Chemical Physics Letters (v.417, #4-6)
Editorial Board (CO2).
Isothermal–isobaric Monte Carlo simulations of liquid lithium using density functional theory by Lev D. Gelb; Theodore N. Carnahan (283-287).
We have performed Monte Carlo simulations of lithium at high temperatures in the isothermal–isobaric and canonical ensembles, using plane-wave density functional theory to provide configurational energies. This is made computationally feasible by the use of an ‘approximate’ empirical potential to generate large Monte Carlo moves with a high likelihood of acceptance. We discuss both simulation results and implementation details. Reasonable results are obtained at high temperatures, though all levels of theory considered systematically overestimate the liquid density.
Electrically triggered insertion of single-stranded DNA into single-walled carbon nanotubes by Takeru Okada; Toshiro Kaneko; Rikizo Hatakeyama; Kazuyuki Tohji (288-292).
The formation of DNA encapsulated carbon nanotubes, which are expected to modify electronic properties of carbon nanotubes, is for the first time demonstrated using a modified electrophoresis method. Radio-frequency and direct-current electric fields are applied to the DNA solution in order to stretch random-coil-shaped DNA and irradiate DNA to carbon nanotubes that are coated onto electrodes immersed in the DNA solution, respectively. Transmission electron microscopy and Raman scattering spectroscopy analyses reveal that DNA can be encapsulated into the carbon nanotubes. In this procedure, the key for the formation of DNA encapsulated carbon nanotubes is found to irradiate the stretched-shaped DNA to the carbon nanotubes.
Excited state enhancement of non-linear optical response in the push–pull imide and diimide chromophores by Shahar Keinan; Mark A. Ratner; Tobin J. Marks (293-296).
We suggest here a family of non-linear optical chromophores that have weak response in the ground state and a significantly enhanced response in the triplet state – hence a non-linear optical ‘switch’. Several promising molecules are proposed and their response mechanism, in which computation shows a significant enhancement of the first hyperpolarizability upon photoexcitation from the singlet to metastable triplet state, are investigated.
Optical limiting with soluble two-photon absorbing quadrupoles: Structure–property relationships by Marina Charlot; Nicolas Izard; Olivier Mongin; Didier Riehl; Mireille Blanchard-Desce (297-302).
The optical power limiting in the visible region of a series of two-photon absorbing quadrupoles built from conjugated backbones bearing electro-active peripheral groups was investigated. Nonlinear absorption experiments demonstrate that these molecules show marked nonlinear behaviour for short pulses (3 ns) in the ns regime. Structure–property relationships could be derived, emphasizing the role of the conjugated connectors and of the end-groups for improving the optical limiting efficiency. Push–push systems are more efficient than pull–pull systems, but at the expense of reduced transparency. Pyridine-N-oxides, terminal moieties which act in synergy as both donor and acceptor end-groups, lead to improved efficiency/transparency trade-off.
Theoretical study of the tandem cross-linkage lesion in DNA by Ru bo Zhang; Leif A. Eriksson (303-308).
The intramolecular radical cross-link reactions of 8,5′-cyclo-purines and 6,5′-cyclo-pyrimidines have been studied using the DFT B3LYP formalism with 6-31+G(d,p) and 6-311++G(d,p) basis sets, and including CPCM bulk solvation effects. In aqueous solution, the largest free energy barrier is 11.1 kcal/mol for dT • → 6,5′-cycloT • and the smallest 9.4 kcal/mol for dA • → 8,5′-cycloA • . Partial radical transfer occurs from the deoxyribose moiety to the connected base upon the formation of the transition structures. The unpaired spin density of the products is mainly localized on N7 in the 8,5′-cyclo-purines and on C5 in the 6,5′-cyclo-pyrimidines. The reaction free energies range from −4.3 kcal/mol (dC • → 6,5′-cycloC • ) to −9.7 kcal/mol (dG • → 8,5′-cycloG • ).
What role do oxonium ions and oxonium ylides play in the ZSM-5 catalysed methanol-to-olefin process? by D. Lesthaeghe; V. Van Speybroeck; G.B. Marin; M. Waroquier (309-315).
The adsorption properties and possible rearrangements of several proposed oxonium ylides and oxonium ions in protonated ZSM-5 are studied using the 2-layered ONIOM(B3LYP/6-31+g(d,p):HF/3-21g) approach. We show that both methyl oxonium methylide and dimethyl oxonium methylide are highly energetic species and unlikely to be intermediates in the formation of a carbon–carbon bond as the zeolite lattice does not offer supplementary stabilisation. The trimethyl oxonium and ethyldimethyl oxonium ions, however, are distinctly stabilised by the surrounding ZSM-5 framework, which does not impose steric constraints on further intermolecular reactions.
Ab initio MO and quasi-classical direct ab initio MD studies on the nitrogen inversion of trimethylamine by Masato Tanaka; Misako Aida (316-319).
A coupled motion of the skeletal inversion and methyl torsion in trimethylamine is investigated theoretically at various levels up to MP4(SDQ)/aug-cc-pVTZ. Among possible structures, the pyramidal C3v is the only minimum energy structure, and the planar Cs is the transition state structure of the nitrogen inversion. Our best estimate of the barrier height (without zero-point energy) is 3290 cm−1. The quasi-classical direct ab initio MD using HF/6-31G* starting from the pyramidal C3v structure indicates that the coupled methyl torsional motion is the primary factor for the nitrogen inversion of trimethylamine.
