@article {46412, title = {Probing the catalytic activity of pristine and doped Pd and Ni metal clusters towards H2O molecule}, journal = {Computational and Theoretical Chemistry}, volume = {1170}, year = {2019}, month = {DEC }, pages = {112624}, type = {Article}, abstract = {

Electrolysis of H2O to produce molecular hydrogen, the most environment friendly and energy efficient fuel, using cost effective catalysts is one of the major global research challenges. To date, Pt remains the best suitable and yet highly expensive electro-catalyst for hydrogen evolution reaction. Design of an alternative cost-effective catalyst requires a fundamental molecular level understanding of the water molecule adsorption and its activation. In that context, we examine the adsorption and activation of water molecule on model alternative catalysts namely, Ni-6 and Pd-6 clusters using density functional theory based methodology. Ni-6 and Pd-6 clusters and their singly doped counterparts are used for this study. Mo, W, Fe, Co and Cu are used as doping elements. To quantify the influence of medium (neutral and alkaline) on the activation of the water molecule, Ni based clusters are considered in neutral and anionic states, respectively. The activity of these clusters towards H2O molecule is evaluated in terms of the adsorption energy, charge transfer, bandgap, red shift in O-H stretching frequency and dissociation barriers for H2O. The studies demonstrate that doping with Co in all the studied clusters (Pd-6, Ni-6 and anionic Ni-6) increases their activity. Best activity is noted for Fe doped neutral Ni b clusters with a dissociation barrier of 5.76 kcal/mol.

}, keywords = {Activation barrier, Ni clusters, O-H activation, Pd clusters, Red shift of O-H stretching frequency, Water adsorption}, issn = {2210-271X}, doi = {10.1016/j.comptc.2019.112624}, author = {Samal, Pragnya Paramita and Joshi, Krati and Kaliaperumal, Selvaraj and Krishnamurty, Sailaja} } @article {46798, title = {Iron-catalyzed C(sp(2))-H alkylation of indolines and benzo[h]quinoline with unactivated alkyl chlorides through chelation assistance}, journal = {ACS Catalysis}, volume = {10}, year = {2020}, month = {JUL }, pages = {7312-7321}, type = {Article}, abstract = {

Regioselective C-H bond alkylation of indolines and benzo[h]quinoline with a wide range of unactivated and highly demanded primary and secondary alkyl chlorides is accomplished using a low-cost iron catalyst. This reaction tolerates diverse functionalities, such as C(sp(2))-Cl, fluoro, alkenyl, silyl, ether, thioether, pyrrolyl, and carbazolyl groups including cyclic and acyclic alkyls as well as alkyl-bearing fatty-alcohol and polycyclic-steroid moieties. The demonstrated iron-catalyzed protocol proceeded via either a five-membered or a six-membered metallacycle. Intriguingly, the C-7-alkylated indolines can be readily functionalized into free-NH indolines/indoles and tryptamine derivatives. A detailed mechanistic investigation highlights the participation of an active Fe(I) catalyst and the involvement of a halogen-atom transfer process via a single-electron-based mechanism. Deuterium labeling and kinetics analysis indicate that the C-H metalation of indoline is the probable turnover-limiting step. Overall, the experimental and theoretical studies supported an Fe(I)/Fe(III) pathway for the alkylation reaction comprising the two-step, one-electron oxidative addition of alkyl chloride.

}, keywords = {alkyl chlorides, Alkylation, C-H activation, chelation assistance, indolines, iron}, issn = {2155-5435}, doi = {10.1021/acscatal.0c02030}, author = {Jagtap, Rahul A. and Samal, Pragnya Paramita and Vinod, C. P. and Krishnamurty, Sailaja and Punji, Benudhar} } @article {47389, title = {Enhanced photocatalytic properties of a chemically modified blue phosphorene}, journal = {RSC Advances }, volume = {11}, year = {2021}, month = {APR }, pages = {13348-13358}, type = {Article}, abstract = {

