Metal complexes of Schiff bases synthesized from condensation of an amine with carbonyl compounds are widely used for industrial purposes such as catalysts, pigments and dyes, intermediates in orga...

REVIEW: Biomedical applications of Schiff base metal complexes

Recent progresses in Schiff bases as aqueous phase corrosion inhibitors: Design and applications

Mesoporous silica sieves are among the most studied nano-objects due to their stable pore structure and easy preparation. In particular, MCM-41 have attracted increasing research attention due to their chemical versatility. This review focuses on the synthesis and regioselective functionalization of MCM-41 to prepare catalytic systems. The topics covered are: mono and di-functionalized MCM-41 as basic and acid catalysts, catalysts based on metallic complexes and heteropolyacids supported onto MCM-41, metallic nanoparticles embed onto functionalized MCM-41 and magnetic MCM-41 for catalytic purposes.

Functionalized Ordered Mesoporous Silicas (MCM-41): Synthesis and Applications in Catalysis

Spectroscopic and thermal nonlinearity study of a Schiff base compound

Heterogeneous catalysts were used in several production processes for the synthesis of different products such as chemicals, drugs, energy resources, fuels and other specific products. In recent years, mesoporous silica, in particular MCM-41 was widely used in several fields, including catalysis and catalytic support, due to its remarkable textural properties. This material cannot be used directly in catalysis due to its inner surface containing only silanol groups. Therefore, several attempts were proposed in order to obtain an effective catalyst. The immobilization of metal complexes on the surface of mesoporous silica is one of the most popular methods. The metal complexes immobilized on the mesoporous silica MCM-41 exhibit significant catalytic activities due to the increased dispersion of the active sites and the faster diffusion of large organic molecules. The strong interactions between the metal and the ligand generate significant stability for this kind of catalyst, which allows them to be reused in several cycles without losing their efficiency. This review mainly discusses the immobilization strategies of different metal complexes supported on the mesoporous silica MCM-41. A recent study was presented and well detailed based on the different preparation methods, catalytic applications and the stability of metal complexes supported on mesoporous silica MCM-41.

Recent Advances on the Preparation and Catalytic Applications of Metal Complexes Supported-Mesoporous Silica MCM-41 (Review)

The condensation reaction of 3-aminopropyltrimethoxysilane with o-hydroxyacetophenone and subsequent complexation with Cu(CH3COO)2·H2O afforded a Schiff base copper complex with a silane moiety. Covalent functionalisation of MCM-41 with the Schiff base copper complex yielded a heterogenised copper complex which mimics the “CuN2O2” coordination site that resembles the galactose oxidase enzyme. The synthesized materials were characterized by UV-DRS, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) studies along with high resolution transmission electron microscopy (HR-TEM) to confirm successful functionalisation. Low-angle X-ray diffraction (LA-XRD) and nitrogen sorption analyses not only revealed the conservation of the textural properties of the support but also the permeability of the copper Schiff base complex into the channel system despite simultaneous decreases in surface area, pore volume and pore size. Electron paramagnetic resonance (EPR) studies confirmed the presence of copper Schiff base in MCM-41 even after dimerisation with o-aminophenol. The catalytic reaction was carried out with tert-butyl hydroperoxide (TBHP) and aqueous peroxide for MCM-41 and heterogenised copper complex under the mild reaction conditions.

Designing a biomimetic catalyst for phenoxazinone synthase activity using a mesoporous Schiff base copper complex with a novel double-helix morphology

The siloxane-functioned Cu(II) complex derived from 3-aminopropyltrimethoxysilane, terephthaldehyde and 2-aminophenol was anchored on hexagonal mesoporous silica MCM-41. The MCM-41 and its Schiff base MCM-41 complex was characterized by FTIR, small-angle X-ray diffraction, SEM-EDX, N2 adsorption and desorption analysis and TGA. The synthesized Cu-Schiff base MCM-41 catalyst has been successfully applied as a catalyst for Ullmann-type coupling reaction of the aryl halides with aryl halides, phenols, amines and N-heterocyclic amines. In the coupling reaction the yields of the products were good and the catalyst was recovered by simple filtration method and can be reused.

Tethering of Cu(II) Schiff base metal complex on mesoporous material MCM-41: catalyst for Ullmann-type coupling reactions

The corrosion inhibition efficiency of newly synthesized Schiff bases, SB-1 [(4E)-N-((Z)-2-((furan-2-yl)methylimino) indolin-3-ylidene)(furan-2-yl)methanamine] and SB-2 [(7Z,8Z)-6-chloro-N2,N4-bis(1-(pyridin-2-yl)ethylidene)pyrimidine-2,4-diamine], was investigated for aluminium corrosion in 1 M H2SO4 medium using mass loss and electrochemical techniques. Potentiodynamic polarization curves show that addition of Schiff bases in the acid solution shifts the corrosion potential (Ecorr) towards positive direction, suggesting that chosen SBs are performed as mixed-type inhibitiors. The adsorption process of Schiff bases on aluminium surface obeys Langmuir isotherm. Further, electrochemical impedance studies (EIS) reveal that the inhibition efficiency remarkably rises with increasing SBs concentration and the maximum inhibition efficiencies of 97% and – 95% were obtained for SB-1 and SB-2, respectively, for the inhibitor concentration of 500 ppm. Additionally, the associated activation parameters and thermodynamic data of adsorption were evaluated. Scanning electron microscope (SEM) studies further confirm that ligands of SB-1 and SB-2 have a strong tendency to adhere on top of aluminium and protect its corrosion against acidic media. The SEM micrographs of corroded and inhibited aluminium surfaces and the maximum inhibition efficiency of aluminium corrosion are achieved to be 97% for Schiff bases (SB-1) in 1 M H2SO4 solution with the concentration of 500 ppm.

Synthesis, Characterization and Inhibition Performance of Schiff Bases for Aluminium Corrosion in 1 M H2SO4 Solution

Synthesis of mesoporous silica nanoparticles with a lychee-like morphology and dual pore arrangement and its application towards biomimetic activity via functionalization with copper(II) complex

Ni(II) Schiff base complex was successfully immobilized on the surface of the MCM-41 material using the organo silane compound 3-aminopropyltrimethoxysilane by the direct synthesis method. The as-synthesized Ni-MCM-41 material was investigated by the characterization techniques like Fourier transform infrared spectroscopy, small angle X-ray powder diffraction, N2 adsorption-desorption isotherms, thermogravimetric analysis, scanning electron microscope and energy dispersion X-ray analysis. The studies show that the Ni-MCM-41 material retained good mesoporous structure and acts as an efficient catalyst for the C−S and C−N cross coupling reactions under prominent reaction conditions. Readily available nature of the starting compounds, synthesis of effective catalyst and reusability of the catalyst makes the present synthetic method a remarkable strategy.

Rajavel Rangappan

Papers

Designing a biomimetic catalyst for phenoxazinone synthase activity using a mesoporous Schiff base copper complex with a novel double-helix morphology

Tethering of Cu(II) Schiff base metal complex on mesoporous material MCM-41: catalyst for Ullmann-type coupling reactions

Synthesis, Characterization and Inhibition Performance of Schiff Bases for Aluminium Corrosion in 1 M H2SO4 Solution

Synthesis of mesoporous silica nanoparticles with a lychee-like morphology and dual pore arrangement and its application towards biomimetic activity via functionalization with copper(II) complex

Ni(II)‐Incorporated MCM‐41 Material ‐ Heterogeneous Catalyst for C‐S and C‐N Cross Coupling Reactions