Fig. 5: Role of water in the formation of the boroxine structure and water-compatible DCBs.
From: Water-stable boroxine structure with dynamic covalent bonds
a, b 1H (a) and 2D (b) NMR spectra of equilibrium mixture of HO-PBA dimer and trimer with various amount of D2O. The initial sample was prepared by dissolving 32.8 mg HO-PBA dimer in 500 μL THF−d8 (a) or THF (b). c 11B NMR spectra of HO-PBA dimer (black line) in THF−d8 and HO-PBA trimer (red line) in D2O–THF−d8 (1:5, v/v) mixture. The chemical shifts of 11B were determined relative to 0.1 mol L−1 boric acid (19.4 ppm, marked with a star)51, which served as the external reference. d Reversible reaction between HO-PBA dimer and D2O to produce HO-PBA trimer–D2O complex. e ESI-Q-TOF mass spectrum of products from mixing HO‑PBA dimers and CF3-HO‑PBA dimers together in a methanol–water (5:1, v/v) solution, acquired in a negative mode. f Illustration of the dynamic exchange between HO‑PBA trimer (T) and CF3-HO‑PBA trimer (T3). The exchange products are denoted by T1 and T2.
