High Quantum Yields from Perfluorinated Binolate Erbium Complexes and Their Circularly Polarized Luminescence.

ABSTRACT

High quantum yield and circularly polarized luminescence (CPL) brightness values are reported from Shibasaki-type erbium complexes supported by a perfluorinated Binol ligand (F12Binol). The total fluorination of the ligand circumvents nonradiative quenching from Csp2-H vibrations and leads to quantum yields of up to 11% and CPL brightness values of up to 317 M-1 cm-1 (a 19- and 6-fold increase, respectively, compared to (Binol)3ErNa3). These values are the highest values for any molecular erbium complex to date, making them comparable to Yb emitters. A series of fluorinated Shibasaki-type complexes are synthesized by varying the alkali metal (K, Na, Li) in the secondary coordination sphere, leading to unexpected structural differences. NMR (19F, 7Li) and chiroptical spectroscopy analyses provide insights into their structural geometry. With much improved quantum yields and CPL brightness values, we provide synthetic design principles toward other practical candidates for use in quantum communication technologies.