@article { ISI:000307494500027, title = {Exploring the potential of doped zero-dimensional cages for proton transfer in fuel cells: a computational study}, journal = {Journal of Physical Chemistry B}, volume = {116}, number = {32}, year = {2012}, month = {AUG}, pages = {9803-9811}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Calculations with density functional theory (DFT) and MP2 have been done to investigate the potential of recently synthesized durable zero-dimensional (OD) nitrogen-based cage structures to perform as efficient proton-exchange membranes (PEMs) in fuel cells. Our calculations suggest that the hydrogenated 0-D cages, in combination with hydrogen-bonding 1,2,3- and 1,2,4-triazole molecules, would perform as highly efficient PEMs. The results are important in the context of the need for efficient PEMs for fuel cells, especially at higher temperatures (greater than 120 degrees C) where conventional water-based PEMs such as Nafion have been found to be ineffective.

}, issn = {1520-6106}, doi = {10.1021/jp303884p}, author = {Mane, Manoj V. and Venkatnathan, Arun and Ghatak, Kamalika and Vanka, Kumar} } @article { ISI:000327467000009, title = {Exploring the effectiveness of different Lewis pair combinations in caged structures for the catalysis of ammonia borane dehydrogenation: a DFT study}, journal = {Physical Chemistry Chemical Physics}, volume = {15}, number = {48}, year = {2013}, month = {OCT}, pages = {20857-20867}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Zero dimensional cage structures containing four phenyl rings separated by imine linkers have recently been synthesized. In the current work, through a computational investigation using density functional theory (DFT), we demonstrate that modifying such cages by replacing the 2, 4, 6 carbon atoms in the phenyl rings to yield new rings, as well as replacing the imine moiety in the linker by other electronegative atoms, can yield interesting new cages that can be reactive in catalysing reactions such as the dehydrogenation of ammonia borane-an important reaction in hydrogen storage research. Specifically, it is predicted that phosphorus-nitrogen pairs (phosphorus in the 2, 4, 6 positions in the ring, nitrogen in the linker position), germanium-nitrogen and germanium-phosphorus pair combinations would lead to effective Lewis pairs that can work in tandem to dehydrogenate ammonia borane efficiently under room temperature conditions.

}, issn = {1463-9076}, doi = {10.1039/c3cp53557f}, author = {Pal, Amrita and Vanka, Kumar} } @article { ISI:000379531300011, title = {Effect of donors on the activation mechanism in ziegler-natta catalysis: a computational study}, journal = {Chemcatchem}, volume = {8}, number = {10}, year = {2016}, month = {MAY}, pages = {1809-1818}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

Full quantum chemical calculations, using density functional theory (DFT), have been conducted to explain the effect of donors on the {\textquoteleft}{\textquoteleft}activation mechanism{\textquoteright}{\textquoteright} in the Ziegler-Natta (Z-N) catalyst system. In the activation mechanism, the inactive (TiCl4)-Cl-IV catalyst converts into the active (TiCl2Et)-Cl-III catalyst with the help of the AlEt3 present in the system. The donors that have been considered in this study are: ethyl benzoate (eb), two representative diether cases, a phthalate donor, and a silyl ester donor. The results indicate that eb and the diether donor cases donor have a negative effect on the barriers for the activation mechanism. However, the eb donor can be displaced from the MgCl2 surface by AlEt3, which matches experimental observations. For the phthalate, silyl ester and TiCl3-OC4H8Cl cases, the results indicate that a significant induction period would be present in Z-N systems employing such donors or having such a catalytic center, before catalysis could commence.

}, keywords = {Alkylation, aluminum, Density functional calculations, surface chemistry, titanium}, issn = {1867-3880}, doi = {10.1002/cctc.201600281}, author = {Kumawat, Jugal and Gupta, Virendra Kumar and Vanka, Kumar} } @article { ISI:000377515200041, title = {Exploration of the diastereoselectivity in an unusual Grignard reaction and its application towards the synthesis of styryl lactones 7-epi-(+)-goniodiol and 8-epi-(-)-goniodiol}, journal = {RSC Advances}, volume = {6}, number = {56}, year = {2016}, month = {MAY}, pages = {50721-50725}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

An unusual diastereoselective Grignard reaction is explored, where the Grignard reagents are derived from 1,n-dihaloalkanes. A steric bias due to the presence of a quaternary centre adjacent to the acetonide ester at the benzylic position is responsible for the formation of an intramolecularly reduced product in almost quantitative yield. This steric hindrance is responsible for the diastereoselectivity observed with a variety of aromatic as well as aliphatic esters. The unusual Grignard reaction furnishes long chain secondary alcohols possessing a terminal olefin, which are synthetically important intermediates. As an application of this method, the diastereoselective synthesis of styryl lactones viz. 7-epi-(+)-goniodiol (29) and 8-epi(-)-goniodiol (30) has been achieved.