It is high time to placate the peak demand for an efficient, economic and green fuel in the form of H-2 through photocatalytic water splitting. Several low dimensional materials have been explored for their photocatalytic properties on account of their surface to volume ratio. The present study illustrates the excellent photocatalytic potential of a two-dimensional material, viz. a chemically tempered blue-phosphorene sheet, with single atom thickness and high carrier mobility. Metal-free element, sulphur, is explored as a dopant in a 32-atom blue-phosphorene sheet. The dopant is inserted at three locations viz. central, edge and central edge positions with varying concentrations from 3.125\% to 18.75\% (corresponding to n = 1 to 6 sulphur atoms within a 32-atom blue-phosphorene sheet, P32-nSn). The cohesive energy studies predict the higher stability of even number S doped sheets as compared to their odd counterparts. Photocatalytic activity is studied in terms of band gap and band alignment for different concentrations of the former. Studies reveal that edge doping demonstrates better water molecule activation independent of S atom concentration. The edge doped systems not only provide the chemical activity to activate water, but also show feasible HER overpotentials of 1.24-1.29 eV at neutral medium. Finally, this work opens up a driving lead of non-corrosive catalysts for water molecule splitting.

}, doi = {10.1039/d0ra10829d}, author = {Maibam, Ashakiran and Das, Sawan Kumar and Samal, Pragnya Paramita and Krishnamurty, Sailaja} } @article {47708, title = {An innovative light assisted production of acetic acid from CO2 and methanol: a first photocatalytic approach using a reusable cobalt(ii) molecular hybrid at atmospheric pressure}, journal = {Green Chemistry}, volume = {23}, year = {2021}, month = {NOV}, pages = {9048-9060}, type = {Article}, abstract = {Acetic acid is an important commodity chemical that is produced either by fermentation processes, or more commonly, through chemical routes such as methanol carbonylation with CO and H-2, acetaldehyde oxidation, or hydrocarbon oxidation. More recently, methanol hydrocarboxylation with CO2 and H-2 under thermal catalytic conditions has attracted interest. The synthesis of acetic acid from easily available CO2 is of great significance yet rarely reported. The present paper describes the first photocatalytic approach for the synthesis of acetic acid from methanol and CO2 under ambient reaction conditions without using molecular hydrogen. The maximum conversion of methanol achieved is 60\% with a selectivity of 81\% towards acetic acid using an octa-sulfur bound cobalt phthalocyanine (CoPc/S8) photocatalyst without an additional sacrificial electron donor. Product analysis, controlled experiments and DFT calculations suggest the formation of methylene carbene as a reactive intermediate. The developed methodology represents a potentially exciting approach for synthesizing acetic acid utilizing CO2 in a sustainable manner.}, issn = {1463-9262}, doi = {10.1039/d1gc02728j}, author = {Saini, Sandhya and Samal, Pragnya Paramita and Krishnamurty, Sailaja and Ray, Anjan and Jain, Suman L.} } @article {47627, title = {Mechanistic investigations on the catalytic transfer hydrogenation of lignin-derived monomers over Ru catalysts: theoretical and kinetic studies}, journal = {ACS Sustainable Chemistry \& Engineering}, volume = {9}, year = {2021}, month = {OCT}, pages = {14040-14050}, type = {Article}, abstract = {The hydrodeoxygenation (HDO) reaction of oxygenated compounds such as lignin-derived phenolics is well studied using molecular H-2 as a hydrogen source, yet the use of high pressures discourages its use on an industrial scale. As an alternative, the catalytic transfer hydrogenation (CTH) pathway provides in situ hydrogenation species, which reduces the need for the high-pressure infrastructure required when molecular hydrogen is used. Nevertheless, this strategy is scantly studied, and in lieu with this, herein we report the kinetic and mechanistic investigations of the CTH strategy for the HDO of guaiacol, phenol, anisole veratrole, and eugenol to their respective products. For potential commercialization purposes, low loading of metal, milder reaction conditions, and high selectivity toward desired products with a high H/C ratio were considered while designing catalysts (0.5 wt \% Ru on SiO2-Al2O3, SiO2, Al2O3-acidic, Al2O3-basic, and Al2O3-neutral) for these reactions. As high as 74\% cyclohexanol yield from guaiacol was achieved at 225 degrees C in the presence of isopropyl alcohol (IPA) as the hydrogen source and over the Ru/Al2O3-acidic catalyst reduced at 150 degrees C. A detailed kinetic study is carried out to understand the interaction of the substrate and intermediates with the catalyst and the influence of reaction parameters on the product formation. It was observed that the cisisomer of 2-methoxycyclohexanol rapidly undergoes further conversion than the trans-isomer. The experimental observations are substantiated through density functional theory (DFT) studies on Ru(0001) and guaiacol molecule complexes. DFT studies indicate that the adsorption of the cis-isomer is more exothermic as compared to that of the trans counterpart, and the underlying electronic factors are elucidated using charge density difference and density of states plots.