Yong Heng Xing

Triazine–polycarboxylic acid complexes: synthesis, structure and photocatalytic activity

Four novel transition metal complexes, [Zn2(Bpz*eaT)2(HBTC)2]·(CH3OH)3 (1), [Co(Bpz*eaT)(HBTC)]·(CH3CH2OH)0.5·(H2O)0.5 (2), [Zn(Bpz*eaT)(H2BTA)(pz*H)] (3) and [Cu4(Mpz*T-O2)4(BTA)(H2O)8]·4H2O (4) (Bpz*eaT, 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-diethylamino-1,3,5-triazine; Mpz*T-O2, 6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4(1H,3H)-dione; pz*H, 3,5-dimethyl-1H-pyrazole; H3BTC, benzene-1,3,5-tricarboxylic acid; and H4BTA, 1,2,4,5-benzenetetracarboxylic acid), were synthesized by the reaction of metal salts (ZnSO4·7H2O, CoCl2·6H2O or CuCl2·2H2O), pincer N-heterocyclic triazine derivatives and aromatic polycarboxylate ligands. All the complexes were characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermal gravimetric analysis and single-crystal X-ray diffraction. Structural analysis reveals that complexes 1 and 2 are 2-D layers and complex 4 is a 3-D network structure with hydrogen bonding. In addition, the photocatalytic performances of complexes 1–4 were studied under UV irradiation at room temperature and their photocatalytic activity was also discussed. The result showed that complex 1 possessed higher photocatalytic activity.

Syntheses and structures of mononuclear and binuclear transition metal complexes (Cu, Zn, Ni) with (salicylideneglycine and imidazole)

Four transition metal (Cu(II), Zn(II) and Ni(II)) complexes with a Schiff-base ligand (salicylideneglycine) have been synthesized. All complexes have been characterized by elemental analysis, IR spectra and UV-vis spectroscopy. Single-crystal analyses were performed with (C9H7NO3)Cu(C3H4N2) (1), (C9H7NO3)Zn(C3H4N2)2 (2), (C9H7NO3)2Ni2(C3H4N2)4 (3) and (C9H7NO3)Ni(C3H4N2)2(C4H5N2O) · CH3OH · 0.5H2O (4) and fluorescence spectra and thermogravimetric analyses were also carried out. Structural analyses show that 1, 2 and 4 have similar coordinated modes with the tridentate amino-Schiff-base ligand, but differ from the binuclear nickel complex 3. The tridentate amino-Schiff-base ligand contains aliphatic nitrogen, phenoxy, and carboxylic oxygen as three donor atoms. In addition, inter- and intra-molecular hydrogen bonds are also discussed.

A New Insulin-Like Vanadyl Complex: Synthesis and Structure of V(IV)O(H2O)2 (2,6-PyridineDicarboxylate)E2H2O

V(IV)O(H2O)2(2,6-pyridinedicarboxylate)·2H2O (1) was obtained by the reaction of VO(acac)2 with 2,6-pyridine dicarboxylic acid in MeOH and water. Complex (1) was characterized by IR spectroscopy, element analysis and X-ray diffraction. It crystallizes in space group P . X-ray structure analysis has shown that complex (1) is a monomeric neutral complex containing vanadyl ion, 2,6-pyridinedicarboxylate ligand and coordinated water, possessing distorted octahedral geometry. Complex (1) is constructed from mononuclear vanadium, V(IV)O(H2O)2(2,6-pyridinedicarboxylate) units and crystallization water molecules held together in an extensive two-dimensional network via O–H···O hydrogen bonds, π–π stacking interactions between parallel aromatic pyridines, and face-to-face stacking interactions between parallel carbonyl groups of 2,6-pyridine dicarboxylic acid ligands along the plane formed by the x, z axis of the unit cell.

Mimicking vanadium haloperoxidases: vanadium(III)–carboxylic acid complexes and their application in H2O2 detection

Vanadium(III) complexes [V(2,6-pdc)2(H2O)2]·2H2O (1) and V(2,6-pdc)(htba)(H2O)2 (2), (2,6-pdc = 2,6-pyridinedicarboxylic acid, htba = 2-acetoxy-4-trifluoromethylbenzoic acid) have been synthesized by the reaction of V2(SO4)3 with 2,6-pdc (for 1) or 2,6-pdc and htba (for 2) under hydrothermal conditions at 120 °C for 36 hours. Because the vanadium(III) was easily oxidized into higher oxidation states, we included the reducing agent vitamin C to protect the vanadium(III) center. The complexes were characterized by elemental analysis, IR and UV-vis spectroscopy, and single-crystal X-ray diffraction. Structural analysis revealed that the central metal V atoms in the complexes 1 and 2 were seven-coordinate, forming pentagonal bipyramid geometries. The complexes catalyzed the bromination of the organic substrate phenol red in the presence of H2O2, bromide and buffer. Compared with vanadium complexes having other oxidation states, the vanadium(III) complexes had better catalytic activity (the maximum reaction rate constant was 2.424 × 102k(mol L−1)−2 s−1). The mimicking vanadium haloperoxidases also overcame some serious disadvantages of natural enzymes. Therefore, the reaction system described herein can be considered as an effective model for hydrogen peroxide determination.

