Cyclometalated Ir(III) Complexes Containing Pyrazole/Pyrazine Carboxylate Ligands

Two cyclometalated Ir(III) complexes using 2-phenylpyridine (ppy-H) as the cyclometalating ligand, and pyrazole-3-carboxylic acid (prca-H) and pyrazine 3,5-dicarboxylic acid (pzdca-H(2)) as ancillary ligands; were synthesized from the chloro-bridged dimer precursor [{(ppy)(2)Ir}(2)(mu-Cl)(2)]. The title compounds [Ir(ppy)(2)(prca)] (1) and [{Ir(ppy)(2)}(2)(pzdca)] (2) are monomeric and dimeric neutral Ir(III) complexes, respectively. Their electrochemical and photophysical properties were examined. They exhibit metal-based oxidations and ligand-based reductions. These complexes exhibit emission in the blue-green region with lifetimes in the micro-second range at room temperature. The nature of the emission spectra indicates differences in the origin of emission in these two compounds.