Recent advancements in the role of N-Heterocyclic receptors on heavy metal ion sensing

ABSTRACT Heavy metal ions have an aggressive impact on human health and the environment if the predictable levels are varied. The development of new strategies constructed on colorimetric and fluorescence techniques has extensively been used to detect the presence of heavy metal ions in real sample analysis and living cells. The interaction between the heavy metal ions and the receptor has shown detectable signals, assessed by its photophysical changes. The various reactivity, readily available starting material and its admirable photophysical actions make nitrogen based heterocycles to be one of the best tools for detection of heavy metal ions. The design of nitrogen heterocycles based receptor developed and employed for the sensing of heavy metal ions for the past ten years by several research groups are explored with selectivity, sensitivity, reversibility, pH effect, stoichiometric ratio, binding constant, LOD values and real time applications. This review paper aims to discuss the recent progress in structural designs of N-heterocyclic based colorimetric and fluorescence sensors, the pathway followed for receptor-metal ion interaction by possible energy/electron transfer mechanisms, and its wide applications. To the best of our knowledge, this is the first comprehensive review describing the N-heterocyclic molecules as ionophores for heavy metal ion recognition.