Why Does One Measure Resonance Raman Optical Activity? A Unique Case of Measurements under Strong Resonance versus...

Area of Science:

• * Molecular spectroscopy
• * Chirality studies
• * Computational chemistry

Background:

• * Raman optical activity (ROA) spectroscopy provides insights into molecular structure, chirality, and conformation.
• * Resonance conditions reveal details on excited electronic states.
• * Density functional theory (DFT) is a powerful tool for analyzing molecular properties.

Purpose of the Study:

• * To present the first combined density functional theory (DFT) analysis of both far from resonance (FFR)-ROA and resonance ROA (RROA) spectra.
• * To investigate the complementary nature of FFR-ROA and RROA for small molecular systems.
• * To apply these methods to cobalamin derivatives using visible and near-infrared light excitation.

Main Methods:

• * Far from resonance (FFR)-ROA spectroscopy
• * Resonance ROA (RROA) spectroscopy
• * Density functional theory (DFT) calculations
• * Near-infrared and visible light excitation

Main Results:

• * RROA spectra, while often monosignate, complement the bisignate nonresonance ROA spectra by providing additional information.
• * The combination of FFR-ROA and RROA with DFT calculations offers a comprehensive spectral analysis.
• * Structural and conformational differences in cobalamin derivatives were effectively revealed.

Conclusions:

• * The integrated approach of FFR-ROA, RROA, and DFT provides a complete spectral picture for molecular analysis.
• * RROA spectroscopy serves as a valuable complement to nonresonance ROA.
• * This combined methodology is effective for discerning structural and conformational variations in molecules like cobalamin derivatives.