Chemical Physics Letters (v.434, #1-3)

Contents (vii-xv).

The 5f3 manifold of the free-ion U3+: Ab initio calculations by Fernando Ruipérez; Björn O. Roos; Zoila Barandiarán; Luis Seijo (1-5).
Term and level energies of the 5f3 configuration of free U3+. Left: CGWB-AIMP calculated terms referred to 4I and shifted 7212 cm−1. Center: CGWB-AIMP calculated level energies referred to the 4I9/2 ground state. Right: Level energies estimated by Carnall and Crosswhite out of experimental data of U3+ in solids.The energy levels of the 5f3 manifold of the free-ion U3+ up to 30 000 cm−1 are calculated with two well stabilized ab initio methods based on the two-component Hamiltonians of Cowan–Griffin–Wood–Boring and Douglas–Kroll–Hess. Although the corresponding experimental data do not exist, estimates made out of experiments on the 5f3 manifold of U3+ in solids are usually referred to as the experimental energies of U3+ in gas phase. On the basis of a discussion on the available data of f-element ions in gas phase and in solids and a discussion on the expected precision of the present calculations, we suggest that the 5f3 energy levels of free U3+ are higher than the estimates and lower than the present ab initio calculations.

Photodissociation of acetaldehyde at 205 nm: The H atom channels by Tae Yeon Kang; Seong Woo Kang; Hong Lae Kim (6-10).
Photodissociation dynamics of acetaldehyde (H3CCOH) at 205 nm has been investigated by measuring laser induced fluorescence spectra of H (2S) especially for the hydrogen atom production channels, from which translational energy releases were measured. The detailed dissociation dynamics were discussed from the measured translational energy releases and the channel branching ratio.Photodissociation dynamics of acetaldehyde (CH3CHO) at 205 nm has been investigated by measuring laser induced fluorescence spectra of H (2S) especially for the hydrogen atom production channels. The translational energy releases in the H + CH2CHO and H + CH3CO channels were measured from the Doppler broadened spectra, which are 156.9 ± 13.0 and 113.8 ± 10.0 kJ/mol, respectively. From the measured channel branching ratio and translational energy releases, it was concluded that the dissociation should take place on the triplet surface with considerable recombination barriers along the reaction coordinates.

Interactions of low-energy electrons with Ir(ppy)3 in the gas phase by A.V. Kukhta; I.N. Kukhta; S.A. Bagnich; S.M. Kazakov; V.A. Andreev; O.L. Neyra; E. Meza (11-14).
The electron impact spectroscopy and density functional theory techniques have been used to study electronic transitions in Ir(ppy)3. No essential differences between optical and electron impact excitation of Ir(ppy)3 have been found, and phosphorescence can be observed mainly owing to intercombination singlet–triplet transitions.The relative efficiency of excitation into singlet and triplet states in the region between 1.5 and 9 eV, their dependence on projectile electron energies for the scattering of monoenergetic electrons with tunable energies from 0 to 50 eV at an angle of 90°, for the widely known electroactive organic material tris(2-phenylpyridine)iridium (Ir(ppy)3) in the gas phase are presented. Some direct singlet–triplet transitions in the region 2.5–2.8 eV and nearby 4.4 eV are observed. No intense singlet–triplet transitions can be observed in spite the presence of the heavy Ir atom; this is probably due to the charge transfer nature of the transition. The spectrum of singlet and the positions of triplet transitions are studied using density functional theory techniques. No essential differences between optical and electron impact excitation of Ir(ppy)3 have been found, and phosphorescence can be observed mainly owing to intercombination singlet–triplet transitions.