}, keywords = {catalytic transfer hydrogenation, Cyclohexanol, DFT, Hydrodeoxygenation, kinetics, lignin monomers, Supported metal catalysts}, issn = {2168-0485}, doi = {10.1021/acssuschemeng.1c02942}, author = {Khan, Tufeil Sartaj and Singh, Dheerendra and Samal, Pragnya Paramita and Krishnamurty, Sailaja and Dhepe, Paresh Laxmikant} } @article {47638, title = {Ni(II)-catalyzed intramolecular C-H/C-H oxidative coupling: an efficient route to functionalized cycloindolones and indenoindolones}, journal = {ACS Catalysis}, volume = {11}, year = {2021}, month = {OCT }, pages = {12384-12393}, type = {Article}, abstract = {Nickel(II)-catalyzed intramolecular C(sp(2))-H/C(sp(3))-H and C(sp(2))-H/C(sp(2))-H oxidative couplings in indoles are achieved via chelation assistance. These reactions provide access to biologically relevant five- and six-membered substituted cyclopentaindolones, carbazolones, and indenoindolones in high yields and good chemoselectivity employing an air-stable and defined nickel catalyst, (bpy)Ni(OAc)(2). The oxidative cyclizations proceeded either through a six-membered or an unconventional seven-membered nickelacycle. An extensive mechanistic investigation by experiments and theoretical calculations revealed a facile indole{\textquoteright}s C(2)-H nickelation and a rate-limiting reductive elimination process. This intramolecular oxidative cyclization operates via a probable Ni(II)/Ni(III) pathway involving single-electron oxidation of nickel without the participation of a carbon-based radical.}, keywords = {C-H activation, cycloindolones, indenoindolones, indoles, Mechanism, Nickel, oxidative coupling}, issn = {2155-5435}, doi = {10.1021/acscatal.1c03314}, author = {Ankade, Shidheshwar B. and Samal, Pragnya Paramita and Soni, Vineeta and Gonnade, Rajesh G. and Krishnamurty, Sailaja and Punji, Benudhar} } @article {47661, title = {Substrate augmented catalytic activity towards NRR: a case study of Li doped Al clusters on defective graphene}, volume = {566}, year = {2021}, month = {NOV}, pages = {150586}, type = {Article}, abstract = {Density Functional Theory (DFT) based methods are applied to examine the potential of lithium doped aluminium clusters consisting of 3-13 atoms for dinitmgen molecule activation in terms of N N bond length, redshift in N N bond stretching frequency, nitrogen interaction energy and frontier molecular orbitals analysis. The present work highlights the role of monovacant C-3 defective graphene as a support in fine tuning the catalytic activity of Li doped Al clusters for reduction of N-2. Fundamental insights to synergic binding of clusters with defective graphene is brought out and its role in enhancing activation of dinitmgen molecule is explained. Supported Aln-1Li clusters with six or more atoms are noted to be more active towards N-2 molecule activation as compared to the clusters without support. Dinitrogen molecule undergoes a maximum bond elongation of 1.56 angstrom corresponding to redshift of 1690 cm(-1) on Al7Li@graphene and Al12Li@graphene. This is maximum value reported in context of activation for N-2 molecule till date.}, keywords = {Al clusters, Al12Li, C-3 defective graphene, DFT, Li Doping, N-2 activation, Red-shift}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2021.150586}, author = {Samal, Pragnya Paramita and Poonam and Krishnamurty, Sailaja} } @article {47629, title = {Thermal stability of an endohedrally doped aluminum nanoclusters: a BOMD study}, journal = {Theoretical Chemistry Accounts}, volume = {140}, year = {2021}, month = {SEP}, pages = {132}, type = {Article}, abstract = {In this article, thermal stability of doped Al-13 nanoclusters has been systematically investigated within the framework of density functional theory (DFT). To explain thermal stability, simulations have been carried out over a temperature range from 300 to 1100 K using Born-Oppenheimer molecular dynamics (BOMD). The atomic displacements have been quantified by calculating delta(rms,) MSD and epsilon(pro.) The thermal stability of different clusters is explained using underlined electronic properties such as HOMO-LUMO, charges and bond length.}, keywords = {BOMD, Bond length fluctuations, Endohedral doping, Mean squared ionic displacements (MSD), Nanoclusters, Root mean squared}, issn = {1432-881X}, doi = {10.1007/s00214-021-02829-7}, author = {Singh, Chandrodai Pratap and Samal, Pragnya Paramita and Krishnamurty, Sailaja} } @article {48107, title = {Free base phthalocyanine coating as a superior corrosion inhibitor for copper surfaces: a combined experimental and theoretical study}, journal = {Colloids and Surfaces A-Physicochemical and Engineering Aspects}, volume = {648}, year = {2022}, month = {SEP }, pages = {129138}, type = {Article}, abstract = {

