Organometallic Fluorophores of d 8 Metals (Pd, Pt, Au)

In this contribution, we review the state-of-the-art in the field of the synthesis and luminescent properties of cyclometalated complexes of noble d8 metals Pd(II), Pt(II), and Au(III), with a large variety of organic ligands. For platinum and gold complexes, special emphasis has been done in the last 3 years (2015–17), because a huge number of outstanding contributions of academic and even industrial interest have appeared in this short period of time, while cyclopalladated complexes have been analyzed with a wider temporal perspective. The intrinsic properties of the metals (oxidation state, geometry, electrophilic character, redox behavior) and the ligands (type of donor atoms, σ-donating strength, π-accepting ability, planarity, rigidity) have been analyzed to determine their influence in the synthesis, through different methods, of the respective cyclometalated complexes, and also in the photophysical properties (type of transitions, tuning as a function of the substituents, etc.). In some selected cases, the application of these complexes to industrial optical devices is presented.