Synthesis, structure, and surface photovoltage properties of a series of novel d7–d10 metal complexes with pincer N-heterocycle ligands

Novel d7–d10 complexes Cu(bpz*eaT)(SCN)2 (1), Ni(bpz*eaT)(SCN)2 (2), Co(bpz*eaT)((SCN)2 (3), [Ni(bpz*eaT)(N3)]·H2O (4) and Co(bpz*eaT)(N3) (5) (bpz*eaT: 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-diethylamino-1,3,5-triazine) were synthesized by the reaction of a metal salt (CuCl2·2H2O, NiCl2·6H2O, CoCl2·6H2O or Co(CH3COO)2·4H2O), pincer N-heterocyclic ligands and KSCN or NaN3 in either acetonitrile or a mixed solution at different temperatures. The structures of these complexes were characterized by elemental analysis, IR and UV-Vis spectroscopy, powder X-ray diffraction (PXRD), thermogravimetric analyses (TG) and single-crystal diffraction analysis. Structural analysis reveals that the metal atoms (Cu and Co) in complexes 1, 3 and 5 are in a five-coordination mode, forming distorted square pyramid geometries with N5 donors; Ni atoms in the complexes 2 and 4 are in a six-coordination mode, forming slightly distorted octahedra with the set of N5S and N6 cores, respectively. In complexes 1–5, the auxiliary N-donor monodentate ligands were only connected with one metal center. In complexes 2 and 4, the two metal centers were connected by bridging coordinated SCN− and N3−, which were different from those in complexes 1, 3 and 5. In addition, surface photovoltage properties of the five complexes have also been studied and discussed in detail. Surface photovoltage spectra (SPS) of the complexes 1–5 show that the surface photovoltage (SPV) response signals increase when the positive electric field is enhanced in the range of 300–800 nm. The results show that these complexes possess potential p-type semiconductor properties and their uses may be extended to semiconductor materials.

Peroxo- and oxovanadium(iv) complexes with tridentate N-heterocycle ligands: synthesis, structure, and catalytic performance

Three peroxo- and oxovanadium(IV) complexes: [VO(O2)(bpz*eaT)·VO(C4H4O6)]·H2O (1), [VOSO4(bpz*eaT)]·C6H8O7 (2) (bpz*eaT = 2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-diethylamino-1,3,5-triazine) and [VO(C12H8N2)(C9H7NO3)]·CH3OH·0.5H2O (3) were synthesized and characterized by elemental analysis, IR spectra, UV-Vis spectroscopy and single-crystal X-ray diffraction. In addition, the catalytic performances of complexes 1–3 and their starting materials (VO(acac)2 and VOSO4) were studied by the reaction of cyclohexane (Cy) oxidation. It is found that complex 1 exhibited the highest catalytic activity (TON(cyclohexanol) = 220, TON(cyclohexanone) = 346, Conv. = 97.9%) with H2O2 as an oxidant and HNO3 as an additive at 24 h, 40 °C, indicating that it is a potential candidate catalyst to oxidize the Cy to cyclohexanol (CyOH) and cyclohexanone (CyO) under mild conditions.

Oxovanadium(IV) pyrazolyl carboxylic acid complexes: synthesis, crystal structures of [VO(pzH)(HMPA)2]2 · 4H2O (1) and VO(OH)(dmpzH)2(C6H5COO) (2) (H2MPA = 5-methyl-1H-pyrazole-3-carboxylic acid, pzH = pyrazole, dmpzH = 3,5-dimethyl pyrazole)

Two new monomeric complexes of oxovanadium(IV), [VO(pzH)(HMPA)2]2 · 4H2O (1) and VO(OH)(dmpzH)2(C6H5COO) (2) (H2MPA = 5-methyl-1H-pyrazole-3-carboxylic acid, pzH = pyrazole, dmpzH = 3,5-dimethyl pyrazole), have been synthesized from reaction of VOSO4 · nH2O with respective ligands. The compounds were characterized by elemental analysis, IR spectra and X-ray diffraction. Structural analysis of 1 and 2 gave the following parameters: 1, monoclinic, P2(1)/n, a = 11.1729(13) Å, b = 23.965(3) Å, c = 13.5591(15) Å, β = 99.969(2)°, V = 3575.8(7) Å3, Z = 4; 2, orthorhombic, Pbcn, a = 13.197(4) Å, b = 15.898(5) Å, c = 18.192(6) Å, V = 3817(2) Å3, Z = 8. In each complex the vanadium is a distorted tetragonal bipyramid, which is typical for oxovanadium(IV) complexes. In both complexes, inter- and intra-molecular hydrogen bonds are also discussed. Complex 1 exists as an infinite chain along the b-axis by intermolecular hydrogen bonds. In addition, thermal analysis and quantum chemistry calculations were performed for analyzing the stability of the complexes.

