Hong-Gen Wang

A novel 3D porous metal–organic framework based on trinuclear cadmium clusters as a promising luminescent material exhibiting tunable emissions between UV and visible wavelengths

A novel 3D porous MOF built with trinuclear cadmium clusters exhibiting rhombohedral topology has been synthesized and characterized as a promising luminescent material that can give tunable emissions between UV and visible wavelengths by controlling the number of guest molecules.

Synthesis of a series of 4-pyridyl-1,2,4-triazole-containing cadmium(II) luminescent complexes

Using two 4-substitued triazole ligands, 4-(pyrid-2-yl)-1,2,4-triazole (L(1)) and 4-(pyrid-3-yl)-1,2,4-triazole (L(2)), a series of novel triazole-cadmium(II) complexes varying from zero- to three-dimensional have been prepared and their crystal structures determined via single-crystal X-ray diffraction. [Cd(2)(micro(2)-L(1))(3)(L(1))(2)(NO(3))(mu(2)-NO(3))(H(2)O)(2)](NO(3))(2).1.75H(2)O (1) is a binuclear complex containing bidendate, monodedate and free nitrate anions. When the bridging anions SCN(-) and dca (dca = N(CN)(2)(-)) were added to the reaction system of 1, one-dimensional (1D) [Cd(L(1))(2)(NCS)(2)](n) (2) and two-dimensional (2D) [Cd(L(1))(2)(dca)(2)](n) (3) were isolated, respectively. When L(2) instead of L(1) was used, [Cd(L(2))(2)(NCS)(2)(H(2)O)(2)] (4) and 1D [Cd(L(2))(2)(dca)(2)](n) (5) were obtained. When the ratio of Cd to L(2) was changed from 1:2 to 1:1 in the reaction system of 5, three-dimensional (3D) {[Cd(3)(micro(2)-L(2))(3)(dca)(6)].0.75H(2)O}(n) (6) with 1D microporous channels along the a direction was isolated. Further investigations on other Cd(ii) salts and the L(2) ligand in a Cd to L(2) ratio of 1:1, an unexpected complex [Cd(mu(2)-L(2))(mu(3)-SO(4))(H(2)O)](n) (7) with a 3D open framework was obtained. All of the complexes exhibit strong blue fluorescence emission bands in the solid state at ambient temperature, of which the excitation and emission maxima are red-shifted to longer wavelength as compared to those in water. Powder X-ray diffraction and thermal studies were used to investigate the bulk nature of the 3D coordination polymers 6 and 7.

Synthesis and characterization of axial coordination cobalt(III) complexes containing chiral Salen ligands

Abstract Cobalt(III) complexes containing both optically active tetradentate Schiff base ligands, (SB=Salen, MeOSalen, t-Bu-Salen) with axial ligands (L) [Co(SB)L2]ClO4 (L=imidazole (Im), 2-methylimidazole (2-MeIm), 1-methylimidazole (MeIm)) have been prepared and characterized. In addition, the crystal structures of [Co(Salen)(MeIm)2]ClO4 (1c), [Co(MeOSalen)(MeIm)2]ClO4 (2c), and [Co(t-Bu-Salen)(MeIm)2]ClO4 (3c) have been determined by X-ray structure analysis. The properties of these hexacoordinate complexes, such as electronic absorption, circular dichroism spectra, and 1H NMR spectra, have been studied.

Magnetic interaction in the keto and enol forms of binuclear copper (II) complexes with a Robson-type ligand. X-ray crystal structure of [Cu2 (HL) (μ-N3) (H2O) (C2H5OH) (ClO4)]

Abstract Three dicopper(II) complexes, [Cu2(H2L) (μ-N3)] (ClO4)2 · 1 2 C 2 H 5 OH ( 1 ) , [Cu2(HL) (μ-N3) (H2O) (C2H5OH) (ClO4)] (2) and [Cu2(L) (μ-N3)] · DMF (3) have been synthesized and characterized, where H3L is the pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoylhydrazone). Because of the existence of a hydrazide structure in the lateral chain, the ligand H3L can lose one, two or three hydrogen atoms to form the keto form (1) or enol form (3) of the binuclear copper (II) complexes, respectively. The crystal structure of 2 has been determined. Crystal dta for 2: monoclinic, space group P21/c, a = 10.967(4), b = 7.684(2), c = 35.724(7) A , β = 90.08°, Z = 4 . The analysis of variable-temperature magnetic susceptibility data indicates that there is an antiferromagnetic interaction between the copper(II) ions in these complexes with the exchange parameters (2J) of −86.8 cm−1 for 1, −132.4 cm−1 for 2 and −176.7 cm−1 for 3. The effect of a tautomeric isomeride on the magnetic interaction was discussed in relation to molecular mechanics and CNDO/2 methods.

