Hongbo Tong

Phosphorescent Cu(I) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives for organic light-emitting diodes†

Mononuclear Cu(I) complexes based on bis(pyrazol-1-yl-methyl)-pyridine derivatives and ancillary triphenylphosphine have been prepared and characterized by 1H NMR, mass spectroscopy and single-crystal X-ray analysis. The thermogravimetric analysis shows that the complexes exhibit high thermal stability. The electronic absorption spectra display two features in the regions of 230–260 and 290–350 nm attributable to mixed ligand-to-ligand (LLCT) and metal-to-ligand-charge-transfer (MLCT) excited states, which is supported by the results of density functional theory (DFT) and time-dependent DFT (TDDFT) calculations on these Cu(I) complexes. These complexes are strongly emissive in the solid state at ambient temperature. Intense blue or green emission in the poly(methyl methacrylate) film is observed in the region of 475–518 nm for these complexes with the emission lifetimes in the microsecond time scale (12–20 μs), indicating that the emission may be phosphorescence emission. Increasing the steric hindrance of the substituents on the pyrazole unit results in a blue-shift of the emission bands and enhanced emission quantum efficiency in PMMA films. The two most emissive complexes have been used for the fabrication of phosphorescent organic light-emitting diodes (POLEDs).

Metal (Mg, Fe, Co, Zr and Ti) complexes derived from aminosilyl substituted aminopyridinato ligand: synthesis, structures and ethylene polymerization behaviors of the group 4 complexes

Lithium N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamidate (2) was prepared from the reaction of new compound N-[(N,N-dimethylamino)dimethylsilyl]-2-pyridylamine (1) and LiBu(n). Treatment of the lithium salt (2) with an equal equivalent of MgBr(2)(THF)(2), FeCl(2) and CoCl(2) afforded the corresponding dinuclear complexes , , and , in which metal atoms possess similar trigonal bipyramidal geometries and each ligand functions as a bimetallic bridging binding aminopyridinato moiety with N-donation from the dimethylamino group. While the stoichiometric reaction of with ZrCl(4) gave the mononuclear zirconium complex (6); the seven coordinated zirconium atom adopts a distorted pentagonal bipyramid geometry and the ligand acts as monoanionic η(2)-aminopyridinato moiety with the pendant arm coordinated via N(CH(3))(2). The reaction of with one equivalent of TiCl(4)(THF)(2) produced the interesting dinuclear titanium complex (7) owing to the elimination of a (N,N-dimethylamino)dimethylsilyl group from the original ligand, and the two titanium centers present different coordination geometries. The molecular structures of the crystalline metal complexes have been confirmed by X-ray single crystal diffraction analysis. Upon activation with methylaluminoxane (MAO), both complexes and exhibited moderate catalytic activities toward ethylene polymerization and produced high molecular weight polyethylenes with broad molecular weight distributions.

Synthesis and structural study of an unsymmetrical aliphatic benzamidinato ligand and its use in the formation of selected Cu(I), Mg(II) and Zr(IV) complexes

The reaction of a Et2O solution of LiN(Cy)SiMe3 (Cy = cyclohexyl) with PhCN in the presence of the Lewis-base donor tetrahydrofuran (THF) or Me2N(CH2)2NMe2 (TMEDA) gave the THF- or TMEDA-solvated unsymmetrical aliphatic lithium benzamidinato compound [{PhC(NCy)(NSiMe3)}Li(THF)]2 (1) or [{PhC(NCy)(NSiMe3)}Li(TMEDA)] (2). Treatment of LiN(Cy)SiMe3 with PhCN in diethyl ether, and further with CuCl, MgBr2(THF)2 or ZrCl4 at a ratio of 1:1, 2:1 and 3:1 allowed the formation of novel metal complexes [{PhC(NCy)(NSiMe3)}Cu]2 (3), [{PhC(NCy)(NSiMe3)}2Mg(OEt2)] (4) and [{PhC(NCy)(NSiMe3)}3ZrCl] (5), respectively. The X-ray structures of complexes 1–4 are presented. Complex 5/MAO system allows the moderate polymerization of ethylene.

Synthesis, crystal structure and photophysical study of luminescent three-coordinate cuprous bromide complexes based on pyrazole derivatives

Abstract The 1 : 2 M-ratio reaction between cuprous bromide and pyrazole derivatives in toluene results in mononuclear Cu(I) complexes [CuBr(pyrazole)2]. The complexes have been characterized by 1H NMR spectroscopy and elemental analysis. The molecular structure, established by single-crystal X-ray diffraction, features a trigonal planar geometry around copper, with monodentate pyrazole derivatives. All the Cu(I) complexes are luminescent in the solid state at ambient temperature. Intense blue or blue-green emission in the solid state is observed for these complexes, with the maxima ranging from 431 to 493 nm. The observed photoluminescence could be ascribed to the metal-to-ligand charge-transfer excited states, probably mixed with some halide-to-ligand character. The microsecond lifetime scale of the complexes implies that these transitions arise from the triplet excited states.

