Theoretical Insights Into Aurophilic Interactions and Optical Properties of [Au((CC) _n COC ₆ H ₅ ) ₂ ]Au(Et ₃ P) ₂ ( <i>n</i>  = 1,2) Complexes

ABSTRACT This work presents a theoretical study of aurophilic interactions in gold(I) complexes using Hartree–Fock, post‐Hartree–Fock (MP2, SCS‐MP2, CCSD(T)), and dispersion‐corrected DFT (PBE‐D3(BJ), TPSS‐D3(BJ)) methods, combined with TD‐DFT and SCS‐CC2 excited state calculations. Four models were examined: [Au(CCH) 2 ][Au(PH 3 ) 2 ], {[Au(CCH) 2 ][Au(PH 3 ) 2 ]} 2 , [Au(C 2 COC 6 H 5 ) 2 ][Au(PEt 3 ) 2 ], and [Au(C 4 COC 6 H 5 ) 2 ][Au(PEt 3 ) 2 ]. Calculated Au–Au distances range between 279 and 297 pm at DFT‐D3(BJ), and between 290 and 315 pm at post‐HF levels, being the latter in line with the experimental trend (314–326 pm). The interaction energies fluctuated from –7.4 to –100.1 kcal/mol, indicating that electronic correlation, orbital, and dispersion energies dominate the stabilization of neutral aggregates, while electrostatics prevails in ionic systems. Excited‐state computations yield absorption maxima at 286 nm for [Au(CCH) 2 ][Au(PH 3 ) 2 ] and 382 nm for {[Au(CCH) 2 ][Au(PH 3 ) 2 ]} 2 , indicating a red shift upon aggregation. SCS‐CC2 predicts main transitions at 300/265 nm for [Au(C 2 COC 6 H 5 ) 2 ][Au(PEt 3 ) 2 ] and 259/218 nm for [Au(C 4 COC 6 H 5 ) 2 ][Au(PEt 3 ) 2 ], in close agreement with the experimental bands observed at 289/258 and 271/304 nm, respectively. These excitations correspond to metal–metal (MMCT) and metal–ligand (MMLCT/LMLCT) charge‐transfer transitions. Overall, the findings establish a direct structure–property relationship linking Au–Au coupling, ligand conjugation, and shifts in absorption energy, guiding the design of gold‐based luminescent materials.