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Published on: February 10, 2022
Circular dichroism of helical structures using semiempirical methods.
Edith Botek1, Benoît Champagne
1Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix, rue de Bruxelles 61, Namur, Belgium. edith.botek@fundp.ac.be
The Journal of Chemical Physics
|December 7, 2007
Summary
A new computational method accurately simulates circular dichroism (CD) spectra for supramolecular systems. This approach offers a cost-effective way to predict CD spectra for complex molecules like helicenes.
Area of Science:
- Computational Chemistry
- Spectroscopy
- Supramolecular Chemistry
Background:
- Circular dichroism (CD) spectroscopy is vital for determining the absolute configuration of chiral molecules.
- Simulating CD spectra of complex supramolecular systems remains computationally challenging.
Purpose of the Study:
- To develop a general and efficient semiempirical scheme for simulating CD spectra of supramolecular systems.
- To assess the performance of the developed method using various theoretical and experimental benchmarks.
Main Methods:
- A semiempirical scheme based on the analytical method of Beck and Hohlneicher for evaluating integrals over Slater atomic orbitals.
- Utilized INDO/S and CNDO/S semiempirical parametrizations.
- Validated by comparing simulated spectra with experimental and theoretical data for helicenes and pyridine-pyrimidine oligomers.
Main Results:
- The INDO/S parametrization successfully reproduced experimental CD spectra of helicenes at low computational cost.
- Rotatory strength in homohelicenes demonstrated a near-linear increase with helix size.
- Packing effects were shown to alter the sign of significant CD bands, aiding structural configuration assignment.
Conclusions:
- The developed semiempirical method provides a computationally inexpensive yet accurate tool for CD spectral simulation of supramolecular systems.
- The study highlights the influence of molecular size and packing effects on CD spectral properties.
- This method can aid in the structural elucidation of chiral supramolecular architectures.
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