Explore water’s protective and assistant role for uracil: A changing role of water at different temperature by Xingbang Hu; Haoran Li; Wanchun Liang; Shijun Han (320-325).
The temperature effects on water’s protective and assistant role for uracil have been investigated at a wide range of temperature. It indicates that the water molecule assisting proton transfer at low temperature could prevent proton transfer at high temperature and the water molecule preventing proton transfer at low temperature could assist proton transfer at high temperature. Further research reveals that the proton transfer of uracil is governed by entropy change. Why the role of water molecule reverse at different temperature was explained. A relationship between strong/weak hydrogen bond and proton transfer could be suggested.
Bound state solutions of the Schrödinger equation for modified Kratzer’s molecular potential by Cüneyt Berkdemir; Ayşe Berkdemir; Jiaguang Han (326-329).
We present the arbitrary angular momentum solutions of the Schrödinger equation for a diatomic molecule with the modified Kratzer potential D e[(r − r e)/r]2. The bound state energy eigenvalues and the corresponding eigenfunctions are obtained by the use of the Nikiforov–Uvarov (NU) method which is related to the solutions in terms of Jacobi polynomials. The bound states are calculated for various values of ℓ with n ⩽ 5 and applied to several diatomic molecules. All of these calculations present an effective and methodological procedure under the NU method to investigate the Kratzer’s molecular systems.
The origin of the band at ∼1025 cm−1 in the SERS of pyridine adsorbed on silver by Maurizio Muniz-Miranda (330-333).
The employment of novel SERS-active colloidal substrates, constituted by Ag-doped silica nanoparticles, allows monitoring the occurrence of the central line at ∼1025 cm−1 between the two intense SERS bands of pyridine at 1008 and 1036 cm−1 during the photoreduction of silver ions with visible laser irradiation. The origin of this band, previously observed in pure Ag hydrosols and in electrochemical cell, is attributed to positively-charged silver clusters bound to the pyridine molecules. These species, stabilised by interaction with the silica surface, are disrupted by coadsorption of chloride anions onto the silver substrate, with the consequent disappearing of the central line.
The lowest quartet electronic states of MnC by Antonio Carlos Borin; João Paulo Gobbo (334-340).
The lowest-lying quartet electronic states of MnC, correlating with the three lowest-lying atomic dissociation channels, were investigated theoretically for the first time, with the state-of-the-art multireference configuration interaction (MRCI) approach, based on complete-active-space self-consistent-field (CASSCF) wave functions and extensive basis sets. Excitation energies, equilibrium internuclear distances, dissociation energies, and spectroscopic constants for eleven electronic states will be reported. Franck–Condon factors, Einstein coefficients, and radiative lifetimes for the first excited state will also be presented.
Evolution of chemical gardens in aqueous solutions of polymers by Edward Bormashenko; Yelena Bormashenko; Oleg Stanevsky; Roman Pogreb (341-344).
We report the formation of chemical gardens grown in water solutions of polymers. Evolution of the chemical garden depends dramatically on the polymer molecular weight. Solution/air interface plays an important role in the process. Inverse, down-directed growth of the chemical garden in the polymer solutions, based on polymers of high molecular weight, was observed.
Theoretical study and rate constants calculation for the ClCH2OH + Cl reaction by Yue-Meng Ji; Jia-yan Wu; Jing-yao Liu; Ze-sheng Li; Chia-chung Sun (345-350).
By means of dual-level direct dynamics method, the multiple channel reaction ClCH2OH + Cl is studied. The results show that methylene-H-abstraction channel is a major pathway compared with hydroxyl-H-abstraction channel. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) level, then single-point energies are further corrected at the MC-QCISD/3 level. The standard enthalpies of formation for ClCH2OH, ClCHOH, and ClCH2O are evaluated at the MC-QCISD/3///MP2 level. Furthermore, with the aid of canonical variational transition state theory including the small-curvature tunneling correction, the rate constants of the title reaction are calculated over a wide temperature range of 240–2000 K. Our results are in good agreement with the available experimental data.
Fluorescence resonance energy transfer induced by conjugation of metalloproteins to nanoparticles by P.P. Pompa; R. Chiuri; L. Manna; T. Pellegrino; L.L. del Mercato; W.J. Parak; F. Calabi; R. Cingolani; R. Rinaldi (351-357).
We show the possibility of realizing a hybrid system composed of a semiconductor nanoparticle (NP) and a metalloprotein, in which the photophysical properties of the two species can be exploited to elicit fluorescence resonance energy transfer mechanisms from the biomolecule to the NP. A specific conjugation process between CdSe/ZnS core/shell water soluble NPs, functionalized with surface exposed thiol groups (–SH), and the apo form of the metalloprotein azurin (Az) has been achieved, resulting in a fixed distance in the donor-acceptor pairs. The increase in the NP fluorescence intensity was found to be dependent on the Az to NP molar ratio.
Formation of double-side teethed nanocombs of ZnO and self-catalysis of Zn-terminated polar surface by Chang Shi Lao; Pu Xian Gao; Ru Sen Yang; Yue Zhang; Ying Dai; Zhong L. Wang (358-362).
