Iridium Luminophore Complexes for Unimolecular Oxygen Sensors

In this study, a series of novel luminescent cyclometalated Ir(III) complexes has been synthesized
and evaluated for use in unimolecular oxygen-sensing materials. The complexes Ir(C6)2(vacac), 1, Ir(ppy)2(vacac), 2, fac-Ir(ppy)2(vppy), 3, and mer-Ir(ppy)2(vppy), 4, where C6 = Coumarin 6, vacac = allylacetoacetate, ppy = 2-phenylpyridine, and vppy = 2-(4-vinylphenyl)pyridine, all have pendent vinyl or allyl groups
for polymer attachment via the hydrosilation reaction. These luminophore complexes were characterized
by NMR, absorption, and emission spectroscopy, luminescence lifetime and quantum yield measurements,
elemental analysis, and cyclic voltammetry. Complex 1 was structurally characterized using X-ray
crystallography, and a series of 1-D (1H, 13C) and 2-D (1H−1H, 1H−13C) NMR experiments were used to
resolve the solution structure of 4. Complexes 1 and 3 displayed the longest luminescence lifetimes and
largest quantum efficiencies in solution (τ = 6.0 μs, φ = 0.22 for 1; τ = 0.4 μs, φ = 0.2 for 3) and, as result,
are the most promising candidates for future luminescence-quenching-based oxygen-sensing studies.