00922nas a2200181 4500008004100000245009400041210006900135260000800204300001600212520025700228100002200485700002200507700001700529700002300546700002100569700002400590856012600614 2008 eng d00aMultiple weak supramolecular interactions stabilize a surprisingly twisted As2L3 assembly0 aMultiple weak supramolecular interactions stabilize a surprising cOCT a3936 - 39383 aA combined crystallographic, DFT and NMR spectroscopic study of a flexible As(2)(3) assembly reveals temperature dependent conformational behavior in solution and a highly asymmetric structure stabilized by As-pi and edge-to-face aromatic interactions.1 aPitt, Melanie, A.1 aZakharov, Lev, N.1 aVanka, Kumar1 aThompson, Ward, H.1 aLaird, Brian, B.1 aJohnson, Darren, W. uhttp://library.ncl.res.in/content/multiple-weak-supramolecular-interactions-stabilize-surprisingly-twisted-as2l3-assembly02584nas a2200217 4500008004100000245016000041210006900201260000800270300001200278490000700290520176700297100002302064700002302087700002502110700001702135700002002152700002202172700002302194700002502217856012402242 2008 eng d00aMultipoint anchoring of the [2.2.2.2]metacyclophane motif to a gold surface via self-assembly: coordination chemistry of a cyclic tetraisocyanide revisited0 aMultipoint anchoring of the 2222metacyclophane motif to a gold s cMAY a3284-910 v473 aA one-pot transformation of bis(2-isocyano-3-methylphenyl)ethane affords gram quantities of 8,16,24,32-tetraisocyano[2.2.2.2]metacyclophane ( 3). The solid state structure of 3 is remarkably close to the lowest energy conformation found on the potential energy landscape for 3 by DFT. In solution, the structure of metacyclophane 3 is mobile but can be locked in a rectangular gauche- anti- gauche- anti conformation by coordination of the isocyanide substituents to the [W(CO) 5] units to give [M] 4(mu 4-eta (1):eta (1):eta (1):eta (1)- 3) ( 5). The tetranuclear [M] 4(mu 4-eta (1):eta (1):eta (1):eta (1)- 3) motif featured in crystallographically characterized 5 may be present in several insoluble complexes of 3 previously described as mononuclear eta (4) species. A self-assembled monolayer of metacyclophane 3 is formed upon exposing a solution of 3 to the gold(111) surface with no precautions to exclude air or light. The monolayer nature of the film was confirmed by optical ellipsometry. The isocyanide stretching band for 3 shifts from 2119 cm (-1) in solution to 2175 cm (-1) upon chemisorption to metallic gold. The FTIR spectrum of the film indicates interaction of 3 with the gold surface via all four of its isocyanide anchors. No gold-facilitated oxidation of the -NC junctions was detected under ambient conditions. The energy cost associated with accessing the conformations of 3 suitable for mu 4-eta (1):eta (1):eta (1):eta (1) interaction of the molecule with the Au(111) surface is under 8 kcal/mol, a value that can be easily offset by formation of a gold-isocyanide bond. Two different mu 4-eta (1):eta (1):eta (1):eta (1) coordination arrangements of 3 with respect to gold atoms on the (111) face of the fcc Au lattice are suggested.1 aToriyama, Masaharu1 aMaher, Tiffany, R.1 aHolovics, Thomas, C.1 aVanka, Kumar1 aDay, Victor, W.1 aBerrie, Cindy, L.1 aThompson, Ward, H.1 aBarybin, Mikhail, V. uhttp://library.ncl.res.in/content/multipoint-anchoring-2222metacyclophane-motif-gold-surface-self-assembly-coordination01656nas a2200217 4500008004100000022001400041245010500055210006900160260007100229300001200300490000600312520083400318653001401152653003001166653003101196653003001227100002101257700001601278700001701294856012701311 2013 eng d a2155-543500aMetal or nonmetal cooperation with a phenyl group: route to catalysis? a computational investigation0 aMetal or nonmetal cooperation with a phenyl group route to catal a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY a920-9270 v33 a

Full quantum mechanical calculations demonstrate that cooperativity in the form of the activation of the M-C bond (M: transition metal or boron, C: the ipso carbon of the coordinated phenyl group) can lead to effective catalysis pathways. Calculations show that the presence of an aromatic bidentate ligand attached to a transition metal, or even a main group element, such as boron, can lead to effective catalysts for,a, range of important reactions, such as the dehydrogenation of ammonia borane and formic acid and the activation of the N-H, bond in aromatic amities. Moreover, it is shown that the design of tridentate pincer complexes with the aromatic group at a terminal end can lead to effective M-C cooperativity. As such, the current work introduces a new concept in cooperativity and bond activation chemistry.