Syntheses and molecular structures of complexes formed in the reaction of dichlorobis[π-cyclopentadienyl)-dicarbonyliron]tin(IV) with polydentate o-(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols

Abstract Eleven complexes having the general formula, [π-C 5 H 5 Fe(CO) 2 ] 2 [RC 6 H 4 C(O)N 2 -CHC 6 H 4 O]Sn (R = H, p -NO 2 , p -Cl, p -Br, p -I, p -CH 3 , p -OCH 3 , m -NO 2 , m -OCH 3 , and 3,5-dinitro) have been synthesized. These complexes have been characterized by 1 H NMR, IR and MS, and by elemental analysis. A single crystal X-ray diffraction study (R = o -NH 2 ) confirmed their molecular structures and revealed that the o -(nuclear substituted α-hydroxybenzylidenehydrazonomethyl)phenols are tridentate planar ligands. The crystals are monoclinic, space group P 2 1 / n with a 13.495(4), b 13.058(2), c 18.311(3) A, β 94.90(2)°, V 3214.9 A 3 , Z = 4, D c 1.66 g/cm 3 . Final discrepancy factors of R = 0.033 and R w = 0.039 were obtained for 3075 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. SnFe bond lengths are 2.5421 and 2.5242 A (av. 2.5332 A). In these complexes, the ligands exist in the enol-form.

Coordination chemistry of organometallic polydentate ligands Studies on the syntheses and properties of FeM binuclear complexes prepared from organometallic tridentate ligand trans-Fe(CO)3(Ph2Ppy)2 (Ph2Ppy = 2-(diphenylphosphino)pyridine)

Abstract The binuclear complexes (CO)3Fe(μ-Ph2Ppy)2MXn (Ph2Ppy = 2-(diphenylphosphino)pyridine, MXn = Mn(SCN)2, Co(SCN)2, CoCl2, NiCl2, Mo(CO)3, Zn(SCN)2, ZnCl2, Cd(SCN)2, CdCl2, HgCl2, HgI2, AgClO4, and SnCl2) were prepared from the new type of organometallic tridentate ligand, trans-Fe(CO)3(Ph2Ppy)2 (1), which contains both a basic metal center and bridging phosphine ligands. The crystal structure of the benzene solvate of 1 was determined by X-ray diffraction. The compound 1·1/2C6H6 crystallizes in the monoclinic space group P21/c with a = 17.560(5), b = 12.110(1), c = 18.176(4) A ; β = 101.27(2)° and Z = 4 . The structure was refined to a conventional R value of 0.077 by using 2670 significant reflections and parameters. The structure of one of the binuclear complexes, namely, (CO)3Fe(μ-Ph2Ppy)2HgI2 (14), has also been determined by X-ray diffraction. The compound 14 crystallizes in the monoclinic space group P21/n, with a = 13.829(2), b = 14.175(2), c = 19.514(3) A , β = 120.27(1)°, V = 3738(2) A 3 and Z = 4 . The structure was refined to a conventional R values of 0.032 by using 3279 significant reflections and parameters. The FeHg distance is 2.678 A, indicative of a metal-metal bond. Results of Mossbauer and electron-absorption spectra suggested the presence of metal to metal interactions in these binuclear complexes.

Synthesis of Me2 Si-η5-C5H4(CO)Fe(CO)2-Fe(CO)-η5-C5H4SiMe2 and a novel reaction between its SiSi and FeFe bonds

Me2Si-η5-C5H4(CO)Fe(CO)2Fe(CO)-η5-C5H4SiMe2 (1) was synthesized by reaction of 1,2-bis (cyclopentadienyl)tetramethyldisilane and pentacarbonyliron. An unexpected product, Me2Si-η5-C5H4Fe(CO)2SiMe 2-η-5-C5H4Fe(CO)2 (2), was obtained from the reaction, which was evidently formed via a novel metathesis reaction between SiSi and FeFe bonds in 1. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction studies.

