02311nas a2200253   4500008004100000022001400041245015100055210006900206260009200275300001200367490000700379520138900386653001101775653000901786653000901795653000901804653002001813653001401833100001901847700001701866700002701883700001601910856013101926       2013                        eng d  a0892-702200aUnderstanding the orientation of water molecules around the phosphate and attached functional groups in a phospholipid molecule: a DFT-based study0 aUnderstanding the orientation of water molecules around the phos  a4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcOCT  a937-9550 v393 a<p>The adsorption of water molecules around a polar region (in particular around the phosphate moiety) in the phospholipid molecules is studied in this work. Phospholipid molecules with different functional groups are known to respond differently to the water molecules. Hence, we attempt to study the adsorption of water molecules around the phosphate group as a consequence of the change of functional group attached to the phosphate group, viz. phosphatidyl ethanolamine (PE), phosphatidyl choline (PC) and phosphatidyl glycerol (PG). As the latter is anionic in nature, the charge is compensated by Na+ counterion. Up to seven water molecules are adsorbed around the phosphate groups in model systems mimicking phospholipid molecule. The corresponding changes in the structural and electronic aspects are analysed. The significant difference between the PE and PC model systems is the formation of clathrate-like structure in the latter. Itisnoticed that as the number of water molecules increases to seven, both the hydrogen atoms in the water molecule participate in hydrogen bonding. However, in the PG model system, the charge-compensating counterion prevents the water molecule to form clathrate-like structures. The adsorption sites for water molecules are validated by density functional theory-based reactivity descriptors, viz. Fukui functions in the PE model system.</p>10acHelpG10aDMPC10aDMPE10aDMPG10aFukui functions10aHydration1 aMishra, Deepti1 aDas, Susanta1 aKrishnamurthy, Sailaja1 aPal, Sourav  uhttps://library.ncl.res.in/content/understanding-orientation-water-molecules-around-phosphate-and-attached-functional-groups-001795nas a2200169   4500008004100000022001400041245021300055210006900268260007100337300001400408490000800422520102600430100001701456700001601473700002601489856011001515       2013                        eng d  a1089-563900aUnderstanding the site selectivity in small-sized neutral and charged AI(n) (4 <= n <= 7) clusters using density functional theory based reactivity descriptors: a validation study on water molecule adsorption0 aUnderstanding the site selectivity in smallsized neutral and cha  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a8691-87020 v1173 a<p>Aluminum clusters are now technologically important due to their high catalytic activity. Our present study on the small-sized aluminum clusters applies density functional theory (DFT)-based reactivity descriptors to identify potential sites for adsorption and eventual chemical reaction. Depending on symmetry, susceptibility of various type of reactive sites within a cluster toward an impending electrophilic and/or nucleophilic attack is predicted using the reactivity descriptors. In addition, the study devises general rules as to how the size, shape, and charge of the cluster influences the number of available sites for an electrophilic and/or nucleophilic attack. The predictions by reactivity descriptors are validated by performing an explicit adsorption of water molecule on Al clusters with four atoms. The adsorption studies demonstrate that the most stable water-luster complex is obtained when the molecule is adsorbed through an oxygen atom on the site with the highest relative electrophilicity.</p>1 aDas, Susanta1 aPal, Sourav1 aKrishnamurty, Sailaja  uhttps://library.ncl.res.in/content/understanding-site-selectivity-small-sized-neutral-and-charged-ain-4-002012nas a2200169   4500008004100000022001400041245007600055210006900131260007100200300001600271490000800287520137800295100001701673700001601690700002601706856011001732       2014                        eng d  a1932-744700aDinitrogen activation by silicon and phosphorus doped aluminum clusters0 aDinitrogen activation by silicon and phosphorus doped aluminum c  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG  a19869-198780 v1183 a<p>N-2 reduction is crucial for life, and very few catalysts are currently available to carry out this process at ambient temperature and pressure. In the present work, density functional theory based calculations reveal doped aluminum clusters to be highly reactive toward molecular nitrogen and hence are prospective materials for its activation at low temperatures. Calculations on silicon and phosphorus doped aluminum clusters with 5-8 atoms demonstrate an enhanced N-2 activation with respect to their pristine ground state and high energy counterparts. This increased efficiency of N-2 activation by doped ground state Al clusters is corroborated by an increment of the N N bond length, a red shift in N N bond stretching frequency, and adsorption energy (E-ad). Ab initio molecular-dynamics simulations demonstrate consequential efficiency of doped clusters toward dinitrogen activation at finite temperature. The ability of doped clusters toward activation of molecular nitrogen is site and shape sensitive. In short, this theoretical study highlights the critical role of doping foreign impurities for future endeavors in the design of cost-effective and efficient catalysts for N-2 activation at ambient temperatures. This observation may spur further studies in the field of aluminum nanocatalysis by doping silicon and phosphorus atom in aluminum clusters.