Porous Phosphorescent Coordination Polymers for Oxygen Sensing

Phosphorescent cyclometalated iridium tris(2-phenylpyridine) derivatives were designed and incorporated into coordination polymers as tricarboxylate bridging ligands. Three different crystalline coordination polymers were synthesized using a solvothermal technique and were characterized using a variety of methods, including single-crystal X-ray diffraction, PXRD, TGA, IR spectroscopy, gas adsorption measurements, and luminescence measurements. The coordination polymer built from Ir3-(2-pyridyl)benzoate(3), 1, was found to be highly porous with a nitrogen BET surface area of 764 m(2)/g, whereas the coordination polymers built from Ir4-(2-pyridyl)benzoate(3), 2 and 3, were nonporous. The (3)MLCT phosphorescence of each of the three coordination polymers was quenched in the presence of O(2). However, only 1 showed quick and reversible luminescence quenching by oxygen, whereas 2 and 3 exhibited gradual and irreversible luminescence quenching by oxygen. The high permanent porosity of 1 allows for rapid diffusion of oxygen through the open channels, leading to efficient and reversible quenching of the (3)MLCT phosphorescence. This work highlights the opportunity of designing highly porous and luminescent coordination polymers for sensing other important analytes.