Excited states of aurocarbons: CASPT2 and CCSD(T) calculations of C₂Au₂ and C₂Au₄

Abstract

We present CASPT2 calculations of vertical excitation energies for low‐lying singlet and triplet states of auroderivatives of acetylene and ethylene representing small model aurocarbons. Data are supplemented by CCSD(T) results for triplet states. All four considered species, namely linear C2Au2 molecule and three conformers of the C2Au4 molecule—Au2C2Au2 (tetraauroethylene, the analog of the parent ethylene molecule) and – and –adducts of the Au2 molecule with the auroacetylene exhibit considerable lowering of low‐lying excitation energies when compared with their parent acetylene and ethylene molecules. Singlet and triplet excitation energies of diauroacetylene drop by 57% and 48%, respectively, and of tetraauroethylene, by 68% and 56% when compared with their respective parent molecules. Even more is lowered the singlet–triplet energy gap. We stress the importance of the dynamical correlation in CASPT2 calculations and discuss problems with selection of the appropriate active space in aurocarbons.

How does multi-reference computation change the catalysis chemistry? DFT and CASPT2 studies of the Cu-catalysed coupling reactions between aryl iodides and β-diketones

“…Nonetheless, CASSCF/CASPT2 has garnered renewed attention as a potential application in quantum computers, with promising implications for the future development of electronic state theory and quantum computers. 14–18 In this study, we focused on a Cu-catalysed cross-coupling reaction as an example of a simple catalytic reaction involving a 3d transition metal complex. We employed both DFT and CASSCF/CASPT2 methods to compare the geometry, electronic structure, and reaction mechanism, and discussed what kind of computational strategy would work for the Cu-catalyzed coupling reaction.…”