Phosphorescent multinuclear complexes for optoelectronics: tuning of the excited-state dynamics

Luminescent transition metal complexes have attracted a great deal of attention in the last two decades from both fundamental and application points of view. The majority of the investigated and most efficient systems consist of monometallic compounds with judiciously selected ligand sphere, providing excellent triplet emitters for both lab-scale and real-market light-emitting devices for display technologies. More recently, chemical architectures comprising multimetallic compounds have appeared as an emerging and valuable alternative. Herein, the most recent trends in the field are showcased in a systematic approach, where the different examples are classified by metal center and ligand(s) scaffold. Their optical and electroluminescence properties are presented and compared as well. Indeed, the multimetallic strategy has proven to be highly suitable for compounds emitting efficiently in the challenging red to near-infrared region, yielding metal-based emitters with improved optical properties in terms of enhanced emission efficiency, shortened excited-state lifetime, and faster radiative rate constant. Finally, the advantages and drawbacks of the multimetallic approach will be discussed.