REGULAR ARTICLE Circular dichroism of some high-symmetry chiral molecules: B3LYP and SAOP calculations Carl Trindle Æ Zikri Altun Received: 16 July 2008 / Accepted: 19 November 2008 / Published online: 9 December 2008 Ó Springer-Verlag 2008 Abstract Computational modeling of optical activity, circular dichroism (CD) and optical rotatory dispersion, is rapidly becoming a useful supplement to experimental studies of absolute configuration. Here, we investigate the predictions of two alternative formulations of the rotational strength based on time-dependent density functional theory (TD-DFT), for a series of high symmetry chiral systems. We employ the TD-DFT method as realized in Gaussian 03 suite with the hybrid functional B3LYP and as incorpo- rated in the Amsterdam density functional (ADF) suite with PBE and SAOP functionals. The high-symmetry systems described here are somewhat larger than those used to evaluate the influence of basis sets and density functional choice, and for such large systems the very extensive basis sets recommended by most investigators may not be suitable for routine use. We observe that useful results for these systems can be obtained in modest bases, and in particular that diffuse functions may not be required for informative use of the ADF implementation. The sta- tistical average of orbital potentials (SAOP) model developed by Baerends is essential to the success of the ADF implementation. In some cases chirality is defined by features of the molecular structure remote from the chro- mophore. This is a severe test of the TD-DFT theory, since high-lying excitations define the most prominent features of the CD spectra, and complicates the use of computations to guide the assignment of absolute configuration. Exper- imental investigation of the high symmetry systems described here is desirable. 1 Introduction The computation of circular dichroism (CD) and optical rotatory dispersion (ORD) has been a continuing challenge to chemical theory since the pioneering work of Eyring [1], Moscowitz [2], and Tinoco [3]. Polavarapu [4] reviewed the general terrain of ORD experiment and theory, addressing both empirical models and computational advances to 2002. Crawford [5] has also surveyed the substantial progress which has taken place since the land- mark work and review of Hansen and Bouman [6]. The emphasis in recent work has rested on ORD, as shown in reviews by Autschbach [7] and Polavarapu [8]. The advances have been both formal—the formulation of optical properties within linear response theory—and practical, as versions of time-dependent density functional theory models have been incorporated into widely avail- able electronic structure codes. The methods have become so powerful to be useful in the determination of absolute configuration [9]. Optical excitation energies and the rotational strength R define both ORD and CD. R 0k ¼ Im 0 hjl k j i k hjm 0 ji Here m is the magnetic dipole moment operator and l is the electric dipole moment operator, both of which mix the ground state 0 and an excited state k. Electronic supplementary material The online version of this article (doi:10.1007/s00214-008-0494-8) contains supplementary material, which is available to authorized users. C. Trindle (&) Chemistry Department, The University of Virginia, Charlottesville, VA 22904, USA e-mail: cot@virginia.edu Z. Altun Physics Department, Marmara University, Istanbul, Turkey 123 Theor Chem Account (2009) 122:145–155 DOI 10.1007/s00214-008-0494-8