Dhrubajit Borah*, Bishnujyoti Bordoloi, Rehnaz Wahid (original) (raw)

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Papers by Dhrubajit Borah*, Bishnujyoti Bordoloi, Rehnaz Wahid

Research paper thumbnail of Impact Factor: 2.785 Global

In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga ri... more In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga river sediments. The acids were investigated by UV-Vis spectroscopy and the heavy metal contents are determined by atomic absorption spectroscopy (AAS).Moreover, E4/ E6 ratio is determined. Our studies reveal that E4/ E6 ratio decreases from 30cm depth soil to surface which indicates that humic acid, at surface contains more aromatic groups compared to other two samples. In addition to that we found that copper (Cu) presents in the soil of river sediment is higher than other metals which can be attributed to association of Cu in process of formation of Humic acid.

Research paper thumbnail of Biochar as Soil Amendment in Climate-Smart Agriculture: Opportunities, Future Prospects, and Challenges

Journal of soil science and plant nutrition, Feb 7, 2024

Research paper thumbnail of Ni(OH) 2 nanoparticles as a recyclable catalyst in acceptorless dehydrogenation of alcohols to acids/acid salts under aerobic conditions

Research paper thumbnail of CCDC 1860391: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1863543: Experimental Crystal Structure Determination

Research paper thumbnail of A cyclometalated Ir(iii)–NHC complex as a recyclable catalyst for acceptorless dehydrogenation of alcohols to carboxylic acids

Dalton Transactions, 2020

The first example of delineating the efficacy of cyclometalated Ir NHC complexes in acceptorless ... more The first example of delineating the efficacy of cyclometalated Ir NHC complexes in acceptorless dehydrogenation of alcohols to acids reported.

Research paper thumbnail of A new PEPPSI type N-heterocyclic carbene palladium(II) complex and its efficiency as a catalyst for Mizoroki-Heck cross-coupling reactions in water

Journal of Chemical Sciences, 2020

A new air and moisture stable PEPPSI (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabili... more A new air and moisture stable PEPPSI (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabilisation, and initiation) themed palladium N-heterocyclic carbene (NHC) complex [Pd(L)Br 2 (Py)] (1) [L: 2-flurobenzyl)-1-(4-methoxyphenyl)-1H-imidazolline-2-ylidene] was synthesized and characterized. The structure of complex 1 was determined by X-ray single-crystal analysis. The palladium center in 1 adopted a square planar geometry with carbene and pyridine ligands occupying the mutual trans position. The complex 1 was employed to catalyze the Mizoroki-Heck cross-coupling reactions of aryl bromides/iodides with styrene in water. To the best of our knowledge, this is the first report where a Pd-PEPPSI catalyst was successfully employed in aqueous-phase Mizoroki-Heck reaction. Good to excellent yields of cross-coupling products were obtained with a range of representative aryl bromides/iodides under relatively mild conditions (100°C, 1 mol% of 1).

Research paper thumbnail of Highly efficient aqueous-phase Sonogashira coupling catalyzed by Pd-PEEPSI/PPh3 under aerobic condition

Journal of Chemical Sciences, Dec 1, 2021

An in situ generated catalytic system comprised of a Pd-PEPPSI [Pyridine enhanced pre-catalyst pr... more An in situ generated catalytic system comprised of a Pd-PEPPSI [Pyridine enhanced pre-catalyst preparation, initiation, and stabilization] complex, (NHC)PdBr2(Pyridine), and PPh3 co-ligand demonstrated excellent activity for the Sonogashira cross-coupling reactions between phenylacetylene with aryl halides in neat water under the aerobic condition in presence of CuI as co-catalyst. The catalytic system was not only compatible with electronically diverse aryl bromides/ iodides but also effective for relatively difficult substrates like heteroaryl bromides. Notably, under similar experimental conditions, the mixed PEPPSI/PPh3 system displayed superior activity over the free Pd-PEPPSI or Pd-phosphine system. This article presents an in situ Pd-PEPPSI/PPh3 catalytic system for aqueous Sonogashira reaction in presence of CuI under aerobic condition which was found to be highly efficient for coupling of anyl/heteroaryl halides with phenylacetylene to form substituted alkynes. Interestingly, it displayed superior activity over simple Pd-PEPPSI or Pd-PPh3 catalysts

Research paper thumbnail of Evaluation of pKa Values of Soil Humic Acids and their Complexation Properties

International Journal of Plant & Soil Science, 2015

Research paper thumbnail of Determination Of Heavy Metals Contamination In Humic Acid Extracted From River Sediments Of Varying Depth

In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga ri... more In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga river sediments. The acids were investigated by UV-Vis spectroscopy and the heavy metal contents are determined by atomic absorption spectroscopy (AAS).Moreover, E4/ E6 ratio is determined. Our studies reveal that E4/ E6 ratio decreases from 30cm depth soil to surface which indicates that humic acid, at surface contains more aromatic groups compared to other two samples. In addition to that we found that copper (Cu) presents in the soil of river sediment is higher than other metals which can be attributed to association of Cu in process of formation of Humic acid.

