Cyanide Sensing and Bioimaging Applications of Dicyanomethylene-4H-Benzopyran Based Electron Donor-Acceptor Molecules

We report the development of two electron donor-acceptor molecules, designated as BCN and BCA, specifically for the selective detection of cyanide ions. Both BCN and BCA molecules were characterized using various spectroscopic methods, and their photophysical properties were systematically examined through UV-visible and both steady-state and time-resolved fluorescence spectroscopy. Screening of different anions demonstrated that both BCN and BCA probes exhibit selective sensitivity toward cyanide, as evidenced by distinct changes in their UV-visible and fluorescence emission behaviors. Notably, upon interaction with cyanide, the original yellow/orange coloration of the probe solution transitions to a colorless state, a change that is discernible to the naked eye. This remarkable cyanide detection mechanism is attributed to the nucleophilic addition of cyanide ions. The detection limits for cyanide sensing were determined to be 0.22 × 10^-6 M and 0.15 × 10^-6 M for the BCN and BCA molecular probes, respectively. This establishes a broader applicability of these probes for the detection of cyanide in real samples, such as tapioca/cassava. Additionally, the study introduced prototype testing strips for the qualitative analysis of cyanide. The Fluorescence microscopy imaging further indicated that the BCN dye exhibited high permeability in the Gram-negative bacterium A. baumannii ATCC 19606.