In the quest of novel, eco-benign copper corrosion inhibitors, free base and a set of six metal Phthalocyanine (Pc) coatings (where metal is Zn, Cu, Fe, Co, Ni, Mn) are systematically evaluated for their corrosion inhibition efficiency. The study demonstrates that the free base Phthalocyanine coatings are superior corrosion inhibitors for Cu surface in HCl with a corrosion inhibition efficiency of 88\% as compared to its metal counterparts. A detailed and indepth study involving concerted electrochemical polarisation, impedance measurements at various concentrations of HCl assert the superior corrosion inhibition efficiency of free base Pc coatings as compared to its metal counterparts. Underlying factors/interface chemistry contributing to it is brought out using first principle based studies. First principles based computational studies establish that superior corrosion inhibition ability of free base phthalocyanine molecule is attributed to its innate binding ability with copper surface and its better inter-molecular packing. Thus, the theoretical adsorption trends of various studied phthalocyanine molecules while clearly following the experimental corrosion inhibition efficiency trends undermine the importance of contribution of chelating factors for the formation of a stable and efficient corrosion inhibition coating on a surface and that the adhesion/adsorption strength of a molecule correlates directly to its corrosion inhibition efficiency. The experimental observations are further substantiated through FE-SEM, EDAX and XPS studies. The corrosion inhibition efficiency of free base phthalocyanine is followed by its zinc based counterpart at 85\%.

}, keywords = {Copper surface, Corrosion inhibitors, DFT studies, Impedance, Phthalocyanine coatings}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2022.129138}, author = {Samal, Pragnya Paramita and Dekshinamoorthy, Amuthan and Arunachalam, Shivakami and Vijayaraghavan, Saranyan and Krishnamurty, Sailaja} } @article {48364, title = {Lewis acid-catalyzed chemodivergent and regiospecific reaction of phenols with quaternary peroxyoxindoles}, journal = {Journal of Organic Chemistry}, volume = {87}, year = {2022}, month = {NOV }, pages = {14155-14167}, type = {Article}, abstract = {

The indium-catalyzed regiospecific coupling of substituted phenol derivatives and quaternary peroxyoxindoles for the synthesis of C2 or C4 benzoxazin-3-one-substituted phenols via skeletal rearrangement is described. This reaction is demonstrated with 17 examples with good yields and diverse aryl substituents. In contrast to the indium-catalyzed reaction, the Cu(OTf)2- catalyzed reaction of the phenol with quaternary peroxyoxindoles afforded C2 or C4 2-oxindole-substituted phenol derivatives. This diverse catalytic reaction generated various biologically important phenol-substituted 2-oxindole derivatives directly without any skeleton rearrangement and was demonstrated with 19 examples in high yield. The regiospecificity and the reaction pathways were explained with the support of density functional theory (DFT).

