Chemical Physics Letters (v.659, #C)

Contents (iii-xvii).

Display OmittedBased on first-principles total energy calculations, we analyze the energetics of the fullerene isomers from C60 to C78, all of which satisfy the isolated pentagon rule, under a parallel electric field. Our calculations show that the total energy of the fullerene is proportional to the square of the external electric field. On the other hand, the coefficient of the quadratic energy profile is sensitive to the fullerene species and their orientation. Furthermore, fullerenes possessing lower symmetry exhibit asymmetric quadratic energy profiles with respect to the field, indicating that they possess intrinsic polarization along particular molecular orientations.
Keywords: Fullerene; Electric field; Spherical dielectric; Intrinsic polarization;

An in-silico walker by Qiran Xiao; Yanping Chen; Tristan Bereau; Yunfeng Shi (6-9).
Display OmittedThe paradox of biomimetic research is to perform bio-functionality, usually associated with sophisticated structures optimized by nature, with minimal structural complexity for the ease of fabrication. Here we show that a three-particle trimer can exhibit kinesin-like autonomous walk on a track via reactive molecular dynamics simulations. The autonomous motion is due to imbalanced transitions resulting from exothermic catalytic reactions, and the spatial asymmetry from the track. This molecular design can be realized by reproducing the particle–particle interactions in functionalized nano- or colloidal particles. Our results open up the possibility of fabricating bio-mimetic nano-systems in a minimalist approach.
Keywords: Nanomotor; Kinesin; Molecular dynamics; Biomimetic; Self-motile;

Polarizable multipolar electrostatics for cholesterol by Timothy L. Fletcher; Paul L.A. Popelier (10-15).
Display OmittedFFLUX is a novel force field under development for biomolecular modelling, and is based on topological atoms and the machine learning method kriging. Successful kriging models have been obtained for realistic electrostatics of amino acids, small peptides, and some carbohydrates but here, for the first time, we construct kriging models for a sizeable ligand of great importance, which is cholesterol. Cholesterol’s mean total (internal) electrostatic energy prediction error amounts to 3.9 kJ mol−1, which pleasingly falls below the threshold of 1 kcal mol−1 often cited for accurate biomolecular modelling. We present a detailed analysis of the error distributions.

Tip-enhanced Raman spectroscopy: From concepts to practical applications by Nan Jiang; Dmitry Kurouski; Eric A. Pozzi; Naihao Chiang; Mark C. Hersam; Richard P. Van Duyne (16-24).
Display OmittedTip-enhanced Raman spectroscopy (TERS) is a powerful technique that integrates the vibrational fingerprinting of Raman spectroscopy and the sub-nanometer resolution of scanning probe microscopy (SPM). As a result, TERS is capable of obtaining chemical maps of analyzed specimens with exceptional lateral resolution. This is extremely valuable for the study of interactions between molecules and substrates, in addition to structural characterization of biological objects, such as viruses and amyloid fibrils, 2D polymeric materials, and monitoring electrochemical and photo-catalytic processes. In this mini-review, we discuss the most significant advances of TERS, including: super high resolution chemical imaging, monitoring of catalytic processes, incorporation of pulsed-excitation techniques, single-site electrochemistry, biosensing, and art conservation. We begin with a short overview of TERS, comparing it with other surface analytical techniques, followed by an overview of recent developments and future applications in TERS.

Display OmittedUsing the expansion in the eigenmodes of 1-D Lienard-Wiechert kernel, the temporal and spectral profiles of the radiation emitted by a fully inverted collection of two-level atoms in a sub-wavelength slab geometry are computed. The initial number of amplifying modes determine the specific regime of radiation. In particular, the temporal profile of the field intensity is oscillatory and the spectral profile is non-Lorentzian with two unequal height peaks in a narrow band centered at the slab thickness value at which the real parts of the lowest order odd and even eigenvalues are equal.
Keywords: Oscillating temporal shape; Non-Lorentzian spectral shape; Cooperative Lamb Shift; Eigenfunctions of 1D Lienard-Wiechert kernel;

Theoretical study of aromatic-antiaromatic pairs as material in organic solar cells of double light harvesting by Iván Martinez; Eduardo Schott; Ivonne Chávez; Juan Manuel Manríquez; Ximena Zarate (31-35).
Display OmittedMolecular light harvesting components of organic solar cells containing antiaromatic and aromatic molecules as organic semiconductors were studied. We found that antiaromatic molecules with indacene core can act as acceptors looking for new options to assemble donor/acceptor interfaces. This is supported by their properties such as molecular orbitals energies, rigid fused core that could promote π-π intermolecular interactions imparting ordered nanostructures, that let high charge mobility thanks to their properly low reorganization energy and the optimum energy offsets of the donor/acceptor interfaces. It was found that pentacene might be an excellent donor and the benzo[g]benz[6,7]indeno[1,2-b]fluorene could act as an acceptor.
Keywords: Organic solar cells; DFT; Indacene; Reorganization energy;

The Al(I) molecule, Ph2COAl and its anion by Xinxing Zhang; Bryan Eichhorn; Hansgeorg Schnöckel; Kit Bowen (36-39).
Display OmittedWe have formed the Al(I)-containing molecule, benzophenone-aluminum, i.e., Ph2COAl, and studied it by conducting density functional theory calculations on both its neutral and anionic forms and by measuring the photoelectron spectrum of its anion. Our calculations identified two nearly iso-energetic anion isomers, (Ph2COAl), the vertical detachment energies (VDE) of which are in excellent agreement with our photoelectron spectrum. Natural population analysis (NPA) of Ph2COAl found the Al moiety to be positively charged by +0.81 e, indicating a strongly ionic bond between Al and Ph2CO, i.e., Ph2COAl+.
Keywords: Photodetachment; Negative ions; Low oxidation state;

Display OmittedIn addition to the well-established Arrhenius-type temperature-dependence of the specific and molar conductivities of molten salts, it turns out that they also depend linearly on the molar volumes, in analogy with the behavior of their fluidities. Similar values of the molar volumes representing the immobilization of the ions result from both kinds of flow phenomena. However, the activation energy for the fluidity is some five times larger than for the conductivity.

