Unmasking the role of anion-π bonding - A new paradigm for iodide selective organic probes

This review article undiscloses the significance of anion-π bonding in iodide-selective supramolecular chemosensors. Due to their lower basicity and nucleophilicity, iodide-selective chemosensors have received less attention than other halide ions. However, several supramolecular organic sensors have emerged by utilizing the larger size of the iodide anion, allowing it to fit into the receptor's cavity or pseudo-cavity readily. Therein, it was frequently presented that iodide-selective sensors typically involved new charge transfer bands in absorbance spectra and a fluorescence quenching, closely resembling the effects of anion-π non-covalent interactions. This review article meticulously explores the substantial evidence confirming the presence of anion-π bonding between the host and guest molecules. The current discovery has the potential to usher in a new paradigm in designing and exploring supramolecular detectors based on anion-π bonding. It should also be emphasized that an important objective is to create awareness among scientists about the less common anion-π bonding and its versatile applications toward anion recognition, non-covalent organic frameworks, and self-assemblies.