Polar surface induced asymmetric growth of single-side teethed ZnO nanocombs was attributed to the self-catalysis of the Zn-terminated (0 0 0 1) surface (Z.L. Wang, X.Y. Kong, J.M. Zuo, Phys. Rev. Lett. 91 (2003) 185502). In this Letter, nanocombs of ZnO with double-sided teeth have been observed. This symmetric growth of the fish-ribbon like teeth has been identified due to the existence of an inversion domain boundary along the ribbon, so that both side surfaces of the ribbon are terminated with the chemically active Zn-(0 0 0 1) plane. A model is also given about the formation of ∼110° double-sided nanocombs based on the nucleus composed of multiply twinned pyramids. The data show that the Zn-terminated (0 0 0 1) surface is responsible for the formation of the teeth, while the oxygen-terminated ( 0 0 0 1 ¯ ) surface is chemically inactive and does not grow teeth.
UV absorption spectrum, formation and disappearance of the oxide radical ion O •− in aqueous solution: A pulse radiolysis study by M.S. Alam; E. Janata (363-366).
The formation and disappearance of O •− in oxygen-free aqueous solution at pH 13 has been studied and its spectrum has been re-determined utilizing pulse radiolysis optical measurements in the UV region. The rate constant for the reaction H • + OH− is determined to be 2.5 × 107 dm3 mol−1 s−1. A determination of the rate constants for the equilibrium • OH + OH - ⇔ O • - was not possible; the pK value for this equilibrium was determined to be 11.9. The rate constant for the demerisation O •− + O •− was measured at 325 nm to be 2k = 2 × 109 dm3 mol−1 s−1. The absorption spectrum of O •− differs significantly from that in the literature below 250 nm.
An ‘Atoms in Molecules’ analysis of the differences between meso and chiral forms of oxirane and cyclobutene derivatives by Ibon Alkorta; José Elguero (367-370).
The energetic, geometric and electronic differences of the meso and chiral form of oxirane and cyclobutene derivatives have been studied using DFT methods. The partition of several molecular characteristics (energy, charge and volume) into atomic contributions has been carried out within the AIM framework. The energetic analysis shows that the main contribution to the energy differences came from the chiral carbon atom, where the different substituents are attached. The molecular volume differences can be explained based on the results obtained for the substituents in the two dispositions.
A theoretical ab initio study of [n.n]paracyclophane complexes with cations by Antonio Frontera; David Quiñonero; Carolina Garau; Pablo Ballester; Antoni Costa; Pere M. Deyà; Fabio Pichierri (371-377).
Geometries and binding energies of complexes of Li+ and Na+ cations with benzene, several [n.n]paracyclophanes (n = 2,3) and a triple-layered [2.2]paracyclophane are computed and compared using ab initio calculations. We have recently demonstrated that the binding capability toward cations of [2.2]paracyclophane using one aromatic ring is superior to benzene in ∼10 kcal/mol. This unexpected difference is explained by the reduction, upon complexation, of the repulsive interaction of the π-systems. In the present work, we demonstrate that the binding ability of the next member of the cyclophane series [3.3]paracyclophane and the triple-layered [2.2]paracyclophane is even superior than [2.2]paracyclophane.
Cavity ringdown spectroscopy of the A ˜ – X ˜ electronic transition of the phenyl peroxy radical by Gabriel M.P. Just; Erin N. Sharp; Sergey J. Zalyubovsky; Terry A. Miller (378-382).
Cavity ringdown spectra (CRDS) of the near IR A ∼ 2 A ′ – X ∼ 2 A ″ electronic transition of phenyl peroxy radical are reported. The electronic origin is observed at 7497 cm−1. Ab initio calculations have been carried out to aid the assignment of the electronic origin and other bands involving vibrational excitation.
Spincoated polyethylene films for single-molecule optics by A.C. Wirtz; M. Dokter; C. Hofmann; E.J.J. Groenen (383-388).
We present first results from single-molecule experiments on spincoated polyethylene films doped with terrylene (Tr) or 2.3,8.9-dibenzanthanthrene (DBATT). Perfectly clear films have been produced with a thickness of 100–200 nm. We have performed both polarization-dependent single-molecule spectroscopy and single-molecule position determination (microscopy) experiments on these samples. Of the two systems we tested, DBATT in polyethylene proved the most practical for single-molecule experiments. We aim to use this system to study the length-scale of locally increased order in the semi-crystalline polymer polyethylene.
Local structural effects on low-frequency vibrational spectrum of liquid water: The instantaneous-normal-mode analysis by K.H. Tsai; Ten-Ming Wu (389-394).
Currently, the designations for the low-frequency vibrational spectrum of liquid water are still diversified. In this Letter, using the instantaneous normal mode (INM) formalism for subensembles, we have examined the effects of local structure on the low-frequency INM spectrum of liquid water. The classified subensembles of water molecules are characterized by either the geometry of Voronoi polyhedron or the H-bond configuration. With these subensembles, the translational contribution to the INM spectrum is investigated. Providing insights into the local structural dependence of the vibrations between H-bonded water molecules, our results are consistent with the conventional designations for the Raman spectrum of liquid water.