}, issn = {0022-3263}, doi = {10.1021/acs.joc.2c01701}, author = {Shaikh, Moseen A. and Samal, Pragnya Paramita and Ubale, Akash S. and Krishnamurty, Sailaja and Gnanaprakasam, Boopathy} } @article {48490, title = {Can Li atoms anchored on boron- and nitrogen-doped graphene catalyze dinitrogen molecules to ammonia? a DFT study}, journal = {ChemPhysChem}, volume = {24}, year = {2023}, month = {JUN}, type = {Article}, abstract = {

The most successful electrochemical conversion of ammonia from dinitrogen molecule reported to date is through a Li mediated mechanism. In the framework of the above fact and that Li anchored graphene is an experimentally feasible system, the present work is a computational experiment to identify the potential of Li anchored graphene as a catalyst for N-2 to NH3 conversion as a function of (a) minimum number of Li atoms needed for anchoring on graphene sheets and (b) the role of chemical modification of graphene surfaces. The studies bring forth an understanding that Li anchored graphene sheets are potential catalysts for ammonia conversion with preferential adsorption of N-2 through end-on configuration on Li atoms anchored on doped and pristine graphene surfaces. This mode of adsorption being characteristic of Nitrogen Reduction Reaction (NRR) through enzymatic pathway, examination of the same followed by analysis of electronic properties demonstrates that tri-Li atoms (Tri Atom Catalysts, TACs) are more efficient as catalysts for NRR as compared to two Li atoms (Di Atom Catalysts, DACs). Either way, the rate determining step was found to be *NH2 -\>*NH3 step (mixed pathway) with Delta G(max)=1.02 eV and *NH2-*NH3 -\>*NH2 step (enzymatic pathway) with Delta G(max)=1.11 eV for 1B doped TAC and DAC on graphene sheet, respectively. Consequently, this work identifies the viability of Li anchored graphene based 2-D sheets as hetero-atom catalyst for NRR.

}, keywords = {computational chemistry, Graphene Sheet, heterogeneous catalysis, Li Nanoparticles, Nitrogen Reduction Reaction}, issn = {1439-4235}, doi = {10.1002/cphc.202200750}, author = {Verma, Tushar Singh and Samal, Pragnya Paramita and Selvaraj, Kaliaperumal and Krishnamurty, Sailaja} } @article {48678, title = {Catalyst-assisted selective vinylation and methylallylation of a quaternary carbon center using tert-butyl acetate}, journal = {Journal of Organic Chemistry}, volume = {88}, year = {2023}, month = {JUL}, pages = {9686-9703}, type = {Article}, abstract = {

The In-(OTf)(3)-catalyzed \& alpha;-vinylationof varioushydroxy-functionalized quaternary carbon centers using in situ generatedisobutylene from tert-butyl acetate is presentedas a novel synthetic methodology. Moreover, tert-butylacetate is a nonflammable feed stock and is a readily available sourcefor the in situ production of vinyl substituents, as demonstratedby the vinylation reaction with quaternary hydroxy/methoxy compounds.Moreover, an excellent selectivity for methylallylation over vinylationwas obtained with Ni-(OTf)(2) as a catalyst. In the case ofperoxyoxindole, methylallyl-functionalized 1,4-benzoxazin-3-one derivativeswere formed through the sequential rearrangement of peroxyoxindolefollowed by the nucleophilic attack by isobutylene. The detailed mechanismfor this reaction and rationalization for the selectivity are providedusing kinetics and density functional theory studies.