Organoamido zirconium(IV) and titanium(IV) complexes and their catalysis towards ethylene polymerization

The reaction of PhN(Li)SiMe3 with 2 equiv. of dimethylcyanamide with further addition of 2 equiv. of CpTiCl3 led via Me3SiCl elimination to dinuclear titanium(IV) compound 1. The reaction of DippN(Li)SiMe3 with 1 equiv. of dimethylcyanamide with further addition of 1 equiv. of CpTiCl3 afforded centrosymmetric dimeric titanium(IV) compound 2 and mononuclear 3 with the elimination of Me3SiCl. The zirconium(IV) compound 4 was obtained by the addition reaction of PhN(Li)SiMe3 with 2 equiv. of dimethylcyanamide and metathesis reaction with ZrCl4. X-ray diffraction studies of 1–4 establish the dinuclear titanium(IV) structure in 1, half-titanocene of 2 and 3, and a propeller-like complex fragment of 4. Complexes 2 and 4 show moderate or high activities in the polymerization of ethylene upon activation with methylaluminoxane (MAO).

Synthesis, Crystal Structures and their Utilities in Tishchenko Reaction of N,O-Bidentate Aluminum Compounds

Deprotonolysis of the N,O-bidentate pyridyl functionalized alkoxy ligands, 1,1-dimethyl-2-(pyridin-2-yl)ethanol (L1H), 1-phenyl-2-(pyridin-2-yl)ethanol (L2H) and 1,1-diphenyl-2-(pyridin-2-yl)ethanol (L3H), with 1 equiv of AlMe3 gave the corresponding dimeric metal-monoalkyl compounds [L1AlMe2]2 (1), [L2AlMe2]2 (2), and [L3AlMe2]2 (3), respectively. Compounds 1–3 were characterized by 1H and 13C NMR spectroscopy analysis, and the molecular structures of 1 and 2 were further confirmed by X-ray diffraction analysis. In the presence of iPrOH, aluminum compounds 1–2 exhibited excellent catalytic activity for the solvent-free Tishchenko reaction under mild conditions. In addition, the catalyst 3 can be easily isolated and recycled three times without a significant decrease in activity.

Bis{μ-N-[(2-(di­methyl­amino)­ethyl]-N′-(tri­methyl­silyl)­benzamidinato}dilithium(I)

The title compound, [Li2(C14H24N3Si)2], has been prepared in hexane and its structure has been determined. It crystallizes as a dimer with twofold rotation symmetry and the coordination geometry around the Li atoms is distorted tetrahedral, with each of the Li atoms bonding to two N atoms of an amidinate fragment in one ligand and to two N atoms of the other ligand in the dimer.

Synthesis and structural characterization of electrochemically reversible bisferrocenes containing bis(acyl-thiourea)s: enantiomers and conformers

Two chiral bisferrocenyl-modified bis(acyl-thiourea) enantiomers, (1R,2R)-bis(ferrocenylcarbonylthioureido)cyclohexane (1) and (1S,2S)-bis(ferrocenylcarbonylthioureido)cyclohexane (2), were synthesized by the reactions of 2.2 equivalents of ferrocenoyl isothiocyanate with (1R,2R) and (1S,2S)-1,2-diaminocyclohexane (1,2-DACH) via a nucleophilic addition reaction, respectively. The two new compounds were fully characterized by 1H NMR, 13C NMR, IR, UV-Vis, elemental analyses and single-crystal X-ray diffraction. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) experiments of compounds 1 and 2 showed roughly similar single reversible redox waves when using nBu4NClO4 (TBAP) as the supporting electrolyte, whereas two CV and DPV waves were observed when using nBu4NBArF4 [ArF4 = 3,5-bis(trifluoromethyl)phenyl]. Furthermore, both compounds 1 and 2 displayed potential antitumor activity against human HepG2 cells. When compounds 1 and 2 were crystallized from diethyl ether, the solvent-free enantiomers (1 and 2) were obtained, respectively. Molecules of both solvent-free enantiomers (1 and 2) assemble into a three-dimensional network structure through hydrogen-bonding and C–H⋯π (cyclopentadienyl rings) interactions. On the other hand, crystallization of compound 1 from benzene produced a benzene disolvate, 1·(C6H6)2. Molecules of the solvent-free and disolvated forms of compound 1 exhibit different molecular conformations and packing arrangements.

CCDC 883524: Experimental Crystal Structure Determination

Related Article: Mei-su Zhou, Mei Fan, Min Wang, Hong-bo Tong, Qiao-kun Yang|2012|Shanxi Daxue Xuebao,Ziran Kex.|35|342|

catena-Poly[[(N,N-di­methyl­cyanamide-κN)lithium]-μ3-bromido]

The title complex, [LiBr(C3H6N2)]n, is the unexpected product of a reaction beteween (Dipp)N(Li)SiMe3 (Dipp = 2,6-diisopropylphenyl), Me2NCN and CuBr. The compound is a one-dimensional polymer with a step structure derived from the association of inversion dimers, formed by bromido ligands bridging two Li+ cations, each of which carries a dimethylcyanamide ligand. The planar (LiBr)2 unit of the polymer core has a regular rhombic shape [Li—Br—Li 77.55 (16)° and Br—Li—Br 102.45 (16)°]. These (LiBr·NCNMe2)2 dimers represent the repeat unit of a polymer system propagated by additional Br—Li and Li—Br bonds generating an infinite step structure along the a-axis direction.