}, issn = {2046-2069}, doi = {10.1039/c6ra03192g}, author = {Chavan, Subhash P. and Khatod, Harshali S. and Das, Tamal and Vanka, Kumar} } @article { ISI:000366590300006, title = {Exploring activity differences between the hydroformylation catalysts: Insights from theory}, journal = {Journal of Organometallic Chemistry}, volume = {801}, year = {2016}, month = {JAN}, pages = {30-41}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Hydroformylation catalysis is the most important homogeneous catalysis process of the current day. The current computational investigation aims to understand the nature of the hydroformylation process when monodentate ligands are employed. The complete catalytic cycle for different monodentate ligands bound to the rhodium center has been studied with full quantum chemical calculations, with density functional theory (DFT). To the best of our knowledge, this is the first systematic investigation of the relative free energy surfaces for mono-coordinate monodentate and bi-coordinated monodentate ligands in hydroformylation catalysis. The results indicate that the barriers are lower for the mono-coordinate monodentate species in comparison to the bi-coordinate monodentate, for all the ligand cases studied, indicating higher activity for the mono-coordinate monodentate active species. (C) 2015 Elsevier B.V. All rights reserved.

}, keywords = {Density functional theory (DFT) calculations, Hydroformylation, Monodentate, Rhodium}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2015.10.015}, author = {Dangat, Yuvraj B. and Rizvi, Masood Ahmad and Pandey, Pippalad and Vanka, Kumar} } @article { ISI:000373630800015, title = {Exploring the reducing role of boron: added insights from theory}, journal = {Dalton Transactions}, volume = {45}, number = {14}, year = {2016}, month = {NOV}, pages = {5978-5988}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Carbon-carbon coupling in CO molecules is a challenging proposition, and very few main group complexes have been shown to effect this process. A recently reported triply bonded diboryne system (1) is notable for coupling four CO molecules to produce a (bis) boralactone species. The current full quantum chemical computational investigation with density functional theory (DFT) provides important insights into the nature of the CO coupling process by triply bonded diboryne systems. The complete reaction pathway leading to the formation of the (bis) boralactone has been determined. Factors that make this system so successful in coupling CO groups have been elucidated, and pertinent issues, such as why the coupling process stops after four CO additions, have been explored. Also, importantly, insights have been gained through the natural bond orbital (NBO) analysis into how the back-donation from diboryne activates CO.

}, issn = {1477-9226}, doi = {10.1039/c5dt03799a}, author = {Dangat, Yuvraj B. and Vanka, Kumar} } @article {45734, title = {Electronic control on linear versus branched alkylation of 2-/3-aroylbenzofurans with acrylates: combined DFT and synthetic studies}, journal = {Chemistry-A European Journal}, volume = {23}, year = {2017}, month = {JUN }, pages = {7570-7581}, type = {Article}, abstract = {

Investigations on the factors that govern unusual branched alkylation of 2-aroylbenzofurans with acrylates by Ru-catalyzed carbonyl-directed C-H activation has been carried out by calculating the kinetics associated with the two key steps-the coordination of the acrylate with the intermediate ruthenacycle and the subsequent migratory insertion reaction-studied with the help of DFT calculations. Eight possible orientations for each mode of alkylation have been considered for the calculations. From these calculations, it has been understood that there is a synergistic operation of the steric and electronic effects favoring the branched alkylation. Further DFT investigations on the alkylation of the isomeric 3-aroylbenzofurans indicated a preference for the linear alkylation and this has been verified experimentally. Overall, the observed/calculated complementary selectivity in the alkylation of 2-/3-aroylbenzofurans with acrylates reveals that the substrate-dependent charge distribution of the Ru-C bond in the intermediate ruthenacycle is an important determining factor and thus the current work opens up a new domain of substrate design for controlling regioselectivity.

