Chemical Physics Letters (v.370, #1-2)

A new approach has been developed for the synthesis of Au@CdS core-shell nanoparticles (CSNs) by a directly self-assembling process. Stable Au@CdS composite colloids were prepared by thiourea, as a double functional reagents acted as the linkage agent between Cd2+ ions and gold nanoparticles. The CdS-capped gold composite nanoparticles were successfully integrated into BaTiO3 films. The third-order nonlinear optical properties of Au@CdS CSNs have been studied using femtosecond optical Kerr effect (OKE) technology at 800 nm. The significant enhancement of nonresonant third-order nonlinear optical nonlinearities of Au@CdS CSNs was reported for the first time.

s-Tetrazine as a new binding unit in molecular recognition of anions by Carolina Garau; David Quiñonero; Antonio Frontera; Antoni Costa; Pau Ballester; Pere M Deyà (7-13).
Noncovalent bonding between anions and the π-cloud of electron-deficient aromatic rings has recently attracted considerable attention. Complexes of anions with the electron deficient s-tetrazine aromatic ring and other binding units (i.e., urea and squaramide) have been studied and compared using both high level MP2/6-311 + G** ab initio and molecular interaction potential with and without polarization (MIPp and MIP, respectively) and molecular electrostatic potential (MEP) calculations, in order to explore the physical nature of the interactions. Our findings reveal that tetrazine is an excellent candidate for constructing anion receptors.

The accuracy of expanding the response of a molecule to an external electric field, E, as a power series in the field is investigated in the model hydrogen-bonded complex, ClH:NH3. Even at field strengths large enough to cause dramatic structural change in the complex, both the structure and vibrational frequencies are quantitatively predicted using only terms linear in E. These results suggest that knowledge of the zero-field molecular potential energy and dipole moment surfaces may be sufficient to accurately model the interactions of molecules in a wide range of external electric fields.

Electronic states for excess electrons in polyethylene compared to long-chain alkanes by David Cubero; Nicholas Quirke; David F. Coker (21-25).
We use a pseudopotential model to calculate the electronic states available to an excess electron in crystalline and amorphous regions of model polyethlyene as well as the molecular crystal of the linear alkane C27H56. It is shown that alkane crystals of whatever chain length are not representative of crystalline polyethylene (PE) although they are often considered to be so. We discuss the implications for electron transport in PE.

The effects of weak magnetic fields (<16 mT) in persistent non-photochemical spectral hole-burning of the R 1-line ( 2 E←4 A 2 transition) in NaMgAl(oxalate)3·9H2O:Cr(III) are reported. The observed hole patterns can be quantitatively rationalized with excited state g-factors, g z ex=1.395±0.015, g x ex=2.00±0.08, and g y ex=1.82±0.08. The deviation from trigonal behavior implies the presence of a significant low symmetry ligand–field. Measuring the hole-burning spectrum in a magnetic field after burning in zero field and vice versa yields the same hole pattern. The latter provides a persistent memory of magnetic fields. Zeeman effects in spectral holes may also be used to stabilize and tune the frequency of single-mode semiconductor lasers.

17O NMR studies of sodalites by T Loeser; D Freude; G.T.P Mabande; W Schwieger (32-38).
Hydrosodalites and hydroxosodalites were analysed by means of 17O, 29Si and 1H MAS NMR in the fields of 17.6 and 11.7 T. The samples covered a range in Si–O–Al bond angle of about 23°. Dependencies between the isotropic 17O chemical shift δ(17 O) and the T–O–T bond angle α for the oxygen sites in sodalites, A and LSX zeolites with Si/Al=1 were investigated and found to be linear in some special cases. The adsorption of water and/or cation exchange with larger cations increases the 17O chemical shift.

Equilibrium geometries, harmonic vibrational frequencies, and dissociation energies were determined for PbS, PbS, PbO and PbO molecules by density functional methods (B3LYP, B3PW91, BLYP and BHLYP), molecular orbital method (MP2) and quadratic CI calculation by including single and double substitutions (QCISD). The calculated results indicate that all methods used in this study have good performance in predicting the geometries, and in most cases harmonic vibrational frequencies. For dissociation energy, BHLYP gives the best agreement with experiments and previous theoretical studies on PbO, compared with other methods used in this study.

