen bonding and anion···π interaction over benzene analogue of L is also analyzed with the help of molecular electrostatic potential surface analyses. To the best of our knowledge, this is the first example for selective colorimetric and turn-on cyanide sensor through AIEE mechanism. This type of fluorine-rich organic material having such an aggregation-induced enhanced emission properties in response to cyanide addition will be useful to construct the new type of material for various sensory applications.

Graphical abstract

Keywords: Aggregation-induced enhanced emission; Colorimetric sensor; Anion⋯π interactions; Anion and cyanide sensors

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01984-2

Chemical Papers 76 (3) 1891–1898 (2022)