Evidence for Effective p(Z)−π(Ar) Conjugations (Z = S, Se, and Te, as Well as Z = O) in 9-(Arylchalcogenyl)triptycenes: Experimental and Theoretical Investigations

The p(Z)−π(Ar) conjugations must operate fully in the ground states of 9-(arylchalcogenyl)triptycenes (p-YC6H4ZTpc:1 (Z = O), 2 (Z = S), 3 (Z = Se), and 4 (Z = Te)), where the p-YC6H4 group is placed in the bisected area between two phenyl planes of the triptycyl group with the parallel orientation. The ground-state geometries, which we call (A: pl), are confirmed by X-ray analysis. However, the conjugations never operate in the transition states between (A: pl) and/or the topomeric structures (A′: pl′), where the Z−CTpc bond is perpendicular to the plane. The site-exchange processes correlate to the conjugations. Temperature-dependent 1H NMR spectra are analyzed for 2 and 3 to demonstrate the effective p(Z)−π(Ar) conjugations. The activation energies for the interconversion between (A: pl) and (A′: pl′) (GR: gear process) were obtained for 2 (ΔG⧧GR(2)) and 3 (ΔG⧧GR(3)). ΔG⧧GR(3) correlate well with ΔG⧧GR(2), and ΔG⧧GR(2) are well analyzed by the Hammett-type dual parameters. ΔG⧧GR(2) and ΔG⧧GR(3) are demonstrated to be controlled by the resonance interaction of the p(Z)−π(C6H4)−p(Y) conjugations. QC calculations are performed on the ground and exited states of 1−4, which clarify the effective p(Z)−π(C6H4)−p(Y) conjugations for Z of heavier atoms.

p(Z)−π(Ar)共轭作用必须在9-(芳基硫属元素取代基)三蝶烯（p-YC₆H₄ZTpc：1（Z=O）、2（Z=S）、3（Z=Se）及4（Z=Te））的基态下完全发生，其中p-YC₆H₄基团位于三蝶烯基团的两个苯平面之间的平分区域且呈平行取向。我们将该基态几何结构记为(A: pl)，其通过X射线衍射分析得以确认。然而，该共轭作用在(A: pl)与（或）拓扑异构体(A′: pl′)之间的过渡态中无法发生，此时Z−CTpc键垂直于该平面。位交换过程与该共轭作用密切相关。针对化合物2和3的温度依赖性1H核磁共振波谱开展分析，以验证p(Z)−π(Ar)共轭作用的有效性。我们获得了(A: pl)与(A′: pl′)之间互变（齿轮型过程（Gear Process, GR））的活化能，分别对应化合物2的ΔG‡_GR(2)与化合物3的ΔG‡_GR(3)。ΔG‡_GR(3)与ΔG‡_GR(2)具有良好的相关性，且ΔG‡_GR(2)可通过哈米特型双参数进行良好解析。研究证实，ΔG‡_GR(2)与ΔG‡_GR(3)均受p(Z)−π(C₆H₄)−p(Y)共轭作用的共振相互作用调控。我们对化合物1~4的基态与激发态开展了量子化学（Quantum Chemistry, QC）计算，结果阐明了对于原子量更大的Z而言，p(Z)−π(C₆H₄)−p(Y)共轭作用的有效性。