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

Facile
one-pot synthetic methods for new alkoxo-functionalized
heteroleptic cyclometalated Ir­(III) compounds have been developed.
Nucleophilic substitution of fluorine atoms in [(dfpypy)2Ir­(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)2pypy]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
(λmax = 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.