Effect of alkyloxy substituents on mesomorphic and photophysical properties of star-shaped tristriazolotriazines

Two series of tristriazolotriazine (TTT) derivatives with different length of aliphatic substituents have been synthesised in order to study the influence of peripheral substitution on mesomorphism and fluorescent properties of these star-shaped compounds. Homologues with methoxy and alkyloxy substituents (series <b>1</b>) are non-mesogenic, in contrast to homologues with two alkyloxy substituents (series <b>2</b>) exhibiting columnar mesophase. The results obtained by quantum-chemical calculations for the monomers and dimers of non-mesogenic TTT series and their comparison with truxenone derivatives having identical substituents made it possible to establish the reasons that deprive series <b>1</b> of mesogenity. Compounds of both TTT series possess good solubility in organic solvents and capable of specific interactions with solvents in the ground and excited states. They form fluorescenting floating layers and thin films. An analysis of the fluorescence spectra showed a high potential for their application, in particular, in the field of molecular sensing and precise non-invasive control.

为探究外围取代基对这类星型化合物介晶性与荧光性能的影响，我们合成了两系列脂肪族取代基链长各异的三三唑并三嗪（tristriazolotriazine, TTT）衍生物。带有甲氧基与单烷氧基取代基的同系物（系列<b>1</b>）不具备介晶性；与之相反，带有双烷氧基取代基的同系物（系列<b>2</b>）可呈现柱状介晶相。通过对非介晶性TTT系列的单体与二聚体开展量子化学计算，并将计算结果与带有相同取代基的三亚苯酮（truxenone）衍生物进行对比，我们得以明确导致系列<b>1</b>丧失介晶性的根本原因。两类TTT系列化合物均在有机溶剂中具备良好溶解性，且在基态与激发态下均可与溶剂发生特异性相互作用。它们可形成荧光漂浮层与薄膜。对其荧光光谱的分析表明，这类化合物具备极高的应用潜力，尤其可应用于分子传感与精准无创调控领域。