One-pot synthesis of Schiff base compounds via photocatalytic reaction in the coupled system of aromatic alcohols and nitrobenzene using CdIn2S4 photocatalyst

Synthesis, crystal structure, thermal stability and biological study of bis{(2-methoxy-6-[(E)-(propylimino)methyl]phenolato}nickel(II) complex

A Schiff base complex of nickel, bis{(2-methoxy-6-[(E)-(propylimino)methyl]phenolato}nickel(II) was synthesised by condensing bis(2-hydroxy-3-methoxybenzaldehyde) nickel (II) and n-propylamine in methanolic medium. Single crystal X-ray diffraction analysis of the complex revealed it to possess planar geometry with a monoclinic crystal system. The non-isothermal TG/DTA runs on this complex in a high purity (99.99 %) nitrogen environment at atmospheric pressure confirmed the absence of any coordinated water. A sharp endotherm in its DTA shows a melting temperature range of 168-171 °C. It is thermally stable up to 243 °C and decomposes in two steps, yielding NiO and carbon as residue. In addition to the methoxy group (-OCH3), infrared analysis (IR) confirmed the presence of the characteristic azomethine group (-C[bond, double bond]N-) which is also responsible for the biological action. It was further analysed by elemental analyser (C, H, N), 1H and 13C NMR as well as mass spectrometry. It showed considerable antibacterial activity towards Escherichia coli and Staphylococcus aureus when the concentration exceeds 200 μg/ml. The antifungal study shows significant inhibition with the antifungal drug imidazole as a positive control (PC). Small values of MIC, MBC/MIC indicate a lesser quantity of complex is required to inhibit the growth of micro-organisms.

Efficient one-pot syntheses of secondary amines from nitro aromatics and benzyl alcohols over Pd/NiTi-LDH under visible light

Solar energy-induced cascade/tandem reactions in one-pot are sustainable and green. Herein, the Pd/NiTi-LDH nanocomposite, with Pd nanoparticles (NPs) (∼3-6 nm) deposited on NiTi-LDH nanosheets, was obtained and was applied in the reaction between nitro aromatics and alcohols to synthesize secondary amines under visible light. The superior performance observed over the as-obtained Pd/NiTi-LDH nanocomposite for this reaction can be attributed to a successful merging of Pd-based hydrogenation and LDH-based photocatalysis, in which consecutive light-induced hydrogenation of nitro compounds to amines, dehydrogenation of alcohols to aldehydes, condensation between the in situ formed aldehydes and amines to imines and the hydrogenation of final imines to generate the desired secondary amines were realized in one pot over Pd/NiTi-LDH under visible light. This work shows an effective and green strategy in the synthesis of secondary amines. This study also demonstrates the high potential of using metal/LDH nanocomposites for light-initiated organic syntheses.

One-Pot Synthesis of Schiff Bases by Defect-Induced TiO2-x-Catalyzed Tandem Transformation from Alcohols and Nitro Compounds

Schiff bases that are generally formed from condensation reactions of aldehydes (or ketones) and amino groups could also be produced by a photodriven one-pot tandem reaction between alcohols and nitro compounds, in our case. Herein, TiO_2-x porous cages derived from NH₂-MIL-125 by a self-sacrificing template route are used to study the organic transformation and exhibit 100% conversion efficiency of nitrobenzene and 100% selectivity for Schiff bases in the system of benzyl alcohol (5 mL) and nitrobenzene (41 μL) upon light irradiation, but hydrogen by dehydrogenation of benzyl alcohol cannot be detected. Successful occurrence of the organic transformation is mainly attributed to Ti(III)-oxygen vacancy associates. Surface oxygen vacancy-related Ti(III) sites are responsible for binding with nitro groups, and low-coordinated Ti_5c sites selectively adsorb hydroxyl groups of benzyl alcohol. The Ti(III) and oxygen vacancy associates capture photogenerated electrons for achievement of multielectron reduction of nitrobenzene and the subsequent Schiff base condensation reaction with the as-formed benzaldehyde.

Green and controllable synthesis of one-dimensional Bi2O3/BiOI heterojunction for highly efficient visible-light-driven photocatalytic reduction of Cr(VI)

BiOI nanosheets have been successfully deposited on the porous Bi₂O₃ nanorobs via a one-pot precipitation method. The physicochemical features of the as-prepared materials were characterized in detail by a series of techniques, and the results revealed that BiOI nanosheets were evenly distributed on the porous Bi₂O₃ nanorobs. Because of higher photogenerated electron-hole pairs separation efficiency and the larger specific surface area compared to the pristine Bi₂O₃ and BiOI, the 50%Bi₂O₃/BiOI composite exhibited significantly enhanced photocatalytic activity for Cr(VI) reduction under visible light irradiation, and the reduction rate constant was 0.02002 min^-1, which was about 27.4 and 2.6 times higher than that of pure Bi₂O₃ (0.00073 min^-1) and BiOI (0.00769 min^-1), respectively. Moreover, the 50%Bi₂O₃/BiOI composite also possessed the excellent photochemical stability and recyclability, thereby facilitating its wastewater treatment application.

