Geometries of all structures were optimized at the PBEh-3c 94 level of theory in ORCA v4.2.1 with tight SCF and de-fault geometry convergence settings, and the "grid3 finalgrid5" grids. PBEh-3c is a PBE -based hybrid functional, combined with a special double-ζ basis set and corrections for London dispersion [DFT-D3(BJ) ] and basis set superposition error (gCP ). For the multireference diagnostics, a test of the weighted fractional occupational electron density (FOD) was done using the default settings, which are TPSS 100 /def-TZVP with TightSCF convergence and an occupation number smearing temperature of 5000 K. To calculate the A λ diagnostic, PBE and PBE0 101,102 calculations were done with the def2-TZVPP basis set.