Related Experiment Video
Updated: Oct 3, 2026

Interactive Molecular Model Assembly with 3D Printing
Published on: August 13, 2020
Thermodynamic Locking of Conformational Chirality in a [9]Cycloparaphenylene
Zhi Zhang1, Quanli Shen1, Zekang Ma1
1Department of Materials Science and Engineering, School of Engineering and Research Center for Industries of the Future, Westlake University, Hangzhou, Zhejiang 310030, P. R. China.
Abstract:
Herein, we report the thermodynamic locking of conformational chirality in a [9]-cycloparaphenylene (CPP) by external appending of (R)- or (S)-BINOL units. Through-space steric interactions induce asymmetric torsion in the CPP backbone, generating a strained nanohoop with the lowest-energy conformer (ΔG = -2.9 kcal mol-1, corresponding to >99% population of the preferred conformer at 293 K). Temperature- and solvent-dependent circular dichroism (CD) spectra exhibit minimal signal variation, in marked contrast to conventional dynamic chiral systems and the monomeric precursor. Variable-temperature NMR reveals rapid interconversion (ΔG ‡ = 12.4 kcal mol-1), confirming fast kinetics that enable equilibration to the thermodynamically favored twisted conformation. Single-crystal X-ray diffraction and time-dependent density-functional theory (TD-DFT) calculations, including model compounds devoid of BINOL chromophores, unambiguously assign the intense Cotton effects to torsionally distorted CPP-centered π-π* transitions.
More Related Videos
06:35Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
Published on: February 15, 2016
10:52Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Related Concept Videos
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
Conformations of Cyclohexane
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
Stereoisomerism of Cyclic Compounds
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Thermal Electrocyclic Reactions: Stereochemistry
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Woodward–Hoffmann Selection Rules and Microscopic Reversibility