We report the mass analyzed threshold ionization (MATI) spectra of p-methoxyaniline recorded via the 00 vibrationless and several vibrational levels in the S1 state. The adiabatic ionization energies (IE) of this molecule is determined to be 57 445±5  cm −1 , which is red shifted from that of aniline by about 4826  cm −1 . This large energy shift is attributed by the electron-donating nature of the OCH3 group, supported by the ab initio calculations. In addition, the presence of the methoxy substituent also influences the vibrational frequencies depending upon the pattern.

Optimised geometries and absolute energies of CO2–(CH2)4–CO2 2−·(H2O) n , n=0,1,2, were determined using density functional methods. The n=1 global minimum was found to contain a bifurcated hydrogen-bond, with the n=2 minimum containing two such bonds. Vertical detachment energies (VDEs) obtained for the n=1,2 global minima at the MP2/6-31+G*//B3LYP/6-31+G* level agree well with experiment, and suggest that the two waters solvate the carboxylate groups separately in CO2–(CH2)4–CO2 2−·(H2O)2. However, a number of different isomers were identified for both clusters with several isomers producing similar VDEs, indicating that the measured VDEs may contain contributions from multiple isomers. Calculations are presented illustrating that IR predissociation spectra would allow the direct identification of these isomers.

Intensity distributions of eight vibronic bands associated with v =0–3 for the C3Δ–X3Δ transition of TiO were observed by dispersed emission spectroscopy, and the variation of the electronic transition moment, R e(r), for the C3Δ–X3Δ system was determined as a function of the internuclear distance r; R e (r)∝{1−2.04(31)(r−r0)+195(43)(r−r0)3} (r0=1.65869  A ̊ and 1.59130  A ̊ ⩽r⩽1.71214  A ̊ ). This r-dependence of R e (r) is discussed in terms of the polarization in the unpaired 10σ orbital.

The stochastic tunneling technique is applied to screen a database of chemical compounds to the active site of dihydrofolate reductase for lead candidates in the receptor–ligand docking problem. Using an atomistic force field we consider the ligand’s internal rotational degrees of freedom. It is shown that the natural ligand (methotrexate) scores best among 10 000 randomly chosen compounds. We analyze the top scoring compounds to identify hot-spots of the receptor. We mutate the amino acids that are responsible for the hot-spots of the receptor and verify that its specificity is lost upon modification.

The structure modification and energetic consequences of the formation of intramolecular hydrogen bonds in the series of chloro substituted 2-(N-dimethylaminomethyl) phenol are discussed on the basis of result of ab initio and DFT calculations. A specific behaviour of derivatives containing the 3-Cl substituent was detected, suggesting formation of the stronger hydrogen bond than in analogous derivatives without such a substituent. It was found that steric repulsion of 3-Cl atom moves the methylamino group towards the OH group, leading to shortening of the OH⋯N hydrogen bridge. The geometric and electronic consequences of such shortening of the hydrogen bond are similar to the effects of the increase of acid–base interactions. The estimation of the corrections on steric interaction in the procedure of the energy of intramolecular hydrogen bond calculation appears to be much more complicated than in the series of the compounds not containing the 3-Cl substituent.

Copper metal nanoparticles have been formed by irradiation with 253.7 nm light from a low pressure Hg-arc lamp in the presence of a protective agent poly(N-vinylpyrrolidone). The role of a photo-sensitizer, benzophenone (BP), in the formation of Cu metal particles was studied. The nanoparticles have been characterized by their absorption maxima and transmission electron micrographs. The average particle size for Cu was 15 nm. It appears that the presence of BP is essential for the photochemical preparation of copper nanoparticles. Laser spectroscopic studies have revealed that BP ketyl radical does not participate in the formation of Cu metal nanoparticles.

