Percorrer por autor "Karmakar, Anirban"
A mostrar 1 - 6 de 6
Resultados por página
Opções de ordenação
- Adenine tagged Mn-based coordination polymer for conversion of carbon dioxide to cyclic carbonates under atmospheric pressurePublication . Eskemech, Alehegn; Bhakhar, Rubi; Biswas, Pritam; Karmakar, Anirban; Krishnan, Venkata; Koner, Rik RaniAbstract Natural processes collectively balance the global carbon cycle, effectively controlling atmospheric carbon dioxide (CO2) levels. However, excessive CO2 emissions due to industrialization and population growth have disrupted natural processes by increasing the atmospheric CO2 concentration. To address this issue, CO2 capture and conversion have been implemented. Metal–organic frameworks (MOFs)/coordination polymers (CPs) with bioligands, such as amino acids and nucleobases, are receiving much interest. However, bio-MOFs are not much reported due to the lack of control over their coordination with metal ions. In this work, we have developed an adenine-tagged Mn-CP with dominant basic sites, [Mn(IPT2–)(Ade)(DMF)]n (IPT2– = isophthalate; Ade = adenine; DMF = N,N′-dimethylformamide). The analysis of isosteric heat (Qst) of CO2 adsorption supported the presence of strong interactions between CO2 and Mn-CP. Mn-CP demonstrated moderate to outstanding performance in coupling CO2 with smaller and larger epoxides at ambient pressure under neat conditions. The thermodynamic activation parameters indicate that Mn-CP operates through an associative mechanism (ΔS⧧ = −283.4 J mol−1 K−1), with a reduced kinetic barrier characterized by ΔH⧧ of 17.28 kJ mol–1 and Ea of 20.5 kJ mol–1. The catalytic efficiency of Mn-CP was particularly notable in the coupling reaction of epichlorohydrin and CO2, yielding 92% of the corresponding cyclic carbonate under atmospheric pressure.
- 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.
- Metal-organic frameworks with pyridyl-based isophthalic acid and their catalytic applications in microwave assisted peroxidative oxidation of alcohols and Henry reactionPublication . Karmakar, Anirban; Martins, Luisa; HAZRA, SUSANTA; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoReactions of 5-{(pyridin-4-ylmethyl)amino} isophthalic acid (H(2)L1) with copper(II), zinc(II), and cadmium(II) were studied, and the obtained metal organic frameworks (MOFs) [{Cu(L1)(DMF)}center dot DMF center dot H2O](n) (1), [Zn(L1)(H2O)(n) (2), and [Cd(L1)](n) (3) were characterized by elemental analysis, Fourier transform infrared spectroscopy, and X-ray single-crystal diffraction. As shown by X-ray crystallography, novel hybrid organic inorganic coordination-driven assemblies were obtained which exhibit different two- and three-dimensional (2D and 3D) polymeric architectures. Compounds 1 and 2 have 2D structures, whereas compound 3 features a 3D network type polymer with a dimetallic core acting as a secondary building unit. These frameworks act as heterogeneous polymeric solid catalysts (the most effective one being the copper MOF 1) for solvent-free microwave assisted peroxidative oxidation of primary and secondary alcohols. They also effectively catalyze the nitroaldol (Henry) reaction of different aldehydes with nitroalkanes in water. These MOF-based heterogeneous catalysts can be easily recovered and reused, at least for a few consecutive cycles, without losing activity.
- Solvent-free microwave-assisted peroxidative oxidation of alcohols catalyzed by Iron(III)-TEMPO catalytic systemsPublication . Karmakar, Anirban; Martins, Luisa; Guedes Da Silva, M. Fátima C.; HAZRA, SUSANTA; Pombeiro, ArmandoThe iron(III) complexes [H(EtOH)][FeCl2(L)(2)] (1), [H(2)bipy](1/2)[FeCl2(L)(2)].DMF (2) and [FeCl2(L)(2,2'-bipy)] (3) (L = 3-amino-2-pyrazinecarboxylate; H(2)bipy = doubly protonated 4,4'-bipyridine; 2,2'-bipy = 2,2'-bipyridine, DMF = dimethylformamide) have been synthesized and fully characterized by IR, elemental and single-crystal X-ray diffraction analyses, as well as by electrochemical methods. Complexes 1 and 2 have similar mononuclear structures containing different guest molecules (protonated ethanol for 1 and doubly protonated 4,4'-bipyridine for 2) in their lattices, whereas the complex 3 has one 3-amino-2-pyrazinecarboxylate and a 2,2'-bipyridine ligand. They show a high catalytic activity for the low power (10 W) solvent-free microwave assisted peroxidative oxidation of 1-phenylethanol, leading, in the presence of TEMPO, to quantitative yields of acetophenone [TOFs up to 8.1 x 10(3) h(-1), (3)] after 1 h. Moreover, the catalysts are of easy recovery and reused, at least for four consecutive cycles, maintaining 83 % of the initial activity and concomitant rather high selectivity. 3-Amino-2-pyrazinecarboxylic acid is used to synthesize three new iron(III) complexes which act as heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation of 1-phenylethanol.
- Solvent-free microwave-assisted peroxidative oxidation of alcohols catalyzed by iron(III)-TEMPO catalytic systemsPublication . Karmakar, Anirban; Martins, Luisa; Guedes Da Silva, M. Fátima C.; HAZRA, SUSANTA; Pombeiro, ArmandoThe iron(III) complexes [H(EtOH)][FeCl2(L)(2)] (1), [H(2)bipy](1/2)[FeCl2(L)(2)].DMF (2) and [FeCl2(L)(2,2'-bipy)] (3) (L = 3-amino-2-pyrazinecarboxylate; H(2)bipy = doubly protonated 4,4'-bipyridine; 2,2'-bipy = 2,2'-bipyridine, DMF = dimethylformamide) have been synthesized and fully characterized by IR, elemental and single-crystal X-ray diffraction analyses, as well as by electrochemical methods. Complexes 1 and 2 have similar mononuclear structures containing different guest molecules (protonated ethanol for 1 and doubly protonated 4,4'-bipyridine for 2) in their lattices, whereas the complex 3 has one 3-amino-2-pyrazinecarboxylate and a 2,2'-bipyridine ligand. They show a high catalytic activity for the low power (10 W) solvent-free microwave assisted peroxidative oxidation of 1-phenylethanol, leading, in the presence of TEMPO, to quantitative yields of acetophenone [TOFs up to 8.1 x 10(3) h(-1), (3)] after 1 h. Moreover, the catalysts are of easy recovery and reused, at least for four consecutive cycles, maintaining 83 % of the initial activity and concomitant rather high selectivity. 3-Amino-2-pyrazinecarboxylic acid is used to synthesize three new iron(III) complexes which act as heterogeneous catalysts for the solvent-free microwave-assisted peroxidative oxidation of 1-phenylethanol.
- 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.