Synthesis, spectroscopic characterizations, photophysical properties and DFT studies of a novel iridium(III) complex containing 2-(2-butoxy-4-fluorophenyl)pyridine ligand

The iridium(III) complex, Ir(bFppy)₂(pyim) (bFppy = 2-(2-butoxy-4-fluorophenyl)pyridine and pyim = 2-(1H-Imidazol-2-yl)pyridine) was excellently prepared between 2-(1H-Imidazol-2-yl)pyridine and chloro-bridged iridium(III) dimer via reflux reaction. Butoxy functional group and fluorine atom were added to the phenyl ring of 2-phenylpyridine at positions 2 and 4 respectively, as cyclometalating ligand. The Ir(bFppy)₂(pyim) complex was characterized by spectroscopic methods: FTIR, NMR, LCMS and UV–Vis absorption. The presence of two sharp peaks at 1256 cm⁻¹ and 1129 cm⁻¹ due to ν(C–O) was revealed by IR analysis. The bands appear in the range of 1594–1567 cm⁻¹ owing to the C[dbnd]C and C[dbnd]N aromatic ring stretching vibrations of phenyl and pyridine. The ¹H NMR spectrum showed signals in the range of δ 5.50–8.60 ppm corresponding to phenylpyridine and pyridylimidazole protons. In contrast, the proton signals in the range of δ 0.80–4.50 ppm, assignable to butyl substituent. The UV–Vis spectrum displayed weaker and broader bands (333 nm and 376 nm) in the visible region due to the spin-forbidden ³MLCT transitions. The steady-state emission spectrum of the Ir(bFppy)₂(pyim) complex in air-equilibrated methylene chloride solution at 298 K exhibited almost blue emission with a λ_max at 466 nm. To support the experimental spectroscopic data, DFT and TD-DFT measurements were conducted using B3LYP in combination with the LanL2DZ basis set. The chemical shifts, vibrational modes and maximum absorptions of the Ir(bFppy)₂(pyim) complex were relatively well reproduced.