Wei-Hong Li

Peking University, Peping, Beijing, China

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Publications (9)8.79 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Four kinds of coordination structures formed by lanthanide–picolinamide complexes, including [La(C6H6N2O)2(H2O)5]Cl3 (La–pa, Pr–pa, Nd–pa, Sm–pa and Gd–pa), [Er(C6H6N2O)2 (H2O)4]Cl3(H2O) (Er–pa), [Pr(C6H6N2O)2(H2O)5]Br3 (PrBr–pa) and [Nd(C6H6N2O)3(NO3)2] (C6H6N2O)(NO3) (NdN–pa) are reported. The crystal structures in the solid state vary with the change of anions and lanthanide ions as revealed by X-ray single crystal diffraction, FTIR, Raman, FIR and THz spectroscopy. In these crystal structures, the pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to metal ions to form a five-membered ring structure or are hydrogen-bonded. The results indicate the differences in the coordination of different lanthanide ions (the Er ion is special for its small atomic radius), the changes of hydrogen bonds and the conformation of the ligands induced by complexation, and the influence of different anions. When nitrate ions are involved in the coordination structure, the coordination number of lanthanide ions is higher. Chloride and bromine ions do not coordinate to metal ions, so lanthanide bromine and lanthanide chloride–pa complexes have similar structures. The results provide models for the coordination structures of lanthanide ions with ligands that have amide groups.
    CrystEngComm 07/2014; 16(33). · 3.88 Impact Factor
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    ABSTRACT: The novel coordination structures of europium and terbium chloride-picolinamide complexes (EuCl3·(C6H6N2O)2·5H2O, Eu-pa and TbCl3·(C6H6N2O)2·5H2O, Tb-pa) are reported. The crystal structures in the solid state are characterized by X-ray single crystal diffraction, FTIR, Raman, FIR, THz and Luminescence spectroscopy. In the crystal structures, the pyridyl nitrogen and carbonyl oxygen atoms in picolinamide are coordinated to the metal ions to form a five-membered ring structure. The experimental results indicate the similar coordination structures of Eu and Tb-pa complexes and the changes of hydrogen bonds and conformation of the ligands induced by complexation. The results provide models for the coordination structures of lanthanide ions with ligands having amide groups.
    Chinese Chemical Letters 06/2014; · 1.18 Impact Factor
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    ABSTRACT: Nicotinic acid and isonicotinic acid were utilized to react with Co(NO3)2 in N,N'- dimethylformamide (DMF) in solvothermal conditions respectively, and resulted in three new coordination polymers: [Co2(μ2-H2O)(nicotinic acid)4·(DMF)] (1), [Co2(isonicotinic acid)4·(DMF)] (2), and [Co(isonicotinic acid)2·(DMF)] (3). Single crystal X-ray diffraction (XRD) and elemental analysis were performed to obtain structural information on these compounds. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and N2 isotherm analysis were utilized to investigate the pore stability of the three compounds. The above experiments reveal that compound 1 has a diamond-like topology, and the one-dimensional (1D) channels in compound 1 are stable after the removal of DMF molecules. Compounds 2 and 3 were synthesized at 100 and 160 °C by the coordination of isonicotinic acid with Co(II), respectively. The coordination modes of isonicotinic acid to Co(II) are completely different in the two compounds, which lead to two different crystal structures. The 1D channels in compounds 2 and 3 were not stable after the removal of DMF molecules.
    ACTA PHYSICO-CHIMICA SINICA 01/2012; 28(8). · 0.87 Impact Factor
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    ABSTRACT: The formation of W/O microemulsions in the extraction system TBP-Pd(II)-HCl was investigated. The solution structural evolution of the palladium loaded organic phases, with the variation in the content of acid into the organic phases, was characterized by various spectroscopic techniques such as DLS, FTIR and 31P-/1H NMR. The results indicated that (1) the extraction behaviors of palladium was related to the formation of W/O microemulsion structure in the loaded organic solutions. Because of the co-extraction of hydrochloric acid, there formed the microscopic aggregates in the loaded organic phases. (2) The variation in the HCl content in organic phase resulted in corresponding changes in solution structure. With the increase in the HCl content, the average radii of nanoscopic aggregates in the organic phases increased and then decreased. The extraction of HCl into the organic phase exhibited a distinct impact on the O-H stretching vibration and O-H-O bending vibration of water molecules in the microscopic W/O micelles. FTIR spectra of the organic phase saturated with acids show that the broad band of O-H stretching vibration of water extended to a very wide range and overlaped with the C-H stretching vibration bands. The higher the acid concentration in the organic phase was, the greater the overlapping. On the other hand, it was also observed that a remarkable change appeared in the O-H-O bending vibration of water and the stretching vibration of P=O in TBP molecules shifted to lower frequency. With the increase in acid content in the TBP organic phases, the observed 31P NMR chemical shifts decreased and varied to up-field; whereas the 1H NMR chemical shift of H+ increased and even became larger than that of deuterium chloride-d at a lower frequency field. The changes in delta 31P to opposite direction of delta H+ means that TBP molecules were associated with acid protons and water molecules in microemulsion pools to form RP=O x H+ or RP=O x H3O+, and then interacted with PdCl4(2-) complex ions, which finally led to the extraction of palladium into the organic phase. (3) When forming the W/O reversed micelles/microemulsions, the concentration of acid within the microscopic micelles was even higher than that of saturated concentrated hydrochloric acid. It was the microscopic structural changes in organic phase microemulsion "water pool" that resulted in the corresponding variations in the palladium extraction behaviors.
