Simulation of circularly polarized luminescence spectra using coupled cluster theory

Abstract

We report the first computations of circularly polarized luminescence (CPL) rotatory strengths at the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) level of theory. Using a test set of eight chiral ketones, we compare both dipole and rotatory strengths for absorption (electronic circular dichroism) and emission to the results from time-dependent density-functional theory (TD-DFT) and available experimental data for both valence and Rydberg transitions. For two of the compounds, we obtained optimized geometries of the lowest several excited states using both EOM-CCSD and TD-DFT and determined that structures and EOM-CCSD transition properties obtained with each structure were sufficiently similar that TD-DFT optimizations were acceptable for the remaining test cases. Agreement between EOM-CCSD and the Becke three-parameter exchange function and Lee-Yang-Parr correlation functional (B3LYP) corrected using the Coulomb attenuating method (CAM-B3LYP) is typically good for most of the transitions, though agreement with the uncorrected B3LYP functional is significantly worse for all reported properties. The choice of length vs. velocity representation of the electric dipole operator has little impact on the EOM-CCSD transition strengths for nearly all of the states we examined. For a pair of closely related β, γ-enones, (1R)-7-methylenebicyclo[2.2.1]heptan-2-one and (1S)-2-methylenebicyclo[2.2.1]heptan-7-one, we find that EOM-CCSD and CAM-B3LYP agree with the energetic ordering of the two possible excited-state conformations, resulting in good agreement with experimental rotatory strengths in both absorption and emission, whereas B3LYP yields a qualitatively incorrect result for the CPL signal of (1S)-2-methylenebicyclo[2.2.1]heptan-7-one. Finally, we predict that one of the compounds considered here, trans-bicyclo[3.3.0]octane-3,7-dione, is unique in that it exhibits an achiral ground state and a chiral first excited state, leading to a strong CPL signal but a weak circular dichroism signal.

Circularly Polarized Luminescence from Axially Chiral BODIPY DYEmers: An Experimental and Computational Study

“…Most importantly, the calculated CPL spectrum for compound 2 a has now the correct sign in keeping with the experiment, namely the predicted CPL band for model (a R )‐ 2 a is positive (see inset in Figure , bottom). It is noteworthy that in all cases described by Pecul and Ruud and Crawford et al., RI‐CC2 or EOM‐CCSD calculations always agreed with TD‐DFT on the predicted sign of CPL bands . The present inconsistency between TD‐DFT and coupled‐cluster calculations is, to the best of our knowledge, unprecedented in the context of CPL, whereas in the context of ECD calculations some discrepancies between TD‐DFT and CC2 have been reported, mostly related to transitions with large charge‐transfer character …”

“…Pecul and Ruud used a similar calculation approach for the CPL spectrum of a β,γ‐enone, and more recently Crawford et al. applied EOM‐CCSD (equation‐of‐motion CC singles and doubles) CPL calculations to a series of ketones and enones . The results of SCS‐CC2 calculations on compounds 1 and 2 a are summarized in Table .…”

Circularly Polarized Luminescence: A Review of Experimental and Theoretical Aspects

“…Other useful codes for dealing with vibronic effects have been developed in the meantime . Other more sophisticated calculations at the equation‐of‐motion coupled cluster singles and doubles (EOM‐CCSD) level of theory have been presented by McAlexander and Crawford …”

“…57,61 Other more sophisticated calculations at the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) level of theory have been presented by McAlexander and Crawford. 62 The simplest way of calculating CPL spectra (not taking into account vibronic contributions) is to evaluate dipole (D 0m ) and rotational strengths (R 0m ) in the excited state geometry optimized by TD-DFT calculations. Fluorescence and CPL bands as function of energy E can be obtained through the following equations:…”

Molecular response properties in equation of motion coupled cluster theory: A time-dependent perspective

“…A large variety of molecular response properties have been successfully determined from EOM-CC response functions and the residues of these response functions. 7,15,[54][55][56][57][58][59][60][61][62][63][64][65][66] In the approach by Stanton and Bartlett, 2 response functions that are valid in CI theory are thus used to obtain response functions that can be used in CC theory. CI and CC theory are, however, very different.…”