Some important formulae using the concept of graphical tree by Bholanath Mandal (395-400).
Some important formulae such as Euler’s polyhedron formula, degree of unsaturations and nitrogen rule along with some of their consequences have been derived using simple concept of graphical tree. Odd–even parities, which are important in graph theory and chemistry, have also been presented in this context.
Asymmetric current–voltage characteristics of molecular junctions containing bipolar molecules by Zbigniew L. Gasyna; Gustavo M. Morales; Arturo Sanchez; Luping Yu (401-405).
The asymmetric current–voltage (I–V) curves are computed for a conjugated biphenyl–bipirimidine diblock oligomer with two thiol end groups sandwiched between Au(1 1 1) electrode surfaces. The method is based on density functional theory and self-consistently determines the electronic structure of the molecule coupled to the gold electrodes with varied electrochemical potentials. Spatial asymmetry in the molecule is found to be essential in generating the I–V asymmetry.
Enhanced photoluminescence from films made of titanium tetraisopropoxide, Eu3+ ions and thenoyltrifluoroacetone blends by Elias Stathatos; Panagiotis Lianos (406-409).
Titanium tetraisopropoxide mixed with thenoyltrifluoroacetone and europium(III) makes uniform and stable intensely photoluminescent films that can be efficiently excited in the near UV. Formation of the film is aided by partial hydrolysis of titanium tetraisopropoxide and condensation due to ambient humidity but also by interaction between this precursor and thenoyltrifluoroacetone. These films make excellent phosphors that can be easily applied on any solid substrate.
Submicron-resolving infrared absorption spectroscopy and analysis in fingerprint region utilizing a free electron laser by Tatsuhiro Masaki; Yasushi Inouye; Satoshi Kawata (410-413).
Submicron-resolving infrared near-field absorption spectroscopy was achieved in fingerprint region by employing a free-electron laser at Tokyo University of Science as a tunable and bright IR light source and a custom-made cantilever probe with a 0.5 μm aperture as a near field probe. Infrared near-field imaging/spectroscopy between 8.3 and 8.7 μm wavelengths convincingly demonstrated observation of dissociation of the C–O–C bonds in cholesteryl oleate with submicron resolution.
A first-principles study of the chemi-adsorption of benzene on Au(1 0 0) surface by Wen-Kai Chen; Mei-Juan Cao; Shu-Hong Liu; Chun-Hai Lu; Ying Xu; Jun-Qian Li (414-418).
Benzene adsorption on the Au(1 0 0)-3 × 3 surface has been studied with a periodical slab model by using the VWN functional. The results of geometry optimization indicate that the hollow site is energetically active for benzene adsorbed on the Au(1 0 0) surface. The two opposite carbon atoms are involved in the adsorption process, leading to a rehybridization of the two carbon atoms from sp2 to sp3 that makes the adsorbate state intermediate between benzene and 1,4-cyclohexadiene. The benzene adsorbed in the bridge and top positions is found to be energetically less favorable. The molecular orbital analysis also indicates the degenerate frontier molecular orbitals lose their degeneracy with a decrease in symmetry. The two carbon atoms in the opposite positions are bonded to the neighboring Au atoms with di-σ bonds.
Covalent attachment of quantum dot on carbon nanotubes by Bifeng Pan; Daxiang Cui; Rong He; Feng Gao; Yafei Zhang (419-424).
The assembly of quantum dot (QD) on the surface of multi-walled carbon nanotubes (MWNT) in aqueous solution leading to QD-MWNT hybrid structures is demonstrated. The assembly of QDs on the MWNTs surface occurs through interaction of the amine groups on the MWNTs with the mercaptoacetic acid modified QDs. Furthermore, QD-MWNT hybrid material shows an excellent solubility in aqueous solution, this will be significant for its potential application in bioassay, bioconjugation, and biosensors.
Picosecond fluorescence dynamics of auramine with a long aliphatic chain by Robson Valentim Pereira; Marcelo Henrique Gehlen (425-429).
The acyl derivative of auramine with dodecyl carbon chain has solvent dependent absorption and emission spectra. The Lippert–Mataga plot shows two trends, a small slope in alcohols and a significant one in polar aprotic solvents. The change of dipole moment between ground and excited-state in aprotic solvent is 12 D, indicating an intramolecular charge-transfer process. Decay components of 5 and 600 ps appear in aprotic polar solvents. In protic polar solvents, the fast component, ranging from 9 ps in ethanol up to 53 ps in n-octanol, is correlated with the Debye dielectric relaxation time of the n-alcohols.
Mixed cation effect in 0.3[xLi2O · (1 − x) R2O] · 0.7B2O3 (R = Na, K, Rb) glasses by Yong Gao (430-433).
The electrical conductivity spectra of three mixed alkali glass systems 0.3[xLi2O · (1 − x)R2O] · 0.7B2O3 (with R = Na, K, Rb; x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) have been studied. For the first time it is reported that the strength of the mixed alkali effect does not always increase with the size difference of the involved alkali ions. The experimental results have been successfully interpreted by the structural model proposed by Swenson and his coworkers in combination with the structural considerations.
Theoretical study of proton transfer reactions of halosulfonic acids with ammonia in hydrated clusters by Shujin Li; Fu-Ming Tao; Renao Gu (434-440).