}, keywords = {acrylates, Alkylation, aroylbenzofuran, C-H activation, Density functional calculations}, issn = {0947-6539}, doi = {10.1002/chem.201700643}, author = {Srinivas, Kolluru and Dangat, Yuvraj and Kommagalla, Yadagiri and Vanka, Kumar and Ramana, Chepuri V.} } @article {43317, title = {Exploiting directional long range secondary forces for regulating electrostatics dominated noncovalent interactions}, journal = {Chemical Science}, volume = {8}, year = {2017}, month = {JAN}, pages = {1378-1390}, abstract = {

It has been well established that long range secondary electrostatic interactions (SEIs) have a significant effect on the stability of supramolecular complexes. However, general rules for exploiting SEIs in the rational design of diverse supramolecular complexes have been difficult to obtain. In this work, we outline a quantum chemical approach for understanding the strength of electrostatic interactions. This approach is seen to provide excellent correlation between the electrostatic force and the binding energy between two partners in hydrogen-bonded complexes, as well as that between two ions in ion-pair complexes. Furthermore, we illustrate how the understanding of the binding allows for the rational design of new complexes where the association constant between the two partners can be increased or decreased, as desired, by several orders of magnitude. Hence, the current work showcases a general, simple and powerful method of understanding and exploiting long range secondary electrostatic interactions.

}, doi = {10.1039/C6SC03642B}, author = {Tiwari, Mrityunjay and Vanka, Kumar} } @article {44458, title = {Easily accessible lithium compound catalyzed mild and facile hydroboration and cyanosilylation of aldehydes and ketones}, journal = {Chemical Communications}, volume = {54}, year = {2018}, month = {APR}, abstract = {Simple and readily accessible lithium compounds such as 2,6-ditertbutyl phenolate lithium (1a), 1,1{\textquoteright} dilithioferrocene (1b) and nacnac lithium (1c) are found to be efficient single site catalysts for hydroboration of...}, doi = {10.1039/C8CC02314J}, author = {Bisai, Milan and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {46690, title = {Effect of solvent-substrate noncovalent interactions on the diastereoselectivity in the intramolecular carbonyl-ene and the staudinger [2+2] cycloaddition reactions}, journal = {Journal of Physical Chemistry A}, volume = {124}, year = {2020}, month = {OCT }, pages = {8019-8028}, type = {Article}, abstract = {

Noncovalent interactions (NCIs) have been identified as important contributing factors for determining selectivity in organic transformations. However, cases where NCIs between solvents and substrates are responsible for a major extent for determining selectivity are rare. The current computational study with density functional theory identifies two important transformations where this is the case: the intramolecular carbonyl-ene reaction and the Staudinger [2 + 2] cycloaddition reaction. In both cases, the role of explicit solvent molecules interacting non-covalently with the substrate has been taken into account. Calculations indicate that the diastereomeric ratio would be 95.0:5.0 for the formation of tricyclic tetrahydrofuran diastereomers via the intramolecular carbonyl-ene reaction and 94.0:6.0 for the formation of the triflone diastereomers via the Staudinger [2 + 2] cycloaddition reaction, which corroborates with the experiment. Interestingly, in both the cases, the calculations indicate that noninclusion of explicit solvent molecules would lead to only a small difference between the competing transition states, which leads to the conclusion that solvent-substrate NCIs are the major cause for diastereoselectivity in both the cases considered.

}, issn = {1089-5639}, doi = {10.1021/acs.jpca.0c05738}, author = {Jain, Shailja and Vanka, Kumar} } @article {47388, title = {Easy and practical approach to access multifunctional cylcopentadiene- and cyclopentene-spirooxindoles via [3+2] annulation}, journal = {Organic \& Biomolecular Chemistry}, volume = {19}, year = {2021}, month = {MAY}, pages = {4338-4345}, type = {Article}, abstract = {

A highly regioselective [3 + 2] annulation of Morita-Baylis-Hillman (MBH) carbonates of isatin with aurone/thioaurone is developed. Spiroheterocycles such as spirooxindole cyclopentadiene and spirooxindole fused hydroxy cyclopentene derivatives are constructed in one pot by exploring the reactivity of Lewis bases. Combined experimental and density functional theory (DFT) calculations offered an insight into the reaction mechanism.

