Mustaffa Shamsuddin

Synthesis, characterization, antibacterial, and cytotoxic activities of organotin(iv) complexes derived from n (4)-cyclohexylthiosemicarbazone: x-ray crystal structure of [ph 2sncl(l)]

Reaction of organotin(IV) chloride(s) with 2-benzoylpyridine-N(4)-cyclohexylthiosemicarbazone, [HL] (1) yielded [MeSnCl2(L)] (2), [BuSnCl2(L)] (3), [Me2SnCl(L)] (4), and [Ph2SnCl(L)] (5). The ligand (1) and its organotin(IV) complexes have been characterized by CHN analyses, molar conductivity, UV-Vis, FT-IR, 1H, 13C, and 119Sn NMR spectral studies. The molecular structure of 5 was also determined by X-ray diffraction. There are two independent molecules in the asymmetric unit and the central tin(IV) atom is six-coordinate in distorted octahedral geometry. The ligand (1) and complexes were screened for their in vitro antibacterial activities. The cytotoxic activities of 1–5 were tested against A2780 and A2780/Cp8 cancer cell lines. The compounds have better antibacterial activities than the free ligand; 2–5 are more potent cytotoxic agents than 1, while the diphenyltin(IV) 5 is more active with IC50 values of 0.05 and 0.54 µmol L−1 against A2780 and A2780/Cp8 cell lines, respectively.

Biostabilised icosahedral gold nanoparticles: synthesis, cyclic voltammetric studies and catalytic activity towards 4-nitrophenol reduction

ABSTRACT A green and cost-effective biosynthetic approach for the preparation of icosahedral gold nanoparticles (AuNPs) using an aqueous leaf extract of Polygonum minus as reducing and stabilising factor is described. The reduction of Au3+ ions to elemental Au rapidly occurred and is completed within 20 minutes at room temperature. The size of the nanoparticles is highly sensitive to the AuCl4−/leaf extract concentration ratio and pH. Transmission electron microscopy and X-ray diffraction data indicated that the nanoparticles were in a crystalline shape (face-centred cubic), mostly icosahedral and nearly monodispersed with an average size of 23 nm. Cyclic voltammetric studies suggested that flavonoids, such as quercetin and myricetin present in the leaf extract had a tendency to donate electrons to Au3+ ions and the formation of elemental Au was possible due to the transfer of electrons from these flavonoids to Au3+ ions. Infrared absorption of the AuNPs and the leaf extract revealed that the oxidised (quinone) form of quercetin and myricetin were presumably the main stabilising agents in the formation of stable nanoparticles. The present biosynthesis of AuNPs was simple, rapid, cost-effective and environmentally friendly. The newly prepared biostabilised icosahedral AuNPs show good catalytic activity in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP).

Masking effect of copper oxides photodeposited on titanium dioxide: exploring UV, visible, and solar light activity

A series of copper oxide loaded TiO2 was prepared by a photodeposition method. It was clarified through XANES that the added copper species solely existed as highly dispersed Cu(II) and it remained as Cu(II) after the photocatalytic reaction. The prepared CuO/TiO2 with various contents (0.1–5 mol%) were used as photocatalysts for 2,4-dichlorophenoxyacetic acid (2,4-D) degradation under UV, visible, and solar simulator irradiation. Under UV light irradiation, the photocatalytic activity of 2,4-D decomposition increased by a maximum factor of 4.3 compared with unmodified TiO2 when TiO2 was loaded with 0.75 mol% CuO. In contrast, under visible light and solar simulator irradiation, the optimum loading of CuO was much lower (0.1 mol%) and enhancements of 22.5 and 2.4 times higher activities were observed, respectively. These results showed that the different masking effects due to the different light sources led to different optimum amounts of CuO, and the added CuO mostly contributed to the visible light activity of TiO2. Therefore, in addition to the increased charge separation and improved visible light absorption, the masking effect shall also be considered in designing highly active photocatalysts under visible and solar light irradiation.

High activity of Ag-doped Cd0.1Zn0.9S photocatalyst prepared by the hydrothermal method for hydrogen production under visible-light irradiation

Summary Background: The hydrothermal method was used as a new approach to prepare a series of Ag-doped Cd0.1Zn0.9S photocatalysts. The effect of Ag doping on the properties and photocatalytic activity of Cd0.1Zn0.9S was studied for the hydrogen production from water reduction under visible light irradiation. Results: Compared to the series prepared by the co-precipitation method, samples prepared by the hydrothermal method performed with a better photocatalytic activity. The sample with the optimum amount of Ag doping showed the highest hydrogen production rate of 3.91 mmol/h, which was 1.7 times higher than that of undoped Cd0.1Zn0.9S. With the Ag doping, a red shift in the optical response was observed, leading to a larger portion of the visible light absorption than that of without doping. In addition to the larger absorption in the visible-light region, the increase in photocatalytic activity of samples with Ag doping may also come from the Ag species facilitating electron–hole separation. Conclusion: This study demonstrated that Ag doping is a promising way to enhance the activity of Cd0.1Zn0.9S photocatalyst.

High photocatalytic activity of mixed anatase-rutile phases on commercial TiO2 nanoparticles

Titanium dioxide (TiO2) is well-known as an active photocatalyst for degradation of various organic pollutants. Over the years, a wide range of TiO2 nanoparticles with different phase compositions, crystallinities, and surface areas have been developed. Due to the different methods and conditions used to synthesize these commercial TiO2 nanoparticles, the properties and photocatalytic performance would also be different from each other. In this study, the photocatalytic removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) was investigated on commercial Evonik P25, Evonik P90, Hombikat UV100 and Hombikat N100 TiO2 nanoparticles. Upon photocatalytic tests, it was found that overall, the photocatalytic activities of the P25 and the P90 were higher than the N100 and the UV100 for the removal of both 2,4-D and 2,4,5-T. The high activities of the P25 and the P90 could be attributed to their phase compositions, which are made up of a mixture of anatase and rutile phases of TiO2. Whereas, the UV100 and the N100 are made up of 100% anatase phase of TiO2. The synergistic effect of the anatase/rutile mixture was reported to slow down the recombination rate of photogenerated electron-hole pairs. Consequently, the photocatalytic activity was increased on these TiO2 nanoparticles.