Nonplanar structure of C6H5SCF3 facilitates πσ-mediated photodissociation reaction on the S1 state by So-Yeon Kim; Jeongmook Lee; Sang Kyu Kim; Young S. Choi (43-47).
Display OmittedVibrational structure of trifluoromethylthiobenzene (C6H5SCF3) on the S1 state has been investigated by resonance-enhanced two-photon ionization spectroscopy and nature of predissociation dynamics is inferred from homogeneously broadened spectral features. As C6H5SCF3 adopts a nonplanar structure in both the S0 and S1 states, the effective adiabatic barrier generated by avoided crossing of optically-bright bound S1 (ππ) and dark-repulsive S2 (πσ) surfaces along the reaction coordinate is significantly lowered, giving the S1 lifetime of ∼300 fs. This experiment demonstrates that the molecular structure spanned by the reactive flux near the curve-crossing region dictates reaction rate as well as nonadiabatic transition probability.
Keywords: Nonadiabatic transition; Conical intersection; Predissociation;

Display OmittedThe solutes dideuterium, 1,3,5-trichlorobenzene and p-dichlorobenzene (pdcb) are co-dissolved in a 61/39 wt% mixture of CBC9CB/5CB, a bimesogenic liquid crystal with two nematic phases. NMR spectra are collected for each solute. The local electric field gradient ( F ZZ ) is obtained from the dideuterium spectrum. A double Maier-Saupe potential (MSMS) is used to rationalize the order parameters of pdcb. The liquid-crystal fields G 1 and G 2 are taken to be due to size and shape interactions and interactions between the solute molecular quadrupole and the mean F ZZ of the medium. The F ZZ ’s obtained from D2 and G 2 (from pdcb) are compared and discussed.

Display OmittedWe report on gas phase UV action spectroscopy and photodynamics of [Ag3(1MT-H/1MU-H)2]+ comprised of a linear silver string and two deprotonated 1-methyl-thymine/uracil (1MT/1MU) ligands. We applied pump–probe femtosecond laser photofragmentation in an electrospray ion trap mass spectrometer and high-level ab initio calculations at the level of approximate coupled-cluster singles-doubles theory. The experimental UV band at 283/275 nm is assigned to a red shifted 1ππ nucleobase located transition. Relaxation of the 1ππ state occurs with time constants of 0.2/1.1 ps and 0.2/4.2 ps for the 1MT and 1MU complexes, respectively, on a similar ultrafast time scale as non-metalated uracil derivatives.
Keywords: Metal-base pairs (MBP); Silver trimer; UV action spectroscopy; Time-resolved spectroscopy; Pump-probe photofragmentation; CC2;

Display OmittedNanohole graphene oxide (NHGO) was obtained in a homogeneous aqueous mixture of graphene oxide (GO) and H2O2 at 120 °C. Supercapacitors were fabricated as the electrode material by using NHGO. A specific capacitance of 240.1 F g−1 was obtained at a current density of 1 A g−1 in 6 m KOH electrolyte and specific capacitance remained 193.6 F g−1 at the current density of 20 A g−1. This was attributed to reducing the inner space between the double-layers, enhanced ion diffusion and large specific surface area. Supercapacitor prepared with NHGO electrodes also exhibited an excellent cycle stability.
Keywords: Graphene oxide; Holey; Hydrothermal process; Supercapacitors; Microstructure;

CdS loaded on coal based activated carbon nanofibers with enhanced photocatalytic property by Jixi Guo; Mingxi Guo; Dianzeng Jia; Xianli Song; Fenglian Tong (66-69).
The coal based activity carbon nanofibers (CBACFs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and acid treated coal. Cadmium sulfide (CdS) nanoparticles loaded on CBACFs were fabricated by solvothermal method. The CdS/CBACFs nanocomposites exhibited outstanding photocatalytic activity.Display OmittedThe coal based activated carbon nanofibers (CBACFs) were prepared by electrospinning a mixture of polyacrylonitrile (PAN) and acid treated coal. Cadmium sulfide (CdS) nanoparticles loaded on CBACFs were fabricated by solvothermal method. The obtained samples were characterized by FESEM, TEM, and XRD. The results reveal that the CdS nanoparticles are homogeneously dispersed on the surfaces of CBACFs. The CdS/CBACFs nanocomposites exhibited higher photoactivity for photodegradation of methyl blue (MB) under visible light irradiation than pure CdS nanoparticles. CBACFs can be used as low cost support materials for the preparation of nanocomposites with high photocatalytic activity.
Keywords: Coal based activated carbon nanofibers; CdS; Visible light photocatalyst;

Temperature dependent product yields for the spin forbidden singlet channel of the C(3P) + C2H2 reaction by Kevin M. Hickson; Jean-Christophe Loison; Valentine Wakelam (70-75).
Display OmittedThe atomic hydrogen formation channels of the C + C2H2 reaction have been investigated using a continuous supersonic flow reactor over the 52–296 K temperature range. H-atoms were detected directly at 121.567 nm by vacuum ultraviolet laser induced fluorescence. Absolute H-atom yields were determined by comparison with the H-atom signal generated by the C + C2H4 reaction. The product yields agree with earlier crossed beam experiments employing universal detection methods. Incorporating these branching ratios in a gas-grain model of dense interstellar clouds increases the c-C3H abundance. This reaction is a minor source of C3-containing molecules in the present simulations.