    Guang pu xue yu guang pu fen xi = Guang pu 10/2008; 28(9):2038-43. · 0.29 Impact Factor
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    ABSTRACT: The complexes of DL-homocysteic acid (DLH) with Na+, Cu2+, Zn2+ and Ni2+ were synthesized and elemental analyses were used to detect the compositions of these complexes. FTIR spectroscopy was employed to study these coordination structures. The results indicated that all the amino, carboxyl and sulfonate groups of DLH may have direct or indirect interactions with Na+, Cu2+, Zn2+ and Ni2+. The bond strength between metal ions and oxygen of the carboxyl as well as that between metal ions and the amino group are in the order of Cu2+ > Zn2+ > Ni2+, where carboxyl with different ions may take different coordination modes in these complexes, as indicated from the difference between its asymmetric and symmetric stretching vibration.
    Guang pu xue yu guang pu fen xi = Guang pu 08/2007; 27(7):1291-4. · 0.29 Impact Factor
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    ABSTRACT: DL-Homocysteic acid (DLH, (NH3 )-CH(COOH)-(CH2 )2-SO3-) is extensively in existence as free amino-acid in the central nervous system of mammal. The infrared (IR) and Raman spectra of DL-Homocysteic acid (DLH) and its La complex [La (DLH)2Cl3 . H2O = LaL2] were measured at high external pressure. The DLH has two pressure-induced phase transitions (near 17 kbar and 37 kbar) and three pressure-phase areas below 50 kbar for there are ten intermolecular hydrogen bonds between the DLH molecules. But there is only one pressure-induced phase transition (near 27 kbar) to be observed in the complex LaL2. These show that the ten intermolecular hydrogen bonds of the DLH molecules changed due to the formation of complex LaL2. In infrared spectra, the changing trend of the pressure sensitivities (dv/dp) of symmetry stretching of SO3- in DLH and asymmetry stretching of SO3- in LaL2 are very different from the other vibrational modes when both compounds undergo high external pressure. In infrared spectra, the average pressure sensitivities of symmetry stretching of SO3- are: low-pressure phase area (0.30 cm(-1) x (kbar)(-1)) < middle-pressure phase area (0.32 cmn(-1) (kbar) (-1)) < high-pressure phase area (0.41 cm(-1) x (kbar)(-1)), but 0.86 cm(-1) x (kbar)(-1) (low-pressure phase area) >0.64 cm(-1) x (kbar)(-1) (middle-pressure phase area) >0.26 cm(-1) x (kbar)(-1) (high-pressure phase area) to other vibrational modes in DLH. The average pressure sensitivities of asymmetry stretching of SO3- in LaL2 are lower in low-pressure phase area than in high-pressure phase area, but the average pressure sensitivities of other modes are higher in low-pressure phase area than in high-pressure phase area.
    Guang pu xue yu guang pu fen xi = Guang pu 10/2005; 25(9):1388-92. · 0.29 Impact Factor
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    ABSTRACT: Fourier transform infrared (FTIR) spectroscopy was used to study the normal and malignant tissues of rectum. The FTIR spectra of tissues were measured by Nicolet Magna IR-750 spectrometer equipped with mid-infrared fiber optics. The results show that the intensity ratios of five pairs of bands can be used to distinguish the normal and malignant tissues. In the spectra of malignant tissues the relative intensities ratios of I2,873/I2,852 and I1,312/I1,245 were higher than those of normal ones; however, the ratios of I1,745/I1,643, I1,458/I1,400 and I1,162/I1,082 were lower. These results, proved by data-analysis of spectra from 21 patients, were generally shown in the spectra of rectum tissues. The study of near-malignant tissues (one centimeter beside the malignant point) of rectum by FTIR shows that these ratios of bands were in a transient state between normal and malignant rectum tissues.
    Guang pu xue yu guang pu fen xi = Guang pu 07/2003; 23(3):498-501. · 0.29 Impact Factor
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    ABSTRACT: In this paper, stained and unstained samples of oral tissues have been investigated using FT-microspectroscopy. The experimental results demonstrated that staining did not influence the characteristic features of the FTIR spectra of the oral tissues, thereby providing abundant opportunity of further understanding of the structural-spectral relationship of normal and malignant tissues.
    Guang pu xue yu guang pu fen xi = Guang pu 07/2002; 22(3):419-22. · 0.29 Impact Factor
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    ABSTRACT: FTIR spectroscopy and thermal analysis were applied to study the nylon 6–lithium salt systems. The DTA results show that lithium ions cause a significant reduction of the melting point of nylon–lithium salt samples. In addition, lithium salts can also prevent the crystallization of molten nylon in the cooling process. Temperature-variable FTIR spectroscopy demonstrates that stronger hydrogen bonds form when nylon–lithium halide is molten. Such stronger hydrogen bonds in molten nylon lithium systems may account for the reduction of the melting point and delaying the crystallization of the amorphous nylon. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2685–2690, 2000
    Journal of Applied Polymer Science 07/2000; 77(12):2685 - 2690. · 1.40 Impact Factor

Publication Stats

7 Citations
8.79 Total Impact Points

Institutions

  • 2000–2014
    • Peking University
      • • National Laboratory of Rare Earth Material Chemistry and Application
      • • College of Chemistry and Molecular Engineering
      • • Department of Chemical Biology
      • • Department of Chemistry
      Peping, Beijing, China