Evidence for effective p(Z)-pi(Ar) conjugations (Z = S, Se, and Te, as well as Z = O) in 9-(arylchalcogenyl)triptycenes: experimental and theoretical investigations.
The p(Z)-pi(Ar) conjugations must operate fully in the ground states of 9-(arylchalcogenyl)triptycenes (p-YC(6)H(4)ZTpc:1 (Z = O), 2 (Z = S), 3 (Z = Se), and 4 (Z = Te)), where the p-YC(6)H(4) 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-C(Tpc) bond is perpendicular to the plane. The site-exchange processes correlate to the conjugations. Temperature-dependent (1)H NMR spectra are analyzed for 2 and 3 to demonstrate the effective p(Z)-pi(Ar) conjugations. The activation energies for the interconversion between (A: pl) and (A': pl') (GR: gear process) were obtained for 2 (DeltaG(GR)(2)) and 3 (DeltaG(GR)(3)). DeltaG(GR)(3) correlate well with DeltaG(GR)(2), and DeltaG(GR)(2) are well analyzed by the Hammett-type dual parameters. DeltaG(GR)(2) and DeltaG(GR)(3) are demonstrated to be controlled by the resonance interaction of the p(Z)-pi(C(6)H(4))-p(Y) conjugations. QC calculations are performed on the ground and exited states of 1-4, which clarify the effective p(Z)-pi(C(6)H(4))-p(Y) conjugations for Z of heavier atoms.
Hayashi
Satoko
S
Department of Material Science and Chemistry, Faculty of Systems Engineering, Wakayama University, 930 Sakaedani, Wakayama 640-8510, Japan.
Nakamoto
Takashi
T
Minoura
Mao
M
Nakanishi
Waro
W