Yuguang Li

Passive Films and Corrosion Protection Due to Phosphonic Acid Inhibitors

Abstract For protecting mild steel from corrosion, aminotrimethylidenephosphonic acid (ATMP) was more effective than 1-hydroxyethylidene diphosphonic acid (HEDP), N.N-dimethylidenephosphonoglycine (DMPG), 1-ethyl-phosphonoethylidenediphosphonic acid (EEDP), and ethylenediaminetetramethylidenephosphonic acid (EDTMP). A 20-min treatment in 1.0 mol/L of ATMP with a pH 0.23 at 45°C formed an anti-corrosive complex film that was composed of 48.4% O, 28.6% P, 7.0% Fe, 4.3% N, and 11.7%C, based on x-ray photoelectron spectroscopy and Auger electron spectroscopy. From differences in binding energies of Fe, N, and O, in the shift of C-N and P-O vibration, in the reflection FTIR spectra, and in the change of P-OH and Fe-N vibration before and after film formation, it was deduced that N and O in ATMP were coordinated with Fe2+ in the film.

Synthesis, molecular docking and biological evaluation of Schiff base transition metal complexes as potential urease inhibitors

Six transition metal compounds of Schiff base ligands were evaluated for the inhibitory activity on jack bean urease, of which compounds 2-6 were determined by single crystal X-ray analysis. It was found that copper(II) complexes 1 and 4 showed strong inhibitory activity against jack bean urease (IC(50) = 0.52 and 0.46 microM), compared with acetohydroxamic acid (IC(50) = 42.12 microM) as a positive reference. Cobalt(II), nickel(II) and zinc(II) compounds also exhibited potent inhibitory activity (IC(50) = 3.88-25.20 microM). A docking analysis using the AUTODOCK 4.0 program could explain the inhibitory activities of 1 and 4 against urease.

Synthesis, structures and urease inhibition studies of copper(II) and nickel(II) complexes with bidentate N,O-donor Schiff base ligands

Five mononuclear copper(II) and nickel(II) complexes of Schiff base ligands derived from 4-hydroxyphenethylamine and 2-phenylethylamine were synthesized and determined by single crystal X-ray analysis. The crystal structures of these complexes presented the square planar coordination geometry at the metal center. The inhibitory activity of all the obtained complexes was tested in vitro against jack bean urease. It was found that Schiff base copper(II) complexes, namely [Cu(C(15)H(13)BrNO(2))(2)]·2(C(6)H(7)N) (1), [Cu(C(15)H(12)Br(2)NO(2))(2)]·2(DMF) (2), Cu(C(19)H(16)NO(2))(2) (3) and Cu(C(19)H(16)NO)(2) (5), showed strong inhibitory activity against jack bean urease (IC(50)=1.45-3.59 μM), while Schiff base nickel(II) complex, [Ni(C(19)H(16)NO(2))(2)]·2(DMF) (4), exhibited weak inhibitory activity (IC(50)>50 μM). Their structure-activity relationships were further discussed.

Synthesis, structures and urease inhibition studies of Schiff base metal complexes derived from 3,5-dibromosalicylaldehyde

Eleven mononuclear copper(II), nickel(II), zinc(II) and cobalt(II) complexes of Schiff base ligands derived from 3,5-dibromosalicylaldehyde/3,5-dichlorosalicylaldehyde were synthesized and determined by single crystal X-ray analysis. The crystal structures of complexes 1, 2, 4, 5, 6, 8 and 11 present the square-planar coordination geometry at the metal center and complexes 7, 9 and 10 show the distorted tetrahedral geometry. While one copper center in 3 has a square-planar geometry, the other copper is slightly distorted square-planar. The inhibitory activities of all the obtained complexes were tested in vitro against jack bean urease. It was found that Schiff base copper(II) complexes 1, 3, 5, 8 and 11 showed strong urease inhibitory activities (IC(50) = 1.51-3.52 μM) compared with acetohydroxamic acid (IC(50) = 62.52 μM), which was a positive reference. Their structure-activity relationships were further discussed.

Decolorization of Acid Orange II dye by peroxymonosulfate activated with magnetic Fe3O4@C/Co nanocomposites

