Ab initio calculations were performed using the ORCA 4.2.1 program. The structural model (2'-Me) used for ab initio calculations was made by replacing phenyl groups of the crystal coordinate of 2 with methyl groups (Table ). Positions of the methyl protons of 2'-Me were optimized at B3LYP/Def2-SVP with the RIJCOSX During the geometry optimization, Gd was replaced with diamagnetic Y. The CASSCF method was applied to 2'-Me with DKH-DEF2-SVP (for C, H, S, O), SARC-DKH-TZVP (for Pt), SARC-DKH-TZVPP (for Gd). 28b AUTOAUX keyword was used to generate the auxiliary basis sets for resolution of identity approximation. The active space consists of the seven orbitals that have 4f character and seven electrons ((7,7) CASSCF). One octet state, 48 sextet states, 392 quartet states, and 784 doublet states were considered and used for the following spin-orbit coupling calculations. The low-lying energy states from spin-orbit coupling are summarized in Table . Ab initio ligand field theory (AILFT) 11b was applied to check the ligand field splitting of 4f-orbitals (Figure ).