Zhongyu Zhang

Synthesis, crystal structure, and DNA interaction of magnesium(II) complexes with Schiff bases

A pair of stereoisomers of magnesium Schiff base complexes, [Mg(C18H16N3O2)2·2CH3OH] n (1) (C18H16N3O2: 2-acetylpyridine-l-tryptophan) and [Mg(C18H16N3O2)2·2CH3OH] n (2) (C18H16N3O2: 2-acetylpyridine-d-tryptophan), was synthesized and characterized by IR, UV, elemental analysis, 1H NMR, and X-ray diffraction single crystal analysis. The analyses of the structures indicate that they all crystallize in the tetragonal crystal system, space group P4 3 2 1 2 and P4 1 2 1 2, respectively. The two magnesium complexes have similar crystal structures. Mg(II) is six-coordinate with two nitrogens from C=N, two nitrogens from pyridine, and two carboxylic oxygens in different ligands forming a distorted octahedral geometry. Through N–H···O intermolecular hydrogen bonds a 2-D layer structure was formed. The interaction between 1 and calf thymus DNA was also investigated by UV absorption spectra, fluorescence emission spectra and viscometry. The results indicate that 1 interacts with DNA very strongly (K b = 2.01 × 107 L mol−1 and K sq = 0.195). The nature of the binding seems to be mainly an electrostatic interaction between DNA and the magnesium complex. Other binding modes, such as hydrogen bonds, may also exist.

Proteasome inhibition and cytostatic effects on human cancer cells by pyrazolone-enamines: a combined crystallographic, structural and computational study

Nine compounds were designed and synthesized by the condensation reaction of the carbonyl in 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HPMBP) with the amino groups in 5-aminoisophthalic acid, 4,4′-diaminodiphenylmethane, 4-aminophenylacetic acid, 4-aminobenzamide, 2-amino-4-methylphenol, 5-amino-2-methylphenol, 2-aminophenol, 3-aminophenol and 4-aminophenol. They were then characterized by IR, 1H NMR, elemental analysis, and X-ray crystallography, which suggested that all of them exist as the pyrazolone-enamine forms in the solid state and in a DMSO solution through tautomeric reactions. The nine compounds (compounds 1–9) were evaluated for their ability to inhibit the proliferation of human liver cancer HepG2 cells. Compounds 5, 6, 7 and 8 demonstrated a strong inhibitory effect on the proliferation of HepG2 cells. The nine compounds can also inhibit the activity of the human cancer cellular 20S proteasome. Further studies on compound 6 as the representative indicate that it can cause the accumulation of ubiquitinated proteins and the proteasome target proteins Bax and p27, and exhibit a cytostatic effect in HepG2 cells in a concentration-dependent and time-dependent manner. The four potential tautomers of compound 6 were optimized and their single point energies were calculated by the density functional theory (DFT) B3LYP method based on the polarized continuum model (PCM) in water to identify the most likely tautomer existing in cancer cells. Based on the optimized structure of the most stable tautomer in water, the Wiberg bond orders, molecular electrostatic potential (MEP) maps and frontier molecular orbital were calculated. As compounds 5, 6, 7 and 8 have hydroxyl in the ortho-position or meta-position, our study can provide some information to study their anticancer mechanism and the substitution effect of different functional groups.

An amino-imino resonance study of 2-amino-4-methylpyridinium nitrate and 2-amino-5-methylpyridinium nitrate.

The contributions of the amino and imino resonance forms to the ground-state structures of 2-amino-4-methylpyridinium nitrate, C(6)H(9)N(2)(+)·NO(3)(-), and the previously reported 2-amino-5-methylpyridinium nitrate [Yan, Fan, Bi, Zuo & Zhang (2012). Acta Cryst. E68, o2084], were studied using a combination of IR spectroscopy, X-ray crystallography and density functional theory (DFT). The results show that the structures of 2-amino-4-methylpyridine and 2-amino-5-methylpyridine obtained upon protonation are best described as existing largely in the imino resonance forms.

