Green carbon-carbon homocoupling of terminal alkynes by a silica supported Cu(II)-hydrazone coordination compound

Experimental and Theoretical Studies of Novel Cadmium(II) N2O-Schiff Base Complexes: Synthesis, Spectroscopic Characterization, X-ray Crystal Structure, and Fluorescent Properties

Three 2,6-dimethoxyaniline Schiff base cadmium(II) complexes were synthesized via a one-pot reaction and characterized by spectroscopic methods (NMR, FT-IR, EA), X-ray crystallography, SEM/EDX and fluorescent spectroscopy. The molecular structures of complexes 1-3 were elucidated by X-ray crystallography, revealing penta-coordinated cadmium(II) centers with distorted square-pyramidal geometries. Mononuclear molecules form supramolecular structures through intermolecular C-H···Cl interactions and π···π stacking interactions, which further stabilize the structures of the complexes. DFT calculations were performed to analyze the electronic structures and frontier molecular orbitals. The fluorescence properties of complexes 1-3 were investigated in both solid-state and solution, exhibiting characteristic emission bands. The study provides insights into the structural and luminescent properties of these cadmium(II) complexes, demonstrating their potential applications as luminescent materials.

Chemical CO2 fixation by a heterogenised Zn(ii)-hydrazone complex

A new Zn(ii) coordination compound, [Zn(HL)(OAc)2] (1), with ONN-donor hydrazone ligand (HL = (E)-4-amino-N'-(1-(pyridin-2-yl)ethylidene)benzohydrazide) was synthesized and structurally characterized by using spectroscopic techniques and X-ray analysis. These analyses indicated that the Zn(ii) ion in the resulting coordination compound is five coordinated and the compound has a free amine functionality on the phenyl ring. Thus, [Zn(HL)(OAc)2] (1) was immobilized on the surface of propionylchloride functionalized silica gel through an amidification process via the reaction of the aniline part of compound 1 and the acyl chloride group of the support. The synthesized heterogeneous catalyst, Si-[Zn(HL)(OAc)2], was characterized by several analytical methods and the results confirmed the successful support of 1 on the surface of the support. Si-[Zn(HL)(OAc)2] was used in a chemical CO2 fixation reaction and styrene epoxide was used as a model substrate to investigate the catalytic performance of the supported Zn(ii) catalyst. Si-[Zn(HL)(OAc)2] can efficiently catalyze the formation of cyclic carbonate from the reaction of epoxide and CO2 in the presence of TBAB as a co-catalyst.

Enhanced methanol electro-oxidation activity of CuO nanoparticles derived from the thermal decomposition of a CuII salophen type coordination compound

Electrocatalysts based on Cu compounds have been considered as a suitable alternative to platinum compounds due to their low cost, high abundance, excellent redox properties, and performing the methanol oxidation reaction (MOR) at low potentials. This article represents a study of CuO nanoparticles (NPs) prepared through a simple method of thermal decomposition of the CuL coordination compound (H2L = N,N'-bis(salicylidene)-4-chloro-1,2-diaminobenzene), C20H13ClCuN2O2, as a precursor by different electrochemical methods. A comparison of the MOR ability of precursor (CuL) and CuO NPs shows that both compounds are active, but CuO NPs present a peak current density of about 248 mA cm- 2 when screened for catalytic MOR in 1.0 M KOH with 0.5 M methanol, which is superior to the performance of CuL and some previously reported related catalysts based on CuO. The methanol oxidation peak at 0.69 V vs. Ag/AgCl is also more intense than CuL (0.77 V). The modified electrode with CuO NPs also shows lower onset potential, lower Tafel slope, higher electrochemically active surface area (ECSA) and better stability compared to the CuL electrode. These advantages can be assigned to the higher activity of catalytic sites and the lower charge transfer resistance of CuO due to its higher electrical conductivity than the CuL.

