Fig. 2: HO‑PBA dimer and its properties.
From: Water-stable boroxine structure with dynamic covalent bonds
a Crystal structure of HO‑PBA dimer with thermal ellipsoids (CCDC 2280484). The dashed brown line represents an intramolecular O–H…O hydrogen bond. b MALDI-TOF mass spectrum of products from the mixture of HO‑PBA dimers and CH3-HO‑PBA dimers, acquired in a negative mode. The peak marked with a blue triangle is attributed to a background signal. c Illustration of the dynamic exchange between HO‑PBA dimer (D0) and CH3-HO‑PBA dimer (D2).The exchange products are denoted by D1. d, e Packing interactions (d) and packing mode of HO‑PBA dimers viewed along the a axis (e). The dashed blue and purple lines in (d) represent intramolecular O–H…O and C–H…O hydrogen bonds, respectively. f SEM image displaying assembled morphology of HO-PBA dimer, where the sample was prepared by dropping one droplet of HO‑PBA solution on a silicon wafer. g SEM image and XRD pattern (inset) of the solid HO‑PBA dimer sample. h Fluorescence spectra and the absolute quantum yields (ΦF, inset) of HO‑PBA dimer in THF (2 × 10−5 mol L−1, λex = 288 nm) and the solid HO‑PBA dimer sample (λex = 313 nm).