Hydration of excess electrons trapped in charge pockets on molecular surfaces by Abraham F. Jalbout; R. Del Castillo; Ludwik Adamowicz (15-19).
In this work we have studied the ability of water to stabilize excess electron density on a surface of cyclohexane rings functionalized with OH groups. We present calculations supporting the fact that the water can be connected to a hypothetical surface through an electron bond forming an AISE state. Our calculations show that these systems are stable with respect to vertical electron detachment (VDE).In this work we strive to design a novel electron trap located on a molecular surface. The process of electron trapping involves hydration of the trapped electron. Previous calculations on surface electron trapping revealed that clusters of OH groups can form stable hydrogen-bonded networks on one side of a hydrocarbon surface (i.e. cyclohexane sheets), while the hydrogen atoms on the opposite side of the surface form pockets of positive charge that can attract extra negative charge. The excess electron density on such surfaces can be further stabilized by interactions with water molecules. Our calculations show that these anionic systems are stable with respect to vertical electron detachment (VDE).

Probing stereodynamics in reactive collisions using helicity filtering by Magnus Gustafsson; Rex T. Skodje (20-24).
For low energy collisions, helicity conservation together with the spectral structure of the quantum bottleneck states lead to separated thresholds for reagent states of different alignment. The DCS product distribution for individual orientation states may be inferred through processing of the orientation-averaged results obtained for two or more rotational states.Stereodynamic effects in the D + H2 reaction are studied using a new method that permits reagent-helicity dependent cross sections to be inferred from the scattering results obtained using randomly oriented reagent molecules. Employing fully converged quantum scattering calculations as a benchmark, it is demonstrated that the method yields useful results for all the helicity states corresponding to j  = 1 and 2 of the H2 diatom.

The anisole–ammonia complex: Marks of the intermolecular interactions by Giovanni Piani; Massimiliano Pasquini; Giangaetano Pietraperzia; Maurizio Becucci; Antonio Armentano; Emilio Castellucci (25-30).
A REMPI-TOF study of the anisole–ammonia jet cooled complex, supported by molecular mechanics, DFT calculations.We report an experimental study, supported by classical and quantum calculations, of the anisole–ammonia jet cooled complex. The origin band of the S1  ← S0 electronic transition is red shifted with respect to the corresponding band for the bare anisole molecule. From the simulation of the origin band rotational contour and the results of quantum mechanical calculations, we have been able to determine the non-planar structure of the complex. The ammonia molecule is bonded to anisole via two hydrogen bonds: one in which the nitrogen lone pair interacts with the hydrogen atoms of the methoxy group; the other involving the ammonia hydrogen atoms and the π-electron density of the aromatic ring.

Investigation of electronic structure and proton transfer in ground state acetylacetone by Stacy A. Broadbent; Lori A. Burns; Chandrima Chatterjee; Patrick H. Vaccaro (31-37).
Despite having been the subject of numerous experimental and theoretical efforts, the structure of the X ∼ 1 A 1 ground electronic state of acetylacetone still remains a matter of controversy. High-level quantum chemical methods have been enlisted to explore this issue, resulting in a global minimum-energy configuration of Cs symmetry.Various quantum chemical methods, including Hartree–Fock (HF), density functional (DFT/B3LYP), Møller–Plesset perturbation (MP2), and coupled-cluster [CCSD, CCSD(T), CC3] schemes, have been exploited with correlation-consistent basis sets in an attempt to resolve controversies surrounding the equilibrium structure of ground-state acetylacetone. Geometry optimizations performed at the CCSD(T)/aug-cc-pVDZ level of theory predict a global minimum-energy configuration of Cs symmetry that exhibits an interoxygen distance of 2.575 Å, with the symmetric (C2v) transition state for proton transfer presenting a potential barrier of 1276.7 cm−1 height. The resulting theoretical description of acetylacetone is in excellent agreement with recent electron diffraction experiments.

