Boronate esters for the binding and detection of low molecular weight volatile amines

Conjugated thiophene-based diboronate esters, 1-4, were synthesized to investigate how substituents on catechol alter the Lewis acidity and accessibility to boron, and influence binding interactions with low molecular weight Lewis basic amines. Crystallographic analysis indicated that both boron centres bind analyte and that Lewis base coordination induces deplanarization of the conjugated system. Spectroscopic studies demonstrate that amine binding disrupts conjugation, producing distinct and reproducible optical responses that depend on analyte basicity and structure, with association constants in organic solvent ranging from 10³ to 10⁶ M^-1. Quantitative binding analyses indicate strong negative cooperativity between the two boron sites. These results establish design principles for cross-reactive optical sensor arrays capable of differentiating volatile amines relevant to environmental monitoring, food quality assessment, and biomedical diagnostics.