A series of luminescent cyclometalated N^C^N [N^C^N = 1,3-bis(N-alkylbenzimidazol-2'-yl)benzene]platinum(II) alkynyl and carbazolyl complexes has been prepared. The structure of one platinum(II) carbazolyl complex has been characterized by X-ray crystallography. The corresponding electrochemical and photophysical properties have been explored and analyzed. The N^C^N platinum(II) complexes displayed rich luminescence in degassed dichloromethane solution, with their emission profiles dependent on the coordinated alkynyl and carbazolyl ligands. Their emission energies are correlated to the electronic properties of the alkynyl and carbazolyl ligands. By varying the electronic properties of the alkynyl and carbazolyl ligands, emission energies could be fine-tuned to cover a wide range of the visible spectrum, as supported by computational studies. A donor-acceptor platinum(II) complex has been utilized to fabricate memory devices that exhibit binary memory performances with low operating voltages, high ON/OFF ratios, and long retention times. Solution-processable OLEDs have been fabricated based on another platinum(II) carbazolyl complex, resulting in a maximum external quantum efficiency of up to 7.2%, which is comparable to that of the vacuum-deposited devices based on the small-molecule counterpart, illustrating the multifunctional nature of the platinum(II)-containing materials.

A new class of bipolar alkynylgold(III) complexes containing triphenylamine and benzimidazole moieties has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). The incorporation of methyl groups in the central phenyl unit has been found to rigidify the molecule to reduce nonradiative decay, yielding a high photoluminescence quantum yield of up to 75% in spin-coated thin films. In addition, the realization of highly efficient solution-processable OLEDs with an extremely small external quantum efficiency (EQE) roll-off has been demonstrated. At practical brightness level of 1000 cd m(-2), the optimized devices exhibited a high EQE of up to 10.0% and an extremely small roll-off of less than 1%.

A new class of cyclometalated tetradentate alkynylgold(III) complexes has been successfully synthesized by post-synthetic modification. Through the judicious design and choice of pincer ligands, post-synthetic cyclization could be achieved to produce the robust and structurally rigid class of tetradentate gold(III) C^N^C^C complexes with high photoluminescence quantum yields of up to 0.49 in solution and 0.78 in doped thin films at room temperature, at least an order of magnitude higher than those of the structurally related uncyclized tridentate alkynylgold(III) analogues. High-performance yellow to orange-red emitting solution-processable organic light-emitting devices have also been achieved with external quantum efficiency of 11.1 %. This work describes for the first time of the use of post-synthetic ligand modification approach to overcome the synthetic challenge for tetradentate alkynylgold(III) complexes.

A new class of luminescent dendritic carbazole-containing alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). These complexes exhibit high photoluminescence quantum yields of up to 80% in spin-coated thin films. In addition, the incorporation of carbazole dendrons into the platinum(II) center can significantly suppress intermolecular interactions in solid-state thin films, giving rise to emission spectra that are similar to those found in solution irrespective of dopant concentrations. High-performance solution-processable OLEDs have also been fabricated, with a maximum external quantum efficiency of up to 10.4%, which is comparable to that of the vacuum-deposited devices based on the small-molecule counterpart. This is one of the highest ever reported values for solution-processable devices based on platinum(II) complexes with tridentate ligands.

A new class of highly luminescent bipolar alkynylplatinum(II) complexes has been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of solution-processable organic light-emitting devices (OLEDs). Through the incorporation of a delicate balance of electron-donating carbazole moieties and electron-accepting phenylbenzimidazole or oxadiazole moieties into the platinum(II) core, the platinum(II) complexes have been demonstrated to exhibit bipolar charge transport character with high photoluminescence quantum yields of up to 0.75 in thin films. The introduction of meta-linkages into the complexes further helps weaken the donor-acceptor interactions, facilitating better carrier-transporting abilities. More importantly, high-performance solution-processable green-emitting OLEDs with maximum current efficiencies of up to 57.4 cd A and external quantum efficiencies of up to 16.0% have been realized. This is among the best performances for solution-processable phosphorescent OLEDs reported based on platinum(II) complexes as well as bipolar metal complexes.