Second hyperpolarizability of the calcium-doped lithium salt of pyridazine Li–H3C4N2 ⋯ Ca by Suélio Marques; Marcos A. Castro; Salviano A. Leão; Tertius L. Fonseca (76-79).
Display OmittedIn this work we report results of coupled cluster calculations for the second hyperpolarizability of the calcium-doped lithium salt of pyridazine (Li–H3C4N2 ⋯ Ca) molecule. In the static limit an unusual value of 4.34 × 10 6  au was obtained at the CCSD level of calculation. Results obtained for the dc-Kerr effect through SCF, CCS and CCSD methods show that γ ( - ω ; ω , 0 , 0 ) is strongly dependent of the electron correlation treatment. Dynamic results obtained at the CCSD level are also reported for the IDRI, dc-SHG and THG nonlinear optical processes.
Keywords: Electrides; Second hyperpolarizability; Lithium salt of pyridazine;

Display OmittedWe propose a simple and accurate model for state-specific dissociation rate coefficients based on the widely used Treanor–Marrone model. It takes into account the dependence of its parameter on temperature and vibrational level and can be used with arbitrary vibrational ladder. The model is validated by comparisons with state-specific dissociation rate coefficients of O2 and N2 obtained using molecular dynamics, and its good accuracy is demonstrated. Non-equilibrium kinetics of O2/O and N2/N mixtures under heat bath conditions is studied; applying the optimized Treanor–Marrone model leads to more efficient dissociation and vibrational relaxation.

Display OmittedCarbon-coated Li2.7Ti2(PO4)3, a new mixed-valence titanium(III/IV) phosphate, is synthesized by the microwave-assisted sol-gel method using citric acid as both a chelating reagent and carbon source for the cathode material in lithium-ion batteries. The contents of Li, Ti and P are analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) and ion chromatography (IC). The microstructure, composition, and electrochemical performance of Li2.7Ti2(PO4)3/C samples are characterized by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope (SEM) and cyclic voltammetry (CV). The Li2.7Ti2(PO4)3/C sample exhibits a high initial discharge capacity of 123.6 mA h g−1 at 0.1C and outstanding cycling ability.
Keywords: Nonstoichiometric composition; Li2.7Ti2(PO4)3/C; Cathode materials; Microwave-assisted synthesis; Electrochemical properties;

Modification of alkali metals on silicon-based nanoclusters: An enhanced nonlinear optical response by Xiaojun Li; Quan Han; Xiaohui Yang; Ruijuan Song; Limei Song (93-99).
Display OmittedStructures, chemical stabilities and nonlinear optical properties of alkali metals-adsorbed niobium-doped silicon (M@Si n Nb+) clusters are investigated using the DFT methods. The alkali metals prefer energetically to be attached as bridged bond rather than M–Si single bond in most of optimized structures. Adsorption of alkali metals on doped silicon clusters gradually enhances their chemical stabilities with increasing cluster size. Noteworthily, the first hyperpolarizabilities (β tot) of the M@Si n Nb+ clusters, obtained by using the long-range corrected CAM-B3LYP functional, are large enough to establish their strong nonlinear optical behavior, especially for M@Si9Nb+ (M = Li, Na, and K), and the enhanced β tot ordering by alkali metals is Na > K > Li.

To bridge or not to bridge: The role of sulfuric acid in the Beckmann rearrangement by Chester R. Lin; Li-Juan Yu; Shuhua Li; Amir Karton (100-104).
Display OmittedBased on ab initio calculations using the Gaussian-4 method, we propose a new catalytic mechanism for the Beckmann rearrangement in concentrated H2SO4. Our calculations suggest that H2SO4 catalyzes the 1,2-proton-shift step via a cyclic transition structure, in which H2SO4 acts as a proton-transfer bridge. The reaction barrier for this mechanism is lower by 48.1 kJ mol−1 than the barrier for the previously suggested catalytic mechanism, which involves a strained 3-memberd-ring transition structure. According to the previous mechanism the 1,2-proton shift has the highest activation energy, while in the revised mechanism the highest activation energy is obtained for the ensuing rearrangement/dehydration step.
Keywords: Beckmann rearrangement; H2SO4 catalyst; CCSD(T); G4 theory;

Pseudocapacitive behavior of unidirectional CdS nanoforest in 3D architecture through solution chemistry by Nikila Nair; Sutripto Majumder; Babasaheb R. Sankapal (105-111).
CdS-C/CdS-P has been synthesized on stainless steel (SS) current collector by a facile solution method at a low temperature (300 K) which attains a specific capacitance of 181 F/g at a scan rate of 5 mV/s.Display OmittedTwo step soft chemical route has been utilized for the fabrication of CdS nanowire electrode in 3D architecture at room temperature (300 K). The electrochemical pseudocapacitive behavior of thin film consisting of CdS nanowires has been evaluated by using cyclic voltammetry, charge-discharge and electrochemical impedance spectroscopy in an aqueous media. The electrochemical test revealed that CdS nanowire attained a specific capacitance of 181 F/g at a scan rate of 5 mV/s. An energy density of 1.72 Wh/kg and power density of 27.14 W/kg has been achieved at 89 mA/g current density in 1 M Na2SO3 solution.

