N,N-Di(6-phenylpyridin-2-yl)aniline (L1), N,N-di(6-(2,4-difluorophenyl)pyridin-2-yl)aniline (L2), N,N-di(3-(pyridin-2-yl)phenyl)aniline (L3), N,N-di(3-(1H-pyrazol-1-yl)phenyl)aniline (L4), N,N-di(3-(3-methyl-1H-pyrazol-1-yl)phenyl)aniline (L5), and N,N-di(3-(4-methyl-1H-pyrazol-1-yl)phenyl)aniline (L6) undergo cyclometalation to produce two types of tetradentate bis-cyclometalated platinum(II) complexes: C--N*N(wedge)C platinum complexes 1 and 2 and N--C*C--N platinum complexes 3-6, respectively, where an "X--Y" (X, Y = C or N) denotes a bidentate coordination to the platinum to form a five-membered metallacycle and "X*Y" denotes a coordination to form a six-membered metallacycle. The crystal structures of 1, 3, and 5 were determined by the single-crystal X-ray diffraction analysis, showing distorted square-planar geometry, that is, two C--N coordination moieties are twisted. Complex 5 showed much greater distortion with largest deviation of 0.193 A from the mean NCCNPt coordination plane, which is attributed to the steric interaction between the two 3-methyl groups on the pyrazolyl rings. Density functional theory (DFT) calculations were carried out on the ground states of 1 and 3-6. The optimized geometries are consistent with the crystal structures. The highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the molecules displayed a localized characteristic with the contribution (18-45%) of the platinum metal to the HOMOs. All complexes are emissive at ambient temperature in fluid with quantum yields of 0.14 to 0.76 in 2-methyltetrahydrofuran. The emission of the complexes covers from blue to red region with lambda(max) ranging from 474 to 613 nm. Excimer emission was observed for 1 and 2 at high concentration of the complexes. The emission lifetime at infinite dilution for 1 and 2 was determined to be 7.8 and 11.4 micros, respectively. Concentration quenching was observed for 3 and 4, but the excimer emission was not observed. The life times for 3-6 were determined to be in the range of micro seconds, but those of 4-6 (3.4-5.7 micros) were somewhat shorter than that of 3 (7.6 micros). The highly structured emission spectra, long life times, and DFT calculations suggested that the emissive state is primarily a (3)LC state with metal-to-ligand charge-transfer (MLCT) admixture. The ZFS of 23 cm(-1) for the emissive triplet state was observed directly by high resolution spectroscopy for 1 in a Shpol'skii matrix, which also suggested an emission from a triplet ligand centered ((3)LC) state with admixture of MLCT character. Complex 1 was incorporated into an organic light-emitting diode (OLED) device as an emitter at 4 wt % in the mixed host of 4,4',4''-tris(N-carbazolyl)triphenylamine (TCTA) and 2,2',2''-(1,3,5-benzenetriyl)tris(1-phenyl-1-H-benzimidazole) (TPBI) and demonstrated excellent performance with maximum external quantum efficiency of 14.7% at the current density of 0.01 mA/cm(-1).

Alkylzinc bromides have been efficiently prepared by the direct insertion of zinc metal (dust, powder, granule, shot), activated with 1−5 mol % I 2 , into alkyl bromides in a polar aprotic solvent. The zinc reagents thus formed undergo Ni-and Pd-catalyzed cross-coupling with aryl halides to produce functionalized alkylarenes in excellent yields.

Phosphorescent cyclometalated platinum complexes are highly attractive compounds for a variety of applications, including organic‐light emitting diodes (OLEDs), chemical and biological sensing and imaging, and photocatalysis. This review deals with the progress made in the last five years in the development of highly luminescent platinum complexes based on bidentate, tridentate, and tetradentate cyclometalating ligands. The ligand design and synthesis, general methods for the formation of cycloplatinated complexes, and their photophysical properties, in particular, the emission energy and photoluminescent quantum efficiency of the complexes, are discussed. The applications of the complexes in OLEDs, chemical sensing, biological imaging, and other fields are briefly covered.

The photophysical properties of tris-cyclometalated iridium(III) complexes have been probed by chemical and geometric variation through the series fac- and mer-Ir(piq)(x)(ppy)(3-x) (x = 1-3; piq = 1-phenylisoquinolinato-N(∧)C(2'), ppy = 2-phenylpyridinato-N(∧)C(2')). The phosphorescent decays were recorded in solution at 295 K and in polymer films from 2 to 295 K. In the heteroleptic complexes, emission occurs based solely on the piq ligand(s), at least by the nanosecond time scale, as its excited states are the lowest energy. Because fac-Ir(piq)(3) and fac-Ir(ppy)(3) possess practically the same oxidation potential, comparison of photophysical properties through the series fac-Ir(piq)(x)(ppy)(3-x) (x = 1-3) revealed the effects of having one, two, or three emissive piq ligands with no confounding effects from differences in electron withdrawing or donating properties between the spectator ppy ligands and the piq ligands. Effects of placement of piq ligands in different coordination geometries were elucidated by comparisons to the mer series.

A series of tridentate cyclometalated platinum(II) complexes (C(∧)N*N)PtL (L = Cl or acetylide) featuring a fused five-six-membered metallacycle were synthesized. The structure of the complexes was confirmed by X-ray crystallography. In contrast to the C(∧)N(∧)N platinum complexes with a fused five-five-membered metallacycle, the platinum coordination in C(∧)N*N complexes is much closer to a square planar geometry. The photophysical properties of the complexes were studied. The geometrical change from C(∧)N(∧)N to C(∧)N*N led to a substantial improvement in phosphorescence efficiency of the complexes with an acetylide ligand in solution at room temperature. For example, the quantum yield of (C(∧)N*N)PtCCPh was measured to be 56%, demonstrating a big jump from 4% reported for (C(∧)N(∧)N)PtCCPh.