</p>1 aDas, Susanta1 aPal, Sourav1 aKrishnamurty, Sailaja  uhttps://library.ncl.res.in/content/dinitrogen-activation-silicon-and-phosphorus-doped-aluminum-clusters-001942nas a2200169   4500008004100000022001400041245006400055210006300119260011000182300001600292490000600308520131200314100002201626700001701648700001601665856009101681       2015                        eng d  a2040-336400aOxidative addition of the C-I bond on aluminum nanoclusters0 aOxidative addition of the CI bond on aluminum nanoclusters  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcJUN  a12109-121250 v73 a<p>Energetics and the in-depth reaction mechanism of the oxidative addition step of the cross-coupling reaction are studied in the framework of density functional theory (DFT) on aluminum nanoclusters. Aluminum metal in its bulk state is totally inactive towards carbon-halogen bond dissociation but selected Al nanoclusters (size ranging from 3 to 20 atoms) have shown a significantly lower activation barrier towards the oxidative addition reaction. The calculated energy barriers are lower than the gold clusters and within a comparable range with the conventional and most versatile Pd catalyst. Further investigations reveal that the activation energies and other reaction parameters are highly sensitive to the geometrical shapes and electronic structures of the clusters rather than their size, imposing the fact that comprehensive studies on aluminum clusters can be beneficial for nanoscience and nanotechnology. To understand the possible reaction mechanism in detail, the reaction pathway is investigated with the ab initio Born Oppenheimer Molecular Dynamics (BOMD) simulation and the Natural Bond Orbital (NBO) analysis. In short, our theoretical study highlights the thermodynamic and kinetic details of C-I bond dissociation on aluminum clusters for future endeavors in cluster chemistry.</p>1 aSengupta, Turbasu1 aDas, Susanta1 aPal, Sourav  uhttps://library.ncl.res.in/content/oxidative-addition-c-i-bond-aluminum-nanoclusters-004280nas a2200277   4500008004100000022001400041245018000055210006900235260007100304300001400375490000700389520321000396100002303606700003103629700001803660700001903678700002303697700001703720700002003737700001703757700001703774700003503791700002603826700002403852856012603876       2016                        eng d  a1528-748300aAdditive mediated syn-anti conformational tuning at nucleation to capture elusive polymorphs: remarkable role of extended pi-stacking interactions in driving the self-assembly0 aAdditive mediated synanti conformational tuning at nucleation to  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAPR  a2416-24280 v163 a<p>Understanding the process of prenucleation clustering at supersaturating stage is of significant importance to envisage the polymorphism in crystalline materials. Preferential formation of a thermodynamically stable crystal form suggests energetically favored patterns of interactions which control molecular aggregation during nucleation. Introduction of additives during crystallization is sometimes used as a suitable strategy to obtain metastable polymorphs in cases where it is not easy to capture the same by conventional crystallization methods. Comparative analysis of energy relationships and intermolecular interactions between thermodynamically stable and metastable crystal forms provides valuable clues about the nature of growth synthons at prenucleation clustering and preferential crystallization of the thermodynamic form. Conformationally flexible sulfonamide/sulfoester derivatives constituting electron rich and electron deficient aromatic rings were synthesized to study the interplay between pi-stacking and hydrogen bonding synthons. We have identified and characterized the thermodynamically stable and metastable elusive polymorphs of aromatic sulfonamides 1 and 2 and sulfoesters 3 and 4. However, these compounds eluded polymorphism during crystallisation from various common solvents/conditions and only produced thermodynamically stable crystals forms (form I crystals). Surprisingly, exploitation of pyrazinamide as an additive in different stoichiometric ratios during crystallization gave elusive polymorphs [three for 1 (form 1II, form 1III, and form 1IV) and one each for 2 (form 2II), 3 (form 3II), and 4 (form 4II)]. Molecules in stable crystal forms of these compounds