Highly vibrationally excited CO generated in a low-temperature chemical reaction between carbon vapor and molecular oxygen by E. Jans; K. Frederickson; M. Yurkovich; B. Musci; J.W. Rich; I.V. Adamovich (112-116).
Display OmittedA chemical flow reactor is used to study the vibrational population distribution of CO produced by a reaction between carbon vapor generated in an arc discharge and molecular oxygen. The results demonstrate formation of highly vibrationally excited CO, up to vibrational level v = 14, at low temperatures, T = 400–450 K, with population inversion at v = 4–7, in a collision-dominated environment, 15–20 Torr. The average vibrational energy per CO molecule formed by the reaction is 0.6–1.2 eV/molecule, which corresponds to 10–20% of reaction enthalpy. The results show feasibility of development of a new CO chemical laser using carbon vapor and oxygen as reactants.

Display OmittedThe spectrum of guanidinium acetate in aqueous solution has been recorded by attenuated total reflectance infrared spectroscopy (ATR-IR). Assignments of the bands have been done using the polarizable continuum model (PCM). Three IR intensive bands at 1670, 1550, and 1410 cm−1 are associated with stretching and bending vibrations of the groups forming a ring of six heavy atoms of the bidentate configuration of guanidinium acetate. The relatively weak broad band near 2200 cm−1 is tentatively assigned to the stretching vibration of the N―H⋯O fragment of the hydrogen-bonded ion pairs.
Keywords: Contact ion pair; Intermolecular hydrogen bonds; DFT computations; Polarizable continuum model; Classical MD simulations;

Possible size control and emission characteristics of Eu3+–doped Y2O3 nanoparticles synthesized by surfactant-assembly by Yukihiko Akita; Takashi Harada; Ryo Sasai; Koji Tomita; Katsura Nishiyama (121-125).
Display OmittedYttrium oxide nanoparticles doped with 2.0 wt% Eu (Eu@Y2O3) were synthesized via the surfactant-assembly method. The average diameter of Eu@Y2O3 (d av) depends on the alkyl chain number (N) of the sodium alkyl sulfates employed as surfactants. Using surfactants with N  = 8, 10, and 12, Eu@Y2O3 with d av  = 35, 200, and 500 nm, respectively were obtained. Such changes in d av are ascribed to the difference in the micelle aggregation numbers, supporting the use of rare-earth ions in the assembly. The Eu@Y2O3 particles synthesized presently emitted through Eu3+ transitions under UV excitation of Y2O3, making them applicable to nanoemitters.
Keywords: Nanoparticles; Rare-earth emission; Micelle template; Nanoemitters;

Display OmittedQuantum chemistry ab initio MP2 and CCSD calculations were performed to investigate the P⋯S hemi bonds and noncovalent interactions in the radical cational systems (H3P:SH2)+, (FH2P:SH2)+ and (H3P:SHF)+. The hydride dimer (H3P:SH2)+ has a P⋯S hemi bonding structure and a H-bonding structure, (FH2P:SH2)+ has two hemi bonding structures and a proton-transferred H-bonding structure, (H3P:SHF)+ has two hemi bonding structures and three noncovalent structures. It is remarkable that these hemi bonds also have characters of pnicogen and chalcogen bonds. The binding energy, stability and bonding nature of the hemi bonds were presented.
Keywords: Hemi bonds; Pnicogen/chalcogen bond; Radical cational dimmer;

Display OmittedAt high temperatures the structural relaxation time in liquids has Arrhenius temperature dependence. At lowering temperature, temperature dependence changes to a super Arrhenius at some temperature TA . This temperature is an important point for the structural relaxation dynamics in supercooled liquids because it reflects the transition to collective relaxation. Here we derive a relation between TA , the glass transition temperature Tg and fragility. We show that the ratio Tg/TA increases with increasing fragility of a liquid. The derived relation is in agreement with the experimental data in a series of molecular, hydrogen bonding and two inorganic glass-formers.

Spatially resolved micro-photoluminescence imaging of porphyrin single crystals by Dawn M. Marin; Jose Castaneda; Meesha Kaushal; Ghallia Kaouk; Daniel S. Jones; Michael G. Walter (137-141).
Display OmittedWe describe the collection of both time-resolved and steady-state micro-photoluminescence data from solution-grown single crystals of 5,15-bis(4-carbomethoxyphenyl)porphyrin (BCM2PP). Linking molecular orientation and structure with excited-state dynamics is crucial for engineering efficient organic solar cells, light-emitting diodes, and related molecular electronics. Photoluminescence features of single porphyrin crystals were imaged using a laser scanning confocal microscope equipped with time-correlated single photon counting (TCSPC). We show enhanced exciton lifetimes (τ s1  = 2.6 ns) and stronger steady-state emission in crystalline BCM2PP samples relative to semicrystalline thin films (τ s1  = 1.8 ns).

Photoelectron spectroscopy of nitromethane anion clusters by Carrie Jo M. Pruitt; Rachael M. Albury; Daniel J. Goebbert (142-147).
Display OmittedNitromethane anion and nitromethane dimer, trimer, and hydrated cluster anions were studied by photoelectron spectroscopy. Vertical detachment energies, estimated electron affinities, and solvation energies were obtained from the photoelectron spectra. Cluster structures were investigated using theoretical calculations. Predicted detachment energies agreed with experiment. Calculations show water binds to nitromethane anion through two hydrogen bonds. The dimer has a non-linear structure with a single ionic C―H⋯O hydrogen bond. The trimer has two different solvent interactions, but both involve the weak C―H⋯O hydrogen bond.
Keywords: Photoelectron imaging; Photoelectron spectroscopy; Weak hydrogen bonds; Nitromethane clusters; Nitromethane anions; Ion solvation;

