Spin frustration, zero-field splittings, and Jahn-Teller effects in trinuclear copper SMMs: Insights from spin-flip calculations

SMMs (single-molecule magnets) are molecules with several unpaired electrons that can be prepared in high-spin states and retain their magnetization for some time. From methodological point of view, SMMs are strongly correlated systems that require specially designed ab initio methods. In our group, we use spin-flip approach (SF). Starting from the highest spin state (usually triplet or quartet), SF treats in a balanced way lower-spin configurations, which is crucial for qualitatively correct description of SMMs. I will present the SF results for copper di- and triradicals. One of the systems has a spin-frustrated trinuclear copper structural motif. Natural orbital analysis indicates that the two lowest doublets and the quartet have purely covalent character thus validating Heisenberg-Dirac-van-Vleck model Hamiltonian. PBE50, a recommended functional from previous benchmarks, matches an experimental estimate for Jahn-Teller splitting of the doublets states – 19 cm^-1. A large zero-field splitting, previously explained through Dzyaloshinskii-Moriya interaction, originating from spin-orbit coupling (SOC). Validation of this idea will be done using our new SOC code withing EOM-CC framework. Additional confirmation comes from El-Sayed rules, predicting a relative magnitude of SOC.