Abstract Three new isostructural coordination complexes, M(pca)3, where M = Co (1), Cr (2), or Rh (3) and 2-pyrazine-carboxylate (pca), have been synthesized solvothermally and characterized
by single crystal X-ray diffraction and powder X-ray diffraction. In structures 1-3, the pca ligand chelates to the metal
centers in a tris-chelating arrangement through proximal nitrogen and oxygen donor atoms. Structures 1-3 are monoclinic and
crystallize in the space group C2/C. In structure 1, a = 28.066(13) ?, b = 8.036(4) ?, c = 13.577(6) ?, and β = 90.2(10)°.
In structure 2 a = 28.318(3) ?, b = 8.089(4) ?, c = 13.792(12) ?, and β = 90.256(2)°. In structure 3, a = 28.679(4) ?, b = 8.051(13) ?,
c=13.847(2) ?, and β = 90.585(2)°.
Graphical Abstract Three new isostructural coordination complexes, M(pca)3, where M = Co, Cr, or Rh and 2-pyrazine-carboxylate (pca), have been synthesized solvothermally and characterized by single
crystal X-ray diffraction and powder X-ray diffraction.
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The coordination ability of the antisecretor agent Famotidine (FMT) was explored using Ni(II) as central ion. [NiFMTH-2] and [Ni(FMT)2]Cl2 were obtained by the solvent evaporation method from the corresponding starting solutions at pH 8 and 4, respectively; the crystal structure was elucidated by single crystal X-ray diffraction in both cases.[NiFMTH-2] resulted in a distorted square-planar geometry, where FMT acts as a tetradentate dianionic ligand through nitrogen atoms belonging to the guanidine group, the thiazolic ring and the side chain, and a sulfur atom from the thioether moiety. [Ni(FMT)2]Cl2 exhibits an octahedral environment composed by two FMT molecules that coordinate by nitrogen atoms deriving from guanidine and thiazole ring moieties, and the thioether sulfur atom. The physicochemical characterization was completed by means of FTIR and UV–Vis spectroscopies, and thermal analysis. Solubility measurements were performed and the results could be satisfactorily correlated with the solvation Gibbs free energy (ΔGsolv) values in aqueous solution obtained using the SDM model by DFT calculations.
Graphic Abstract
Ni(II) and famotidine form an octahedral complex at pH 4 where famotidine acts as a tridentate neutral ligand. In basic medium, it behaves as a tetradentate dianion, resulting in a quasi-planar complex. Spectroscopic and thermal data are consistent with single crystal X-ray diffraction structural elucidation. The relative stabilities were assessed by theoretical studies.
NiPtB nanoalloy catalysts with various Ni contents were prepared by chemical reduction method at room temperature using NaBH4 as reducing agent. Pt and Ni cations were completely reduced to metals, and small amount of boron was also reduced and form alloy with metals. NiPtB formed nanosized alloy structure and X-ray diffraction patterns showed its amorphous nature. The particle size distribution and the surface composition were affected by Ni/Pt ratio in the starting materials and the temperature of heat treatment. The catalytic activity of the nanoalloys was tested for hydrogenation of p-chloronitrobenzene (p-CNB). The activity and selectivity to p-chloroaniline (p-CAN) were affected by the content of Ni in the catalyst. For NiPt0.01B catalyst, the occurrence of surface segregation of B was driven by the strain energy at high reaction temperature. For NiPt0.03B and NiPt0.01B catalysts, Pt segregated to the surface by H2 affinity. Ni/Pt ratio decreased as the reaction temperature increased. The activity was essentially affected by the addition of Ni on Pt in the NiPtB catalyst, as expected, because Pt is more active than Ni for this reaction. The hydrogenation of p-CNB was very selective and yielded p-CAN exclusively on NiPtB catalysts than that on Pt catalyst. 相似文献