Fluorination-control of electronic and magnetic properties in GeC-hybrid by L.B. Drissi; F.Z. Ramadan; N.B-.J. Kanga (148-153).
Display OmittedThis study reports the effect of fluorination on germanene-graphene hybrid within DFT. Stability, structural, electronic and magnetic properties of full-fluorinated F-GeC-F and two semi-fluorinated F-GeC and GeC-F configurations are discussed. Calculations reveal that fluorination is an exothermic adsorption leading to stable structures. Moreover, it is shown that controlling the adsorbed atoms modulates the properties. It is found that chemical modification with F-atoms increase the gap and induce magnetism in F-GeC, however it reduces the gap in non-magnetic F-GeC-F and in ferromagnetic GeC-F. The findings of this work open a spectrum of possible new GeC-based nanodevices with controlled and tuned properties.
Keywords: GeC sheet; Ab initio calculations; Electronic properties; Stability analysis; Magnetic properties;

Display OmittedExciton annihilation in dye-sensitized nanocrystalline semiconductor (Al2O3) films has been studied through laser-induced fluorescence spectroscopy. The relative quantum yield of the fluorescence decreases with increasing excitation light intensity, the indication being that exciton annihilation occurred. The rate constants of the annihilation were estimated for three dyes, N719, D149, and MK2, that are known to be sensitizing dyes for efficient dye-sensitized solar cells. The hopping time between dye molecules and the diffusion length of excitons within their lifetime were also estimated to facilitate discussion of the relevance of exciton annihilation to primary processes in dye-sensitized solar cells.

Display OmittedThe effect of surfactants on the synthesis of shape-controlled palladium (Pd) nanocrystals was studied using computational simulation methods. We found that the functional groups in surfactant molecules played an important role in the specific adsorption on Pd surfaces. Citric acid and ascorbic acid were found to be preferentially adsorbed onto Pd(1 1 1) and (1 0 0) planes resulting in the formation of octahedral and cubic nanocrystals, respectively.
Keywords: Shape-control; Palladium nanocrystal; Molecular dynamics; Density functional theory;

Display OmittedSalt-induced change in the structure of water molecules inside multi-lamellar vesicles is experimentally studied with terahertz time-domain spectroscopy. The complex dielectric constant of 1, 2-ditetradecanoyl-sn-glycero-3-phosphocholine model membranes dispersed in NaCl solution with different salt concentrations are measured. Structure of water molecules in the solution is characterized from the measured dielectric constant using Debye relaxation model. Combined with small-angle X-ray scattering observation, it is found that salt-induced change of water structure, especially fast water fraction, show strong correlation with the increase in nanometer-scale multi-lamellar repeat space. This suggests that water could be critical in nanometer-scale membrane-membrane communications.
Keywords: Hydrogen bond network; NaCl; Small-angle X-ray scattering; Terahertz spectroscopy; Water molecules;

Proton transfer pathways in an aspartate-water cluster sampled by a network of discrete states by Marco Reidelbach; Fridtjof Betz; Raquel Maya Mäusle; Petra Imhof (169-175).
Display OmittedProton transfer reactions are complex transitions due to the size and flexibility of the hydrogen-bonded networks along which the protons may “hop”. The combination of molecular dynamics based sampling of water positions and orientations with direct sampling of proton positions is an efficient way to capture the interplay of these degrees of freedom in a transition network. The energetically most favourable pathway in the proton transfer network computed for an aspartate-water cluster shows the pre-orientation of water molecules and aspartate side chains to be a pre-requisite for the subsequent concerted proton transfer to the product state.
Keywords: Proton transfer; Discretisation; Transition network; Sampling; Reaction pathways;

Display OmittedThe unprecedentedly undissociated HCl hydrates, and unconventional cis-linear conformation of the water dimer at ambient condition were found in a novel organic crystal by direct crystallographic evidences. The peculiar tricyclo[6.2.0.0]-type configuration of hydrogen-bonding network induces such unexpected undissociated HCl hydrates, and unusual cis-linear conformation of the water dimer.
Keywords: Organic crystal; Crystallography; Hydrogen-bonding network; Undissociated HCl hydrate; Cis-linear conformation of the water dimer;

The calculated fast and slow electronic signals and their comparison with experimental results.Display OmittedIn this letter we present the extended usage of short-time Chebyshev wave packet method in the laser induced molecular photoionization dynamics. In our extension, the polynomial expansion of the exponential in the time evolution operator, the Hamiltonian operator can act on the wave packet directly which neatly avoids the matrix diagonalization. This propagation scheme is of obvious advantages when the dynamical system has large Hamiltonian matrix. Computational simulations are performed for the calculation of photoelectronic distributions from intense short pulse ionization of K2 and NaI which represent the Born–Oppenheimer (BO) model and Non-BO one, respectively.
Keywords: Time-dependent wave packet; Photoionization; Chebyshev polynomials;

Synthesis, crystal structure and EPR studies of vanadyl doped [Co(2-nbH)2(ina)2(H2O)] complex by Esat Bozkurt; Yunus Çelik; Fatma Çöpür; Necmi Dege; Yıldıray Topcu; Bünyamin Karabulut (186-191).
The unit cell of cobalt(II) complex showing the octahedrons around metal ion.Display OmittedA novel aquabis(isonicotinamide-κN1)bis(2-nitrobenzoato-κ2O,O′;κO)cobalt(II), (hereafter [Co(2-nbH)2(ina)2(H2O)]; 2-nbH: 2-nitrobenzoic acid; ina: isonicotinamide), complex was synthesized and characterized by using various techniques. The crystal structure was determined by X-ray diffraction (XRD) method. The magnetic properties of VO2+ doped [Co(2-nbH)2(ina)2(H2O)] complex were obtained by electron paramagnetic resonance (EPR) technique. The angular variation of EPR spectra shows that two different VO2+ complexes are present in the lattice. The FT-IR spectra of this compound were discussed in relation to other compounds containing 2-nitrobenzoato or isonicotinamide ligands. Thermal stability and reactivity of this complex were also studied by thermal analysis methods (TG/DTG/DTA).
Keywords: XRD; EPR; FT-IR; TG/DTG/DTA; Vanadyl ion; Isonicotinamide; 2-Nitrobenzoic acid;