10acatalysis10aDensity functional theory10ametal-ligand cooperativity10asmall molecule activation1 aGhatak, Kamalika1 aMane, Manoj1 aVanka, Kumar uhttp://library.ncl.res.in/content/metal-or-nonmetal-cooperation-phenyl-group-route-catalysis-computational-investigation-002237nas a2200193 4500008004100000022001400041245008200055210006900137260007100206300001400277490000700291520153500298100002201833700002701855700002001882700001701902700002201919856010201941 2015 eng d a0020-166900aMechanism of oxygen atom transfer from Fe-V(O) to olefins at room temperature0 aMechanism of oxygen atom transfer from FeVO to olefins at room t a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL a6112-61210 v543 a

In biological oxidations, the intermediate Fe-V(0)(OH) has been proposed to be the active species for catalyzing the epoxidation of alkenes by nonheme iron complexes. However, no study has been reported yet that elucidates the mechanism of direct O-atom transfer during the reaction of Fe-V(0) with alkenes to form the corresponding epoxide. For the first time, we study the mechanism of O-atom transfer to alkenes using the Fe-V(0) complex of biuret-modified Fe-TAML at room temperature. The second-order rate constant (k(2)) for the reaction of different alkenes with Fe-V(0) was determined under single-turnover conditions. An 8000-fold rate difference was found between electron-rich (4-methoxystyrene; k(2) = 216 M-1 s(-1)) and electron-deficient (methyl transcinnamate; k(2) = 0.03 M-1 s(-1)) substrates. This rate difference indicates the electrophilic character of Fe-V(0). The use of cis-stilbene as a mechanistic probe leads to the formation of both cis- and trans-stilbene epoxides (73:27). This suggests the formation of a radical intermediate, which would allow C-C bond rotation to yield both stereoisomers of stilbene-epoxide. Additionally, a Hammett rho value of -0.56 was obtained for the para-substituted styrene derivatives. Detailed DFT calculations show that the reaction proceeds via a two-step process through a doublet spin surface. Finally, using biuret-modified Fe-TAML as the catalyst and NaOCl as the oxidant under catalytic conditions epoxide was formed with modest yields and turnover numbers.

1 aSingh, Kundan, K.1 aTiwari, Mrityunjay, K.1 aDhar, Basab, B.1 aVanka, Kumar1 aGupta, Sayam, Sen uhttp://library.ncl.res.in/content/mechanism-oxygen-atom-transfer-fe-vo-olefins-room-temperature-002016nas a2200193 4500008004100000245014400041210006900185260000800254300001400262490000700276520128500283100002401568700002201592700002301614700002401637700001701661700002001678856012401698 2016 eng d00aMechanistic insights into pincer-ligated palladium-catalyzed arylation of azoles with aryl Iodides: evidence of a Pd-II-Pd-IV-Pd-II pathway0 aMechanistic insights into pincerligated palladiumcatalyzed aryla cMAR a875–8860 v353 a

Pincer-based (R2POCNR′2)PdCl complexes along with CuI cocatalyst catalyze the arylation of azoles with aryl iodides to give the 2-arylated azole products. Herein, we report an extensive mechanistic investigation for the direct arylation of azoles involving a well-defined and highly efficient (iPr2POCNEt2)PdCl (2a) catalyst, which emphasizes a rare PdII–PdIV–PdII redox catalytic pathway. Kinetic studies and deuterium labeling experiments indicate that the C–H bond cleavage on azoles occurs via two distinct routes in a reversible manner. Controlled reactivity of the catalyst 2a underlines the iodo derivative (iPr2POCNEt2)PdI (3a) to be the resting state of the catalyst. The intermediate species (iPr2POCNEt2)Pd-benzothiazolyl (4a) has been isolated and structurally characterized. A determination of reaction rates of compound 4a with electronically different aryl iodides has revealed the kinetic significance of the oxidative addition of the C(sp2)–X electrophile, aryl iodide, to complex 4a. Furthermore, the reactivity behavior of 4a suggests that the arylation of benzothiazole proceeds via an oxidative addition/reductive elimination pathway involving a (iPr2POCNEt2)PdIV(benzothiazolyl)(Ar)I species, which is strongly supported by DFT calculations.

