Visualizing anions by color changing response: Exploitation of pyrimidine-based probe for simultaneous detection of CN− and F− ions

Abstract

An easily scalable pyrimidine-based charge-transfer probe has been synthesized that can be utilized for simultaneous detection of both CN− and F− ions. The orange-colored solution of compound turns into yellow upon addition of F− ion, while the spiking of CN- ion leads to a colorless solution. Such color-changes have also been noticed on solid-supported materials, such as modified paper strips. Interestingly, the interaction with F- is found to be rapid as well as reversible (checked against water), while for cyanide ion, the scenario is completely opposite, the interaction is rather slow (∼10 min incubation time), and irreversible. The detailed spectroscopic investigation indicated that F−, being basic in nature, participates in the hydrogen bonding interaction. However, CN− ion, due to its highly nucleophilic character, formed Michael addition reaction product. Both these interactions substantially curtail the extent of intramolecular charge transfer and thereby resulting distinct changes in visible color. Detection of multiple anions via distinct naked-eye color changing response is not very common in the literature and therefore will be beneficial for future development of new sensory systems.