On the stability of noble gas molecules by Tsung-Hui Li; Ya-Lin Liu; Ren-Jie Lin; Tai-Yan Yeh; Wei-Ping Hu (38-41).
The XNgY molecules can undergo dissociation by the two channels: (a) XNgY → X + Ng + Y, and (b) XNgY → Ng + XY. The stability is determined by the dissociation rate constants.We have tested the MP2 and CCSD(T) theory with various basis sets on the reaction energies and barrier heights of the two dissociation channels for the noble gas (Ng) molecules of the type XNgY: (a) XNgY → X + Ng + Y, and (b) XNgY → Ng + XY. We demonstrated that the MP2 method systematically overestimates the bond energies of XNgY molecules. We also obtained the theoretical half-lives of HArF and HCCArF as a function of temperature and energy barriers by calculating the unimolecular thermal rate constants of the two dissociation channels.

Effects of salt addition on strength and dynamics of hydrophobic interactions by Takatoshi Fujita; Hirofumi Watanabe; Shigenori Tanaka (42-48).
A typical snapshot of large solvation shell assisting methane clustering. Green spheres represent chloride ions, and pink spheres represent methane solutes. (For interpretation of the references to colour, the reader is referred to the web version of this article.) Gdm+ ions and water molecules are depicted by spacefill and stick representations, respectively.Effects of salt addition on strength and dynamics of hydrophobic interactions are investigated by molecular dynamics simulations for hydrophobic solutes in aqueous solution of various salts such as sodium chloride, ammonium chloride, and guanidinium chloride. Hydrophobic interaction is reduced by ammonium chloride, enhanced by sodium chloride, and strongly enhanced by guanidinium chloride. Addition of salts tends to delay the relaxations of hydrophobic associations by reducing water diffusivities and enhancing structuring of water. The underlying molecular mechanisms are discussed in detail.

The microheterogeneous model represents an ion-exchange membrane as a multiphase system containing at least two phases, gel phase and electroneutral solution, with volume fractions f 1 and f 2, respectively, the sum f 1  +  f 2 being equal to 1. The gel phase represents a nanopore medium, globally electroneutral; it includes fixed and mobile ions, polymer matrix, and water. The electroneutral solution, the properties of which are assumed to be the same as these of the outer equilibrium solution, fills the inner parts of meso- and macropores as well as fissures and cavities (=intergel spaces).Influences of the concentration of different electrolyte solutions on the water content of the CMS cation exchange membrane were studied. Based on the microheterogeneous model of electromembrane, we determined the fraction of the interstitial phase in presence of NaCl and H2SO4 solutions by using the conductivity results obtained from impedance spectroscopy. The polyelectrolyte theory was applied to explain the dependence of the water content and the fraction of the interstitial phase on the nature of the counter ions.

Linear and non-linear optical response properties of singlet 2-electron quantum dots by Manas Ghosh; Ram Kuntal Hazra; S.P. Bhattacharyya (56-62).
We explore the pattern of linear and non-linear optical (NLO) response of 2-electron singlet quantum dots in two dimensions with or without anharmonicity in the confinement potential. The influence of transverse magnetic field strength (B) on linear (α), first (β), and second (γ) NLO response of the system are analyzed. A simple, exactly solvable model involving two interacting harmonic oscillators is exploited to explain some of the observations.We explore the pattern of linear and non-linear optical (NLO) response of 2-electron singlet quantum dots in two dimensions with or without anharmonicity in the confinement potential. The influence of transverse magnetic field strength (B) on linear (α), first (β), and second (γ) NLO response of the system are analyzed. A simple, exactly solvable model involving two interacting harmonic oscillators is exploited to explain some of the observations.

Current oscillations are employed to investigate the chlorate effect on the iron passivity in sulphuric acid solutions. It is shown that chlorates induce pitting corrosion due to the chlorides produced via the reduction of chlorates by ferrous ions. General and pitting corrosion are explained by using a point defect model.Current oscillatory phenomena were used to investigate the effect of chlorates on the passive state of iron in sulfuric acid solutions. Experimental results show that chlorates cause pitting corrosion, besides general corrosion. It is shown that pitting is not due to the chlorate ion itself, but to chlorides produced via the reduction of chlorates by ferrous ions. General and pitting corrosion are explained in terms of a point defect model proposed to describe the oxide growth and breakdown.

