Toward Rhenium-Based Circularly Polarized OLEDs Using Tailored Chiral Re(CO)₃ Emitters

Chiral rhenium(I) emitters exhibiting circularly polarized phosphorescence (CPP) are an attractive mainstay for CP organic light-emitting diodes (CP-OLEDs). However, the efficiency of such emitters is not ideal, and they have never been explored for circularly polarized electroluminescence (CPEL) applications. Here, we have tailored robust chiral Re(I) complexes with improved CPP properties, and demonstrated CPEL from rhenium emitters for the first time. Two pairs of enantiomeric Re(I) complexes have been synthesized by introducing of one or two chiral menthol groups into 1,10-phenanthroline unit (phen) of archetypical emitters [ReBr(CO)₃(phen)]. The designed complexes exhibit a yellow CPP with enhanced |g_lum| factors (up to 2.5×10^-2) and a good quantum efficiency. The pioneering Re(I)-based CP-OLEDs (based on the obtained emitters) exhibit yellow CPEL with |g_EL| factors of up to 6.2×10^-3 and a maximal external quantum efficiency of 13.2 %. This work highlights the good potential of chiral Re(I) emitters for CPEL applications, and opens up a new shortcut to CPP-active Re(I) complexes.