A novel organic salt with water/humidity-induced fluorescence switching and heat-induced coloration performance

A novel organic salt, namely (H2PO3)2·(H3PO3)·(phenH)2·H2O (1), is synthesized and characterized, and shows a 3D tessellate-type supramolecular structure containing 1D [(phenH+)·(H2PO3−)]n supramolecular chains. Compound 1 is a multifunctional material: it displays infrequent water/humidity-induced fluorescence switching performance at room temperature, whose fluorescent color can be reversibly changed between blue, cyan and violet by placing at different relative humidities or adding various amounts of water; moreover, compound 1 shows interesting heat-induced coloration at high temperature, whereby its color can be changed from colorless to red by heat. The mechanisms of the fluorescence switching and coloration are also investigated.