Diastereoselective Synthesis and Photophysical Properties of Bis-Cyclometalated Ir(III) Stereoisomers with Dual Stereocenters

Diastereoselective synthesis of bis-cyclometalated Ir(III) stereoisomers Δ/Λ-[Ir(C∧N)2(d-pro)] and Δ/Λ-[Ir(C∧N)2(l-pro)] (where C∧N is 2-phenylpyridine (Hppy), (4,6-difluorophenyl)pyridine (Hdfppy), and 2-phenylquinoline (Hpq) and pro is proline) with dual stereogenic centers at the metal and auxiliary ligand has been developed. The diastereomers Λ-l and Λ-d, and Δ-l and Δ-d exhibit distinguishable photophysical properties in both solution and the solid state. The thermodynamically stable diastereomers Λ-[Ir(ppy)2(l-pro)], Λ-[Ir(dfppy)2(l-pro)], and Λ-[Ir(pq)2(l-pro)] emit a green emission at 524 nm (Φ = 3.5% and τ = 35 ns), a blue-green emission at 480 nm (Φ = 4.5% and τ = 59 ns), and a red emission at 588 nm (Φ = 6.5% and τ = 200 ns) in DCM solution, respectively, which are blue-shifted accompanied by a large quantum yield and long lifetime relative to the corresponding unstable diastereomers Δ-[Ir(ppy)2(l-pro)] at 537 nm (Φ = 2.3% and τ = 29 ns), Δ-[Ir(dfppy)2(l-pro)] at 489 nm (Φ = 2.8% and τ = 43 ns)...