}, issn = {1477-0520}, doi = {10.1039/d1ob00514f, Early Access Date = APR 2021}, author = {Warghude, Prakash K. and Sabale, Abhijeet S. and Dixit, Ruchi and Vanka, Kumar and Bhat, Ramakrishna G.} } @article {48137, title = {Enantioselective Cu(I)-catalyzed borylative cyclization of enone-tethered cyclohexadienones and mechanistic insights}, journal = {Nature Communications}, volume = {13}, year = {2022}, month = {FEB }, pages = {854}, type = {Article}, abstract = {

Rapidly building molecular structures with both elements of complexity and flexibility is a key goal of organic synthesis. Here the authors show a tandem copper-catalyzed beta-borylation/Michael addition on prochiral enone-tethered 2,5-cyclohexadienones, to generate bicyclic borylated products in high yield and enantioselectivity. The catalytic asymmetric borylation of conjugated carbonyls followed by stereoselective intramolecular cascade cyclizations with in situ generated chiral enolates are extremely rare. Herein, we report the enantioselective Cu(I)-catalyzed beta-borylation/Michael addition on prochiral enone-tethered 2,5-cyclohexadienones. This asymmetric desymmetrization strategy has a broad range of substrate scope to generate densely functionalized bicyclic enones bearing four contiguous stereocenters with excellent yield, enantioselectivity, and diastereoselectivity. One-pot borylation/cyclization/oxidation via the sequential addition of sodium perborate reagent affords the corresponding alcohols without affecting yield and enantioselectivity. The synthetic potential of this reaction is explored through gram-scale reactions and further chemoselective transformations on products. DFT calculations explain the requirement of the base in an equimolar ratio in the reaction, as it leads to the formation of a lithium-enolate complex to undergo C-C bond formation via a chair-like transition state, with a barrier that is 22.5 kcal/mol more favourable than that of the copper-enolate complex.

}, issn = {0039-7881}, doi = {10.1038/s41467-022-28288-7}, author = {Jadhav, Sandip B. and Dash, Soumya Ranjan and Maurya, Sundaram and Nanubolu, Jagadeesh Babu and Vanka, Kumar and Chegondi, Rambabu} } @article {48755, title = {Enhancing diradical character of chichibabin{\textquoteright}s hydrocarbon through fluoride substitution}, journal = {ChemPlusChem}, volume = {88}, year = {2023}, month = {AUG}, pages = {e202300273}, type = {Article}, abstract = {

In this work, 5-SIDipp [SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] (1) derived Chichibabin{\textquoteright}s hydrocarbon with an octafluorobiphenylene spacer (3) has been reported. The addition of two equivalents of 5-SIDipp with decafluorobiphenyl in presence of BF3 gives the double C-F bond activated imidazolium salt with two tetrafluoroborate anions, 2. Further reduction of 2 gives the fluorine substituted 5-SIDipp based Chichibabin{\textquoteright}s hydrocarbon, 3. Quantum chemical calculations suggested a singlet state of 3 with a singlet-triplet energy gap (?ES-T) of 3.7 kcal mol(-1), which is substantially lower with respect to the hydrogen substituted NHC-based Chichibabin{\textquoteright}s hydrocarbons (10.7 kcal mol(-1), B3LYP). As a result, the diradical character (y) of 3 (y=0.62) is also noticeably higher than the hydrogen substituted CHs (y=0.41-0.43). The ?ES-T was found to be higher in CASSCF (22.24 kcal mol(-1)) and CASPT2 (11.17 kcal mol(-1)) for 3 and the diradical character (d) is 44.6 \%.

}, keywords = {C-F Bond Activation, Chichibabin \& PRIME, DFT, N-Heterocyclic carbene, s Hydrocarbon}, issn = {2192-6506}, doi = {10.1002/cplu.202300273}, author = {Kundu, Gargi and Dash, Soumya Ranjan and Kumar, Ravi and Vanka, Kumar and Ghosh, Aryya and Sen, Sakya S.} } @article {49037, title = {Effect of position of donor units and alkyl groups on dye-sensitized solar cell device performance: indoline-aniline donor-based visible light active unsymmetrical squaraine dyes}, journal = {ACS Om.}, volume = {9}, year = {2024}, month = {MAR}, pages = {16429-16442}, type = {Article}, abstract = {

