The synthesis and characterization of eight unprecedented phosphorescent C^C* cyclometalated mesoionic aryl-1,2,3-triazolylidene platinum(II) complexes with different β-diketonate ligands are reported. All compounds proved to be strongly emissive at room temperature in poly(methyl methacrylate) films with an emitter concentration of 2 wt %. The observed photoluminescence properties were strongly dependent on the substitution on the aryl system and the β-diketonate ligand. Compared to acetylacetonate, the β-diketonates with aromatic substituents (mesityl and duryl) were found to significantly enhance the quantum yield while simultaneously reducing the emission lifetimes. Characterization was carried out by standard techniques, as well as solid-state structure determination, which confirmed the binding mode of the carbene ligand. DFT calculations, carried out to predict the emission wavelength with maximum intensity, were in excellent agreement with the (later) obtained experimental data.

Platinum(II) complexes with rigid and electron donating ligands are efficient phosphorescent emitters at room temperature. However, the excited‐state lifetimes of these complexes are, in general, relatively long. This problem, which can result in the degradation of the emitter, can be overcome by exploiting the natural tendency of platinum to form metallophilic interactions and aggregates. Herein, we report platinum(II) bimetallic complexes with 100 % quantum yield and at the same time exceptionally short radiative decay times, which in some cases are up to a hundredfold faster than the analogous monometallic complexes.

Recent studies have shown that anionic palladium complexes are viable catalysts for a range of catalytic cross-coupling reactions. We present a one-step synthesis of the anionic "ligandless" palladium complex [NBu 4 ][Pd-(DMSO)Cl 3 ] together with its crystal structure. This compound has been shown to be an active precatalyst in the Mizoroki−Heck reaction. Under Jeffery conditions, activated aryl chlorides can be coupled in yields of up to 94% without the need of an additional ligand. The presence of a small amount of water was necessary for product formation. An Amatore−Jutand-type catalytic cycle is consistent with the results presented herein. For comparison with the known mixed complex [(pym-Im-Me) 2 PdCl][Pd(DMSO)Cl 3 ], the cationic complex [(pym-Im-Me) 2 PdCl]PF 6 (pym = pyrimidyl, Im = imidazolin-2-ylidene) has been synthesized and characterized using standard techniques.

The structural motif of platinum(II) complexes bearing cyclometalating N‐heterocyclic carbene ligands can be used to design deep‐blue phosphors for application in organic light‐emitting diodes. However, the photophysical properties of the resulting molecules are also highly dependent on the auxiliary ligand. These often allow molecular deformations in the excited state which contribute to non‐radiative decay processes that diminish the attainable quantum yield. The use of bis(pyrazolyl)borate‐based auxiliary ligands enforces a high molecular rigidity due to their unique geometry. The steric crowding in the coordination sphere inhibits deformation processes and results in highly efficient deep‐blue platinum(II) emitters with CIE coordinates below (0.15; 0.15).

Control of the excited state geometry by rational ligand design leads to a new class of phosphorescent emitters with extraordinary photophysical properties. Extension of the π-system in the triplet state leading to a significant bathochromic shift of the emission was avoided by introduction of additional steric demand. We report the synthesis, characterization and photophysical properties of novel platinum(II) complexes bearing C^C* cyclometalated mesoionic carbene (MIC) with different β-diketonate ligands. The MIC ligand precursors were prepared from 1-phenyl-1,2,3-triazole using arylation protocols, introducing phenyl or mesityl functionalities. A solid state structure confirming the NMR assignments is presented. The emission properties were investigated in detail at room temperature and 77 K and are supported by DFT calculations and cyclic voltammetry. All complexes, with emission maxima between 502-534 nm, emit with quantum efficiencies ranging from 70-84 % in PMMA films.