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- A copper-amidocarboxylate based metal organic macrocycle and framework: synthesis, structure and catalytic activities towards microwave assisted alcohol oxidation and Knoevenagel reactionsPublication . Karmakar, Anirban; Soliman, Mohamed Mostafa Aboelhassan; Alegria, Elisabete; Rubio, Guilherme; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoReactions of 3,3 '-{(pyridine-2,6-dicarbonyl)bis(azanediyl)}dibenzoic acid (H2L) with copper(ii) nitrate were studied and the obtained compounds [Cu-2(1:2 kappa(OO2)-O-1,2:3 kappa(OO4)-O-3-L)(mu-NO3)(mu(3)-OH)(MeOH)(2)](2)center dot 2MeOH center dot 1DMF (1) and [Cu(mu-1 kappa O-1:2 kappa O-2,3 kappa O-3:4 kappa O-4-L)(DMF)](n)center dot 4n(DMF) (2) were characterized by elemental analysis, FT-IR spectroscopy, and single-crystal and powder X-ray diffraction. Compound 1 is a macrocyclic tetranuclear Cu(ii) complex possessing a central, quasi-planar rhomboid shaped {Cu-4} cluster, which is the first example of a Cu(ii) based macrocyclic tetranuclear complex using such a linker. Compound 2 is a 2D metal organic framework having dinuclear paddlewheel type Cu(ii) assemblies that act as secondary building blocks. The topological analysis of framework 2 revealed that it has a 2,4-connected binodal net. Both compounds act as heterogeneous, easily recovered and reusable catalysts (the catalysts could be reused at least four times without significant loss of activity) for the microwave-assisted oxidation of several alcohols, as well as for the Knoevenagel condensation reaction of various aldehydes. The effect of reaction parameters such as temperature, time and type of oxidant was investigated. This study demonstrates that compound 1 can act as an efficient catalyst for the conversion of secondary alcohols (1-phenylethanol) to the corresponding ketones with high selectivity and yields up to 93% after 1 h of reaction at 120 degrees C and using t-BuOOH as an oxidant. Moreover, these compounds effectively catalyze the Knoevenagel condensation reactions of aldehydes with malononitrile and produce reaction yields between 64 and 99% within a very short period (10 min) under low power microwave irradiation. Furthermore, we have also studied the effectiveness of our catalyst 1 towards peroxidative oxidation/Knoevenagel condensation cascade reactions under microwave conditions.
- ZnO nanoparticles: An efficient catalyst for transesterification reaction of alpha-keto carboxylic estersPublication . Soliman, Mohamed Mostafa Aboelhassan; Karmakar, Anirban; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Rubio, Guilherme; Saraiva, Marta S.; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoPure ZnO nanoparticles were synthesized by a sustainable precipitation method using zinc nitrate and sodium hydroxide in aqueous medium at room temperature. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis) spectroscopy and Brunauer-Emmett-Teller (BET) analysis. The XRD patterns indicate the formation of the hexagonal wurtzite phase with high purity and SEMEDS analysis confirm the purity and a homogenous distribution of the nanostructures. The ZnO nanostructures present plate-like agglomerates, resulting in a quasi-spherical morphology. The catalytic activity of the formed ZnO nanoparticles was evaluated towards the transesterification reaction of different carboxylic esters in the presence of various alcohols. This catalyst is highly selective for the transesterification of alpha-keto carboxylic ester (methyl benzoylformate) and leads to ca. 97% of product yield within 24 h of reaction time.