Research paper thumbnail of CCDC 1973746: Experimental Crystal Structure Determination

Research paper thumbnail of Effect of PH on the Adsorption of Methylene Blue on Clay Material

The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solut... more The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solution by laboratory-made clay material prepared from magnesium sulphate and aluminium sulphate.The effect of pH on the adsorption of the dye on the clay material was found to be quite distinct; the change of adsorption is regular with increase of pH. The results have revealed that both physical and chemisorption are occurring here. INTRODUCTION In the last couple of decades, a myriad of technologies have been developed to remove metals from waters: precipitation, ion exchange, membrane separation, and adsorption. Of these, adsorption processes are relatively preferable for eliminating metals from waters, especially at very low metal concentrations.In this purpose, different adsorbents can be used but activated carbons are the most widely used, either as powders or grains, because of their versatile physical and chemical properties [1]. Activated carbon fibers and clothes have recently draw...

Research paper thumbnail of Highly efficient aqueous-phase Sonogashira coupling catalyzed by Pd-PEEPSI/PPh3 under aerobic condition

Journal of Chemical Sciences

Research paper thumbnail of EFFECT OF PH ON THE ADSORPTION OF METHYLENE BLUE ON CLAY MATERIAL

The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solut... more The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solution by laboratory-made clay material prepared from magnesium sulphate and aluminium sulphate.The effect of pH on the adsorption of the dye on the clay material was found to be quite distinct; the change of adsorption is regular with increase of pH. The results have revealed that both physical and chemisorption are occurring here.

Research paper thumbnail of Impact Factor: 2.785 Global

In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga ri... more In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga river sediments. The acids were investigated by UV-Vis spectroscopy and the heavy metal contents are determined by atomic absorption spectroscopy (AAS).Moreover, E4/ E6 ratio is determined. Our studies reveal that E4/ E6 ratio decreases from 30cm depth soil to surface which indicates that humic acid, at surface contains more aromatic groups compared to other two samples. In addition to that we found that copper (Cu) presents in the soil of river sediment is higher than other metals which can be attributed to association of Cu in process of formation of Humic acid.

Research paper thumbnail of Biochar as Soil Amendment in Climate-Smart Agriculture: Opportunities, Future Prospects, and Challenges

Journal of soil science and plant nutrition, Feb 7, 2024

Research paper thumbnail of Ni(OH) 2 nanoparticles as a recyclable catalyst in acceptorless dehydrogenation of alcohols to acids/acid salts under aerobic conditions

Research paper thumbnail of CCDC 1860391: Experimental Crystal Structure Determination

Research paper thumbnail of CCDC 1863543: Experimental Crystal Structure Determination

Research paper thumbnail of A cyclometalated Ir(iii)–NHC complex as a recyclable catalyst for acceptorless dehydrogenation of alcohols to carboxylic acids

Dalton Transactions, 2020

The first example of delineating the efficacy of cyclometalated Ir NHC complexes in acceptorless ... more The first example of delineating the efficacy of cyclometalated Ir NHC complexes in acceptorless dehydrogenation of alcohols to acids reported.

Research paper thumbnail of A new PEPPSI type N-heterocyclic carbene palladium(II) complex and its efficiency as a catalyst for Mizoroki-Heck cross-coupling reactions in water

Journal of Chemical Sciences, 2020

A new air and moisture stable PEPPSI (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabili... more A new air and moisture stable PEPPSI (PEPPSI: pyridine-enhanced pre-catalyst preparation, stabilisation, and initiation) themed palladium N-heterocyclic carbene (NHC) complex [Pd(L)Br 2 (Py)] (1) [L: 2-flurobenzyl)-1-(4-methoxyphenyl)-1H-imidazolline-2-ylidene] was synthesized and characterized. The structure of complex 1 was determined by X-ray single-crystal analysis. The palladium center in 1 adopted a square planar geometry with carbene and pyridine ligands occupying the mutual trans position. The complex 1 was employed to catalyze the Mizoroki-Heck cross-coupling reactions of aryl bromides/iodides with styrene in water. To the best of our knowledge, this is the first report where a Pd-PEPPSI catalyst was successfully employed in aqueous-phase Mizoroki-Heck reaction. Good to excellent yields of cross-coupling products were obtained with a range of representative aryl bromides/iodides under relatively mild conditions (100°C, 1 mol% of 1).