Chemical CO2 fixation using a cyanido bridged heterometallic Zn(II)-Mn(II) 2D coordination polymer

A new cyanido bridged Zn(II)-Mn(II) mixed-metal coordination polymer, {[Zn(μ-L)(μ-CN)2Mn0.5]·(CH3OH)}n (1), has been synthesized by the reaction of Zn(CN)2, Mn(II) salts and a hydrazone ligand (HL = (E)-N'-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide) in methanol. Compound 1 was characterized using various analytical methods (including elemental analysis, photoluminescence, FT-IR, XRD, SEM, and EDX analyses, and TGA), and its structure was determined by X-ray analysis. These analyses confirmed the formation of a mixed metal Zn(II)-Mn(II) coordination polymer containing both cyanide and hydrazone bridging ligands. This mixed metal coordination polymer exhibits interesting emission spectra by having several emissions via excitation at 230, 270, 375 and 385 nm. The catalytic activity of compound 1 in chemical CO2 fixation was investigated in the presence of epoxides, and the effects of various parameters on its catalytic performance were evaluated. The results of catalytic studies show that compound 1 can efficiently catalyze the chemical CO2 fixation reaction under mild conditions. The amount of co-catalyst, temperature of the reaction, nature of the solvent and also the substituent connected to the epoxide ring are some of the important parameters that have considerable effects on the catalytic activity of 1.

Synthesis of chiral Cu(II) complexes from pro-chiral Schiff base ligand and investigation of their catalytic activity in the asymmetric synthesis of 1,2,3-triazoles

A pro-chiral Schiff base ligand (HL) was synthesized by the reaction of 2-amino-2-ethyl-1,3-propanediol and pyridine-2-carbaldehyde in methanol. The reaction of HL with CuCl2·2H2O and CuBr2 in methanol gave neutral mononuclear Cu(II) complexes with general formula of [Cu(HL)Cl2] (1) and [Cu(HL)Br2] (2), respectively. By slow evaporation of the methanolic solutions of 1 and 2, their enantiomers were isolated in crystalline format. The formation of pure chiral crystals in the racemic mixture was amply authenticated by single crystal X-ray analysis, which indicated that S-[Cu(HL)Cl2], R-[Cu(HL)Cl2], and S-[Cu(HL)Br2] are crystallized in chiral P212121 space group of orthorhombic system. Preferential crystallization was used to isolate the R and S enantiomers as single crystals and the isolated compounds were also studied by CD analysis. Structural studies indicated that the origin of the chirality in these compounds is related to the coordination mode of the employed pro-chiral ligand (HL) because one of its carbon atoms has been converted to a chiral center in the synthesized complexes. Subsequently, these complexes were used in click synthesis of a β-hydroxy-1,2,3-triazole and the results of catalytic studies indicated that 1 and 2 can act as enantioselective catalysts for the asymmetric synthesis of β-hydroxy-1,2,3-triazole product under mild condition. This study illustrates the significant capacity of the use of pro-chiral ligands in preparing chiral catalysts based on complexes which can also be considered as an effective approach to cheap chiral catalysts from achiral reagents.

Palladium anchored to BisPyP@bilayer-SiO2@NMP organic-inorganic hybrid as an efficient and recoverable novel nanocatalyst in suzuki and stille C-C coupling reactions

The palladium anchored to BisPyP@bilayer-SiO2@NMP organic-inorganic hybrid was employed as an effective and recyclable organometallic catalyst in Suzuki and Stille C-C coupling reactions. The structure of this magnetic nanocatalyst was determined using various techniques such as SEM, TEM, FT-IR, EDS, ICP-OES, VSM, N2 adsorption-desorption isotherms, XRD, and TGA. In both of the mentioned coupling paths, the yields of the products were very favorable and ranged from 90 to 98%. Also, they had significant features compared to previous reports, such as very short reaction time (5-15 and 7-20 min respectively in the Suzuki and Stille reactions), easy work-up, broad substrate scope, ease of separation of the catalyst using a magnet, suitable reproducibility of the catalyst in 6 runs, heterogeneous nature of the catalyst and not washing it during consecutive runs with confirmation of hot filtration and ICP-OES methods.