1 aKhake, Shrikant, M.1 aJagtap, Rahul, A.1 aDangat, Yuvraj, B.1 aGonnade, Rajesh, G.1 aVanka, Kumar1 aPunji, Benudhar uhttp://library.ncl.res.in/content/mechanistic-insights-pincer-ligated-palladium-catalyzed-arylation-azoles-aryl-iodides02529nas a2200409 4500008004100000022001400041245011800055210006900173260000800242490000700250520127700257653001301534653003001547653001401577653001501591653000801606653001001614653001801624653001601642653001901658653001901677653002101696653001001717653002301727653001401750100003001764700001901794700001801813700001901831700001901850700002401869700001701893700002701910700003001937700002801967856012401995 2017 eng d a0947-653900aMixed-stack charge transfer crystals of pillar[5]quinone and tetrathiafulvalene exhibiting ferroelectric features0 aMixedstack charge transfer crystals of pillar5quinone and tetrat cSEP0 v233 a

Ferroelectric materials find extensive applications in the fabrication of compact memory devices and ultra-sensitive multifunctional detectors. Face-to-face alternate stacking of electron donors and acceptors effectuate long-range unidirectional ordering of charge-transfer (CT) dipoles, promising tunable ferroelectricity. Herein we report a new TTF-quinone system-an emerald green CT complex consisting pillar[5]quinone (P5Q) and tetrathiafulvalene (TTF). The CT crystals, as determined by single crystal synchrotron X-ray diffraction, adopt a 1:1 mixed-stack arrangement of donor and acceptor with alternating dimers of TTF and 1,4-dioxane encapsulated P5Q. The TTF-P5Q.dioxane crystal possesses a macroscopic polarization axis giving rise to ferroelectricity at room temperature. The CT complex manifests ferroelectric features such as optical polarization rotation, temperature-dependent phase transition and piezoelectric response in single crystals. Ferroelectric behavior observed in P5Q-based CT complex widens the scope for further work on this structurally intriguing and readily accessible cyclic pentaquinone.

10aAcceptor10aCharge-transfer complexes10aChemistry10aConductors10aDDQ10aDonor10aferroelectric10aMacrocycles10aOrganic Metals10aPi-interaction10aPillar[5]quinone10asalts10aTransfer Complexes10aTransport1 aShivakumar, Kilingaru, I.1 aSwathi, Kadaba1 aGoudappagouda1 aDas, Tamal, C.1 aKumar, Ashwani1 aMakde, Ravindra, D.1 aVanka, Kumar1 aNarayan, Kavassery, S.1 aBabu, Sukumaran, Santhosh1 aSanjayan, Gangadhar, J. uhttp://library.ncl.res.in/content/mixed-stack-charge-transfer-crystals-pillar5quinone-and-tetrathiafulvalene-exhibiting01892nas a2200193 4500008004100000245006700041210006700108260000800175300001200183490000700195520124100202100003401443700002901477700002401506700003201530700001701562700002701579856009201606 2017 eng d00aMolecular motifs for additives that retard PEO crystallization0 aMolecular motifs for additives that retard PEO crystallization cAUG a857-8640 v573 a

We investigate the influence of several bifunctional phenol additives (resorcinol: RES, hydroquinone: HYD, p-hydroxybenzoic acid: PHBA, and p-nitrophenol: PNP) on the crystallization of matrix polymer, polyethyleneoxide. We employ solid state Nuclear Magnetic Resonance spectroscopy (NMR), Differential Scanning Calorimetry (DSC), optical microscopy, and Small Angle X-ray Scattering (SAXS) to investigate crystallization of the additivated PEO and compare with Density Functional Theory (DFT) calculations of additive-PEO interactions. Additive-polymer interactions are a function of the functional groups on the additive. Temperature-dependent spherulitic growth rate measurements from optical microscopy and SAXS lamellar long spacings indicate a distinct trend in the effect of additives on PEO crystallization. Change in PEO crystallization is most pronounced with PNP, followed by PHBA and finally RES and HYD. This trend correlates qualitatively with the binding energies of additive-PEO interactions from DFT studies. Our results suggest that DFT calculations might be a useful screening tool to evaluate the influence of additives on polymer crystallization. POLYM. ENG. SCI., 2016. © 2016 Society of Plastics Engineers