Interactions and proton transfer reactions of halosulfonic acids (HSO3X, X = F, Cl, Br) with ammonia (NH3) in the hydrated clusters, HSO3X–NH3–(H2O) n (n = 0,1,2,3), are investigated by density functional theory and ab initio molecular orbital theory. The HSO3X–NH3 systems alone are hydrogen-bonded despite of the high acidity of HSO3X, while one water molecule is enough to assist the transfer of a proton from the acid to ammonia. Large hydration energies and favorable free energies are found for each of the first few water molecules, indicating high stabilities of the small hydrated clusters in the gas phase.
Luminescent properties and excitation mechanism of organic–inorganic single quantum well containing organic heterojunction by Lei Qian; Feng Teng; Sheng Yi Yang (441-444).
In this Letter, organic–inorganic quantum well containing organic heterojunction (OIQWOH) ITO⧹SiO x ⧹MEH-PPV⧹Alq3⧹SiO x ⧹Al has been fabricated. The electroluminescence of OIQWOH includes three different peaks under alternative-current voltages: blue emission (410 nm), green emission (510 nm) and orange emission (588 nm). The source of these three emissions was investigated. Moreover, it was found that the permittivity confinement effect and the quantum size effect can obviously affect the optical and electrical properties of OIQWOH. Mixed excitation was observed in OIQWOH structure under alternating-current applied voltages by studying its brightness oscillogram.
Spectral properties of bipyridyl ligands by time-dependent density functional theory by Frédéric Labat; Philippe P. Lainé; Ilaria Ciofini; Carlo Adamo (445-451).
The properties of a series of bipyridyl ligands, which take an active part in numerous inorganic dyes designed for photovoltaic applications, are studied by the means of density functional theory and time-dependent DFT. In particular, the properties of the 2,2′-bipyridine (bpy) ligand and those of the 4,4′-dicarboxy-2,2′-bipyridine (4,4′-dcbpyH2) and 5,5′-dicarboxy-2,2′-bipyridine (5,5′-dcbpyH2) derivatives (in their neutral and anionic forms) were computed. The calculations were carried out in the gas phase and in solution, represented by a continuum. Beyond the good agreement with experimental data, our results show that the carboxylic groups behave as electron-withdrawing groups showing no specific spectral signature.
Investigation of the liquid–liquid interface with high spatial resolution using near-field Raman spectroscopy by M. De Serio; H. Mohapatra; R. Zenobi; V. Deckert (452-456).
Local spectroscopic investigation of liquid–liquid interfaces and their surroundings is experimentally challenging. Highly localized illumination by a near-field optical probe is a possibility, but precise positioning of the probe very close to such an interface prior to measurement has been very difficult. Here, we show how this difficulty is overcome with greatly improved instrumentation. Near-field Raman spectroscopy was used to study the water–carbon tetrachloride interface with a spatial resolution of 200 nm. A blue shift of the OH stretching vibration of water was observed when approaching the interface, indicative a weaker H-bond in the vicinity of the apolar CCl4.
Syntheses and aggregate behaviors of liquid crystalline alkoxycarbonyl substituted perylenes by Xiong Mo; Hong-Zheng Chen; Min-Min Shi; Mang Wang (457-460).
The molecular aggregations in liquid crystalline 3,4,9,10-tetra-(n-alkoxy-carbonyl)-perylenes (PTAC, n = 4, 8, 12), which were prepared via an innovative route of a simple phase transfer catalysis method, were investigated through UV/Vis absorption, XRD, DSC, and polarization microscopy. Some interesting aggregate behaviors caused by the length of attached alkyl chains were observed. It was found that it was easier for PTAC derivatives with shorter alkyl chain to form crystal films and liquid crystals.
Strong quantum confinement effects in thin zinc selenide films by S. Baskoutas; P. Poulopoulos; V. Karoutsos; M. Angelakeris; N.K. Flevaris (461-464).
Thin Zinc Selenide films in the thickness range 3–50 nm have been prepared on high quality glass substrates by e-beam evaporation under ultrahigh vacuum conditions. Optical absorption spectroscopy experiments reveal a systematically increasing blue shift of the effective bandgap energy as the film thickness decreases, reaching a maximum value of 0.32 eV for the thinner film. The experimental results, which indicate the presence of strong quantum confinement effects, are fairly well described by theoretical calculations based on the potential morphing method, using as a confining potential the finite square well potential with height of the barriers equal to 5 eV.
The role of magnetic fields on the membrane-based separation of aqueous electrolyte solutions by S. Murad (465-470).
Molecular simulations using the method of molecular dynamics have been carried out to examine the role that external magnetic fields can play in the transport of water via reverse osmosis (RO) across membranes. Our results show that magnetic fields can increase the transport rate of water across such membranes significantly. These observations can have an important impact on making RO separation processes that involve the removal of water from solutions more efficient, since low flux rates across membranes is an important problem encountered in most current RO processes. We are aware of no experimental studies of such effects.
Absolute line intensity with FT-ICLAS: 12C2H2 near 12 800 cm−1 by P. Macko; M. Herman (471-474).
