02157nas a2200157 4500008004100000022001400041245010400055210006900159260011000228300001600338490000700354520148600361100001601847700001701863856011901880 2013 eng d a1477-922600aProposing late transition metal complexes as frustrated Lewis pairs - a computational investigation0 aProposing late transition metal complexes as frustrated Lewis pa aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUL a13866-138730 v423 a

There has been considerable interest in recent times to develop transition metal complex systems that can demonstrate metal-ligand cooperativity. It has recently been shown (Wass et al., J. Am. Chem. Soc., 2011, 133, 18463) that early transition metals can cooperate with ligands carrying phosphines as pendant groups, working as metal analogues to frustrated Lewis pairs (FLPs) to mediate in a variety of important reactions. What the current work attempts to do is to show how this concept of metal containing FLPs can be expanded to include late transition metal complexes as well: complexes that have been modified from existing systems that serve as efficient catalysts for homogeneous polymerization. A modified palladium complex has been considered in this regard as an example of a potential late transition metal FLP and studied with full quantum mechanical calculations. The calculations indicate that this complex would be effective at catalyzing ammonia borane dehydrogenation. The possibility of competing side reactions such as reductive elimination have also been considered, and it has been found that such processes would also yield stable products which could act as an FLP in catalyzing reactions such as the dehydrogenation of ammonia borane. The current work therefore expands the scope of metal containing FLPs to include late transition metals and demonstrates computationally the potential of such complexes for exhibiting metal-ligand cooperativity.

1 aPal, Amrita1 aVanka, Kumar uhttp://library.ncl.res.in/content/proposing-late-transition-metal-complexes-frustrated-lewis-pairs-computational-001621nas a2200157 4500008004100000022001400041245011000055210006900165260007100234300001200305490000800317520098200325100002001307700001701327856011901344 2014 eng d a1932-744700aProposing efficient new pendant group polymer electrolyte membranes for fuel cells: a computational study0 aProposing efficient new pendant group polymer electrolyte membra a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJAN a784-7950 v1183 a

There is a need to develop new membranes for fuel cells that can conduct protons with high efficiency and at high temperatures. This paper reports a theoretical study of proton transfer barriers in newly proposed polymer electrolyte membranes (PEMs), having pendant nitrogen containing crown ether groups on an alkyl backbone. The proton transfer in the proposed pendant group PEMs would occur without the need of an external agent such as water or phosphoric acid, and without the need for the pendant groups to rotate and reorient themselves after each proton transfer. The current study shows that this would make the proposed PEMs very efficient, with low proton transfer barriers. This has been seen to be true for a range of different PEM cases considered, differing in the number of linker atoms in the alkyl backbone and in the number of nitrogens contained in each pendant group, thus, indicating the potential of the proposed structures as PEMs for fuel cells.

