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 nu(C-O) was revealed by IR analysis. The bands appear in the range of 1594-1567 cm-1 owing to the C--C and C--N aromatic ring stretching vibrations of phenyl and pyridine. The 1H NMR spectrum showed signals in the range of delta 5.50-8.60 ppm corresponding to phenyl-pyridine and pyridylimidazole protons. In contrast, the proton signals in the range of delta 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 lambda 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.