Nonadiabatic dynamics simulations on internal conversion and intersystem crossing processes in gold(i) compounds.

Area of Science:

• Photochemistry
• Computational Chemistry
• Materials Science

Background:

• Intersystem crossing (ISC) rates in gold(i) naphthalene derivatives are experimentally linked to the position of a second gold(i)-phosphine group.
• The underlying physical mechanisms for this observed phenomenon remain unclear.

Purpose of the Study:

• To elucidate the physical origin of the influence of gold(i)-phosphine group positioning on ISC rates.
• To investigate the excited-state relaxation dynamics, including ISC and internal conversion, in gold(i) naphthalene compounds.

Main Methods:

• Generalized trajectory-based surface-hopping dynamics simulations were employed.
• Simulations focused on ISC from singlet states (S₁) to triplet manifolds (T_n) and internal conversion within triplet states.

Main Results:

• Predicted ISC rates show excellent agreement with experimental data.
• Ultrafast ISC is primarily driven by small energy gaps and large spin-orbit couplings (SOCs) between S₁ and T_n.
• The second gold(i)-phosphine group decreases, rather than increases, SOCs between S₁ and T_n, indicating state-specific heavy-atom effects.
• The attachment position of the gold(i)-phosphine group critically influences electronic structures, energy gaps, and SOCs, thereby modulating ISC rates.

Conclusions:

• The positioning of substituents significantly impacts excited-state dynamics and photoluminescence properties of gold(i) compounds.
• Isomeric variations can lead to distinct excited-state relaxation pathways.
• These findings provide valuable insights for designing gold-containing materials with tailored photoluminescent characteristics.