m-Phenylene linked macrocycle composed of electron-rich dithienogermole and electron-deficient tricoordinate boron units

Incorporation of non-conventional elements into pi-conjugated systems is a powerful tool to control the electronic structures. In this work, electron-deficient tricoordinate boron units were combined with electron-rich dithienogermole units to provide an element-hybrid conjugated macrocycle with m-phenylene linkers. In contrast to the absorption spectra which were unaffected by solvent polarity, the element-hybrid macrocycle exhibited clear solvatochromism in the fluorescence spectra originating from the charge transfer (CT) transition between the dithienogermole and tricoordinate boron units. The addition of fluoride to the solution of the macrocycle resulted in the stoichiometric formation of tetracoordinate borate species. Interestingly, the fluorescence was intensified by the addition of fluoride, and the mechanism was confirmed by fluorescence spectroscopy and TDDFT calculations.

Automated summary

Incorporating non-conventional elements into pi-conjugated systems allows for control of electronic structures. In this study, electron-deficient tricoordinate boron units were combined with electron-rich dithienogermole units to create a hybrid conjugated macrocycle with m-phenylene linkers. The fluorescence spectra of the element-hybrid macrocycle exhibited solvatochromism, and the addition of fluoride intensified the fluorescence. This mechanism was confirmed through fluorescence spectroscopy and TDDFT calculations.