Indoline (In) and aniline (An) donor-based visible light active unsymmetrical squaraine (SQ) dyes were synthesized for dye-sensitized solar cells (DSSCs), where the position of An and In units was changed with respect to the anchoring group (carboxylic acid) to have In-SQ-An-CO2H and An-SQ-In-CO2H sensitizers, AS1-AS5. Linear or branched alkyl groups were functionalized with the N atom of either In or An units to control the aggregation of the dyes on TiO2. AS1-AS5 exhibit an isomeric pi-framework where the squaric acid unit is placed in the middle, where AS2 and AS5 dyes possess the anchoring group connected with the An donor, and AS1, AS3, and AS4 dyes having the anchoring group connected with the In donor. Hence, the conjugation between the middle squaric acid acceptor unit and the anchoring -CO2H group is short for AS2, AS5, and AK2 and longer for AS1, AS3, and AS4 dyes. AS dyes showed absorption between 501 and 535 nm with extinction coefficients of 1.46-1.61 x 10(5) M-1 cm(-1). Further, the isomeric pi-framework of An-SQ-In-CO2H and In-SQ-An-CO2H exhibited by means of changing the position of In and An units a bathochromic shift in the absorption properties of AS2 and AS5 compared to the AS1, AS3, and AS4 dyes. The DSSC device fabricated with the dyes contains short acceptor-anchoring group distance (AS2 and AS5) showed high photovoltaic performances compared to the dyes having longer distance (AS1, AS3, and AS4) with the iodolyte (I-/I-3(-)) electrolyte. DSSC device efficiencies of 5.49, 6.34, 6.16, and 5.57\% have been achieved for AS1, AS2, AS3, and AS4 dyes, respectively; without chenodeoxycholic acid (CDCA), small changes have been observed in the device performance of the AS dyes with CDCA. Significant changes have been noted in the DSSC parameters (open-circuit voltage V-OC, short-circuit current J(SC), fill factor ff, and efficiency eta) for the AS5 dye while sensitized with CDCA and showed highest DSSC efficiency of 8.01\% in the AS dye series. This study revealed the potential of shorter SQ acceptor-anchoring group distance over the longer one and the importance of alkyl groups on the overall DSSC device performance for the unsymmetrical squaraine dyes.

}, issn = {2470-1343}, doi = {10.1021/acsomega.4c00123}, author = {Singh, Amrita and Singh, Ambarish Kumar and Dixit, Ruchi and Vanka, Kumar and Krishnamoorthy, Kothandam and Nithyanandhan, Jayaraj} } @article {49021, title = {Exploring unconventional σ-hole interactions: computational insights into the interaction of XeO3 with non-aromatic coordinating solvents}, journal = {Chemphyschem}, volume = {25}, year = {2024}, month = {MAR}, type = {Article}, abstract = {

In order to control the explosiveness and shock sensitivity of XeO3, we have investigated its plausible interaction with various non-aromatic coordinating solvents, serving as potential Lewis base donors, through density functional theory (DFT) calculations. Out of twenty six such solvents, the top ten were thus identified and then thoroughly examined by employing various computational tools such as the mapping of the electrostatic potential surface (MESP), Wiberg bond indices (WBIs), non-covalent interaction (NCI) plots, Bader{\textquoteright}s theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, and the energy decomposition analysis (EDA). The amphoteric nature of XeO3 was also explored by investigating the extent of back donation from the lone pair of Xe to the antibonding orbital of the donating atom/group of the solvent molecules. The C-H \& mldr;O interactions were also found to be a contributing factor in the stabilization of these adducts. Although these aerogen-bonding interactions were found to be predominantly electrostatic, significant contributions from the orbital contributions, as well as dispersion interactions, were observed. The top three non-aromatic solvents (among the twenty six studied) which form the strongest adducts with XeO3 are proposed to be hexamethylphosphoramide (HMPA), N,N {\textquoteleft}-dimethylpropyleneurea (DMPU) and tetramethylethylenediamine (TMEDA).

}, keywords = {Aerogen bonding, Non-Aromatic Solvents, non-covalent interactions, Sigma-hole, XeO3}, issn = {1439-4235}, doi = {10.1002/cphc.202300908}, author = {Dash, Soumya Ranjan and Vanka, Kumar} }