The synthesis and characterization of two phthalocyanine (Pc) structural isomers, 1 and 2, in which four 2,6-di(hexyloxy)phenyl units were attached directly to the 1,8,15,22- or 1,4,15,18-positions of the Pc rings, are described. Both Pcs 1 and 2 exhibited low melting points, i.e., 120 and 130 °C respectively, due to the reduction in intermolecular π-π interaction among the Pc rings caused by the steric hindrance of 2,6-dihexyloxybenzene units. The thermal behaviors were investigated with temperature-controlled polarizing optical microscopy, differential scanning calorimetry, powder X-ray diffraction, and absorption spectral analyses. Pc 1, having C4h molecular symmetry, organized into a lamellar structure containing lateral assemblies of Pc rings. In contrast, the other Pc 2 revealed the formation of metastable crystalline phases, including disordered stacks of Pcs due to rapid cooling from a melted liquid.

中文翻译：

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通过空间保护的酞菁的分子对称性控制堆积

两种酞菁 (Pc) 结构异构体 1 和 2 的合成和表征，其中四个 2,6-二（己氧基）苯基单元直接连接到 1,8,15,22- 或 1,4,15，描述了 Pc 环的 18 个位置。由于 2,6-二己氧基苯单元的空间位阻导致 Pc 环之间的分子间 π-π 相互作用减少，Pcs 1 和 2 均表现出低熔点，即分别为 120 和 130 °C。用温控偏振光学显微镜、差示扫描量热法、粉末 X 射线衍射和吸收光谱分析研究了热行为。Pc 1 具有 C4h 分子对称性，组织成包含 Pc 环横向组装的层状结构。相比之下，其他 Pc 2 揭示了亚稳晶相的形成，