Colorimetric analysis of malononitrile via the formation of a novel NBD-based CH-acidic dye

Abstract Malononitrile is a key starting material used in synthetic organic, medical, and industrial chemistry, but it is also a notorious cyanogenic toxicant. However, selective and sensitive analytical methods for this key chemical are rare. In this research, a novel reaction-based colorimetric signaling probe for the selective analysis of malononitrile via the SNAr-type nucleophilic substitution reaction of an NBD-based phenyl selenoether was investigated. The probe exhibited a pronounced colorimetric response, with a color change from yellow to violet due to its CH-acidity. The interference of sulfide ions and several transition metal ions was effectively circumvented with the use of copper foil as a sulfide scavenger and EDTA as a masking agent for the metal ions. The detection limit of the probe for malononitrile was found to be 264 nM. It was also demonstrated that this convenient colorimetric analysis of malononitrile in chemical and industrial applications using the probe can be conducted with an office scanner.