Effect of surface methoxy groups on the 27Al quadrupole parameters of framework aluminum atoms in calcined zeolite H–Y by Wei Wang; Andreas Buchholz; Andreas Arnold; Mingcan Xu; Michael Hunger (88-93).
Via conversion of 13C-enriched methanol and applying a new stopped-flow protocol, the Brønsted acid sites (SiOHAl groups) of a calcined zeolite H–Y were highly covered by surface methoxy groups (SiOCH3Al). These methoxy groups (δ 13C=56.6 ppm) were formed at bridging OH groups in the direct vicinity of framework aluminum atoms. The methylated zeolite Y was used to perform first 27Al spin-echo NMR investigations of the influence of surface methoxy groups on zeolitic framework aluminum atoms. The formation of methoxy groups on calcined zeolite H–Y was found to decrease the 27Al quadrupole coupling constant of framework aluminum atoms from 14.8±0.2 MHz (uncovered SiOHAl groups) to 12.8±0.2 MHz (SiOCH3Al).

The excited multiplet states of 5,10,15-tri-n-pentyl-20-(1,1,3,3-tetramethylisoindolin-2-yloxyl-5-yl)porphyrinato zinc(II) by Kazuyuki Ishii; Steven E Bottle; Shinsuke Shimizu; Craig D Smith; Nagao Kobayashi (94-98).
Photo-physical properties of 5,10,15-tri-n-pentyl-20-(1,1,3,3-tetramethylisoindolin-2-yloxyl-5-yl)porphyrinato zinc(II), 1, have been investigated using time-resolved EPR (TREPR) and transient absorption measurements. A formation of the excited doublet (D1) and quartet (Q1) states constituted by excited triplet zinc porphyrin (ZnP) and doublet nitroxide is confirmed by TREPR. This is the first D1 and Q1 observation in a system where the nitroxide is directly substituted to a porphyrin ligand. Compound 1 exhibits the longest lifetime of any nitroxide–porphyrin systems in the lowest excited state, indicating a relatively weak electron exchange interaction between triplet ZnP and doublet nitroxide.

A derivative version of the well-known direct inversion in the iterative subspace (DIIS) algorithm is presented. The method is used to solve the coupled perturbed Hartree–Fock (CPHF) equation to obtain the first and second derivatives of the density matrix with respect to an external electric field which, in this case, leads to the electric molecular polarizability and hyperpolarizability. Some comparisons are presented and the method shows good convergences in almost all cases.

RhO molecules have been generated from laser-ablated rhodium atoms and 16 O 2 or 18 O 2 and studied spectroscopically. Thirty LIF band features in the 500–650 nm region have been examined. Dispersed fluorescence and excited state lifetime data have been recorded. Measurements on vibrational levels v=0 to 5 of the molecular ground state give ω e =807  cm −1 and ω e x e =5  cm −1 . Excited state vibrational parameters have been estimated. Evidence is found for low-lying electronic states at 3744, 5980 and 6477 cm−1.

The important process by which the translational energy of GaCl molecules diminishes before their adsorption on the GaAs surface, in halide and hydride epitaxial growth, is difficult to study experimentally. In the present work, we study the dynamical behavior of GaCl molecules on the GaAs(0 0 1) 2×4  β2 surface in order to reveal the relaxation mechanism of GaCl. At incident angles of 60° and 75°, the observed dynamical processes are in contrast to the ones predicted by the famous hard- and soft-cube models. It is shown that the high degree of surface corrugation strongly influences the dynamical behavior in general, and the relaxation processes in particular.

UV- and IR-induced photoisomerizations of acetylacetone trapped in a nitrogen matrix at 10 K have been carried out using a tunable (UV and IR) laser, or a mercury lamp, and have been studied by UV and FTIR spectrometries. After deposition the main form of acetylacetone is the chelated form (enol). Upon UV irradiation the intramolecular H-bond is broken, leading to non-chelated forms. These forms have been then irradiated, by a resonant Π→Π UV irradiation, or by resonant ν OH IR irradiations. Interconversions between the non-chelated forms have been observed, providing a great amount of data for identifying acetylacetone isomers and thus for exploring intramolecular reactivity paths.