1 aMane, Manoj, V.1 aVanka, Kumar uhttp://library.ncl.res.in/content/proposing-efficient-new-pendant-group-polymer-electrolyte-membranes-fuel-cells-001215nas a2200205 4500008004100000245009200041210006900133260000800202300001400210490000700224520050100231100002100732700001900753700003100772700002400803700002500827700001700852700002000869856012000889 2017 eng d00aPorous porphyrin organic polymer (PPOP) for visible light triggered hydrogen production0 aPorous porphyrin organic polymer PPOP for visible light triggere cAPR a4461-44640 v533 aA visible light active porphyrin-based porous organic polymer having high chemical stability and surface area has been synthesized and its ability to influence the photocatalytic activity of large band gap-TiO2 nanoparticles has been tested. The resultant composite shows improved photocatalytic activity as compared to the parent precursors. This study provides insights into the photosensitizing ability of the polymer in addition to its ability to firmly harbor nanoparticles onto its surface.1 aMukherjee, Gargi1 aThote, Jayshri1 aAiyappa, Harshitha, Barike1 aKandambeth, Sharath1 aBanerjee, Subhrashis1 aVanka, Kumar1 aBanerjee, Rahul uhttp://library.ncl.res.in/content/porous-porphyrin-organic-polymer-ppop-visible-light-triggered-hydrogen-production00916nas a2200181 4500008004100000245011900041210006900160260000800229300001600237490000700253520024500260100001900505700002600524700001900550700001700569700001800586856013000604 2017 eng d00a p-Selective (sp(2))-C-H functionalization for an acylation/alkylation reaction using organic photoredox catalysis0 apSelective sp2CH functionalization for an acylationalkylation re cNOV a12337-123400 v533 ap-Selective (sp(2))-C-H functionalization of electron rich arenes has been achieved for acylation and alkylation reactions, respectively, with acyl/alkylselenides by organic photoredox catalysis involving an interesting mechanistic pathway.1 aPandey, Ganesh1 aTiwari, Sandip, Kumar1 aSingh, Bhawana1 aVanka, Kumar1 aJain, Shailja uhttp://library.ncl.res.in/content/p-selective-sp2-c-h-functionalization-acylationalkylation-reaction-using-organic-photoredox01691nas a2200205 4500008004100000022001400041245011200055210006900167260000800236300001400244490000700258520097800265100001701243700002501260700001601285700002201301700001701323700001801340856012701358 2021 eng d a2041-652000aPhosphite mediated asymmetric N to C migration for the synthesis of chiral heterocycles from primary amines0 aPhosphite mediated asymmetric N to C migration for the synthesis cJUL a8996-90030 v123 aA phosphite mediated stereoretentive C-H alkylation of N-alkylpyridinium salts derived from chiral primary amines was achieved. The reaction proceeds through the activation of the N-alkylpyridinium salt substrate with a nucleophilic phosphite catalyst, followed by a base mediated [1,2] aza-Wittig rearrangement and subsequent catalyst dissociation for an overall N to C-2 alkyl migration. The scope and degree of stereoretention were studied, and both experimental and theoretical investigations were performed to support an unprecedented aza-Wittig rearrangement-rearomatization sequence. A catalytic enantioselective version starting with racemic starting material and chiral phosphite catalyst was also established following our understanding of the stereoretentive process. This method provides efficient access to tertiary and quaternary stereogenic centers in pyridine systems, which are prevalent in drugs, bioactive natural products, chiral ligands, and catalysts.1 aRani, Soniya1 aDash, Soumya, Ranjan1 aBera, Asish1 aAlam, Md, Nirshad1 aVanka, Kumar1 aMaity, Pradip uhttp://library.ncl.res.in/content/phosphite-mediated-asymmetric-n-c-migration-synthesis-chiral-heterocycles-primary-amines02589nas a2200205 4500008004100000022001400041245011100055210006900166260000900235300001400244490000700258520185700265100002402122700002502146700001902171700001702190700002402207700002402231856012802255 2022 eng d a1528-748300aPolymorphs of green fluorescence protein chromophore analogue: fluorescence switching with thermal stimuli0 aPolymorphs of green fluorescence protein chromophore analogue fl cMAR  a1892-19050 v223 a

Polymorphs of fluorescent organic materials offer significant implications in optoelectronics and advanced materials as they modulate photoluminescence properties. A slight alteration in the conformation/packing of molecules in the crystals shows variation in photoluminescence. This necessitates the polymorph screening of these materials to develop novel crystalline forms with distinct fluorescence emissions for broader application. In continuation of our work on the polymorph screening of Green Fluorescence Protein Chromophore (GFPc), we have synthesized a new imidazoline derivative, ethyl (Z)-2-(2-methyl-5-oxo-4-(3,4,5-trimethoxybenzylidene)-4,5-dihydro-1H-imi dazol-1- yl)acetate (1). Polymorph screening of 1 under different crystallization conditions revealed three polymorphs, Form I (needle), Form II (block), and Form III (polycrystalline material). Forms I and II are the outcome of solution crystallization, whereas Form III was produced from the melt crystallization of Forms I and II. DSC, HSM, and powder and single-crystal XRD studies indicate the conversion of Form I and Form III crystals to Form II crystals on thermal stimuli. The photoluminescence studies revealed cyan, yellow, and yellowish-green fluorescence emission for Forms I, II, and III crystals, respectively. The difference in photoluminescence could be due to the variance in aggregation modes like H-aggregation in Form I and J-aggregation in Form II crystals. Form I, Form II, and Form III crystals also showed irreversible thermal fluorescent switching from cyan-yellow-green due to polymorphic phase transitions. The study correlates the direct observation of the modulation of the excited-state transition under thermal stimuli in the crystalline phase. It will help augment the pace in the research of thermally responsive fluorescent materials.