New metallic cobalt loaded magnetic nanocomposites (Fe3O4@C/Co) were prepared by calcination and in situ reduction of the Co2+-impregnated magnetic carbon nanoparticles of Fe3O4@C at 900 °C under a nitrogen atmosphere. Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), vibrating sample magnetometry, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the properties of the composites and the loading of metallic Co0 in the material was clarified. The catalytic properties of the nanocomposites Fe3O4@C/Co in activating peroxymonosulfate (PMS) for decolorization of Acid Orange II (AO II) dye in aqueous solution were investigated. Fe3O4@C/Co nanocomposites exhibited high activity in PMS activation for AO II decolorization. Complete decolorization of AO II solution could be achieved in 20 min within near neutral pH range (pH 6.4–8.5), while a complete decolorization occurred in 40 min for the as-prepared solution without pH adjustment (pH 4.05). The effects of several parameters including pH, catalyst load, PMS concentration and reaction temperature on the catalytic activity were also investigated. Sulfate free radicals activated from PMS were proposed to be the dominant active species in the “Fe3O4@C/Co + PMS” system for AO II decolorization. The catalytic and decolorization mechanism was suggested. The catalyst Fe3O4@C/Co could be recycled easily by a magnet with good reusability. This study provides a promising method for the activation of “green” oxidant, PMS, by the new magnetic nanocomposites for environmental remediation and oxidation catalysis.

Synthesis, structure and urease inhibition studies of Schiff base copper(II) complexes with planar four-coordinate copper(II) centers

Seven new Schiff base copper(II) complexes with planar four-coordinate copper(II) centers have been synthesized and structurally characterized. The solid state structures of complexes 1, 3, 4, 5, 6 and 7 present a square-planar coordination geometry at the metal centers while complex 2 shows a slightly distorted square-planar geometry. Density functional theory calculations have been performed to evaluate the electronic structure of copper(II) complex 7. Inhibition of jack bean urease by copper(II) complexes 1-7 have also been investigated, and potent inhibitory activities with IC50 range of 2.60-17.00μM have been observed for these mononuclear copper(II) complexes. A docking analysis using a DOCK program was conducted to explain the urease inhibitory activity of the copper(II) complexes and the structure-activity relationships were further discussed.

Synthesis, characterization, and antibacterial activity of two silver(I) compounds with 4-dimethylaminopyridine

Two new silver(I) compounds, [Ag(4-dmapy)2(p-bromophenylacetate)] · H2O (1) and [Ag(4-dmapy)2(p-hydroxyphenylacetate)]·2H2O (2) (4-dmapy = 4-dimethylaminopyridine), have been synthesized and characterized. X-ray crystallographic analysis reveals that 1 and 2 contain a linear Ag(4-dmapy)2 chromophore, which further forms dimeric silver(I) units via weak silver–silver interaction. The short Ag ··· Ag separations in 1 and 2 are 3.0395(12) and 3.2697(10) Å, respectively. Compounds 1 and 2 have good anti-Bacillus subtilis activity in vitro (minimum inhibitory concentration, MIC = 12.5 µg mL−1) but were inactive against Staphylococcus aureus and Escherichia coli (MIC > 50 µg mL−1).

Synthesis, molecular docking, and activity of Schiff-base copper(II) complex with N-n-butylsalicylaldiminate as Helicobacter pylori urease inhibitor

A Schiff-base copper(II) complex, bis(N-n-butylsalicylaldiminato)copper(II), was synthesized and its solid-state structure was determined by X-ray crystallography. Its inhibitory activity against Helicobacter pylori urease was evaluated in vitro and it showed strong inhibitory activity against urease (IC50 = 0.95 µM), compared with acetohydroxamic acid (IC50 = 42.47 µM) as a positive reference. A docking analysis using the AUTODOCK 4.0 program was performed to explain the potent inhibitory activity of the complex against urease.

Synthesis, crystal structures, and urease inhibition studies of two new Schiff-base copper complexes derived from n-butylamine

Two Schiff-base copper(II) complexes, bis(N-n-butyl-5-chlorosalicylaldiminato) copper(II) (1) and bis(N-n-butyl-4-methoxysalicylaldiminato) copper(II) (2), were synthesized and their solid-state structures were determined by X-ray crystallography. Complex 1 displays a distorted square-planar geometry, while 2 possesses square-planar geometry. Copper(II) complexes 1 and 2 showed strong inhibitory activity against jack bean urease (IC50 = 2.7, 3.5 µmol L−1), compared with acetohydroxamic acid (IC50 = 63.00 µmol L−1). A molecular modeling study was carried out via the DOCK program to gain understanding of the potent inhibitory activity of these copper species against jack bean urease.

XPS, AES and Raman Studies of an Antitarnish Film on Tin

Abstract For protecting tin from tarnishing, ethylenediamine-tetramethylidene-phosphonic acid (EDTMP) was found to be more effective than chromate, molybdate, and other agents. A 10-minute treatment in 5 to 10 g/L of EDTMP with a pH of 1 to 4 at 25 to 80°C formed a corrosion-resistant complex film, which was composed of 48.0% 0, 10.7% Sn, 7.7% N, 23.1% C, and 10.5% P, based on x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) determinations. From differences in the binding energies of Sn, N and O before and after film formation, and from the R-PO32− and Sn-N vibrations in the Raman spectra for the film it was deduced that N and O in EDTMP were coordinated with Sn in the film.