Display OmittedHeavy Rydberg behaviour in the B Σ u + 1 and B ″ B ‾ Σ u + 1 ion-pair states of H2 and the B Σ u + 1 state of D2, is analysed in terms of the absolute quantum defects of the vibronic levels. The influence of the inner repulsive wall of ion-pair potentials on heavy Rydberg behaviour is considered and shown to determine the size of both absolute quantum defects and their energy dependence.

Single-electron aerogen bonds: Do they exist? by Mehdi D. Esrafili; Fariba Mohammadian-Sabet; Mohammad Solimannejad (196-202).
Display OmittedA novel type of σ-hole interaction is characterized between some noble gas containing molecules (KrOF2, KrO3, XeOF2 and XeO3) and methyl (CH3) or ethyl (C2H5) radical by means of ab initio calculations. This interaction is named as single-electron aerogen bond (SEAB), in view of the concepts of aerogen bond and single-electron bond interactions. The properties of SEABs are studied by molecular electrostatic potential, quantum theory of atom in molecules, natural bonding orbital and noncovalent interaction index analyses. The formation of an O⋯H interaction tends to increase the strength of the SEAB, when they coexist in a ternary complex.
Keywords: Molecular electrostatic potential; Ab initio; QTAIM; NBO; Cooperativity;

Display OmittedIn this letter, we introduce new definitions of energy and temperature based on the information theory model, and we show that our definition of informational energy is related to the kinetic energy of the Thomas-Fermi model, meanwhile the definition of informational temperature proposed, permit identify ‘hot’ and ‘cold’ zones of an atom, such zones are related to the changes in the local electron energy wherein the chemical and physical changes can occur; informational temperature also can reproduce the shell structure of an atom.
Keywords: Informational energy; Informational temperature; Information theory;

Line shape in a free-jet hypersonic expansion investigated by cavity ring-down spectroscopy and computational fluid dynamics by Nicolas Suas-David; Vinayak Kulkarni; Abdessamad Benidar; Samir Kassi; Robert Georges (209-215).
Display OmittedExperiments are carried out for spectroscopic studies using hypersonic jet of carbon monoxide seeded in argon as a carrier gas. Probing of this jet using cavity ring-down spectroscopy revealed a double peak structure for various absorption lines. Flow field simulation using computational fluid dynamics is used to understand the shape of such lines integrated over line of sight. Absorption contribution from warmer non-isentropic part of the jet, owing to its transverse velocity variation, is found responsible for those line shapes.

Variation of adsorption energy (E ads ) of C2X (X = K-Br)―CO interaction at different computational levels within density functional theory (DFT).Display OmittedIn this work, we present our calculations, based on density functional theory (DFT) to explore chemical reactivity of C2X (X = K-Br) towards CO molecule. Computed condensed Fukui function ( f - ) reveals the carbon atom of C2X (X = K-Br) to be the most active site for the CO interaction. This fact is also confirmed by the comparatively lesser average local ionization energy ( I ( r ) ¯ ) for the active carbon atom. Bader’s topological parameters such as electron density ρ  > 0.30 a.u. with negative ∇ 2 ρ and H BCP (total energy density) at the bond BCP of the carbon atoms of both C2X (X = K-Br) and CO infers the CO interaction in all the cases to be of shared-kind.
Keywords: Main-row group dicarbides; Regioselectivity; Density functional theory; Fukui function; QTAIM;

Effect of F/O atomic ratio on photocatalytic activity of BixOyFz by Wenhao Gu; Guoliang Zhang; Fei Teng; Yiran Teng; Zhengyang Zhao; Wenzheng Fan (221-224).
The photocatalytic activity of BixOyFz is mainly controlled by the internal electric field (IEF) that varies with F/O ratio.Display OmittedWe have, for the first time, prepared BiO0.9F2.35 as a new photocatalyst by a simple hydrothermal method. It is found that at different ratios of fluorine to oxygen (F/O), the BixOyFz samples have the varied internal electric field (IEF) and electrical conductivities, thus showing different photochemistry properties for the degradation of RhB. The bulk IEF and conductivity can be conveniently controlled by the F/O ratio, thus improving the photochemistry properties of layered BixOyFz. This study provides a new strategy to develop efficient photocatalysts.
Keywords: Crystal structure; Semiconductors; F/O ratio; Internal electric field (IEF); Electrical conductivity;

PEG functionalized luminescent lipid particles for cellular imaging by Suman Rana; K.C. Barick; Neena G. Shetake; Gunjan Verma; V.K. Aswal; Lata Panicker; B.N. Pandey; P.A. Hassan (225-229).
Display OmittedWe report here the synthesis, characterization and cellular uptake of luminescent micelle-like particles with phospholipid core and non-ionic PEG based surfactant polysorbate 80 shell. The adsorption of polysorbate 80 at the interface of lipid containing microemulsion droplets and its solidification upon removal of solvent leads to anchoring of PEG chain to the lipid particles. Hydrophobic partitioning of luminescent molecules, sodium 3-hydroxynaphthalene-2-carboxylic acid to the phospholipid core offers additional functionality to these particles. Thus, the cooperative assembly of lipid, non-ionic amphiphile and organic luminescent probe leads to the formation of multifunctional biocompatible particles which are useful for simultaneous imaging and therapy.
Keywords: Lipid particles; Functionalization; Luminescent; Cellular imaging;

