Circular Dichroism Spectrum of [Co(en)3]3+ in Water: A Discrete Solvent Reaction Field Study

In this work we investigate the circular dichroism (CD) spectrum of [Co(en)3]3+ in water, using the discrete solvent reaction field (DRF) model. The DRF model is a polarizable quantum mechanics/molecular mechanics (QM/MM) model. The implementation of the DRF model for CD spectra calculations based on time-dependent density functional theory (TDDFT) is presented. The combination of DRF with TDDFT allows for a computationally attractive solution for calculating chirooptical properties of molecules in solution when explicit solvent structures are of interest. Using a mixed coarse/fine-grained parallel computation, we show that average CD spectra from snapshots of the solvent structure can be obtained routinely. Classical polarizable molecular dynamics (MD) simulations have been used to obtain the solvent structure around the [Co(en)3]3+ (en = ethyldiamine) solute. We show that the final spectrum converges quickly with respect to the number of configurations. The DRF results were compared with results obtained from the much simpler conductor-like screening model (COSMO). Both models predicted similar blue shifts of the CD bands, but none of the Correspondence to: L. Jensen; e-mail: [email protected]. edu.; or J. Autschbach; e-mail: [email protected] Contract grant sponsor: NSF. Contract grant number: CHE-0447321. This article contains supplementary material available via the Internet at http://www.interscience.wiley.com/jpages/0020-7608/ suppmat/. International Journal of Quantum Chemistry, Vol 106, 2479–2488 (2006) © 2006 Wiley Periodicals, Inc.