1,2,4,6-Thiatriazinyl Radicals and Dimers: Structural and Electronic Tuning through Heteroaromatic Substituent Modification

The
functionalization of thiatriazinyl (TTA) radicals with pyridyl
and thienyl moieties is described, and their influence at both the
molecular and solid-state level has been investigated. Comparative
electron paramagnetic resonance studies of 3,5-bis-(2-pyridyl)-1,2,4,6-thiatriazinyl
(Py2TTA) and 3,5-bis-(2-thienyl)-1,2,4,6-thiatriazinyl
(Th2TTA) reveal
the impact of heteroaromatic substitution on the electronic structure,
which is supported by density functional theory calculations. Single
crystal X-ray analysis emphasizes the importance of intermolecular
contacts on the crystal packing and demonstrates the potential for
structural control through S---N′ and N---HC′ interactions,
which are enhanced in Py2TTA and Th2TTA by the presence of the pyridyl and thienyl groups, respectively.
This work represents a fundamental study of heterocyclic aromatic
substitution in thiazyl-based radicals and investigates how varying
these functional groups influences the molecular properties and long-range
order within the supramolecular structure.

本研究报道了采用吡啶基与噻吩基基团对噻三嗪基（TTA）自由基进行功能化修饰的方法，并从分子与固态两个层面探究了该类修饰对自由基的影响。针对3,5-二(2-吡啶基)-1,2,4,6-噻三嗪基（Py₂TTA）与3,5-二(2-噻吩基)-1,2,4,6-噻三嗪基（Th₂TTA）开展对比电子顺磁共振（electron paramagnetic resonance）研究，结果揭示了杂芳环取代对自由基电子结构的调控作用，该结论得到密度泛函理论（density functional theory）计算的佐证。单晶X射线衍射分析表明，分子间相互作用对晶体堆积具有重要意义，并证实了通过S---N′与N---HC′相互作用实现结构调控的潜力；其中Py₂TTA与Th₂TTA分别因吡啶基与噻吩基的引入，强化了上述两类分子间相互作用。本工作为噻唑基自由基的杂芳环取代修饰提供了基础性研究支撑，并探究了不同官能团的变化如何影响自由基的分子性质与超分子结构内的长程有序性。