Oxidation of CO on Ir(1 1 1) was investigated between 420 and 530 K under a constant CO+O2 gas flux and varied fractions of CO (Y) and O2 (1−Y). Upon variation of Y in the ‘up’ and ‘down’ direction, the stationary CO2 rates exhibit bistability below 530 K between two temperature dependent limiting Y values. An analysis of the bistability at 500 K revealed that the equilibrium CO2 rates on the two branches are stable in excess of 20 h. The observed phenomena, including feed gas pulsing effects, are reproduced by the solutions of appropriate kinetics equations.

A molecular-beam apparatus with a spray-jet technique for studying neutral non-volatile molecules by Toshiki Yamada; Hidenori Shinohara; Ge Maofa; Shinro Mashiko; Katsumi Kimura (132-138).
A molecular-beam apparatus has been newly constructed for studying neutral non-volatile molecules, consisting of (1) a sample inlet system with a supersonic nebulizer, an inlet chamber, and a pulsed nozzle, (2) a set of skimmers, and (3) a high-vacuum chamber in which pulsed-laser photoionization and mass detection are carried out. A heavy mist of sample solution is initially prepared with the nebulizer, and then stored in the inlet chamber, from which a molecular beam is ejected into vacuum through the pulsed nozzle and skimmers. In this report we want to emphasize several advantages of this technique and its broad applicability.

Dynamics of ground-state reverse proton transfer in the 7-azaindole/carboxylic acid systems by Wei-Ping Hu; Ru-Min You; Shih-Yao Yen; Fa-Tsai Hung; Po-Hung Chou; Pi-Tai Chou (139-146).
Dual-level direct dynamics calculation of the ground-state proton transfer reaction is reported for the 7-azaindole(7AI)/carboxylic acid system. The reaction path was calculated and the two-dimensional potential energy surface scan was performed at various levels of theory. Only one transition state geometry was resolved in the ground state from the ab initio calculation. The zero-point corrected barrier for the reverse proton transfer was found to be small (∼0.2 kcal/mol). The calculated reverse rate constant (1.45×1012   s −1 ) at 300 K is significantly higher than the rate of tautomer emission (3.8×108   s −1 ) from the S 1 excited state.

Hyperconjugation versus intramolecular hydrogen bond: origin of the conformational preference of gaseous glycine by Weizhou Wang; Xuemei Pu; Wenxu Zheng; Ning-Bew Wong; Anmin Tian (147-153).
Three experimentally detected low-energy conformers of gaseous glycine are selected as models to investigate the origin of the conformational preference of nonionized glycine, employing the atoms in molecules (AIM) and natural bond orbital (NBO) analysis methods. At the B3LYP/6-311++G(3d,3p) theory level, it is found that the importance of intramolecular hydrogen bond was overemphasized in the previous studies and it is hyperconjugation not intramolecular hydrogen bond that determines the order and relative energy of the conformers considered in this Letter.

Effects of oxygen atom in the side chain on physical and optical properties of dodecapentoxypentasilane by Haruhisa Kato; Takashi Karatsu; Akira Kaito; Kayori Shimada; Akihide Kitamura (154-160).
The effects of the alkoxy side chain on the conformation of oligosilane have been studied for perpentoxypentasilane. The UV-absorption maxima shifted extremely to a shorter wavelength than that of peralkyloligosilane. Molecular dynamics and ab initio MO calculations showed that the excitation energy of the twisted structure for peroxyloligosilane (a model of perpentoxypentasilane) was smaller than that of permethyloligosilane, because of the interaction between the n orbital of the oxygen atom and the σ orbital of the Si–Si bond. The Coulomb repulsion energies between the oxygen atoms greatly affect the stability of the twisted conformation of the silicon backbone.

In order to accurately describe the van der Waals interaction between rare-gas atoms by the density functional theory, we adjusted the exchange-functional developed by Perdew and Wang (PW). The van der Waals interactions of He, Ne, Ar and Kr dimers were investigated. The results clarified that the adjustment improves the overestimation of the interactions by the original PW exchange-functional, providing the qualitatively accurate trend in van der Waals interactions of He, Ne, Ar and Kr dimers. However, we also found that the adjusted functional for He and Ne underestimates the DNA base-stacking interaction between cytosine monomers. This may indicate that the PW exchange-functional requires a further modification or a van der Waals correction in order to give accurate DNA base-stacking interaction.

