Exploring the Synthesis and Electronic Properties of Axially Substituted Boron Subphthalocyanines with Carbon-Based Functional Groups

With peripheral fluorination and chlorination known to significantly influence the solubility, fluorescence quantum yield and redox properties of boron subphthalocyanines (BsubPcs), it is the intent of this study to further expand a matrix of BsubPcs to correlate structural changes to properties. Here, we have adapted previous synthetic methodologies for accessing axially substituted BsubPcs with a variety of alkyne substituents along with incorporating various peripheral halogens. While axial substitution of BsubPcs results in minimal shifts of longest-wavelength absorptions, relative fluorescence quantum yields decrease with the increasing number of axial carbon-carbon triple bonds. Cyclic voltammetry studies reveal that BsubPcs can form a radical anion more easily with each additional carbon-carbon triple bond, the most significant change happening when going from one to two triple bonds. Also, the reduction profile is influenced by peripheral halogenation as well as by the radical-stabilizing ability of an axial arylethynyl group. In all, axial alkyne-based substituents have influential impact on the characteristics of BsubPcs.