Isomeric Benzenediol-Linked Organophosphonates as a Handy Reusable Emitting Platform: Diversity in Polyamine Vapor Detection

This work introduces metal/column-free facile quantitative access to conformationally twisted catechol-linked organophosphonate (CAP) as a blue-emitting solid that could reversibly detect only 1,3-diaminopropane (DAP) and 1,2-ethylenediamine (EDA) vapors, belonging to industrially and pharmaceutically abundant crucial diamines. In CAP, two adjacent hydroxy groups in a benzene ring facilitate selective diamine–dihydroxy (amine–phenol type) interactions in the solid phase, leading to a quenched emission with selectively smaller aliphatic PAs, that is, DAP and EDA. The disparity was noticed with an isomeric resorcinol-linked emitter (RAP), detecting various polyamine vapors with superior sensitivity. A one-carbon-away placed hydroxy group in RAP can only generate a monoamine–hydroxy complex, not diamine–dihydroxy. The more acidic nature of resorcinol would prefer ionizing the amines and, consequently, creating amine/hydroxy interactions. More systematic investigations reveal an exciting role of amine–hydroxy realization for the catechol analog in the solid phase with a syn–anti conformation for CAP. Unlike CAP, RAP’s available crystal void space creates considerable room in which to come closer and facilitates amine–phenol interactions. The role of phosphonates in the selective detection of PAs is also examined. Observed outcomes are substantiated by FT-IR, single-crystal X-ray diffraction, SEM, XPS, and mass spectroscopic studies. The proposed amine–hydroxy interactions are further supported by DFT-optimized molecular structures.