Molecular recognition by a novel boronate-containing CTG derivative for hydroxyanthraquinones

C₃-functionalized cyclotriguaiacylene (CTG) derivatives were employed in the development of highly selective recognition compounds due to their unique molecular structures. Here, a novel C₃-functionalized CTG containing boronate (PPB-CTG) was synthesized and its molecular recognition ability for hydroxyanthraquinones was investigated by fluorescence spectroscopy. The addition of the synthesized PPB-CTG led to a large increase in the fluorescence intensity of only alizarin and not 1-hydroxyanthraquinone, 2-hydroxyanthraquinone nor quinizarin. It was, thus, suggested that the cyclotriveratrylene (CTV) structure plays an important role in the recognition ability toward alizarin since the mono-phenyl boronate compound (m-TPBAP) showed poor fluorescence properties toward alizarin. Moreover, it was found that the 1:1 mixture of PPB-CTG and alizarin was effective as a fluorescence-enhanced probe toward fluoride ions.