Effect of halogen displacements on magnetic coupling for methyloxo-bridged copper(II) dimers is investigated by means of DFT-BS (broken-symmetry) approach. Both coupling constants J and bridging O atomic charges(Q O) increase with the increasing displacement degree n. The displacements lead to β electron transfer from Cl to Cu atoms, α electron from O atoms to methyl groups, which brings down spin densities on Cu2O2 core and further spread them toward the periphery of the models. The resulted spin delocalization reduces antiferromagnetic coupling strength for methyloxo-bridged copper (II) dimers. Furthermore, the decrease of spin densities on O p x , O p y and Cu d xy orbitals is the leading reason for the reduction of coupling strength as halogen displacements.

The variation of hole states with Pr doping for Y x Pr1−x Ba2Cu3O7 and Y x Pr1−x Ba2Cu4O8 has been investigated by O K-edge X-ray absorption spectroscopy. Upon Pr substitution, T c suppression rate in Y x Pr1−x Ba2Cu4O8 is slower than that in YxPr1−x Ba2Cu3O7. For both systems, hole carriers in the CuO2 planes and CuO chains decrease monotonically with increasing Pr doping level. The depletion rate of hole carriers in the CuO2 planes with Pr doping in Y x Pr1−x Ba2Cu4O8 is considerably slower than that in Y x Pr1−x Ba2Cu3O7. The oxygen content affects the depletion rate of hole carriers in cuprates with Pr doping.

The electron capture dynamics in water dimer (H2O)2 has been investigated by means of direct ab initio trajectory method. It was found that the solvent reorientation of the water cluster anion occurs spontaneously following the vertical electron capture of the neutral water dimer: namely, the linear form water dimer which is the most stable structure of neutral water dimer, was drastically changed by accepting an excess electron to a dipole orientation form in which the two dipoles of the water molecules coordinate equivalently to the excess electron. The electron was located around the center of two water molecules at the final structure. The water dimer’s solvation time was calculated to be about 150–400 fs. The mechanism of the solvent reorientation was discussed on the basis of theoretical results.

Molecular aggregation effects on the static and dynamic electronic polarizability and hyperpolarizability are estimated within the time-dependent Hartree–Fock scheme by using a decomposition procedure over the atomic orbitals. For each molecule, the total property value consists in an algebraic sum of two contributions: an intrinsic part coming only from the atomic orbitals belonging to the molecule and a mixed contribution coming from the crossed terms associated with atomic orbitals describing the target molecule and its neighbors. All-trans hexatriene molecular clusters are examined to illustrate this decomposition scheme and to analyze the electronic cooperative behavior of the building units.

Coherent infrared–ultraviolet double-resonance spectroscopy of CH3 by Thomas B Settersten; Roger L Farrow; Jeffrey A Gray (204-210).
Two-color polarization spectroscopy (TC-PS) and two-color resonant four-wave mixing spectroscopy (TC-RFWM) are used to detect photolytically produced CH3 radicals. An infrared laser pumps individual lines in the ν 3 fundamental of the X ̃ 2 A 2″ state, and an ultraviolet laser probes the pumped levels to reveal rotationally resolved spectra of transitions to the predissociated B ̃ 2 A 1 state. The spectra are fit with a complex Lorentzian lineshape and yield an updated value of 46 239.4±1.2  cm −1 for T 0 of the B ̃ state. A detection limit of 2×1013 CH3 molecules per cm3 per quantum state is observed for these coherent double-resonance techniques.

The change (Δμ) in the permanent dipole moment on the S1←S0 electronic excitation is determined for Coumarin 153 (C153) in a molecular beam from the spectral change induced by applying a strong dc electric field up to 200 kV/cm. The comparison of the observed fluorescence excitation spectra under various external fields with the corresponding simulations for a pendular-state molecule yields Δμ=7.1±0.4  D for both the syn and anti conformers of C153. Previous experimental results on Δμ in the condensed phase, as well as the theoretical predictions reported in the literature, are discussed on the basis of the present value under an isolated condition.

