The transition metal complexes were optimized using the ORCA 5.0.1 suite of programs . The Kohn-Sham DFT optimization technique was considered with the PBE0 functional . Relativistic energy corrections were introduced with the zeroth order regular approximations (ZORA) Hamiltonian at scalar (SR) level . ZORA-TZVP basis sets were used for the transition metals and ZORA-def2-TZVP basis sets were used for the ligand atoms . The SARC/J auxiliary basis was used for the metal center and autoaux feature was utilized to generate the auxiliary basis sets for the light atoms . A resolution of identity (RI) approximation was employed to accelerate the two-electron integral calculations . Numerical precision due to the integration grid relied on the default grid control system in ORCA 5 (keyword "defgrid2") and an increased radial grid of value 7 was considered for the metal centers with the keyword "SpecialGridIntAcc". "Tight" SCF convergence criteria correspond to the energy change at 10 -8 scale and root-mean-square (RMS) density change at 0.5×10 -9 was considered. The geometry optimizations were performed at normal mode with "Opt" corresponding to the changes in the RMS gradient and RMS step at 10 -4 and 2 × 10 -3 scale.