Untangling the Mechanochromic Properties of Benzothiadiazole-Based Luminescent Polymorphs through Supramolecular Organic Framework Topology

Two new luminophore
polymorphs of 4-bromo-7-(4-nonylphenyl)­benzo­[c]­[1,2,5]­thiadiazole
(1α and 1β) exhibiting different
color emissions, which switch into each other
in response to shear force and solvent vapors, are presented and their
X-ray structure is determined. Supramolecular organic framework topology
(SOFT) studies on the two polymorphic structures led us to conclude
that the mechanochromic phase transformation can be explained on the
basis of modifications in their respective topological nets: mab and pcu for 1α and 1β, respectively, as a result of the breaking and restoration
of a number of weak supramolecular interactions. The color changes
accompanying this transformation have been rationalized with the help
of time-dependent density functional theory. We firmly believe that
our findings will inspire future research on the design of novel stimuli-responsive
organic materials with switchable properties based on their supramolecular
interactions by establishing clear SOFT-property relationships.

本文报道了4-溴-7-(4-壬基苯基)苯并[c][1,2,5]噻二唑的两种新型发光多晶型物（1α和1β），二者呈现出差异化的荧光发射色彩，且可响应剪切力与溶剂蒸气实现相互转换；同时我们解析了其X射线晶体结构。针对这两种多晶型结构开展超分子有机框架拓扑（Supramolecular Organic Framework Topology, SOFT）研究后，我们得出结论：力致变色相变可通过各自拓扑网络的修饰机制予以阐释——1α与1β分别对应mab和pcu拓扑网络，该相变过程源于若干弱超分子相互作用的断裂与重建。伴随该相变产生的颜色变化，我们借助含时密度泛函理论完成了合理化论证。我们坚信，本研究通过明确超分子有机框架拓扑-性能关联关系，将为基于超分子相互作用设计具备可切换特性的新型刺激响应型有机材料提供研究灵感。