One Well-Placed Methyl Group Increases the Solubility of Phenoxy Boronsubphthalocyanine Two Orders of Magnitude

Boronsubphthalocyanine (BsubPc) derivatives are materials that have recently seen an increase in attention, particularily for application as colorants and functional materials in organic electronic devices. However, the solubilities of most BsubPc derivatives are too low to utilize solution-based processing techniques. Where there are derivatives that are soluble, they rely on the addition of large alkyl chains for solubilization the result of which is an increase in the molecular weight and a decrease of the specific absorptivity of the BsubPc. In this paper we disclose the identity of two mass-efficient, highly soluble BsubPc derivatives: 3-methylphenoxy-BsubPc and 3,4-dimethylphenoxy-BsubPc. We compare their solubilities and crystal packing structures to previously known BsubPc derivatives. We put forward a symmetry-based argument for the reason for their surprisingly high solubility wherein we treat the molecules as two separate fragments: the phenoxy group and the BsubPc group. The symmetry-based argument suggests that by ignoring the BsubPc fragment common to each derivative a better estimate of the relative solubilities can be estimated through previously established empirical formulas.