{2,2′-[(2,2-Dimethyl­propane-1,3-di­yl)bis­(nitrilo­methyl­idyne)]diphenolato}palladium(II) ethanol hemisolvate

The asymmetric unit of the title complex, [Pd(C19H20N2O2)]·0.5C2H5OH, contains two molecules of a PdII complex of a Schiff base ligand with an N2O2 donor set and one ethanol molecule. The PdII centers are in distorted square-planar geometries with the N2O2 donor atoms of the tetradentate Schiff base dianions. The ethanol molecule takes part in an O—H⋯O hydrogen bond. In the crystal structure, molecules are stacked approximately along the b-axis direction. The O atom and three H atoms of the solvent molecule are disordered over two positions; the site occupancy factors are ca 0.8 and 0.2.

Electro-generated ortho-quinoide intermediates: templates for feasible construction of a series of novel imidazo[2,1-b]thiazole derivatives through one-pot five-step domino hetero-annulation process

A series of novel polycyclic structures, with an imidazothiazole central core, were successfully synthesized through the anodic oxidation of catechols in the presence of 2-imidazolidine thione, as nucleophiles in aqueous solution. The cyclic voltammetric results indicated that one-pot multi-step sequential reactions occur between the electrochemically derived o-benzoquinones intermediates and nucleophiles affording fused polyheterocyclic compounds. The mechanism of these catalyst-free, tandem reactions are proved as ECECE or ECECCE pathways using potentiostatic and galvanostatic coulometries. In addition, the electrosyntheses of fused imidazo[2,1-b]thiazoles have been successfully performed in ambient conditions in an undivided cell using an environmentally friendly method with high atom economy and current efficiency. The novel fused polyheterocycles were fully characterized by FT-IR, 1H NMR, 13C NMR, and HR-MS spectrometric methods.Graphical abstract

Preparation of high activity Ga and Cu doped ZnS by hydrothermal method for hydrogen production under visible light irradiation

Ga(0.1),Cu(x)-ZnS (x = 0.01, 0.03, 0.05) photocatalysts were successfully synthesized by hydrothermal method. The synthesized Ga and Cu codoped ZnS photocatalysts showed photocatalytic property effective for hydrogen production from aqueous solution containing Na2SO3 and Na2S as sacrificial reagent under visible light irradiation. The rate of hydrogen production was found to be strongly dependent on Cu doping content. The highest photocatalytic activity is observed for Ga(0.1),Cu(0.01)-ZnS with hydrogen production rate of 114 µmol/h. The addition of Ga as codoped increased the photocatalytic activity to 58 times as compared to single doped Cu-ZnS. The Ga and Cu codoped ZnS photocatalysts are also stable under long irradiation. The enhancement in the photocatalytic activity of Ga and Cu codoped photocatalyst can be attributed to the synergistic effect between Ga and Cu. The photocatalytic activity was greatly enhanced with the addition of 0.5 wt% Ru as cocatalyst with a hydrogen production rate of 744 µmol/h.

Palladium(II) Picoline Thiourea Complex as Homogenous Catalyst in Heck Cross-Coupling Reaction in the Formation of C=C Bond

Palladium (II) complex containing picoline thiourea (Pd-PTu) was prepared by reacting bis (benzonitrile) palladium (II) chloride (Pd-PhCN) with N’-2-(5-picolyl)-N-4-bromobenzoylthiourea (PTu). All synthesized compounds have been characterized via several selected typical spectroscopic and analytical techniques namely elemental analysis, Infrared (IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy, Nuclear Magnetic Resonance (1H and 13C NMR) and gas chromatography-flame ionization detector (GC-FID). For Pd-PTu, IR spectrum showed significant shift in the ν (C=N) on the pyridine ring and ν (C=S) stretching vibration at around 30cm-1 compared to the free ligand. The finding indicated that the expected coordination of ligand to the palladium metal centre took place via N and S atoms. The catalytic reaction was monitored using GC-FID with conversion of 83.81 %, proved that Pd-PTu can be used as an ideal homogenous catalyst in any Heck cross-coupling reactions in the near future.

Photocatalyst composites of luminescent trinuclear copper(I) pyrazolate complexes/titanium oxide for degradation of 2,4-dichlorophenoxyacetic acid

Here phosphorescent trinuclear copper (I) pyrazolate complexes ([Cu3Pz3]), synthesized from 3,5-dimethyl and 4-(3,5-dimethoxybenzyl)-3,5-dimethyl pyrazole ligands for complexes [Cu3Pz3]1 and [Cu3Pz3]2, were successfully impregnated into TiO2 with concentration of 0.1 mol%. These luminescent photocatalyst composites ([Cu3Pz3]1or 2/TiO2) gave 60% and 49% of dichlorophenoxyacetic acid (2,4-D) degradation after 1 h for [Cu3Pz3]1/TiO2 and [Cu3Pz3]2/TiO2, while TiO2 only showed 48%. The higher activity observed on [Cu3Pz3]1/TiO2 than the TiO2 would come from the efficient reduction of electron-hole recombination, while less dispersion of complex [Cu3Pz3]2 with more rigid structure compared to complex [Cu3Pz3]1 gave similar activity of the [Cu3Pz3]2/TiO2 to the TiO2.