Where is the Heavy‐Atom Effect? Role of the Central Ligand in Tetragold(I) Ethynyl Complexes

He ain't heavy: The heavy-atom effect is not the sole factor that determines the efficiency of intersystem crossing and triplet radiative decay rates. Theoretical calculations along with experimental evidence show that the central ligand plays a decisive role in the luminescence behavior of tetragold(I) ethynyl complexes (see structures and representations of the highest occupied molecular orbitals).