A porous organic salt (POS) composed of 2-sulfophenyl anthracene (2-SPA) and triphenylmetylamine (TPMA) forms five types of porous crystals, POS-a-e, by recognizing subtle differences in the molecular structure of incorporated guest molecules. This structurally variable POS was hierarchically designed on the basis of a supramolecular cluster with a directionally flexible linker formed by the organic salt. X-ray crystallographic analysis reveals that the salt forms six conformers attributable to rocking and rotational motions of the phenylene group in 2-SPA. The clusters form POS crystals through different porous networks according to the conformers. The POS crystals show a wide range of fluorescence spectra that are responsive to differences in the molecular and electronic structure of the guest molecule. This remarkable behavior has potential application in sensitive chemical sensors that are responsive to slight differences in molecular structures.
Keywords: cluster compounds; crystal engineering; fluorescence; host-guest systems; supramolecular chemistry.
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