Synthesis and Structure of the Mn(II) Complexes with Tripyrazolylborate Ligands: Mn[HB(pz)3]2 and Mn[HB(3,5‐Me2‐pz)3]2

Abstract Mn(II) complexes Mn[HB(pz)3]2 (1) (pz = pyrazole) and Mn[HB(3,5‐Me2‐pz)3]2 (2) have been obtained by the reaction of Mn(OOCCH3)2 with NaHB(pz)3 and NaHB(3,5‐Me2‐pz)3 in MeOH, respectively. The two complexes (1) and (2) were characterized by IR, elemental analyses, and x‐ray diffraction. Complex (1) crystallizes in the space group C2/c, a = 18.971(3) Å, b = 13.700(3) Å, c = 19.056(3) Å, β = 111.378(10), V = 4612.0(13) Å3, Z = 2. Complex (2) crystallizes in the space group R‐3, a = 10.9832(18) Å, b = 10.983(2) Å, c = 24.785(3) Å, γ = 120°, V = 2589.3(7) Å3, Z = 3. X‐ray structure analysis has shown that the complexes (1) and (2) all are monomeric neutral complexes, and possess similar coordination modes around the metal Mn centers. In addition, some related bonding distances, angles, and structural properties are discussed.

Photoelectric properties and potential nitro derivatives sensing by a highly luminescent of Zn(II) and Cd(II) metal–organic frameworks assembled by the flexible hexapodal ligand, 1,3,5-triazine-2,4,6-triamine hexaacetic acid

Two new coordination polymers, [Cd4(μ3-O)(TTHA)(H2O)2]·3H2O (1) and [Zn5Na2(TTHA)2(H2O)10] (2), based on the flexible hexapodal ligand 1,3,5-triazine-2,4,6-triamine hexaacetic acid (H6TTHA), have been synthesized under hydrothermal condition. The two coordination polymers were characterized by the elemental analysis, IR spectroscopy, PXRD, thermogravimetric analysis and UV-vis spectroscopy. The single crystal X-ray diffraction analysis revealed that coordination polymer 1 exhibited a 2D sheet structure, which was arranged alternately by two different types of building blocks (Cd4O6 and Cd2O2), and 2 possessed a fascinating 3D network framework with three different types of the building blocks (Zn4(COO)6O8N2, Zn(COO)4 and Na(COO)4O2). In the structures, all of the coordination modes of the ligand were firstly discovered, which are μ8–η1η1η1η3η2η1η2η1η2η1η2 and μ9–η1η1η1η1η1η1η1η1η2ηN1η2η1, respectively. In order to furthermore expand functional characteristics of both the coordination polymers 1 and 2, we also carried out experiments of the surface photovoltage spectroscopy (SPS) and electric-field-induced surface photovoltage spectroscopy (EFISPS), which showed that 1 and 2 could behave as p-type semiconductors. Whats more, the fluorescence sensing experiments showed the luminescent quenching of the coordination polymers 1 and 2 were especially obvious with the increasing of the nitro derivatives concentration, even if the nitro derivatives were at a very low concentration, which can also be detected, that indicating both coordination polymers 1 and 2 have very high sensitivity sensing properties.

Synthesis and characterization of three ionic pairs of Fe(II) and Co(II) complexes with tridentate salicylideneglycine

Three new transition metal complexes, [FeII(H2O)6][(C9H7NO3)2FeII] · H2O (1), H[K(H2O)3][(C9H7NO3)2CoII] · H2O (2), and [CoII(H2O)6][(C9H7NO3)2CoII] · H2O (3), with salicylideneglycine have been synthesized and characterized by elemental analysis, IR spectra, UV-Vis spectroscopy, and X-ray crystallography. The structure analyses indicate that the tridentate salicylideneglycine binds through aliphatic nitrogen, phenoxy, and carboxylic oxygen in the anion. There are many inter- and intra-molecular hydrogen bonds among lattice water, the anion, and the cation to form a 3-D network. The thermogravimetric analyses and the quantum chemistry calculations of compounds 1, 2, and 3 are also discussed.