A computational procedure is proposed for calculating the lattice energy of molecular crystals using the ab initio MO method. Our method does not require any adjustable parameters and provides a general description for various molecular crystals including electron donor–acceptor (EDA) complexes. Using the method, the packing structure of H3N–BF3 crystal was optimized at the HF/3-21 + G level and the lattice energy was calculated at the MP2/6-311 + G* level. The calculation reproduced the experimental lattice constants with reasonable accuracy. Moreover, the structural feature of the H3N–BF3 crystal was discussed based on the molecular interactions in the crystal.

Time- vs. frequency-domain femtosecond surface sum frequency generation by Sylvie Roke; Aart W Kleyn; Mischa Bonn (227-232).
We present an experimental and theoretical investigation into time- vs. frequency-domain femtosecond sum frequency spectroscopy at the metal–liquid interface. Although frequency and time-domain measurements are theoretically equivalent it is demonstrated here experimentally that the two approaches are sensitive to different physical aspects of the system and provide complementary information. Time-domain measurements are demonstrated to be more clearly influenced by the inhomogeneity of adsorption sites, since the decay of the vibrational polarization can be mapped directly. A generalization of existing models allows for the simultaneous description of both frequency and time-domain measurements.

An ab initio investigation of the He–H2O complex by G Calderoni; F Cargnoni; M Raimondi (233-239).
We determined the potential energy surface (PES) of the He–H2O complex by means of Coupled-Cluster, Møller–Plesset, and valence bond calculations. The main features of the different PES are discussed and compared to previous literature results. We determined the rotovibrational structure of the complex under the assumption that the water molecule rotates freely. Whatever the computational scheme, the complex is predicted to have a single bound vibrational state and three rotational excitations.

The reaction products of copper atoms with acetylene or acetylene and carbon monoxide mixtures in solid argon have been studied using infrared absorption spectroscopy and density functional theoretical calculations. The Cu(C2H2)2 molecule is the only product of the copper and acetylene reaction, which was predicted to have a 2 B 2u ground state with planar D2h structure. When acetylene and carbon monoxide mixture was used as reagent, the CuCO(C2H2) molecule was also formed and characterized. The CuCO(C2H2) molecule has a 2 B 2 ground state with planar C2v structure.

The translational energy (E T) dependence of CO chemisorption has been investigated on Pd(1 1 0). A steep increase from 0.61 to 0.93 is observed in the initial sticking probability S 0 with increasing E T from 27 to 93 meV. Comparison to density functional theory calculations suggests a steering-mediated adsorption channel, driving slow molecules towards less favorable surface sites. This long-range interaction between CO and the Pd d-orbitals screens the potential influence of the surface structural corrugations on the CO adsorption and thus provides an explanation to the well-known structure insensitivity of CO adsorption on Pd surfaces. For E T>93 meV the adsorption reverts back to the direct chemisorption mechanism found on other Group VIII metals.

Quasiquenching size effects in gold nanoclusters embedded in silica matrix by S Dhara; R Kesavamoorthy; P Magudapathy; M Premila; B.K Panigrahi; K.G.M Nair; C.T Wu; K.H Chen; L.C Chen (254-260).
The surface plasmon energy of gold clusters formed by Ar+ ion beam mixing of Au/silica is investigated for the size effect. The redshift with decreasing cluster size is assigned to the ‘spillout’ effect in small clusters (<5 nm). Core-electron contribution to the metal dielectric function is mainly responsible for the blueshift with decreasing cluster size (quenching of the size effect) in case of bigger cluster size (>5 nm), assisted with annealing treatment. The competition between ‘spillout’ effect and the frequency dependence of interband dielectric function leads to a quasiquenching of the size effects in the optical response.