1 aShrivastava, Sudhakar, Dinesh1 aEldho, Kavalakal, Mathai1 aRajamohanan, P., R.1 aAjithkumar, Thalasseril, G.1 aVanka, Kumar1 aKumaraswamy, Guruswamy uhttp://library.ncl.res.in/content/molecular-motifs-additives-retard-peo-crystallization02239nas a2200205 4500008004100000022001400041245009000055210006900145260000800214300001400222490000700236520155700243100002401800700001801824700002101842700002401863700001701887700002001904856010901924 2018 eng d a0276-733300aMechanism of nickel(II)-catalyzed C(2)-H alkynylation of indoles with alkynyl bromide0 aMechanism of nickelIIcatalyzed C2H alkynylation of indoles with  cJUL a2037-20450 v373 a

The nickel system (THF)(2)NiBr2/phen has recently been shown as an efficient catalyst for the C-H bond alkynylation of diverse heteroarenes with (triisopropylsilyl)alkynyl bromide via monodentate chelation assistance. Herein, we report an extensive mechanistic investigation for the direct alkynylation of indoles involving the well-defined nickel catalyst, which features a coordinative insertion pathway of alkynyl bromide with the Ni(II) catalyst. Catalytic relevant nickel complexes, (phen)NiCl2 (5), (phen)(2)NiCl2 (6) and [(phen)(3)Ni].NiCl4 (7) were isolated, and the complexes 6 and 7 were structurally characterized. Well-defined complexes were as competent as the in situ generated catalyst system (THF)(2)NiBr2/phen for the alkynylation of indoles. Various controlled studies and reactivity experiments were performed to understand the probable pathway for the alkynylation reaction. Kinetics analysis highlights that the complex (phen)NiX2 acts as a precatalyst, and the involvement of substrate indole and LiO'Bu are essential for the generation of the active catalyst. Deuterium labeling and kinetic studies suggest that the process involving C-H cleavage and carbo-nickelation of indole is a crucial rate influencing step. Reactivity study of various alkynyl compounds with nickel-species highlights a migratory insertion route for the reaction. DFT calculations firmly support the experimental findings and suggest the coordinative insertion pathway of alkynyl bromide rather than oxidative addition toward the nickel(II) center.

1 aKhake, Shrikant, M.1 aJain, Shailja1 aPatel, Ulhas, N.1 aGonnade, Rajesh, G.1 aVanka, Kumar1 aPunji, Benudhar uhttp://library.ncl.res.in/content/mechanism-nickelii-catalyzed-c2-h-alkynylation-indoles-alkynyl-bromide02044nas a2200205 4500008004100000022001400041245010400055210006900159260000800228300001400236490000700250520133400257100002101591700001801612700002201630700002401652700001701676700002001693856012501713 2018 eng d a0276-733300aMechanistic aspects of pincer nickel(II)-catalyzed C-H bond alkylation of azoles with alkyl halides0 aMechanistic aspects of pincer nickelIIcatalyzed CH bond alkylati cMAR a1017-10250 v373 a

The quinolinyl-based pincer nickel complex, kappa(N),kappa(N),kappa(N)-{C9H6N-(mu-N)-C6H4-NMe2}NiCl [((NNNMe2)-N-Q)-NiCl; (1)] has recently been demonstrated to be an efficient and robust catalyst for the alkylation of azoles with alkyl halides under copper-free conditions. Herein, we report the detailed mechanistic investigation for the alkylation of azoles catalyzed by ((NNNMe2)-N-Q)NiCl (1), which highlights an iodine atom transfer (IAT) mechanism for the reaction involving a Ni-II/Ni-III process. Deuterium labeling experiments indicate reversible cleavage of the benzothiazole C-H bond, and kinetic studies underline a fractional negative rate order with the substrate benzothiazole. The involvement of an alkyl radical during the alkylation is validated by radical clock and external additive experiments. An active intermediate species ((NNNMe2)-N-Q)Ni(benzothiazolyl) (5a) has been isolated and structurally characterized. The complex ((NNNMe2)-N-Q)Ni(benzothiazoly1) (5a) is found to be the resting state of catalyst 1. Kinetic analysis of electronically different intermediates suggests that the step involving the reaction of 5a with alkyl iodide is crucial and a rate-influencing step. DFT calculations strongly support the experimental findings and corroborate an IAT process for the alkylation reaction.