1 aMali, Bhupendra, P.1 aDash, Soumya, Ranjan1 aBiswas, Anupam1 aVanka, Kumar1 aManoj, Kochunnoonny1 aGonnade, Rajesh, G. uhttp://library.ncl.res.in/content/polymorphs-green-fluorescence-protein-chromophore-analogue-fluorescence-switching-thermal02229nas a2200193 4500008004100000022001400041245009700055210006900152260000900221300001600230490000600246520156000252100002101812700002501833700001801858700001801876700001701894856012401911 2022 eng d a2470-134300aPredicting the redox potentials of phenazine derivatives using DFT-assisted machine learning0 aPredicting the redox potentials of phenazine derivatives using D cAPR  a11742-117550 v73 a

This study investigates four machine-learning (ML) models to predict the redox potentials of phenazine derivatives in dimethoxyethane using density functional theory (DFT). A small data set of 151 phenazine derivatives having only one type of functional group per molecule (20 unique groups) was used for the training. Prediction accuracy was improved by a combined strategy of feature selection and hyperparameter optimization, using the external validation set. Models were evaluated on the external test set containing new functional groups and diverse molecular structures. High prediction accuracies of R2 > 0.74 were obtained on the external test set. Despite being trained on the molecules with a single type of functional group, models were able to predict the redox potentials of derivatives containing multiple and different types of functional groups with good accuracies (R2 > 0.7). This type of performance for predicting redox potential from such a small and simple data set of phenazine derivatives has never been reported before. Redox flow batteries (RFBs) are emerging as promising candidates for energy storage systems. However, new green and efficient materials are required for their widespread usage. We believe that the hybrid DFT-ML approach demonstrated in this report would help in accelerating the virtual screening of phenazine derivatives, thus saving computational and experimental costs. Using this approach, we have identified promising phenazine derivatives for green energy storage systems such as RFBs.

1 aGhule, Siddharth1 aDash, Soumya, Ranjan1 aBagchi, Sayan1 aJoshi, Kavita1 aVanka, Kumar uhttp://library.ncl.res.in/content/predicting-redox-potentials-phenazine-derivatives-using-dft-assisted-machine-learning01973nas a2200241 4500008004100000245014200041210006900183260000800252300001600260490000600276520110900282653001801391653001801409653002801427653003701455653002501492100001801517700001901535700001701554700001701571700001801588856012501606 2023 eng d00aPd nanoparticles supported on N-incorporated hybrid organosilica as an active and selective low-temperature phenol hydrogenation catalyst0 aPd nanoparticles supported on Nincorporated hybrid organosilica  cJUN a11500-115120 v63 a

A heterogeneous Pd-NPMO hybrid-silicacatalyst is synthesized andits application for aqueous phase selective hydrogenation of phenolto cyclohexanone at near ambient temperature (40 degrees C) and underatmospheric hydrogen pressure is demonstrated. The homogeneously distributedPd nanoparticles on N-bridged hybrid mesoporous organosilica showedremarkable activity and selectivity for cyclohexanone compared tothe unmodified Pd-SBA-15 catalyst. Control experiments strongly claimthe role of nitrogen domains in the organic framework of hybrid silicasupport in stabilizing small Pd nanoparticles and possibly modifyingthe Pd sites responsible for catalysis to activate the substrate moleculesin water. The hybrid silica catalyst was stable and reused severaltimes without any significant drop-in activity, proving the heterogeneityof the bifunctional Pd catalyst. Based on the density functional theorystudy and experimental interventions, a possible reaction mechanismfor the low-temperature phenol hydrogenation explaining the role oforganic domains in the hybrid-silica framework is proposed.