First-principles study of intercalation of alkali ions in FeSe for solid-state batteries by Zhiqiang Jiang; Xiao Gu; Linxia Wang; Li Huang (230-233).
Electrochemical properties of alkali ions (Li+, Na+, and K+) intercalating into FeSe have been studied based on first-principles calculations within density functional theory. The intercalation sites of lithium ions are found to be different from sodium and potassium ions due to the small ionic radius of lithium. Calculations of minimum energy path on the diffusions of Li+, Na+, and K+ in FeSe show that the activation energies for those alkali ions increase with their ionic radii. Lithium ions have a rather smaller diffusion barrier of about 0.20 eV, which leads to a bigger diffusion coefficient of about 6.3 × 10 - 6 cm 2 / s . We also show that FeSe has a flat discharging stage at about 1.0 V with lithium ions. These results indicate that XFe2Se2 (X = Li, Na, K) may be potential electrochemical active materials, especially for solid-state electrolyte and supercapacitors.

Unexpected effect of substituents on the zero-field splitting of triplet phenyl nitrenes by Denis V. Korchagin; Alexander V. Akimov; Elena A. Yureva; Sergei M. Aldoshin; Eugenii Ya. Misochko (234-236).
Display OmittedThe EPR spectrum of triplet 2,4,6-tribromophenyl nitrene was obtained in glassy methylcyclohexane at 15 K. Surprisingly, the zero-field splitting parameter D  = 0.989 cm−1 derived from this spectrum is much lower than that reported previously for triplet 3,5-diazido-2,4,6-tribromophenyl nitrene and has the same value as in phenyl nitrenes composed with light atoms. DFT calculations of the zero-field splitting parameters support this unexpected experimental observation. Experimental and theoretical data provide evidence that the enhanced by bromine atoms spin-orbit contribution to the parameter D (the so called “heavy-atom effect”) is strongly modulated by other substituents attached to the aromatic cycle.
Keywords: High-spin molecules; Zero-field splitting; EPR spectroscopy; Heavy-atom effect; Nitrenes;

14-cycles in anthracene, phenanthrene, and pyrene.Display OmittedThe conjugated circuits model of aromaticity in benzenoids is reconsidered. Values for the parameters R1, R2, and R3 are rederived from experimental enthalpies of formation. It is shown that the value of R3 depends on the shape as well as the size of a 14-cycle. R3 values are found to obey the relation R3 pyrene  > R3 anthracene  > R3 phenanthrene.

The effect of stacking arrangement on the conjugation in azochromophores revealed by combination of Raman spectroscopy and DFT calculations by Olga D. Fominykh; Marina Yu. Balakina; Timur I. Burganov; Sergey A. Katsyuba (242-246).
Display OmittedConjugation in azochromophores DR, DO3, DR1, and their stacking dimers was studied to clarify physical factors underlying strong influence of stacking dimerization on first hyperpolarizability β of the chromophores revealed earlier. Raman spectroscopy and quantum-chemical computations were employed for this purpose. Characteristic features of Raman spectra of three different types of stacked dimers are revealed. It is shown that conjugation in the studied azochromophores is essentially deteriorated by stacking dimerization, while formation of shifted stacked dimers strengthens conjugation. These findings suggest conjugational origin of influence of the stacking pairing of the chromophores on first hyperpolarizability β.
Keywords: Raman spectroscopy; DFT calculations; Nonlinear-optical azochromophores; Stacking dimers; Non-covalent interactions; Conjugation;

Theoretical-computational characterization of the temperature-dependent folding thermodynamics of a β -hairpin peptide by Isabella Daidone; Laura Zanetti-Polzi; Lipi Thukral; Emal M. Alekozai; Andrea Amadei (247-251).
Display OmittedA theoretical-computational approach is presented to characterize the temperature-dependent thermodynamics of protein folding. Making use of the Quasi-Gaussian Entropy (QGE) theory and temperature exchanged molecular dynamics (TREMD) simulations, a complete picture of the folding thermodynamics can be obtained. The strategy is applied to analyze the folding thermodynamics of a β -hairpin peptide, Peptide 1, the folding process of which was experimentally characterized by means of infrared spectroscopy. The results provided by the approach here presented very well reproduce the experimental results, showing that the methodology can be successfully utilized to investigate the thermodynamics of folding processes in a wide temperature range.
Keywords: TREMD simulations; Protein folding; Thermodynamics; Folding enthalpy; Folding free energy; Quasi Gaussian entropy theory;

Display OmittedThe equilibrium and kinetic properties of protein aggregation systems in the presence of crowders are investigated using simple, illuminating models based on mass-action laws. Our model yields analytic results for equilibrium properties of protein aggregates, which fit experimental data of actin and ApoC-II with crowders reasonably well. When the effects of crowders on rate constants are considered, our kinetic model is in good agreement with experimental results for actin with dextran as the crowder. Furthermore, the model shows that as crowder volume fraction increases, the length distribution of fibrils becomes narrower and shifts to shorter values due to volume exclusion.

Display OmittedWe have calculated the exchange interaction J and the first hyperpolarizability β for photochromic diarylethenes (DAEs), 5,5′-diphenyl-di(3-thienyl)ethene 1, 5,5′-diphenyl-di(2-thienyl)ethene 2, 2,5-diphenyl-di(3-thienyl)ethene 3, and their corresponding oxidized derivatives. The switching direction of DAE 2 is found to be opposite from DAE 1. The switching direction of DAE 3 is opposite from DAE 1 for J, but not for β. For all molecules, the switching efficiency (SE) values of β are smaller than those of J. Oxidizing the sulfur atoms yields rather small variations on SEs of J and β. The non-trivial structure-property relationships for J and β are rationalized.

