Vibrational optical activity: From discovery and development to future challenges

Vibrational optical activity (VOA) consisting of infrared vibrational circular dichroism (VCD) and vibrational Raman optical activity (ROA) was predicted, discovered, and confirmed between 1971 and 1975. My path to VOA was mentored by three pioneers of chirality and vibrational spectroscopy: Professors Albert Moscowitz, Warner L. Peticolas, and Philip J. Stephens, and while they are no longer alive today, the Chirality Medal, my award address, and this paper are dedicated to each of them. Since the discovery of VOA, a number of key advances have made possible the current era of widespread applications. The principal instrumental advances were Fourier-transform VCD (FT-VCD) and multichannel charge coupled detector (CCD) ROA. Computational advances include the first complete quantum chemistry formulation of VCD leading to the magnetic field perturbation (MFP) and the nuclear velocity perturbation (NVP) theories. The strength of VOA is the comparison between measured and calculated spectra that enables the determination of absolute configuration and solution-state conformations. More recently, VCD has uncovered supramolecular chirality in amyloid fibrils and ROA to high-order protein structure. Future challenges for VOA include describing the effects of weak intermolecular interactions, transfer of chirality, solvent effects, supramolecular chirality, and the generation of nuclear velocity electron current density.