10acyclohexanone10aHybrid silica10apalladium nanoparticles10aPeriodic mesoporous organosilica10aphenol hydrogenation1 aBetsy, K., J.1 aBajpai, Priyam1 aLazar, Anish1 aVanka, Kumar1 aVinod, C., P. uhttp://library.ncl.res.in/content/pd-nanoparticles-supported-n-incorporated-hybrid-organosilica-active-and-selective-low01977nas a2200169 4500008004100000022001400041245011700055210006900172260000800241300001400249490000800263520134800271100001501619700002701634700001701661856012901678 2023 eng d a1932-744700aPotential role of lewis acid-base adducts in enhancing stereoselectivity in ziegler-natta catalysts: a DFT study0 aPotential role of lewis acidbase adducts in enhancing stereosele cAPR a7220-72290 v1273 a

Ziegler-Natta (Z-N) systems have been well established as heterogeneous catalysts that produce isotactic polypropylene and polyethylene with great efficiency. Such systems benefit considerably from donors (Lewis bases), whose addition significantly improves the stereoselectivity of polymerization. There is a consensus that the primary role of the external donors is to coordinate at the vacant site created by the extraction of internal donors and thus maintain the stereoselectivity. However, the bite difference between internal donors such as phthalates or succinate derivatives and external donors such as alkoxysilanes raises the question of how external donors can effectively replace internal donors. In order to investigate this, we have chosen four external alkoxysilane donors: (1) diisopropyl dimethoxysilane, (2) dicyclopentyl dimethoxysilane, (3) disec-butyl dimethoxysilane, and (4) sec-butyl(methyl) dimethoxysilane. DFT studies reveal that the bite difference problem can be overcome by the favorable formation of adducts between the alkoxysilane external donors and AlEt2Cl in the Z-N systems. These adducts tend to coordinate in the vicinity of the active site. Furthermore, our findings demonstrate the potential of these Lewis acid-base adducts to enhance the stereoselectivity of Z-N catalysts significantly.

1 aRaj, Vipin1 aGupta, Virendra, Kumar1 aVanka, Kumar uhttp://library.ncl.res.in/content/potential-role-lewis-acid-base-adducts-enhancing-stereoselectivity-ziegler-natta-catalysts02260nas a2200241 4500008004100000022001400041245011100055210007000166260000900236490000700245520143100252653001901683653002501702653001501727653002001742653000901762100001901771700001801790700002101808700001701829700002301846856014901869 2025 eng d a0947-653900aPair of dinuclear Fe(II) enantiomers: syntheses and structures of ΛΔ/ΔΛ-Bis(Dihydridoborate) complexes0 aPair of dinuclear FeII enantiomers syntheses and structures of Λ cFEB 0 v313 a

In our effort to establish a direct synthetic approach for bis(dihydridoborate) complexes of first-row transition metals, we have investigated the reactivity of [Cp*Fe(dppe)Cl] (dppe =1,2-bis(diphenylphosphino)ethane) with Na[BH3L] (L =2-mercaptopyridine (mp) and 2-mercaptobenzothiazole (mbz)) that led to the formation of iron(II) dihydridoborate complexes, [Cp*Fe{kappa 3-S,H,H-(H2BH(L))}] 1 a-b (L=mp (1 a) and L=mbz (1 b)). Further, in an attempt to isolate the bis(dihydridoborate) complex of iron by the insertion of borane into the kappa 2-N,S-chelated iron complex, [(dppe)Fe{kappa 2-N,S-(mp)}2] (2), we have isolated and structurally characterized a rare example of dimeric iron bis(dihydridoborate) complex, [Fe{kappa 3-S,H,H-(H2BH(mp))}2]2, Lambda Delta/Delta Lambda-3 as pair of enantiomers. Interestingly, these enantiomers Lambda Delta/Delta Lambda-3 have two trans-[Fe{kappa 3-S,H,H-(H2BH(mp))}2] moieties bridged through sulfur atoms of 2-mercaptopyridinyl ligands, where the iron centres are hepta-coordinated. The natural bond-orbital (NBO) analyses of Lambda Delta-3 and Delta Lambda-3 show considerable electron donation from the filled sigma B-H bonding orbital to vacant dz2 \${{d}_{{z}<\^>{2}}}\$ orbital of iron with a substantial contribution from the hydrogen atoms. The localized orbital bonding analysis (LOBA) method suggests that all the iron centres are in +2 oxidation state.

10aB-H activation10aBis(dihydridoborate)10aEnantiomer10aHeptacoordinate10airon1 aKaur, Urminder1 aGayen, Sourav1 aSharma, Himanshu1 aVanka, Kumar1 aGhosh, Sundargopal uhttp://library.ncl.res.in/content/pair-dinuclear-feii-enantiomers-syntheses-and-structures-%CE%BB%CE%B4%CE%B4%CE%BB-bisdihydridoborate-complexes