We have used a Fourier transform intracavity laser absorption spectrometer to measure the absolute intensity of lines in the ν 1 + 3ν 3 band of 12C2H2 at 12675 cm−1. Under optimal conditions the agreement is found to be within 5% of reference values measured by conventional Fourier transform spectroscopy [F. Herregodts et al., Mol. Phys., 101 (2003) 3427]. The absolute intensity of 21 weaker lines not experimentally investigated in the latter work, is listed. Various tests of the instrumental method are presented, also demonstrating its ability to determine pressure self-broadening coefficients.
On the carbon-13 chemical shift tensors of bent-core mesogens by Ronald Y. Dong; J. Zhang; K. Fodor-Csorba (475-479).
Solid state NMR techniques are used to study bent-shape achiral molecules which can form a new type of mesophases, known as ‘banana’ or B phases. In particular, a recent method called SUPER is applied to two solids of this type of polar mesogens, rotating at the magic angle, to extract carbon-13 chemical shift anisotropy tensors. They are useful not only to aid 13C peak assignments in the isotropic state, but are necessary for accounting the observed chemical shifts of various carbon sites, resided on the bent-core aromatic part, in the spectrum of an aligned mesophase. An example to extract ordering information is given for one of the studied mesogens.
Absolute rate determinations and temperature dependences of the gas-phase reactions of O(3P) with halogenated propenes by Pablo M. Cometto; Mariano A. Teruel; Raúl A. Taccone; Silvia I. Lane (480-485).
The rate constants for the gas-phase reactions of ground state oxygen atoms with CF3CH＝CH2 (1), CF3CF＝CF2 (2) and CF3CCl＝CCl2 (3) have been measured directly using a discharge flow tube employing the O(3P) chemiluminescence titration method. The experiments were carried out under pseudo-first-order conditions with [O(3P)]0 ≪ [propene]0. The temperature dependences of the reactions were studied for the first time in the range 298–363 K. The Arrhenius expressions obtained (in units of cm3 molecule−1 s−1) were: k 1 = (0.28 ± 0.09) × 10−11 exp[−(10.4 ± 0.9) × 103/RT], k 2 = (1.57 ± 0.72) × 10−11 exp[−(15.6 ± 1.3) × 103/RT], k 3 = (2.23 ± 1.27) × 10−11 exp[−(16.0 ± 1.6) × 103/RT]. All the rate coefficients display a positive temperature dependence which points to the importance of the irreversibility of the addition mechanism for these reactions. Halogen substitution in the alkenes is discussed in terms of reactivity with O(3P) and its relation with the ionization potential.
Intermolecular structure and dynamics in an ionic liquid: A Car–Parrinello molecular dynamics simulation study of 1,3-dimethylimidazolium chloride by B.L. Bhargava; S. Balasubramanian (486-491).
Ab initio molecular dynamics (AIMD) and classical molecular dynamics (MD) simulations of the room temperature ionic liquid (RTIL), 1,3-dimethylimidazolium chloride, were performed in order to study its intermolecular structure and dynamics. Differences in the spatial distribution of chloride ions around the cation between AIMD and MD data are explained as due to the formation of a hydrogen bond between the acidic hydrogen on the imidazolium ring and the chloride ion. A strong interaction between the π electron clouds of neighboring imidazolium rings enables the ring planes to be aligned nearly parallel to each other. The cation–anion hydrogen bond present in the melt is observed as a red shift in the C–H stretching frequency.
Iterative time independent calculation of the cumulative reaction probability within a basis adapted preconditioner by F. Woittequand; M. Monnerville; S. Briquez (492-497).
A band preconditioner matrix coupled to an iterative approach based on the generalized minimal residual (GMRes) method is presented to determine the cumulative reaction probability (CRP) N(E). The CRP is calculated using the Seideman, Manthe and Miller Lanczos-based boundary condition method [J. Chem. Phys. 96 (1992) 4412; 99 (1993) 3411]. Using this basis adapted preconditioner, the iterative GMRes scheme is found to be more efficient than a direct method based on the LU decomposition. The efficiency of this approach is illustrated by calculating the CRP for the H + O2 → HO + O reaction, assuming zero total angular momentum.
Implicit and explicit internal signal stochastic resonance in calcium ion oscillations by Ya Ping Li; Qian Shu Li (498-502).
Responses of Ca2+ oscillations to random perturbation are investigated at the conditions where the system stays at a steady state (before bifurcation point) or an oscillatory state (after bifurcation point). It is found that noise can induce both implicit and explicit internal signal stochastic resonance (IISSR and EISSR). In particular, the internal signal stochastic bi-resonance is also observed. When an external signal is added to the system, no IISSR or EISSR phenomenon occurs, implying an external signal destroys cooperation of Ca2+ signal and environment noise.
Growth and fluorescence properties of perylene nanocrystals produced by ultra-rapid evaporation by Y. Wakayama; T. Mitsui; T. Onodera; H. Oikawa; H. Nakanishi (503-508).
The growth process of molecular nanocrystals on a solid surface was explored through the application of a vacuum evaporation technique. The combination of ultra rapid evaporation, a patterned intended surface, and a perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) buffer layer was found to be effective in producing small perylene nanocrystals (ca. 100 nm) at a high density (13.6 μm−2). The prepared perylene nanocrystals exhibited characteristic fluorescence properties. The fluorescence spectra contained luminescence peaks attributed to a free exciton and self-trapped exciton, which were the result of nanometer-scale size effects.
