Md. Lutfor Rahman

Highly active thiol-functionalized SBA-15 supported palladium catalyst for Sonogashira and Suzuki–Miyaura cross-coupling reactions

Highly ordered mesoporous silica SBA-15 with pendent 3-mercaptopropyl groups has been prepared by condensation of surface silanols and (3-mercaptopropyl)trimethoxysilane. Treatment of the mercaptopropylated SBA-15 with (CH3CN)2PdCl2 gave a heterogeneous Pd-catalyst. The immobilized Pd-catalyst served as an efficient heterogeneous catalyst for Sonogashira and Suzuki–Miyaura cross coupling reactions of aryl halides. Furthermore, the SBA-15 supported Pd-catalyst was recovered by a simple filtration from the reaction mixture and reused five times without significant loss of its catalytic activity.

Heck, Suzuki and Sonogashira cross-coupling reactions using ppm level of SBA-16 supported Pd-complex

SBA-16 supported 1,2-diaminocyclohexane Pd-complex (100–500 mol ppm of Pd) was found to be an efficient catalyst in the palladium-catalyzed Mizoroki–Heck, Suzuki–Miyaura and copper-free Sonogashira cross-coupling reactions of aryl halides under mild reaction conditions. The Pd-complex efficiently promoted all of these coupling reactions with appropriate coupling partners to afford the corresponding coupling products with almost quantitative yield. The supported Pd-complex was readily recovered and used five times without a significant loss of its catalytic activity.

Preparation of mesoporous SBA-16 silica-supported biscinchona alkaloid ligand for the asymmetric dihydroxylation of olefins

Optically active cinchona alkaloid was anchored onto mesoporous SBA-16 silica and the as-prepared complex was used as a heterogeneous chiral ligand of osmium tetraoxide for the asymmetric dihydroxylation of olefins. The prepared catalytic system provided 90-93% yield of vicinal diol with 92-99% enantioselectivity. The ordered mesoporous SBA-16 silica was found to be a valuable support for the cinchona alkaloid liganded osmium catalyst system which is frequently used in chemical industries and research laboratories for olefin functionalization.

Waste Corn-Cob Cellulose Supported Bio-Heterogeneous Copper Nanoparticles for Aza-Michael Reactions

Bio-heterogeneous poly(amidoxime) copper nanoparticles were prepared on the modified surface of waste corn-cob cellulose through a graft copolymerization process. The Cu-nanoparticles (0.05 mol% to 50 mol ppm) selectively promoted the aza-Michael reaction of aliphatic amines to give the corresponding alkylated products at room temperature in methanol. The supported nanoparticles were easy to recover and reused eight times without a significant loss of their activity.

Pyridinyl Functionalized MCM-48 Supported Highly Active Heterogeneous Palladium Catalyst for Cross-coupling Reactions

An MCM-48 supported 2-pyridinylmethanimine Pd-catalyst was found to be a highly efficient catalyst in the Mizoroki–Heck, Suzuki–Miyaura and copper-free Sonogashira cross-coupling reactions of aryl halides under aqueous reaction conditions. The catalyst efficiently promoted these coupling reactions with ppm levels of palladium to afford the corresponding coupling products in up to 98% yield. The supported Pd-catalyst was readily recovered and reused several times without significant loss of its catalytic activity.

Bio-waste Corn-cob Cellulose Supported Poly(hydroxamic acid) Copper Complex for Huisgen Reaction: Waste to Wealth Approach

Corn-cob cellulose supported poly(hydroxamic acid) Cu(II) complex was prepared by the surface modification of waste corn-cob cellulose through graft copolymerization and subsequent hydroximation. The complex was characterized by IR, UV, FESEM, TEM, XPS, EDX and ICP-AES analyses. The complex has been found to be an efficient catalyst for 1,3-dipolar Huisgen cycloaddition (CuAAC) of aryl/alkyl azides with a variety of alkynes as well as one-pot three-components reaction in the presence of sodium ascorbate to give the corresponding cycloaddition products in up to 96% yield and high turn over number (TON 18,600) and turn over frequency (TOF 930h-1) were achieved. The complex was easy to recover from the reaction mixture and reused six times without significant loss of its catalytic activity.