Display OmittedSimulated growth of four global-minimum Lennard-Jones clusters of sizes N  = 561, 823, 850 and 923, representing multishell icosahedra and decahedron, always leads to formation of regular polyicosahedral clusters. Observation of cluster structure evolution revealed that new atoms form anti-Mackay islands spreading over the cluster surface by making strong island-island junctions at cluster edges. Analysis of potential energies of atoms composing different local structures shows that energy-driven preference for decahedral arrangement of several atoms initiating the junction of pentagonal symmetry on the cluster surface is responsible for kinetic effect in the cluster growth.
Keywords: Lennard-Jones nanoparticles; Mackay icosahedra; Cluster growth from vapour; Polyicosahedral internal structure; Kinetic effects; Potential energy of selected-structure atoms;

Display OmittedWe report a qualitative difference in molecular band structures and frontier orbital nodal structures in DFT calculations using GGA vs. hybrid functionals and Hartree Fock in molecules used in electrochemical power sources. This can have a significant effect in applications sensitive to redox potentials and to orbital overlaps (excitations, electron transfer rates) but for which the use of hybrid functionals is impractical, such as solids or interfaces used in electrochemical energy conversion and storage technologies. We show that correct band structures and nodal structures (ordering) of frontier orbitals can be obtained by applying a Hubbard correction to selected atomic states.
Keywords: Redox potentials; Electron transfer; Density functional theory; Band structure; Generalized gradient approximation;

Dielectric properties of polyamide 12-chromium(III) oxide nanocomposites by Vjacheslav V. Zuev; Ekaterina S. Shapoval; Aleksandr S. Sakhatskii (277-281).
Display OmittedBroadband dielectric spectroscopy was employed to study polymer nanocomposites based on PA12 filled with of nanosized chromium(III) oxide. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. Three relaxation processes and Maxwell-Wagner-Sillars (MWS) interfacial polarizations were observed. It was found that presence of nanosized amphoteric chromium(III) oxide leads to softening of polyamide matrix that manifested in decrease of the activation energy of the α- and β-relaxation processes and glass transition temperatures. The softening of polymer matrix is the reason of the decrease of mechanical strength of polymer nanocomposites as compared with neat PA12.
Keywords: Nanocomposites; Polyamide 12; Chromium(III) oxide; Relaxation processes; Activation energy; Dielectric spectroscopy;

Display OmittedStructure, stability and electronic properties are evaluated computationally for small Ben (n = 5–9) cluster cages accommodating atomic H inside and forming core-shell species. These parameters are predicted to vary significantly upon insertion of H, for ionic derivatives, and with the system size. In particular, the energy barrier for H-atom exit from the cage changes significantly for ions compared to the neutral counterparts. The corresponding effects predicted for cage assemblies suggest the possibility of efficient charge-control of hydrogen release. This, together with a high capacity for storing hydrogen in extended such assemblies might indicate a possible way towards feasible hydrogen-storage solutions.

Display OmittedMercury emissions to the atmosphere primarily consist of Hg(0), which tends not to enter ecosystems until it is oxidized. Atomic bromine initiates oxidation of Hg(0) via the BrHg • intermediate, but the further reactions of BrHg • are just beginning to be explored. Here we use quantum chemistry to determine that hydrogen abstraction from hydrocarbons by BrHg • is so endothermic as to be irrelevant. Bonds between BrHg • and carbon atoms are so weak that BrHg • addition to carbon-carbon double bonds atoms will be somewhat ineffective in leading to further reactions.
Keywords: Atmospheric chemistry; Reactive gaseous mercury; Kinetics; Radicals;

Predicted PAR1 inhibitors from multiple computational methods by Ying Wang; Jinfeng Liu; Tong Zhu; Lujia Zhang; Xiao He; John Z.H. Zhang (295-303).
Display OmittedMultiple computational approaches are employed in order to find potentially strong binders of PAR1 from the two molecular databases: the Specs database containing more than 200,000 commercially available molecules and the traditional Chinese medicine (TCM) database. By combining the use of popular docking scoring functions together with detailed molecular dynamics simulation and protein-ligand free energy calculations, a total of fourteen molecules are found to be potentially strong binders of PAR1. The atomic details in protein-ligand interactions of these molecules with PAR1 are analyzed to help understand the binding mechanism which should be very useful in design of new drugs.

Rotational quenching of CS in ultracold 3He collisions by Rajwant Kaur; T.J. Dhilip Kumar (304-309).
Display OmittedQuantum mechanical scattering calculations of rotational quenching of CS (v  = 0) collision with 3He are performed at ultracold temperatures and results are compared with isotopic 4He collision. Rotational quenching cross sections and rate coefficients have been calculated in the ultracold region for rotational levels up to j  = 10 using the He–CS potential energy surface computed at the CCSD(T)/aug-cc-pVQZ level of theory. The quenching cross sections are found to be two orders of magnitude larger for the 3He than the 4He isotope under ultracold conditions. Wigner threshold law is found to be valid below 10−3  K temperature.
Keywords: Cross section; Rate coefficient; Resonances; Ultracold; van der Waals complex;

Corrigendum to “Remote catalyzation for growth of boron nitride nanotubes by low pressure chemical vapor deposition” [CPLETT 652 (2016) 27–31] by Liangjie Wang; Taotao Li; Lin Ling; Jie Luo; Kai Zhang; Yancui Xu; Huifen Lu; Yagang Yao (310).