Research paper thumbnail of Highly efficient aqueous-phase Sonogashira coupling catalyzed by Pd-PEEPSI/PPh3 under aerobic condition

Journal of Chemical Sciences, Dec 1, 2021

An in situ generated catalytic system comprised of a Pd-PEPPSI [Pyridine enhanced pre-catalyst pr... more An in situ generated catalytic system comprised of a Pd-PEPPSI [Pyridine enhanced pre-catalyst preparation, initiation, and stabilization] complex, (NHC)PdBr2(Pyridine), and PPh3 co-ligand demonstrated excellent activity for the Sonogashira cross-coupling reactions between phenylacetylene with aryl halides in neat water under the aerobic condition in presence of CuI as co-catalyst. The catalytic system was not only compatible with electronically diverse aryl bromides/ iodides but also effective for relatively difficult substrates like heteroaryl bromides. Notably, under similar experimental conditions, the mixed PEPPSI/PPh3 system displayed superior activity over the free Pd-PEPPSI or Pd-phosphine system. This article presents an in situ Pd-PEPPSI/PPh3 catalytic system for aqueous Sonogashira reaction in presence of CuI under aerobic condition which was found to be highly efficient for coupling of anyl/heteroaryl halides with phenylacetylene to form substituted alkynes. Interestingly, it displayed superior activity over simple Pd-PEPPSI or Pd-PPh3 catalysts

Research paper thumbnail of Evaluation of pKa Values of Soil Humic Acids and their Complexation Properties

International Journal of Plant & Soil Science, 2015

Research paper thumbnail of Determination Of Heavy Metals Contamination In Humic Acid Extracted From River Sediments Of Varying Depth

In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga ri... more In this work humic acids were extracted from surface, below 15 cm and 30 cm depth of Kakodonga river sediments. The acids were investigated by UV-Vis spectroscopy and the heavy metal contents are determined by atomic absorption spectroscopy (AAS).Moreover, E4/ E6 ratio is determined. Our studies reveal that E4/ E6 ratio decreases from 30cm depth soil to surface which indicates that humic acid, at surface contains more aromatic groups compared to other two samples. In addition to that we found that copper (Cu) presents in the soil of river sediment is higher than other metals which can be attributed to association of Cu in process of formation of Humic acid.

Research paper thumbnail of CCDC 1973746: Experimental Crystal Structure Determination

Research paper thumbnail of Effect of PH on the Adsorption of Methylene Blue on Clay Material

The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solut... more The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solution by laboratory-made clay material prepared from magnesium sulphate and aluminium sulphate.The effect of pH on the adsorption of the dye on the clay material was found to be quite distinct; the change of adsorption is regular with increase of pH. The results have revealed that both physical and chemisorption are occurring here. INTRODUCTION In the last couple of decades, a myriad of technologies have been developed to remove metals from waters: precipitation, ion exchange, membrane separation, and adsorption. Of these, adsorption processes are relatively preferable for eliminating metals from waters, especially at very low metal concentrations.In this purpose, different adsorbents can be used but activated carbons are the most widely used, either as powders or grains, because of their versatile physical and chemical properties [1]. Activated carbon fibers and clothes have recently draw...

Research paper thumbnail of Highly efficient aqueous-phase Sonogashira coupling catalyzed by Pd-PEEPSI/PPh3 under aerobic condition

Journal of Chemical Sciences

Research paper thumbnail of EFFECT OF PH ON THE ADSORPTION OF METHYLENE BLUE ON CLAY MATERIAL

The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solut... more The paper reports the effect of PH on the adsorption of a dye (methylene blue) from aqueous solution by laboratory-made clay material prepared from magnesium sulphate and aluminium sulphate.The effect of pH on the adsorption of the dye on the clay material was found to be quite distinct; the change of adsorption is regular with increase of pH. The results have revealed that both physical and chemisorption are occurring here.