A study of the non-electrostatic interaction micelle/charged ligand: A comparison of the results obtained by two different methods by R. Jiménez; E. García-Fernández; E. Grueso; I. Fernández; I. Marín; J.J. Sanz; L.A. Torrado; D. Villegas; L. González; H.K. Stürekow; M. Leon; F. Lería; E.M. Machuca; L.M. Martinez; J. Morales; I. Villa-Bernaldez; R. Prado-Gotor (509-514).
A kinetic study of the reaction between [Fe(CN)6]4− (hexacyanoferrate (II)) and [Co(en)2Cl2]+ (trans-dichlorobis cobalt(III) bis(ethylenediammine)) has been carried out in sodium dodecyl sulphate (SDS) micellar solutions containing NaCl. The results are discussed by using an approach based on the pseudophase model. Trends in the observed reactivity are explained by a change in the degree of association of one of the reactants ([Co(en)2Cl]+ in the present Letter) to the micelles, which depends on the surface potential of the micelles. The electrostatic and non-electrostatic components of the free energy of binding are determined by two different methods and the results of these determinations are compared.
Adsorption of Cu4, Ag4 and Au4 particles on the regular MgO(0 0 1) surface: A density functional study using embedded cluster models by Chan Inntam; Lyudmila V. Moskaleva; Ilya V. Yudanov; Konstantin M. Neyman; Notker Rösch (515-520).
Cu4, Ag4, and Au4 species adsorbed on the regular MgO(0 0 1) surface are studied using a density functional method and cluster models embedded in an elastic polarizable environment. The structure of the coinage metal tetramers is only slightly distorted by adsorption on the oxide surface compared to the rhombic-planar arrangement in the gas phase. The most stable adsorption complexes of all three systems feature upright metal planar particles with the M4 moiety orthogonal to the surface and two metal atoms attached to surface oxygen anions. Au4 and Cu4 exhibit substantially stronger binding to the surface than Ag4.
Characterization of N-representable n-particle densities when N is infinite by Mats-Erik Pistol (521-523).
We have found necessary and sufficient conditions for the n-particle density to be N-representable for infinite N, if n is even. There are some mild restrictions on the one-density for these conditions to apply. The method is based on the Mercer expansion theorem. We suggest a simple method for total energy calculations based on this characterization also if the number of particles is finite.
Observing the complete solvation response of DCS in imidazolium ionic liquids, from the femtosecond to nanosecond regimes by Sergei Arzhantsev; Hui Jin; Naoki Ito; Mark Maroncelli (524-529).
Femtosecond Kerr-gated emission spectroscopy and picosecond time-correlated single photon counting are used to measured the full solvation response of 4-dimethylamino-4′-cyanostilbene in three imidazolium ionic liquids. The liquids studied are comprised of the 3-butyl-1-methylimidazolium cation ‘ ( Im 41 + ) ’ and the anions hexafluorophosphate, bis(trifluoromethylsulfonyl)imide (‘Tf2N−’), and tris(trifluoromethylsulfonyl)methide (‘Tf3C−’). In all three liquids the solvation response is widely distributed in time with important contributions extending from 100 fs to 10 ns. The amplitude of the fastest (<1 ps) portion of the dynamics is correlated to the relative size and/or mass of the anion and it increases in the order Tf 3 C - < Tf 2 N - < PF 6 - .
Reduced parameter set determinable from geminate kinetics by Noam Agmon (530-534).
By fitting time-resolved measurements to models of diffusion influenced reactions it is possible to determine only parameters with no spatial dependence. The original set of distance-dependent parameters is reduced to a set of distance-independent parameters, and only these can be determined by fitting the model to the data. The present work demonstrates this point for reversible geminate recombination in one and three dimensions, showing how the reduced set of parameters is found by utilizing dimensional analysis or known analytic solutions. It is applied to the kinetic detection of proton-wires in the green fluorescent protein.
A study of the dispersions of metal oxide nanowires in polar solvents by F.L. Deepak; Pearl Saldanha; S.R.C. Vivekchand; A. Govindaraj (535-539).
Dispersions of the nanowires of Al2O3, ZnO and MgO in dimethylformamide (DMF), dimethylsulfoxide (DMSO) and acetonitrile have been studied by electron microscopy and PL spectroscopy, and by examining their sedimentation behavior. Stable nanowire dispersions were best obtained in DMF. The best PL spectra of the nanowires were also generally obtained with DMF dispersions.
Ambipolar single electron transistors using side-contacted single-walled carbon nanotubes by Kenta Matsuoka; Hiromichi Kataura; Masashi Shiraishi (540-544).
We report on single electron transistor (SET) operation in single-walled carbon nanotubes (SWNTs) to estimate the length of ballistic conduction in laser-synthesized SWNTs. The devices were fabricated by an alternating current-aligned method and the SWNTs were side-contacted to the electrodes. At 5 K, Coulomb oscillation and Coulomb diamonds were observed and the Coulomb island length, i.e., the ballistic conduction length, was calculated to be about 200–300 nm. To the best of our knowledge, this is the first report of an SET using an aligned-fabrication methodology and a solution process.
