Columnar Iridium(III) Metallomesogens Based on Polycatenar Pyridyltetrazolate with Ambipolar Carrier Mobility Behavior

In this paper, we have designed and synthesized a series of neutral liquid-crystalline iridium­(III) complexes based on polycatenar 2,5-diphenylpyridine and pyridyltetrazolate derivatives. Iridium­(III) complexes all display highly emissive behavior with photoluminescence quantum yields in the range of 0.45–0.66 and a maximum emission wavelength at ∼563 nm. Hexagonal columnar mesophases of iridium­(III) complexes can be obtained by changing the number and length of peripheral alkoxyl chains attached to a 2,5-diphenylpyridine ligand (main ligand) and a pyridyltetrazolate ligand (auxiliary ligand). Moreover, experimental results of the charge transport properties for these iridium­(III) complexes, which were measured by the space charge limited-current method, exhibit ambipolar carrier mobility behavior. In particular, the liquid-crystalline iridium­(III) complexes can self-organize into one-dimensional (1D) nanostructure after thermal annealing treatment in their liquid-crystalline phase. The devices based on liquid crystal film display improved charge transport behavior compared with that of the devices based on polycrystalline film, indicating 1D nanostructure is beneficial to charge carrier injection and transportation.