Macrocyclic Oligothiophene with Stereogenic [2.2]Paracyclophane Scaffolds: Chiroptical Properties from π‐Transannular Interactions

Abstract

The enantiomers of a new cyclic oligothiophene, bridged by two pseudo-ortho[2.2]paracyclophanes, were synthesized as a new class of the chiral π-conjugated system. Single-crystal X-ray diffraction analysis revealed a twisted structure for these oligothiophenes induced by a torsion of the cyclophane moieties. The embedding oligothiophenes into the inherent planar chirality provided a significant enhancement in circular dichroism (CD) spectra thanks to the large magnetic/electric transition dipole moments. In the dicationic state, an intramolecular π dimer was formed due to the strong interactions of the oligothiophenes. We further recorded unprecedented wide ranges of CD spectra in 250-1800 nm region. The transitions are reasonably described by the exciton coupling of the oligothiophenes.

Circularly Polarized Luminescence of a Stereogenic Curved Paraphenylene Anchoring a Chiral Binaphthyl in Solution and Solid State

“…[24] Cyclic curved p-conjugated systems, such as cycloparaphenylene( CPP) [25][26][27] and carbon nanobelts [28,29] amongo thers,a re of considerable interest owing to their attractive molecular structures, unique photophysical applications.W hen cyclic punits are connected inahelical arrangement along the axial direction, the resulting p-conjugated system exhibits chirality. [30][31][32][33] Such stereogenic distortion endows singular chiroptical properties including CPL.…”

Radical Cation π‐Dimers of Conjugated Oligomers as Molecular Wires: An Analysis Based on Nitronyl Nitroxide Spin Labels

“…From the diamagnetic character of the terthiophene radical cation π‐dimer, it was proposed that the π‐dimeric interchain interaction can act as an alternative charge carrier to bipolaron (an intrachain closed‐shell dication) in macroscopic conduction . Since then, various oligothiophene‐based π‐dimers have been prepared to understand the electronic structure of p ‐doped polythiophenes . Nevertheless, the microscopic conductive properties of long‐bonded π‐dimers as molecular wire have not been verified because of the absence of a suitable model system.…”

“…[27] Since then, various oligothiophene-based p-dimers have been prepared to understandt he electronic structure of p-doped polythiophenes. [28][29][30][31][32][33][34][35][36][37][38] Nevertheless, the microscopicc onductive properties of long-bonded p-dimersa sm olecular wire have not been verified because of the absence of as uitable model system. Knowledge of these properties wouldb ei ndispensable for the applicationo fp-dimer-based conductive supramolecular wires.…”

Chiroptical Redox Switching of Tetra‐Cationic Derivatives of Azoniahelicenes

“…Spiral‐shaped condensed aromatic helicenes with quaternary nitrogen atoms are called helquats, N‐heterohelicenia or azoniahelicenes. Recently, helquats were introduced as a new link between helicenes and viologens . Their electron‐accepting character makes them suitable electron‐transfer mediators.…”

“…[7][8][9] The influence of the redox state on chiral properties of spiral-shaped compounds was reported. [10][11][12][13][14][15][16][17][18][19][20][21] Other examples of redox switching include cyclic structure of binaphthyl and viologens, [22] oligothiophene linked to paracyclophane, [23] and azaacene. [24] Chiral gold nanoparticles can be prepared.…”