Coordination Chemistry of Boron Subphthalocyanine With BINOL Derivatives: Unexpected Oxidation to Oxa[4]Helicene and Properties of the Resulting Axially Coordinated Complexes Containing Oxa[4]Helicene and/or BINOL Derivatives

In the course of our research on axially coordinated metalloporphyrinoids with stable bonding based on the hard and soft acid–base (HSAB) theory, we focused on boron subphthalocyanine because of the hard acid character of the boron(III) center. 1,1′‐Bi‐2‐naphthol (BINOL) was selected as an axial ligand to introduce chirality into the otherwise achiral subphthalocyanine. Surprisingly, treatment of unsubstituted BINOL with boron subphthalocyanine resulted in the formation of a complex coordinated to an oxa[4]helicene derivative formed via a ring‐closure reaction of BINOL. In contrast, treatment of the monomethyl ether of BINOL with boron subphthalocyanine afforded the expected axially coordinated complex. Based on several control experiments, we propose a reaction mechanism for the formation of the oxa[4]helicene involving coordination of BINOL, followed by deprotonation and racemization, and subsequent intramolecular ring‐closure via an ionic process. To characterize and elucidate the fundamental properties of the resulting complexes, single‐crystal x‐ray diffraction, NMR spectroscopy, UV–vis absorption spectroscopy, and electrochemical studies were carried out. Furthermore, we investigated the chirality‐derived properties of the complexes, and the chirality‐induced spin selectivity (CISS) effect was evaluated using magnetic conductive atomic force microscopy (mc‐AFM), revealing a large spin polarization.