Self-Assembly of CdS/CdIn2S4 Heterostructure with Enhanced Photocascade Synthesis of Schiff Base Compounds in an Aromatic Alcohols and Nitrobenzene System with Visible Light

A series of novel CdS/CdIn₂S₄ composite materials were prepared via a one-pot solvothermal process. The as-obtained photocatalysts were characterized by several techniques and the photocatalytic properties of CdS/CdIn₂S₄ photocatalysts were studied by photocascade synthesis of Schiff base compounds in a photocatalytic reaction system of aromatic alcohols and nitrobenzene irradiated with visible light. The results reveal that the resulting CdS/CdIn₂S₄ heterostructure samples show outstanding photocatalytic activities toward the photocascade production of Schiff base compounds in an aromatic alcohols and nitrobenzene reaction system irradiated with visible light. An optimized 50.0% CdS/CdIn₂S₄ heterostructure sample shows the highest Schiff base yield of 42.0% irradiated with visible light for 4 h, which is approximately 19.1 and 1.54 times higher than those of sole CdS and CdIn₂S₄ samples, respectively. The fabrication of heterogeneous structure improves the spatial separation and migration of photoinduced electron-hole pairs, thus contributing to the enhancement of photocatalytic properties. We foresee that this finding can offer a strategy to develop heterostructure composites for efficient synthesis of organics by photocatalysis under mild conditions.

Silver-loaded In2S3-CdIn2S4@X(X=Ag, Ag3PO4, AgI) ternary heterostructure nanotubes treated by electron beam irradiation with enhanced photocatalytic activity

Ternary heterostructure nanotubes of In₂S₃-CdIn₂S₄@X(X = Ag, Ag₃PO₄, AgI) were synthesized with enhanced photocatalytic activity for efficiently degrading pollutants. Electron beam irradiation was employed to artificially introduce interface defects to the heterostructure nanotubes. The experimental results for degrading carmine and Cr⁶⁺ under visible light irradiation showed that the photocatalytic efficiency of In₂S₃-CdIn₂S₄ was improved to some extent by the introduction of silver compounds. DRS results confirmed that the band gaps of In₂S₃-CdIn₂S₄ were reduced to 1.62 eV and 1.58 eV by introducing Ag₃PO₄ and AgI, respectively. Interestingly, the band gap of In₂S₃-CdIn₂S₄@AgI after electron beam irradiation was further reduced to 1.56 eV, resulting in that the degradation time of both Cr⁶⁺ and carmine by In₂S₃-CdIn₂S₄@AgI after high-energy electron beam irradiation was shortened to only 5 min. The XRD spectra of the photocatalysts after five cycles could maintain the original crystal form to a large extent. The OH stretching vibration peaks of In₂S₃-CdIn₂S₄@AgI after electron beam irradiation at 3387 cm^-1 became wider and sharper, thus indicating that the number of free hydroxyl groups on the heterostructure surface significantly increased. PL results showed that electron beam irradiation could significantly reduce the PL emission peak and enhance the utilization of photogenerated charge carriers. EIS results further confirmed that In₂S₃-CdIn₂S₄@AgI processed by electron beam irradiation had higher photogenerated electron-hole separation efficiency. Based on the experimental results, a feasible reaction pathway and photocatalytic mechanism for the degradation of carmine was investigated. ESR results showed that the main active groups in the whole photocatalytic system were •O₂^- and h⁺.

Efficient utilization of photogenerated electrons and holes for photocatalytic redox reactions using visible light-driven Au/ZnIn2S4 hybrid

In this study, a new photocatalytic reaction system for simultaneous selective oxidation of aromatic alcohols to corresponding aldehydes and reduction of protons to H₂ has been developed. The results reveal that compared with pure ZnIn₂S₄, the ZnIn₂S₄ photocatalysts modified with noble metal gold (Au/ZnIn₂S₄) significantly promote the photocatalytic performance. Among them, the 0.5% Au/ZnIn₂S₄ nanosheets shows the highest photocatalytic activity for selective oxidation of benzyl alcohol to benzaldehyde and hydrogen production, and the yields of H₂ and benzaldehyde are 326.68 and 352.04 μmol under visible light irradiation for 4 h, respectively. Those are about 4.4 and 3.6 times higher than those of pure ZnIn₂S₄ sample (74.0 μmol H₂ and 98.04 μmol benzaldehyde), respectively. The utilization ratio of photogenerated electrons to holes can achieve 92.8%. Additionally, the control experiments demonstrate that the photogenerated electrons and holes play significant roles during the reaction process. It is hoped that the current work can offer an avenue to utilize the photogenerated carriers more efficiently and to develop other photocatalytic reaction systems, such as nitrogen fixation and reduction of carbon dioxide.

A plasmonic AuPd bimetallic nanoalloy decorated over a GO/LDH hybrid nanocomposite via a green synthesis route for robust Suzuki coupling reactions: a paradigm shift towards a sustainable future

A plasmonic AuPd bimetal-decorated GO/LDH nano-photocatalyst displays encouraging Suzuki coupling performance under visible light illumination.