Density functional theory (DFT) and time-dependent (TD) DFT calculations were performed using Gaussian 16 (ES64L-G16, RevB.01) to elucidate the electronic structures of [Au24Pt(TBBT)18] 0 , [Au24Pt(TBBT)12(TDT)3] 0 , and [Au24Pt(TBBT)12(PDT)3] 0 . The structures obtained from the SCXRD of each molecule were used as the initial structures, with TBBT replaced by methanethiolate (SMe) to reduce the calculation cost. No changes were made to the TDT and PDT moieties. The BP86 functional was used to optimize the structure of ground state S0, and the basis sets were Def2-SVPP (for Au and Pt) 56 and 6-31G(d,p) (for S,C, and H) . For metal atoms, we incorporated SDD pseudopotentials with scalar relativistic effect . The absence of imaginary frequencies was confirmed by vibration analysis. Next, the vertical transition from S0 to Sn (n = 1-150) was calculated at the TD-B3LYP functional level for the obtained S0-optimized structure. The same basis sets and pseudopotentials were used for structural optimization. Absorption spectra were reproduced with a width of σ = 800 cm -1 using bar spectra obtained from single-point calculations. Molecular orbitals were visualized using Avogadro.