Theoretical Insights Into the Phosphorescence and Excited-State Properties of Cyclometalated Pt(II) and Pd(II) Dimer Complexes.

In this study, we performed computational studies on two tetradentate ligand precursors and their corresponding Pt(II) and Pd(II) metal complexes containing fused 6/5/6 metallocycles, whose synthesis has been previously reported. We analyzed how the metallophilic interactions, molecular geometry, and π-π stacking influence the optoelectronic and photophysical properties of square-planar Pt(II) and Pd(II) complexes in dimeric forms involved in spin-flip transition using density functional theory (DFT) and time-dependent DFT (TD-DFT) at the M06-2X level of theory with Grimme's D3 dispersion correction. These metal-organic complexes exhibit distinct optical and excited-state properties, resulting from the interaction between the inorganic metal center and the organic ligand. The absorption and emission properties of these complexes were investigated, along with calculations of radiative rate constants, making them efficient and reliable triplet emitters for OLED applications. We also computed their phosphorescence lifetimes and compared them with available experimental data.