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.

硼亚酞菁（Boronsubphthalocyanine, BsubPc）衍生物是一类近年来受到广泛关注的材料，尤其可作为有机电子器件中的着色剂与功能材料。然而，多数BsubPc衍生物的溶解度较低，难以采用溶液加工工艺。即便部分衍生物具备可溶性，也需通过引入大体积烷基链实现增溶，这会导致其分子量升高，同时降低BsubPc的比吸光度。本研究报道了两种质量效率优异且高可溶性的BsubPc衍生物：3-甲基苯氧基-BsubPc与3,4-二甲基苯氧基-BsubPc。我们将这两种衍生物的溶解度与晶体堆积结构，与已报道的BsubPc衍生物进行了对比。针对其出乎意料的高溶解性，我们提出了基于对称性的解释：将分子拆分为苯氧基与BsubPc两个独立结构片段。该对称性分析表明，若忽略所有衍生物共有的BsubPc结构片段，即可通过已建立的经验公式更准确地预测其相对溶解度。