A multi state-CASPT2 vs. TD-DFT study of the electronic excited states of RCo(CO)4 (R = H, CH3) organometallic complexes by David Ambrosek; Sébastien Villaume; Leticia González; Chantal Daniel (545-549).
The electronic spectroscopy of RCo(CO)4 (R = H, CH3) has been investigated by means of MS-CASPT2/CASSCF and TD-DFT calculations. The UV energy domain of the absorption spectrum is dominated by a series of low-lying 1E metal-to-sigma-bond-charge-transfer (MSBCT) and 1E and 1A1 metal-to-ligand-charge-transfer (MLCT) allowed transitions corresponding to 3 d Co → σ Co – R ∗ and 3 d Co → π CO ∗ excitations, respectively, slightly red shifted (by ca. 1800 cm−1) in the methyl substituted complex. TD-DFT underestimates the transition energies calculated by MS-CASPT2 by more than 0.5 eV and predicts some of the MLCT states to be intercalated between the two low-lying MSBCT states.
Femtosecond time-resolved solvation process of a solution: Constraints of vibrational degrees of freedom in the supercooled state by Hiroshi Murakami (550-554).
Femtosecond time-resolved fluorescence spectra have been measured for a dye solution from 170 to 296 K. The time evolution of the spectra shows that there are three energy relaxation components of about 0.1 ps, a few ps and a time constant changing from 10 ps to 1 ns with decreasing temperature. It is considered from the temperature dependence of the relaxation process that a part of the solvation process responsible for the two fast components slows down because vibration-like degrees of freedom are constrained under strong hydrogen-bonded networks near the supercooled state.
Controlling the Ru-catalyzed Belousov–Zhabotinsky reaction by addition of hydroquinone by Do Sung Huh; Young Min Choe; Do Young Park; Sung Hyun Park; Yan Suhang Zhao; Young Joon Kim; Tomohiko Yamaguchi (555-560).
Oscillation patterns in the photosensitive Belousov–Zhabotinsky reaction composed of malonic acid / BrO 3 - / Ru ( bpy ) 3 2 + / H + were modulated by addition of less than 100 mM of hydroquinone. In dark, the limit cycle oscillations bifurcated into mixed-mode oscillations of 11 and 12 with hydroquinone concentration, where the superscripts indicate the number of small-amplitude oscillations. Under illumination, three types of pattern change were observed depending on the initial composition of the reaction mixture. A probable mechanism to explain the role of hydroquinone is proposed on the basis of the Field–Körös–Noyes mechanism and the photocycle of the Ru-catalyst.
Effects of ions on dynamics of ice surface by Tomoko Ikeda-Fukazawa; Katsuyuki Kawamura (561-565).
Surface melting of ice below the bulk melting point is well-established but little-understood phenomenon. In order to investigate the effects of impurities on the surface melting, we performed molecular dynamics simulations of ice surfaces containing NO 3 - , Cl−, Na+, and H+. The vibrational density of state showed that collective dangling vibrations of the free O–H bonds are excited around the ions with the negative charge. This mode is not excited around the positive ions. We conclude that the collective vibration is the dominant factor governing the enhancement of the surface melting.
Comment on “The enthalpy of the O–H homolytic dissociation: Basis-set extrapolated density functional theory and coupled cluster calculations” by B.J. Costa Cabral and S. Canuto [Chem. Phys. Lett. 406 (2005) 300–305] by Gino A. DiLabio; Peter Mulder (566-569).
Costa Cabral and Canuto [B.J. Costa Cabral, S. Canuto, Chem. Phys. Lett. 406 (2005) 300] have studied the O–H bond dissociation enthalpy in water, hydrogen peroxide, methanol, phenol and catechol using a number of theoretical methods. Their choice of experimental O–H bond dissociation enthalpies for phenol and catechol are not the best available values and led them to several erroneous conclusions about the performance of methodologies they tested. In this work, we present more rigorous experimental O–H bond dissociation enthalpies for phenol and catechol and discuss the implications these data have on the conclusions presented by Costa Cabral and Canuto. We also demonstrate the importance of the inclusion of higher-order excitations in the coupled-cluster treatment of bond dissociation enthalpy of the O–H bond in H2O2 and HOO • .
Reply to comment on ‘The enthalpy of the O–H bond homolytic dissociation: Basis-set extrapolated density functional theory and coupled cluster calculations’ by B.J. Costa Cabral; Sylvio Canuto (570-572).
Based on a recent re-evaluation of the O–H bond dissociation enthalpy (BDE) of phenol by Mulder et al. as 86.7 ± 0.7 kcal/mol, Di Labio and Mulder put under dispute the reliability of basis-set extrapolated coupled cluster calculations with single and double excitations (CCSD) for predicting the gas-phase BDEs of phenol and cathecol. Here, we stress again that our results support the experimental values for phenol recommended by Santos and Simões (88.7 kcal/mol) and by DeTuri and Erwin (90.1 ± 3.1 kcal/mol). We also verified that perturbative inclusion of triple excitations do not change our previous conclusions. We provide further elements that indicate why the recommended value of Mulder et al. for the phenol O–H BDE is not a definitive reference value.
Author Index (573-582).