Vibrational Circular Dichroism and Electronic Currents from First Principles
Final Report Abstract
Chiroptical spectroscopy provides an increasingly important, cost-effective methodology for the study of chiral substances. In recent years, vibrational circular dichroism (VCD) - the chiral form of IR absorption spectroscopy - has come into focus being a very sensitive probe of molecular conformation and environment. VCD differs from electronic circular dichroism in that it relates directly to vibrational transitions in system determined by covalent as well as non-covalent interactions. Hence, functional groups but also the supramolecular chiral framework are addressed. VCD spectroscopy has become an invaluable tool in the determination of absolute configurations by assigning recorded spectra to structural information obtained from theoretical calculations. Yet, it is highly sensitive towards supramolecular effects around the chiral centre, be it the dependence of a solution spectrum on the solvent or the influence of chiral crystal packing in solid-state. A crucial point lies in the availability of efficient theoretical models that are to be referred to when interpreting experimental results. This project dealt with the calculation of VCD spectra based on realistic models that describe the system in the condensed phase. Within the frameworks of very accurate methods, such as ab initio molecular dynamics (AIMD) and Nuclear Velocity Perturbation Theory (NVPT), predictions of complicated VCD spectra has been achieved. As a new feature, our numerical simulations considered also non-local terms, which describe the vibrational coupling between molecules. It turned out that the computation of VCD for molecular crystals and subsequent spatial analysis of the results delivers valuable information on the crystal system and its chirality, which acts independently from molecular chirality. This filled a gap in the highly demanded interpretation of peculiar solid-state VCD measurements and thus became a main focus of this project. Along with the elaboration of the scientific results, all methods and algorithms that have been developed and that are required to deal with AIMD trajectories and non-local VCD terms have been provided through a versatile, open-access, and ready-to-use software package, ChirPy, written in Python. Collaborations with theoretical as well as experimental groups at the host institution and beyond have strongly contributed to the success of this project based on a lively exchange of ideas, data, and knowledge. Among other things, this made possible the implementation of VCD into a polarizable force field directed by one of theoretical partner groups.
Publications
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Data: How Crystal Symmetry Dictates Non-Local Vibrational Circular Dichroism in the Solid State
S. Jähnigen et al.
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“Computation of VCD in the Periodic Gauge”, 7th International Conference on Vibrational Optical Activity, Edmonton, Canada.
S. Jähnigen
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“Periodic Calculations of Vibrational Circular Dichroism: How are they supposed to work?“, 123rd Annual Conference of the German Bunsen Society for Physical Chemistry, Aachen, Germany.
S. Jähnigen
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”Computation of Vibrational Circular Dichroism in the Condensed Phase: An Interplay of Structure and Dynamics“, Università di Brescia, Italy.
S. Jähnigen
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”Periodic Calculations of Vibrational Circular Dichroism: How are they supposed to work?“, Theoretical Chemistry Colloquium, Ruhr-Universität Bochum, Germany.
S. Jähnigen
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”Vibrational Circular Dichroism in the Solid State”, UZH (Luber Group), Zürich, Switzerland.
S. Jähnigen
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”Vibrational Circular Dichroism of Chiral Crystals: The Interplay of Symmetry and Chirality“, 12th International Conference on Advanced Vibrational Spectroscopy, Krakow, Poland.
S. Jähnigen
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”Vibrational Circular Dichroism of Crystals: The Interplay of Symmetry and Chirality“, 31st Annual Meeting Of The German Crystallographic Society, Frankfurt a. M., Germany.
S. Jähnigen
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”Vibrational Circular Dichroism of Molecular Crystals: The Interplay of Symmetry and Chirality“, Seminar of the Molecular Physics Department, Fritz Haber Institute, Berlin, Germany.
S. Jähnigen
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How Crystal Symmetry Dictates Non‐Local Vibrational Circular Dichroism in the Solid State. Angewandte Chemie International Edition, 62(5).
Jähnigen, Sascha; Le Barbu‐Debus, Katia; Guillot, Régis; Vuilleumier, Rodolphe & Zehnacker, Anne
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”Computation of Vibrational Circular Dichroism in the Periodic Gauge“, Journées Théorie, Modélisation et Simulations 2022, Rennes, France.
S. Jähnigen
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Vibrational Circular Dichroism Spectroscopy of Chiral Molecular Crystals: Insights from Theory. Angewandte Chemie International Edition, 62(41).
Jähnigen, Sascha
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Vibrational Circular Dichroism Spectroscopy with a Classical Polarizable Force Field: Alanine in the Gas and Condensed Phases. ChemPhysChem, 25(8).
Bowles, Jessica; Jähnigen, Sascha; Agostini, Federica; Vuilleumier, Rodolphe; Zehnacker, Anne; Calvo, Florent & Clavaguéra, Carine