1 aPatel, Ulhas, N.1 aJain, Shailja1 aPandey, Dilip, K.1 aGonnade, Rajesh, G.1 aVanka, Kumar1 aPunji, Benudhar uhttp://library.ncl.res.in/content/mechanistic-aspects-pincer-nickelii-catalyzed-c-h-bond-alkylation-azoles-alkyl-halides01556nas a2200217 4500008004100000022001400041245009800055210006900153260000800222300001400230490000700244520081000251100002501061700003201086700001801118700001501136700001701151700002001168700002401188856012601212 2018 eng d a1359-734500aMechano-responsive room temperature luminescence variations of boron conjugated pyrene in air0 aMechanoresponsive room temperature luminescence variations of bo cJUN a6028-60310 v543 a

Stimuli responsive tunable luminescence is a promising field of research. Even though mechanofluorescence is widely studied, mechanophosphorescence remains unexplored. Here we report the mechano-driven fluorescence and phosphorescence variations of a pyrene tetraboronic ester derivative. The fluorochromic and room temperature phosphorescence features are supported by theoretical studies and single crystal analysis. The mechanically ground fluorescence active but phosphorescence inactive pyrene tetraboronic ester exhibits room temperature phosphorescence in air withmechanical force. The efficient intermolecular electronic coupling in the dimer formed upon scratching enables a good communication between singlet and triplet states, hence resulting in room temperature mechanophosphorescence.

1 aWakchaure, Vivek, C.1 aRanjeesh, Kayaramkodath, C.1 aGoudappagouda1 aDas, Tamal1 aVanka, Kumar1 aGonnade, Rajesh1 aBabu, Sukumaran, S. uhttp://library.ncl.res.in/content/mechano-responsive-room-temperature-luminescence-variations-boron-conjugated-pyrene-air01068nas a2200181 4500008004100000022001400041245009700055210006900152260000900221300001400230490000700244520042200251100002100673700002100694700001700715700002600732856012800758 2019 eng d a0022-326300aMetal-free regioselective cross dehydrogenative coupling of cyclic ethers and aryl carbonyls0 aMetalfree regioselective cross dehydrogenative coupling of cycli cFEB  a2039-20470 v843 a

A highly regioselective, efficient, and metal-free oxidative cross dehydrogenative coupling (CDC) of aryl carbonyls with cyclic ethers has been developed. This method offers easy access to substituted alpha-arylated cyclic ethers with a high functional group tolerance in good to excellent yields. The regioselectivity of this CDC reaction was confirmed by density functional theory (DFT)-based calculations.

1 aMane, Kishor, D.1 aMukherjee, Anagh1 aVanka, Kumar1 aSuryavanshi, Gurunath uhttp://library.ncl.res.in/content/metal-free-regioselective-cross-dehydrogenative-coupling-cyclic-ethers-and-aryl-carbonyls02052nas a2200277 4500008004100000022001400041245011600055210006900171260000800240300001500248490000900263520112800272653002901400653001401429653001901443653002201462653003101484100001701515700001701532700002201549700001501571700001701586700001701603700002401620856013001644 2022 eng d a1434-193X00aMechanistically guided one pot synthesis of phosphine-phosphite and its implication in asymmetric hydrogenation0 aMechanistically guided one pot synthesis of phosphinephosphite a cJAN ae2021014470 v20223 a

Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an 0-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72%). When L1 was treated with [Rh], P-31 NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92%). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1-2 bar H-2 pressure, at room temperature. The practical relevance of Ll is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson's disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.

10aasymmetric hydrogenation10acatalysis10aDOPA synthesis10aOne pot synthesis10aPhosphine-phosphite ligand1 aSen, Anirban1 aKumar, Rohit1 aPandey, Swechchha1 aRaj, Vipin1 aKumar, Pawan1 aVanka, Kumar1 aChikkali, Samir, H. uhttp://library.ncl.res.in/content/mechanistically-guided-one-pot-synthesis-phosphine-phosphite-and-its-implication-asymmetric