Electrochemical hydrogen evolution reaction (HER) refers to the process of generating hydrogen by splitting water molecules with applied external voltage on the active catalysts. HER reaction in the acidic medium can be studied by different mechanisms such as Volmer reaction (adsorption), Heyrovsky reaction (electrochemical desorption) or Tafel reaction (recombination). In this paper, facile hydrothermal methods are utilized to synthesis a high-performance metal-inorganic composite electrocatalyst, consisting of platinum nanoparticles (Pt) and molybdenum disulfide nanosheets (MoS2) with different platinum loading. The as-synthesized composite is further used as an electrocatalyst for HER. The as-synthesized Pt/Mo-90-modified glassy carbon electrode shows the best electrocatalytic performance than pure MoS2 nanosheets. It exhibits Pt-like performance with the lowest Tafel slope of 41 mV dec-1 and superior electrocatalytic stability in an acidic medium. According to this, the HER mechanism is related to the Volmer-Heyrovsky mechanism, where hydrogen adsorption and desorption occur in the two-step process. According to electrochemical impedance spectroscopy analysis, the presence of Pt nanoparticles enhanced the HER performance of the MoS2 nanosheets because of the increased number of charge carriers transport.
The asymmetric unit of the title complex, [Pd(C15H13FNO)2], contains one half of the mol-ecule with the Pd(II) cation lying on an inversion centre and is coordinated by the bidentate Schiff base anion. The geometry around the cationic Pd(II) centre is distorted square planar, chelated by the imine N- and phenolate O-donor atoms of the two Schiff base ligands. The N- and O-donor atoms of the two ligands are mutually trans, with Pd-N and Pd-O bond lengths of 2.028 (2) and 1.9770 (18) Å, respectively. The fluoro-phenyl ring is tilted away from the coordination plane and makes a dihedral angle of 66.2 (2)° with the phenolate ring. In the crystal, mol-ecules are linked into chains along the [101] direction by weak C-H⋯O hydrogen bonds. Weak π-π inter-actions with centroid-centroid distances of 4.079 (2) Å stack the mol-ecules along c.
This paper reports the synthesis, characterization, anticancer screening and quantum chemical calculation of a tetradentate Schiff base 2,2'-((1E,1'E)-((2,2-dimethylpropane-1,3-diyl)bis- (azanylylidene))bis(methanylylidene))bis(4-fluorophenol) (L2F) and its Pd (II) complex (PdL2F). The compounds were characterized via UV-Visible, NMR, IR spectroscopy and single crystal x-ray diffraction. Density Functional Theory (DFT) and time-dependent DFT calculations in gas and solvent phases were carried out using B3LYP, B3P86, CAM-B3LYP and PBE0 hybrid functionals combined with LanL2DZ basis set. Complexation of L2F to form PdL2F was observed to cause a bathochromic shift of the maximum absorption bands of n-π* from 327 to 410 nm; an upfield shift for δ (HC = N) from 8.30 to 7.96 ppm and a decreased wavenumber for ν(C = N) from 1637 to 1616 cm-1. Overall, the UV-Vis, NMR and IR spectral data are relatively well reproduced through DFT and TD-DFT methods. L2F and PdL2F showed IC50 of 90.00 and 4.10 μg/mL, respectively, against human colorectal carcinoma (HCT116) cell lines, signifying increased anticancer activity upon complexation with Pd (II).
Hydroxamic acids [R(CO)N(OH)R'] are flexible compounds for organic and inorganic analyses due to their frailer structures compared to the carboxylic acid. The syntheses and characterization of benzohydroxamic acid (BHA), its CH3-, OCH3-, Cl- para-substituted derivatives and their Cr(III) complexes are reported herein. The metal complexes were synthesized by reacting the hydroxamic acids with chromium(III) chloride hexahydrate in 2:1 molar ratio. The compounds were characterized via melting point, elemental analysis, FTIR, 1H and 13C NMR, TGA, mass spectrometry, molar conductance and UV-Visible. Data analysis suggests that each complex has the Cr(III) center coordinated to the carbonyl and hydroxy oxygen atoms of the hydroxamic acids in bidentate O,O manner and two water molecules to form octahedral geometry. Non-electrolytic behavior of the complexes was shown through their low molar conductivity. Cytotoxicity study against HCT116 and alpha-glucosidase inhibition test revealed that all complexes have higher activity than their parent ligands. Molecular docking study shows that the docking of active complexes is thermodynamically favorable and the inhibition efficiency may depend on the types and the numbers of molecular interactions established in the corresponding stable conformers.