Pressure effect studies on the 3D spin crossover system: {Fe(3CN-py)2[M(CN)2]2} ·  nH2O (n  ⩽ 2/3, M = Ag(I), Au(I)) by Ana Galet; Ana Belén Gaspar; Gloria Agustí; M. Carmen Muñoz; José Antonio Real (68-72).
Pressure effect investigations on the magnetic behaviour of the 3D SCO polymers {Fe(3CN-py)2[Ag(CN)2]2} · 2/3H2O (1) and {Fe(3CN-py)2[Au(CN)2]2} · 2/3H2O (2) have been carried out in the range of 105  Pa to 0.7 GPa. Despite both compounds are isostructural their magnetic behaviour under applied hydrostatic pressures is very different. Strong nonlinearity in the T c(P) vs. P plot has been observed for compound 1 a fact which contrasts with the almost linear dependence observed for each spin transition in 2. However, both compounds are extremely sensitive to the application of pressure as well as the T c(P) vs. P plots denote.Pressure effect investigations on the magnetic behaviour of the 3D SCO polymers {Fe(3CN-py)2[Ag(CN)2]2} · 2/3H2O (1) and {Fe(3CN-py)2[Au(CN)2]2} · 2/3H2O (2) have been carried out in the range of 105  Pa to 0.7 GPa. Despite both compounds are isostructural their magnetic behaviour under applied hydrostatic pressures is very different. Strong nonlinearity in the T c(P) vs. P plot has been observed for compound 1 a fact which contrasts with the almost linear dependence observed for each spin transition in 2. However, both compounds are extremely sensitive to the application of pressure as well as the T c(P) vs. P plots denote.

High performance supercapacitor from chromium oxide-nanotubes based electrodes by Grzegorz Lota; Elzbieta Frackowiak; Jagjiwan Mittal; Marc Monthioux (73-77).
Pseudocapacitance effects CrO a (OH) b  +  δH+  +  δ e  ↔ CrO aδ (OH) b+δ related to the chromium oxide present in hybrid material together with high conducting properties of SWNTs allow building efficient electrodes for supercapacitor. Exceptionally quick charge propagation was observed, doubtless due to the overall physical and textural properties of SWNTs material. Especially, unique conductivity of SWNTs due to their one dimensional electronic structure, texture perfection and ballistic electronic transport enable them to carry high currents (50 A g−1).Single wall carbon nanotubes (SWNTs) filled and doped with chromium oxide have been used as attractive electrodes for supercapacitors. Pseudocapacitance effects related to the presence of nanosized chromium oxide finely dispersed at the nanoscale together with high conducting properties of SWNTs allow building efficient electrodes from this hybrid material. Even if capacitance values are not very high (ca. 60 F g−1), however, extremely quick charge propagation was observed, doubtless due to the overall physical and textural properties of SWNT material. The positive effect – with respect to empty-SWNTs – brought by the presence of chromium oxide in and probably in-between the SWNTs indicates that chromium oxide is accessible to the electrolyte in spite of its encapsulated location, because of the numerous side entries created all along the SWNT walls during the filling step.

FeCl2-CVD production of carbon fibres with graphene layers nearly perpendicular to axis by Thomas Laude; Hiroaki Kuwahara; Kazuhiko Sato (78-81).
Acetylene reacted with un-decomposed FeCl2 vapours to mass-produce semi-crystalline carbon fibres belted by iron rings at centres, and readily crystallisable into a large-angle conical piling along fibre axis.We decomposed acetylene by chemical vapour deposition in presence of FeCl2 vapours, which react with carbon radicals without thermal decomposition (500 °C). This produced a large volume of wool-like product around the FeCl2 reservoir, composed of semi-crystalline carbon fibres, with high conversion rate (40 mass%). Fibres showed remarkable morphology, with iron nano-rings belting their centres and mirror symmetry. Fibres were mono or multi filament (each filament belted with metal). Semi-crystalline fibres were readily transformed by thermal treatment into a large-angle conical structure with turbostratic piling along fibre axis. These observations suggest a catalytic growth on the inner wall of iron rings.

