Fig. 2. (A) Crystal structure of 2-APBA with thermal ellipsoids at 50% probability. The dashed green line represents an intramolecular N–H⋯O hydrogen bond. (B and C) 11B MAS (B) and 1H–15N CP-MAS (C) NMR spectra of the solid 2-APBA sample. (D) Explanation of the luminescence behavior of HBQ in response to 2-APBA and Neu5Ac. (E) Two dimers connected through intermolecular O–H⋯N hydrogen bonds (dashed orange lines). (F) Packing mode of 2-APBA viewed along the a axis (CCDC 2024024†). (G) Nearest distance between the phenyl rings (dashed plum lines) in the crystal structure.
