Spectroscopic insight into supramolecular assemblies of boric acid derivatives and β-cyclodextrin

Interactions of select boric acid derivatives with beta-cyclodextrin were investigated. All products were obtained employing the grinding-induced mechanochemical approach. It was found that phenylboronic acid, benzoxaborole and boric acid form non-covalent, hydrogen bonding-based systems with beta-cyclodextrin, whereas catechol and pinacol esters of phenylboronic acid as well as ferroceneboronic acid form host-guest inclusion complexes. The interactions were probed using spectroscopic methods: H-1 NMR, H-1-H-1 ROESY NMR, H-1 DOSY NMR, FT-IR. Association constant values were evaluated by H-1 DOSY NMR. The highest association constant was found for boric acid (117.5 +/- 2.5 M-1), whilst the lowest for benzoxaborole (14.8 +/- 0.3 M-1). The study shows the influence of boron compound structure on the nature of the assembly formed with beta-cyclodextrin, laying up the basis for future work with such supramolecular systems.