}, issn = {0022-3263}, doi = {10.1021/acs.joc.2c03072}, author = {Mohanta, Nirmala and Samal, Pragnya Paramita and Pandey, Akanksha M. and Mondal, Shankhajit and Krishnamurty, Sailaja and Gnanaprakasam, Boopathy} } @article {48445, title = {Expounding lemonal terpenoids as corrosion inhibitors for copper using DFT based calculations}, journal = {Applied Surface Science}, volume = {614}, year = {2023}, month = {MAR}, pages = {156066}, type = {Article}, abstract = {

The most important bottleneck in identifying an innovative and yet viable corrosion inhibitor for copper surfaces is discerning the chemical interactions at the interface of adsorbate and adsorbent. The present work, primarily, discerns the interface chemistry of green corrosion inhibitors, viz., lemonal terpenoids, with the copper surfaces for the first time. The interface chemistry is evaluated for distinct facets of copper, modelled by periodic surfaces to finite sized aggregates, with two stereoisomers viz., citral and neral through density functional calculations. The adsorption/ interaction properties between the surface and the corrosion inhibiting molecule are analysed through the electronic properties such as density of states, charge density difference plots and Bader charges where in distinct bonding mechanisms are identified as a function of varying facets. Apart from the adsorption properties, molecular packing properties are of paramount importance towards the design of an efficient corrosion inhibitor for a surface. Hence, we also analyse the intermolecular stacking energies between the inhibitors when packed among themselves in vacuum and when adhered on to metal surfaces. The studies bring forth an understanding that lemon terpenoids are highly potential corrosion inhibitors for copper surfaces, particularly, for Cu (110) surfaces both in neutral and protonated form.

}, keywords = {Copper surface, Density Functional Theory (DFT), Green corrosion inhibitors, Interface chemistry, Lemonal terpenoids, Molecular stacking}, issn = {0169-4332}, doi = {10.1016/j.apsusc.2022.156066}, author = {Samal, Pragnya Paramita and Singh, Chandrodai Pratap and Krishnamurty, Sailaja} } @article {48765, title = {MnXWO4 nanostructure-based catalysts for single-step oxidation of cyclohexane and methane to oxygenates}, journal = {ACS Applied Nano Materials}, volume = {6}, year = {2023}, month = {APR}, pages = {7245-7258}, type = {Article}, abstract = {

Activation of the C-H bond in cyclohexane (CYH) and methane is a crucial step to obtain desirable oxygenated products using nanostructured catalyst and is a great challenge and an efficient route to mitigate the inauspicious effects of climate change. The active sites were identified using XRD, HR-TEM, SEM, N2 sorption analysis, TPR, Raman, XPS, TGA, in situ DRIFT, XAS, etc. In optimal reaction conditions, 46\% of CYH was converted into adipic acid (AA) on MnxWO4 nanostructures within 6 h. The recyclability test confirmed the catalyst heterogeneity, which revealed no appreciable loss of catalytic activity even after three consecutive reactions. In situ DRIFT study reveals that CYH is oxidized to cyclohexanone and cyclohexanol (KA oil) and is further oxidized to AA via carboxylate intermediates. DFT studies disclosed that MnOx species are responsible for the C-H activation of CYH, and the Mn2+/Mn3+ redox centers play a vital role in the absorption of KA oil to form AA. Herein, we demonstrated the significant role of the {\textquoteleft}{\textquoteleft}MnOx{\textquoteright}{\textquoteright} species and that adequate Lewis and Bronsted acidic sites, redox centers of (Mn2+/Mn3+), and lattice oxygen are accountable for the CYH conversion toward the AA. Additionally, we have reported the oxidation of methane to methanol (146 mu mole per gram of catalyst) in the presence of water at 75 degrees C without over-oxidation products.

}, keywords = {Adipic Acid, C-H bond activation, Cyclohexane oxidation, methane activation, MnOx chain, Redox center}, doi = {10.1021/acsanm.3c00319}, author = {Prabu, Marimuthu and Manikandan, Marimuthu and Samal, Pragnya Paramita and Gurrala, Lakshmi Prasad and Mekala, Siva Prasad and Archana, Ramakrishnan and Nayak, Chandrani and Bhattacharyya, D. and Jha, S. N. and Krishnamurty, Sailaja and Raja, Thirumalaiswamy} }