Azolate‐Based Osmium(II) Complexes with Luminescence Spanning Visible and Near Infrared Region

Abstract

AbstractMononuclear osmium(II) complexes bearing azolate chromophoric chelates constituted a new class of emitters that are isoelectronic to the iridium(III) complexes, i. e., all with low‐spin d6 electronic configuration. The high reactivity of azole toward the osmium reagent Os3(CO)12 via N−H oxidative addition gives eventual formation of various mononuclear osmium(II) complexes showing bright emission ranging from sky‐blue to near infrared. Tuning of luminescence was executed by variation of the nature and π‐conjugation of chelates, as well as changing the metal‐based electron density by further ligand substitution. One important result is the successful isolation of two classes of NIR emissive osmium(II) complexes; those with the ligand‐to‐ligand charge transfer process at the excited state seems to be less efficient than those facilitated by the distinctive intra‐ligand charge transfer process. In addition, fabrication and characterization of OLED devices were elaborated, confirming their potential to serve as efficient saturated‐red and NIR phosphors.