Efficient removal of heavy metals from electroplating wastewater using polymer ligands

Poly(hydroxamic acid)-poly(amidoxime) chelating ligands were synthesized from poly(methyl acrylate-co-acrylonitrile) grafted acacia cellulose for removing toxic metal ions from industrial wastewaters. These ligands showed higher adsorption capacity to copper (2.80 mmol·g−1) at pH 6. In addition, sorption capacities to other metal ions such as iron, zinc, chromium, and nickel were also found high at pH 6. The metal ions sorption rate (t1/2) was very fast. The rate of adsorption of copper, iron, zinc, chromium, nickel, cobalt, cadmium and lead were 4, 5, 7, 5, 5, 8, 9 and 11 min, respectively. Therefore, these ligands have an advantage to the metal ions removal using the column technique. We have successfully investigated the known concentration of metal ions using various parameters, which is essential for designing a fixed bed column with ligands. The wastewater from electroplating plants used in this study, having chromium, zinc, nickel, copper and iron, etc. For chromium wastewater, ICP analysis showed that the Cr removal was 99.8% and other metal ions such as Cu, Ni, Fe, Zn, Cd, Pb, Co and Mn removal were 94.7%, 99.2%, 99.9%, 99.9%, 99.5%, 99.9%, 95.6% and 97.6%, respectively. In case of cyanide wastewater, the metal removal, especially Ni and Zn removal were 96.5 and 95.2% at higher initial concentration. For acid/alkali wastewater, metal ions removing for Cd, Cr and Fe were 99.2%, 99.5% and 99.9%, respectively. Overall, these ligands are useful for metal removal by column method from industrial wastewater especially plating wastewater.

Synthesis of tapioca cellulose-based poly(hydroxamic acid) ligand for heavy metals removal from water

ABSTRACT A graft copolymerization was performed using free radical initiating process to prepare the poly(methyl acrylate) grafted copolymer from the tapioca cellulose. The desired material is poly(hydroxamic acid) ligand, which is synthesized from poly(methyl acrylate) grafted cellulose using hydroximation reaction. The tapioca cellulose, grafted cellulose and poly(hydroxamic acid) ligand were characterized by Infrared Spectroscopy and Field Emission Scanning Electron Microscope. The adsorption capacity with copper was found to be good, 210 mg g−1 with a faster adsorption rate (t1/2 = 10.5 min). The adsorption capacities for other heavy metal ions were also found to be strong such as Fe3+, Cr3+, Co3+ and Ni2+ were 191, 182, 202 and 173 mg g−1, respectively at pH 6. To predict the adsorption behavior, the heavy metal ions sorption onto ligand were well-fitted with the Langmuir isotherm model (R2 > 0.99), which suggest that the cellulose-based adsorbent i.e., poly(hydroxamic acid) ligand surface is homogenous and monolayer. The reusability was checked by the sorption/desorption process for six cycles and the sorption and extraction efficiency in each cycle was determined. This new adsorbent can be reused in many cycles without any significant loss in its original removal performances.

Poly(hydroxamic acid) functionalized copper catalyzed C–N bond formation reactions

Highly active poly(hydroxamic acid) functionalized copper catalysts were synthesized by the surface modification of khaya cellulose through graft copolymerization and subsequent hydroximation processes. The prepared catalysts were well characterized by FTIR, FESEM, HRTEM, ICP-AES, UV-vis and XPS analyses. The supported catalysts effectively promoted C–N bond formation reactions and provided excellent yields of the corresponding products under mild reaction conditions. The catalysts were easy to recover from the reaction mixture and were reused several times without any significant loss of their catalytic activity.

Crystal structure of 4-({(1E,2E)-3-[3-(4-fluoro-phen-yl)-1-isopropyl-1H-indol-2-yl]allyl-idene}amino)-1H-1,2,4-triazole-5(4H)-thione.

The asymmetric unit of the title compound comprises two independent molecules which exist in the trans conformation with respect to the methene C= C and the acyclic N=C bonds. In the crystal, molecules are linked via N—H⋯N hydrogen bonds, forming chains along the b-axis direction.