Fundamental mechanisms of 3He relaxation on glass by R.E Jacob; B Driehuys; B Saam (261-267).
We present a model of 3 He relaxation on the surface of borosilicate glass which accurately predicts observed relaxation rates and their temperature dependence. Above room temperature 3 He dissolves into Pyrex, where interactions with Fe3+ ions result in a relaxation time of ≈1 ms. Gas exchange across the glass surface of an enclosed vessel leads to T 1 −1=A/V(3.9±1.4)×10−2 cm/h at room temperature, where A/V is the surface-to-volume ratio. The activation energy for relaxation is 13.7±0.7 kJ/mol and is dominated by the activation energy of 3 He diffusion in glass. This is the first successful confirmation of predicted 3 He relaxation rates in glass vessels.

A dimeric structure of eosin molecules on Au(1 1 1) surface by Gui-Jin Su; Shu-Xia Yin; Li-Jun Wan; Jin-Cai Zhao; Chun-Li Bai (268-273).
In situ scanning tunneling microscopy (STM) and cyclic voltammetry have been employed to investigate the adsorption of eosin molecules on Au(1 1 1) in aqueous HClO4 solution. The eosin molecules are found to form a highly ordered adlayer on the well-defined Au(1 1 1) surface. A dimeric structure of eosin molecules is clearly resolved in high-resolution STM image. Based on the STM observation and theoretical calculation, a structural model is tentatively proposed. The interaction between the bromide atoms is assumed to be responsible for the formation of the dimeric structure.

Direct growth of macroscopic fibers composed of large diameter SWNTs by CVD by Q.H Yang; S Bai; T Fournier; F Li; G Wang; H.M Cheng; J.B Bai (274-279).
Macroscopic nanotube fibers, composed of aligned large diameter single-walled carbon nanotubes (SWNTs), were prepared by a simple CVD method. These fibers, which constitute the nanotube ropes of loose structure like hemp cords, can be divided into the nanotube threads (mesoscopically) and subdivided into nanotube bundles (microscopically). The samples show good alignment at different scales. The fibers, several micrometers in diameter, have a relatively stable structure and only dissociated partially under ultrasonic dispersion. The obtained SWNTs have good crystalline structure and good purity. The influence of the CVD conditions on the fiber morphology was also investigated.

New docking CFF91 parameters specific for cyclodextrin inclusion complexes by F. Melani; P. Mura; M. Adamo; F. Maestrelli; P. Gratteri; C. Bonaccini (280-292).
A method that correlates the docking energy of inclusion complexes between cyclodextrins and guest molecules was developed and tested. The docking energies of the host–guest inclusion complexes were optimised through a new parameterisation of the consistent force field (CFF91). The developed model gave a good relationship between the experimental stability constant values and the corresponding calculated docking energies (R 2=0.860). The model showed a good predictive power (R rg 2=0.755). Analysis of the modifications to the force field parameters, compared with the standard values of the original CFF91, suggested interesting information about the most favourable guest properties for obtaining stable inclusion complexes.

Excited state dynamics studies of iron(III) phthalocyanine using femtosecond pump–probe techniques by Guohong Ma; Jun He; Chiang-Huen Kang; Sing-Hai Tang (293-299).
Iron(III) tetracarboxylic phthalocyanine (FePcC) was synthesized and the S1 excited state dynamics of the monomer solution was investigated by femtosecond (fs) pump–probe and picosecond time-resolved photoluminescence (ps-TRPL) measurement. The singlet state S1 relaxation comprises of three components with lifetimes of hundreds of fs, 130 ps and 1.3 ns, respectively. The fs optical Kerr effect (OKE) signals of FePcC show an ultrafast response under both on-resonant and off-resonant excitation. The magnitude of χ (3) in FePcC was determined to be about 10−11 esu (corresponding to 10−19   m 2   V −2 ) under both on-resonant and off-resonant conditions.

The ionization potential of large metallic clusters is IP=WF+α(e 2/4πε 0 R), where WF is the work function, R is the cluster radius, and α is a constant that is equal to 3/8 or 1/2 depending on the method the above formula was derived. This electrostatic paradox was resolved here by using proper values for the work function. In the image charge method WF refers to a plane (denoted as W ), whereas in the spherical-capacitor approach WF refers to the surface of a grounded metallic ball, which is W −(1/8)(e 2/4πε 0 R).