are linked via extended chains of parallel displaced pi...pi stacking interactions that seem to play a vital role in driving the self-assembly of molecules and subsequently governing the nucleation process. In contrast, molecules in metastable polymorphs are devoid of such extended pi-stacking assemblies. Interestingly, differential scanning calorimetry, hot stage microscopy, and X-ray crystallographic studies confirmed the thermal crystal-to-crystal transition of all three metastable polymorphs of 1 (form 1II, form 1III, and form 1IV) to its thermodynamically stable crystal form (form 1I). Conformational analysis of molecule 1 using density functional theory calculations also validated higher stability for syn conformation (observed in Form 1I crystals) over anti and midway conformations (seen in metastable polymorphs). Melt crystallization of form 1I crystals of 1 on the larger face (001) of delta-pyrazinamide and lattice matching analysis (GRACE) revealed that the layered arrangement of molecules of delta-pyrazinamide (on 001 face) during heterogeneous nucleation acts as a template (heteroepitaxy) to provide a preferential site for the nucleation of new metastable polymorphs by selectively inhibiting the most preferred crystal form from growing into the nucleus. Solution state one- and two-dimensional (NOESY) H-1 NMR, scanning electron microscopy, and a Cambridge Structural Database survey were conducted to substantiate the role of additives during crystallization.</p>1 aGawade, Rupesh, L.1 aChakravarty, Debamitra, K.1 aKotmale, Amol1 aSangtani, Ekta1 aJoshi, Pranaya, V.1 aAhmed, Awais1 aMane, Manoj, V.1 aDas, Susanta1 aVanka, Kumar1 aRajamohanan, Pattuparambil, R.1 aPuranik, Vedavati, G.1 aGonnade, Rajesh, G.  uhttps://library.ncl.res.in/content/additive-mediated-syn-anti-conformational-tuning-nucleation-capture-elusive-polymorphs01519nas a2200181   4500008004100000022001400041245007600055210006900131260007100200300001400271490000800285520085200293100001701145700002201162700002701184700001601211856011001227       2016                        eng d  a1089-563900aElectron detachment and subsequent structural changes of water clusters0 aElectron detachment and subsequent structural changes of water c  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcFEB  a1065-10730 v1203 a<p>A cost-effective equation of motion coupled cluster method, EOMIP-CCSD(2), is used to investigate vertical and adiabatic ionization potential as well as ionization-induced structural changes of water clusters and compared with CCSD(T), CASPT2, and MP2 methods. The moderate N-5 scaling and low storage requirement yields EOMIP-CCSD (2) calculation feasible even for reasonably large molecules and clusters with accuracy comparable to CCSD(T) method at much cheaper computational cost. Our calculations shed light on the authenticity of EOMIP-CCSD(2) results and establish a reliable method to study of ionization energy of molecular clusters. We have further investigated the performance of several classes of DFT functionals for ionization energies of water clusters to benchmark the results and to get a reliable functionals for the same.</p>1 aDas, Susanta1 aSengupta, Turbasu1 aDutta, Achintya, Kumar1 aPal, Sourav  uhttps://library.ncl.res.in/content/electron-detachment-and-subsequent-structural-changes-water-clusters-001784nas a2200169   4500008004100000022001400041245006500055210006400120260007100184300001600255490000800271520118700279100002201466700001701488700001601505856009301521       2016                        eng d  a1932-744700aTransition metal doped aluminum clusters: an account of spin0 aTransition metal doped aluminum clusters an account of spin  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY  a10027-100400 v1203 a<p>The influence of spin on the properties of small sized transition metal doped aluminum clusters are investigated in the framework of density functional theory (DFT). Detailed analysis on minimum spin doped aluminum clusters has shown prominent indication of odd even oscillation in various calculated properties, supporting the presence of jellium shell structures within them. However, optimized high spin ground state counterparts, on the other hand, show rather smooth trends consistent with the properties of bulk materials. Resemblance to the bulk transition metals is further reflected in the gradual declining trends of heat of adsorption of CO2 molecule on cluster surface by sequentially changing the dopant atom from scandium to zinc. All the observations are also compared and found to be consistent with the earlier theoretical and experimental findings as obtained in the current literature. The similarities in the properties between atomic clusters and the bulk material is of utter importance and indeed precious considering the promising influence of the acquired information in understanding the process of evolution of nanoparticles from constituent atoms.</p>1 aSengupta, Turbasu1 aDas, Susanta1 aPal, Sourav  uhttps://library.ncl.res.in/content/transition-metal-doped-aluminum-clusters-account-spin