The asymmetric unit of the title complex, [Ni(C14H11FNO)2], contains one-half of the mol-ecule with the Ni(II) cation lying on an inversion centre coordinated by a bidentate Schiff base anion. The cationic Ni(II) center is in a distorted square-planar coordination environment chelated by the imine N and phenolate O donor atoms of the two Schiff base ligands. The N and O donor atoms of the two ligands are mutually trans with Ni-N and Ni-O bond lengths of 1.9242 (10) and 1.8336 (9) Å, respectively. The fluoro-phenyl ring is almost orthogonal to the coordination plane and makes a dihedral angle of 82.98 (7)° with the phenolate ring. In the crystal, mol-ecules are linked into screw chains by weak C-H⋯F hydrogen bonds. Additional C-H⋯π contacts arrange the mol-ecules into sheets parallel to the ac plane.
In the title complex, [Pd(C16H16NO2)2]·CHCl3, the Pd(II) cation lies on an inversion center. One Cl atom of the CHCl3 solvent mol-ecule lies on a twofold axis and the C-H group is disordered with equal occupancies about this axis with the other Cl atom in a general position with full occupancy. The Pd(II) cation is four-coordinate and adopts a square-planar geometry via coordination of the imine N and phenolic O atoms of the two bidentate Schiff base anions. The N and O atoms of these ligands are mutually trans. The plane of the benzene ring makes a dihedral angle of 73.52 (10)° with that of the meth-oxy-phenolate ring. In the crystal, mol-ecules of the Pd(II) complex are arranged into sheets parallel to the ac plane, and the chloro-form solvent mol-ecules are located in the inter-stitial areas between the complex mol-ecules. Weak inter-molecular C-H⋯O and C-H⋯π inter-actions stabilize the packing.
The asymmetric unit of the title compound, [Ni(C15H14NO2)2], comprises an Ni(II) cation, lying on an inversion centre, and a Schiff base anion that acts as a bidentate ligand. The Ni(II) cation is in a square-planar coordination environment binding to the imine N and phenolate O atoms of the two Schiff base ligands. The N- and O-donor atoms of the two ligands are mutually trans, with Ni-N and Ni-O bond lengths of 1.9191 (11) and 1.8407 (9) Å, respectively. The plane of the meth-oxy-benzene ring makes a dihedral angle of 84.92 (6)° with that of the phenolate ring. In the crystal, mol-ecules are linked into screw chains by weak C-H⋯O hydrogen bonds. Additional C-H⋯O hydrogen bonds, together with C-H⋯π contacts, arrange the mol-ecules into sheets parallel to the ac plane.
A Schiff base bearing two methyl substituents, namely, 6,6'-((1E,1'E)-((2,2-dimethylpropane-1,3-diyl) bis(azanylylidene)) bis(methanylylidene)) bis(2-methylphenol) [H2AD1Me] was synthesized and characterized through physicochemical and spectroscopic analyses. Then, the Schiff base was complexed with Pd(II) and Ni(II) to form [Pd(AD1Me)] and [Ni(AD1Me)], respectively. Both metal complexes were successfully obtained and characterized through several analyses, viz., melting point, elemental analysis, molar conductivity, magnetic susceptibility, FTIR, 1H NMR, UV-vis, and single crystal X-ray diffraction. A quantitative analysis of the intermolecular interactions in the crystal structures has been performed using Hirshfeld surface analysis. Both metal complexes were crystallized in a monoclinic crystal system with the space group of P21/c. Additionally, the deprotonated phenolic oxygen atom (O1/O2) and azomethine nitrogen atom (N1/N2) of the ligand chelate the Pd(II) and Ni(II) ions, forming a slightly distorted square-planar complex containing three six-membered rings encircling the metal core with dsp2 hybridization. The shift of ν(C=N) to a higher frequency in FTIR by 26-28 cm-1 indicated that the complexation to Pd(II) and Ni(II) through the azomethine N was established. It was further supported through the shifting of the azomethine proton signal to higher or lower chemical shifts with Δδ = 0.43-1.15 ppm in 1H NMR. In addition, the shifting of the n-π*(C=N) band in UV-vis spectra with Δλ = 24-40 nm indicated the involvement of azomethine nitrogen in the complexation. All the compounds showed no significant antibacterial activity against three bacterial strains, namely, Staphylococcus aureus subsp. aureus Rosenbach (ATCC 6538), Streptococcus mutans Clarke (ATCC 700,610), and Proteus vulgaris (ATCC 6380), as the percent growth inhibition calculated was less than 90%.