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.
Blue phosphorescent (dfpypy) 2 Ir(mppy), where dfpypy = 2',6'-difluoro-2,3'-bipyridine and mppy = 5-methyl-2-phenylpyridine, has been synthesized by newly developed effective method and its solid state structure and photoluminescent properties are investigated. The glass-transition and decomposition temperature of the compound appear at 160 o C and 360 o C, respectively. In a crystal packing structure, there are two kinds of intermolecular interactions such as hydrogen bonding (C-H F) and edge-to-face C-H π(py) interaction. This compound emits bright blue phosphorescence with λ max = 472 nm and quantum efficiencies of 0.23 and 0.32 in fluid and the solid state. The emission band of the compound is red-shifted by 40 nm relative to homoleptic congener, Ir(dfpypy) 3 . The ancillary ligand in (dfpypy) 2 Ir(mppy) has been found to significantly destabilize HOMO energy, compared to Ir(dfpypy) 3 , (dfpypy) 2 Ir(acac) and (dfpypy) 2 Ir(dpm), without significantly changing LUMO energy.
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