DFT-D investigation of the interaction between Ir (III) based photosensitizers and small silver clusters Ag_n (n = 2–20, 92)

Highlights: • Dispersion effects in weakly bonded systems containing silver clusters are investigated. • Different dispersion models and their parametrizations are discussed. • Reparametrization of C₆ coefficients for Ag and Ir is performed using MP2 and RPA as a reference. - Abstract: A dispersion-corrected density functional theory study of the photosensitizer [Ir(ppy)₂(bpy)]⁺ and its derivatives bound to silver clusters Ag_n (n = 2–20, 92) is performed. The goal is to provide a new system-specific set of C₆ interaction parameters for Ag and Ir atoms. To this end a QM:QM scheme is employed using the PBE functional and RPA as well as MP2 calculations as reference. The obtained C₆ coefficients were applied to determine dissociation curves of selected IrPS–Ag_n complexes and binding energies of derivatives containing oxygen and sulphur as heteroatoms in the ligands. Comparing different C₆ parameters it is concluded that RPA-based dispersion correction produces binding energies close to standard D2 and D3 models, whereas MP2-derived parameters overestimate these energies