Synthesis, crystal structures, luminescent properties, theoretical calculation, and DNA interaction of the cadmium(II) and lead(II) complexes with o-aminobenzoic acid and 1,10-phenanthroline

Two complexes, namely [Cd(Phen)(o-AB)2] (I) and [Pb(Phen)(o-AB)] (II) (Phen = 1,10-phenanthroline, o-AB = o-aminobenzoic acid), have been synthesized and characterized by elemental analysis and X-ray diffraction single-crystal analysis (CIF files CCDC nos. 910307 (I), 898292 (II)). Complex I is six coordinated by two nitrogen and four oxygen atoms from the Phen and o-AB to furnish a distorted octahedral geometry. Complex II is six coordinated by two nitrogen and four oxygen atoms from the Phen and o-AB to furnish an umbrella-like geometry. The complexes exhibit intense fluorescence at room temperature. The interaction between complex I and calf thymus DNA was also investigated by UV absorption spectra, fluorescence emission spectra and viscometry. The nature of the binding seems to be mainly an electrostatic interaction between DNA and complex I. Theoretical studies of the title complexes were carried out by density functional theory (DFT) B3LYP method.

Synthesis, Crystal Structure, Fluorescence and Thermostability of Ni(II), Zn(II), Cd(II) Complexes with Schiff Base 2-Acetylpyridine-D-tryptophan

Three novel transition metal coordination polymers, [Ni(C18H16N3O2)2·2CH3OH]n (1), [Zn(C18H16N3O2)2·4CH3OH]n (2) and [Cd(C18H16N3O2)2·2CH3OH]n (3) (C18H16N3O2=2-acetylpyridine-d-tryptophan) were synthesized and characterized by elemental analysis, IR, UV, 1H NMR and X-ray diffraction single crystal analysis. The analyses of the structures indicate that all three materials crystallize in the tetragonal crystal system, space group P41212. They have similar structures; i.e., the Schiff base coordinates in its deprotonated form and behaves as a hexadentate (4N+2O) coordinated ligand to form a distorted octahedron geometry. On the other hand, as a result of the alternate arrangement of chains through N–H···O intermolecular hydrogen bonds interactions, 2-D layers are formed for the three complexes. Furthermore, the luminescent properties and thermal stabilities of the three complexes were investigated.

2-Amino-5-methyl-pyridinium nitrate.

In the title salt, C6H9N2 +·NO3 −, the 2-amino-5-methylpyridinium cation and the nitrate anion are cyclically linked through pyridinium and amine N—H⋯O hydrogen bonds [graph set R 4 3(12)]. These units are extended into a zigzag chain structure lying parallel to the a axis, through a second cyclic R 2 2(8) association involving amine N—H⋯O and aromatic C—H⋯O hydrogen bonds to nitrate O-atom acceptors.

Synthesis, Crystal Structure, and Theoretical Calculation of the Cd(II) Complex with 2-Aminobenzothiazole

A novel complex, [CdL2(CH3COO)2] (1), was synthesized and characterized by IR, elemental analysis, and X-ray diffraction single-crystal analysis. Its crystal structure was compared with a previously reported complex, [ZnL2(CH3COO)2] (2). Complex (1) crystallizes in orthorhombic, space group Pna2(1) with a = 8.8821 (7) Å, b = 27.480 (3) Å, c = 9.0267 (8) Å, α = 90°, β = 90°, γ = 90°, V = 2203.3 (3) nm3, Z = 4, F(000) = 1064, S = 1.087, Dx = 1.601 g·cm−3, R 1 = 0.0322, wR 2 = 0.0708, μ = 1.211 mm−1. Theoretical studies of complexes (1) and (2) were carried out by density functional theory (DFT) B3LYP method. CCDC: Complex (1): 886802, Complex (2): 901631. Supplemental materials are available for this article. Go to the publishers online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Crystal structure of 2-aminobenzothiazolinium nitrate and theoretical study of the amino-imino tautomerism of 2-aminobenzothiazole

Abstract 2-Aminobenzothiazolinium nitrate (1) was characterized by elemental analysis, melting point, IR, 1H NMR, and X-ray crystallography. The driving force for the 2-aminobenzothiazole tautomerism in methanol solution was studied using theoretical calculations. It is suggested that the 2-aminobenzothiazolinium cation is an intermediate product between the amino form (2) and imino form (3) of 2-aminobenzothiazole. The tautomerization reaction can proceed in two steps through protonation and deprotonation between the two forms 2 and 3.