Synthesis and structure of pentacoordinate tin(IV) complexes

Ten complexes formulated as Ph2SnL, where L is RC6H4C(O)N2CHC6H4O with R = H, p-NO2, p-Cl, p-Br, p-CH3, p-OCH3, o-NH2, m-NO2, m-OCH3, and 3,5-dinitro, have been prepared and were characterized by 1H NMR, IR, and mass spectroscopy and elemental analyses. A single crystal X-ray diffraction study of the complex with R=o-NH2 confirms the molecular structure. The crystals are triclinic, space group P1 with a 9.608(2), b 11.826(4), c 21.478(6) A, α 76.17(2), β 76.53(2), γ 88.91(2)°, V 2302.7(4) A3, Z = 4, Dc 1.52 g/cm3. The final discrepancy factors are R = 0.050 and Rw = 0.057 for 3129 observed independent reflections. The tin atom has a distorted trigonal bipyramidal coordination. The two SnO bonds of 2.073(6) and 2.116(6) A, respectively and one SnN bond (of 2.143(7) A)1 are shorter than those found in related complexes. A comparison of the IR spectra of the ligands with those of the corresponding complexes, reveals that the disappearance of the bands assigned to carbonyl unambiguously confirms that the ligands coordinate with the tin in the enol form.

Synthesis and reactivity of Group 6 metal carbonyl complexes containing bis(triazol-1-yl)methane: linkage coordination polymers

Abstract The reaction of bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, CH2(3,5-Me2Tz)2, with M(CO)6 (M=Cr, Mo or W) in refluxing DME produces CH2(3,5-Me2Tz)2M(CO)4 in moderate yield. The crystal structures determined by X-ray analysis show that bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane acts as a chelating bidentate ligand with two endodentate nitrogen atoms in these complexes. Reactions of complexes CH2(3,5-Me2Tz)2M(CO)4 (M=Mo or W) with R2SnX2 (R=Ph or Me; X=Cl or Br) in a 1:1 or 1:2 ratio, respectively, only yield 1:1 adducts. In these adducts, bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane may coordinate to tin atom through exodentate nitrogen atoms on the 4-position of triazole rings to form linkage coordination polymers. Possibly owing to weak donors of 4-position exonitrogen atoms on triazole rings to organotin acceptors, the dissociation of these adducts in solution could exist. Adduct of CH2(3,5-Me2Tz)2W(CO)4·SnPh2Br2 absorbs one water molecule while crystals are growing and becomes the hydrolysis product [SnPh2Br2(H2O)]·(CH2(3,5-Me2Tz)2W(CO)4), which is characterized by X-ray crystallography, indicating that tin atom is five coordinate with a trigonal bipyramid geometry, the water molecule coordinates to the tin atom, and is simultaneously connected to the exonitrogen atoms on the 4-position of triazole rings of two adjacent CH2(3,5-Me2Tz)2W(CO)4 units through hydrogen bonds to form linkage coordination polymers, in which two coordination modes are observed.

Synthesis and crystal structures of Group 6 metal carbonyl complexes containing S-rich bis(pyrazol-1-yl)methane ligands

Abstract The reaction of 3(5)-methylthio-5(3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions only affords a new ligand, bis(3-phenyl-5-methylthiopyrazol-1-yl)methane. However, the reaction of 3(5)-methylthio-5(3)-p-methoxyphenylpyrazole or 3(5)-methylthio-5(3)-tert-butylpyrazole with dibromomethane under the same conditions yields three isomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring during the formation of ligands. Treatment of these potential polydentate ligands with M(CO)6 (M=Cr, Mo or W) under UV irradiation at room temperature affords (NN)M(CO)4 derivatives, in which some complexes contain asymmetric substituted bis(pyrazol-1-yl)methane ligands. The X-ray crystal structure analyses indicate that the sulfur atoms in these complexes do not take part in the coordination to the metal centers, and S-rich bis(pyrazol-1-yl)methanes actually act as bidentate chelating ligands by two nitrogen atoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in these complexes are oriented away from the metal centers.