Effective Alkoxylation of Phosphorescent Heteroleptic Iridium(III) Compounds Bearing Fluorinated Bipyridine Ligands

Abstract

Facile one-pot synthetic methods for new alkoxo-functionalized heteroleptic cyclometalated Ir(III) compounds have been developed. Nucleophilic substitution of fluorine atoms in [(dfpypy) 2 Ir(μ-Cl)] 2 (dfpypy = 2′,6′-difluoro-2,3′-bipyridine) by a methoxyethanol in the presence of an ancillary ligand led to the formation of the new alkoxo-functionalized heteroleptic Ir(III) compounds Ir[(RO) 2 pypy] 2 (N ∧ O) in good yields. These compounds have a distorted octahedral geometry around the Ir(III) center with an N,N-trans-meridional configuration. They exhibit intense blue to yellow phosphorescence (λ max = 453–558 nm) with moderate to excellent quautum efficiencies (0.22 to 0.96). Comparative studies on the fluoro analogues, Ir(dfpypy) 2 (N ∧ O), were also carried out. Our investigation established that the substitution of a fluorine atom by an alkoxy chain can greatly improve the solubility of the compounds in common organic solvents without significantly altering the emission color and efficiencies, making alkoxy-functionalized Ir(III) compounds potential candidates for use in solution-processable phosphorescence OLEDs.