Solid‐State Circular Dichroism Spectroscopy

Abstract Chirality is a fundamental concept in nature because the biological world is homochiral, with proteins being made up of l ‐amino acids and nucleic acids of d ‐deoxyribose. Hence, chirality is important for the understanding of the origin of life as well as for manufacturing bioactive compounds in the food, agricultural, medicinal, and chemical industries. Chirality in the solid and condensed phases provides particularly valuable information because molecular interactions are much stronger in the solid state as compared with the solution phase, achieving chirality transfer, amplification, and discrimination. However, solid‐state chiroptical measurements cannot be generally achieved with conventional circular dichroism (CD) or circular birefringence (CB) spectrophotometers because of strong macroscopic anisotropies, that is, linear birefringence and linear dichroism. These artifact signals are often much stronger than the CD or CB signals. Only a CD spectrophotometer integrated into the Stokes–Mueller matrix analysis for a solid sample devised in 2001 is applicable for accurate chirality measurements for samples with macroscopic anisotropies. This novel CD spectrophotometer was named the universal chiroptical spectrophotometer (UCS) system because of its ability to measure all polarization phenomena, which is indispensable for obtaining the true CD and true CB signal in the solid state. Therefore, the presented UCS system opens a new door for solid‐state chiral investigations of optically anisotropic samples, for example, single crystal, microcrystalline powdered sample, gel, and film. This article presents a short and elementary discussion of solid‐state CD spectroscopy in polymer science and its use in the interpretation and design of experiments in polarization spectroscopy.