Binuclear C^C* cyclometalated NHC platinum(II) compounds with bridging amidinate ligands were synthesized to evaluate their photophysical properties. Their three-dimensional structures were determined by a combination of 2D NMR experiments, mass spectrometry, DFT calculations, and solid-state structure analysis. The bridging amidinate ligands enforce short distances between the platinum centers of the two cyclometalated structures, which gives rise to extraordinary photophysical properties.

A new class of platinum­(II) compounds, the 4,5-dimethyl-3-aryl-thiazole-2-ylidene platinum­(II) acetylacetonato complexes, are described. Their efficient phosphorescent emission at room temperature makes them suitable for potential applications in organic light-emitting diodes. A new synthetic pathway that allows the preparation of a broad range of different N-arylthiazole-2-thiones and their subsequent conversion into the corresponding N-arylthiazolium perchlorate and hexafluorophosphate salts has been developed. Not only electron-rich (4-OMe, 4-Me, 3-Me) N-arylthiazoles but also electron-deficient ligands with a cyano or an ester group could be synthesized. From commercially available anilines N-arylthiazolium perchlorate and hexafluorophosphate salts were synthesized via ring-closure of in situ generated N-aryldithiocarbamate salts followed by a sulfur-oxidation/-substitution protocol to the air-stable carbene precursors. All reactions were performed in multigram scale in good yields. The synthesis of the corresponding platinum­(II) complexes involves generating the corresponding N-arylthiazole-silver­(I)-carbene complexes, transmetalation to platinum, cyclometalation, and reaction with acetylacetonate (acac). Solid-state structures of two N-arylthiazole-2-thiones, one N-arylthiazolium salt, and three N-arylthiazole-2-ylidene-platinum­(II) complexes complement the analytic characterization including 195Pt NMR. The unsubstituted complex 4,5-dimethyl-3-phenylthiazole-2-ylidene-platinum­(II)-acac was additionally characterized by 2D-NMR techniques (COSY, HSQC, HMBC, NOESY). Photoluminescence measurements were performed in amorphous poly­(methyl methacrylate) films and revealed bluish-green emission maxima (∼500 nm) independent of the electronic structure of the thiazoles, whereas the variation of the substitution pattern at the cyclometalating aryl system led to excellent quantum efficiencies and decay lifetimes of 8.1–21.4 μs.

We present the synthesis and characterization of novel cyclometalated ruthenium N-heterocyclic carbene (NHC) complexes of the general formula [Ru(C^C*)(bpy)]PF (bpy = 2,2'-bipyridine), with the C^C* ligand being based on different 1-phenylimidazoles. They were synthesized in a one-pot procedure starting from the corresponding p-cymene NHC complexes [Ru(C^C*)(p-cymene)Cl]. Their structural, spectroscopic, and electrochemical properties were investigated by NMR, X-ray, UV/vis, and CV, as well as density functional theory methods. Because of the stronger electron-donating carbene ligands, these complexes represent a new class of bisheteroleptic dyes with improved photophysical and electrochemical properties.

We report the synthesis of seven novel backbone functionalized N-phenyl-1,3-thiazol-2-ylidene platinum(ii) complexes and their photophysical properties. Electronically diverse N-phenyl-1,3-thiazol-2-thiones were prepared by a reaction of aniline with carbon disulfide and different α-haloketone compounds. Oxidative desulfuration and salt metathesis yielded the desired NHC-precursors with hexafluorophosphate counterions. In addition, a new route for the synthesis of N-phenyl-1,3-benzo[d]thiazole tetrafluoroborate via N-arylation using hypervalent iodine species is presented. All complexes were prepared from the corresponding NHC precursor in a one-pot process using silver(i)oxide, transmetalation to platinum and reaction with the β-diketone acetylacetone under basic conditions. These complexes exhibit strong phosphorescence with quantum yields up to 72% in 2 wt% PMMA films with decay lifetimes of 8.8-12.3 μs. The influence of methyl- and phenyl-groups, and an ester-substituent at the 4- and/or 5-position of the 1,3-thiazole moiety, as well as the N-phenyl-1,3-benzo[d]thiazole-derived motif is discussed. The 4,5-unsubstituted-N-phenyl-1,3-thiazol-2-ylidene platinum(ii) acetylacetonato complex served as a reference in this study to evaluate the electronic effects originating from the backbone substitution. All complexes emit in a narrow range of the bluish-green spectrum of the visible light (510 ± 10 nm).

We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η(6)-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBAr(F)4) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru](+)[BAr(F)4](-). Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η(6)-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group "atop" is retained in the bimetallic complexes.