Circular dichroism: electronic

First-principles calculations of electronic circular dichroism (ECD) are widely used to determine absolute configurations of chiral molecules. In addition, ECD is a sensitive probe for the three-dimensional molecular structure, making ECD calculations a useful tool to study conformational changes. In this review, we explain the origin of ECD and optical activity using response theory. While the quantum-mechanical underpinnings of ECD have been known for a long time, efficient electronic structure methods for ECD calculations on molecules with more than 10-20 atoms have become widely available only in the past decade. We review the most popular methods for ECD calculation, focusing on time-dependent density functional theory. Although single-point vertical ECD calculations yield useful accuracy for conformationally rigid systems, inclusion of finite-temperature effects is necessary for flexible molecules. The scope and limitations of modern ECD calculations are illustrated by applications to helicenes, fullerenes, iso-schizozygane alkaloids, paracyclophanes, beta-lactams, and transition metal complexes. (c) 2011 John Wiley & Sons, Ltd.