Time-Dependent Formulation of Resonance Raman Optical Activity Spectroscopy

Area of Science:

• Computational Chemistry
• Spectroscopy
• Chiroptical Methods

Background:

• Resonance Raman (RR) spectroscopy provides detailed molecular vibrational information.
• Simulating RR spectra for larger systems is computationally challenging.
• Chiral molecules exhibit unique optical activity properties not fully captured by standard RR methods.

Purpose of the Study:

• To extend theoretical frameworks for simulating resonance Raman optical activity (RROA) spectra.
• To develop a versatile computational tool for analyzing chiral molecular spectra.
• To validate the new method on small and medium-sized chiral molecules.

Main Methods:

• A time-dependent (TD) formulation for RROA calculations.
• Transition tensors derived from cross-correlation functions.
• Support for adiabatic/vertical models, Cartesian/internal coordinates, and Herzberg-Teller effects.
• Integration within a quantum-chemistry program to include solvation and anharmonicity.

Main Results:

• Successful validation of the TD-RROA method on methyloxirane.
• Accurate simulation of RROA spectra for medium-sized molecules like naproxen-OCD3, quinidine, and 2-Br-hexahelicene.
• Good agreement between simulated and experimental spectral data.

Conclusions:

• The developed TD-RROA method provides a robust and general approach for simulating chiral molecular spectra.
• This computational tool enhances the understanding of chiroptical properties and vibrational dynamics.
• The method's ability to incorporate environmental and anharmonic effects broadens its applicability in molecular science.