It is shown, via current–voltage analysis, that modifying the surface of an ultra-thin gold electrode with a self-assembled thiolate polar monolayer is an effective means of circumventing the well documented abrupt negative vacuum level shift, which forms when the amorphous molecular semiconductor N,N′-bis(3-methylphenyl)-N,N′diphenyl-1,1′biphenyl-4,4′-diamine (TPD) is thermally deposited onto gold electrodes.This Letter, reports the hole-injection characteristics of an ultra-thin, transparent gold electrode derivatized with a thiolate polar monolayer into the amorphous molecular semiconductor, N,N′-bis(3-methylphenyl)-N,N′diphenyl-1,1′biphenyl- 4,4′-diamine (TPD). Thermionic emission with image force lowering gives an excellent description of the injection mechanism over a large range of temperatures and electric field strengths, yielding a zero field Schottky barrier height of ∼0.4 eV. This study demonstrates that derivatizing the surface of this novel gold electrode with a 4-nitrophenylthiolate monomolecular layer is an effective means of circumventing the abrupt negative vacuum level shift, which forms when TPD is thermally deposited onto gold electrodes.

The Stone–Wales defect SWNTs generated by axial bond rotation (ABR) are generally more stable compared to those resulted by circumferential C–C bond rotation (CBR).The formation energy of single Stone–Wales (SW) defect with possible two different orientations in (5, 5) single-walled carbon nanotubes (SWNTs) has been investigated using Hartree–Fock and MP2 methods and B3LYP functional. The formation energies computed at the B3LYP/6-31G(d) level are in good agreement with those obtained at the MP2/6-31G(d) level. A 90° rotation of an axial C–C bond is slightly more preferred than the circumferential C–C bond in forming the Stone–Wales defect in (5, 5) SWNT. The reactivity of the C–C bond shared by two heptagons in the SW defect of SWNTs depends on the orientation of the SW defect.

Treatment of acid oxidised multi-wall carbon nanotubes with the alkali metal hydroxides LiOH, KOH and NaOH is shown to be a facile means of reducing the work function by as much as 0.4 eV via metal cation exchange with protons associated with acidic surface moieties.We report a large reduction in the work function of acid oxidised multi-wall carbon nanotubes upon exchange of protons associated with acidic surface groups with the alkali metal cations Li+, Na+ and K+ measured using ultra-violet photoelectron spectroscopy. X-ray photoelectron spectroscopy provides compelling evidence for the preferential uptake of Na+, over Li+ and K+ and yields an estimate of the density of surface bound carboxylic acid moieties onto which functional organic molecules can be chemically attached.

Surface photovoltage study of photogenerated charges in ZnO nanorods array grown on ITO by Qidong Zhao; Dejun Wang; Linlin Peng; Yanhong Lin; Min Yang; Tengfeng Xie (96-100).
Surface photovoltage of chemically synthesized ZnO nanorods array shows spectrum-dependent characteristic. The feature is demonstrated by Kelvin probe and lock-in amplifier based measurement. The figure shows exciton-related photovoltage response when the interface between ITO and ZnO nanorods is excited.A well-aligned nanorods array of ZnO was chemically grown on conductive ITO substrate at low temperature. The photogenerated charges at surface and interface were examined by surface photovoltage techniques based on both Kelvin probe and lock-in amplifier with dc bias. The photovoltage response bands related to band-to-band transition and bound excitons were discriminated. We demonstrated the spectrum-dependent transfer characteristic of photogenerated charges at the surface of ZnO nanorods array and the interface between ZnO and ITO.

The properties of 5-aminolevulinic acid (5ALA) and its alkyl esters are studied by density functional theory methods.5-Aminolevulinic acid (5ALA) is the key synthetic building block in protoporphyrin IX (PpIX), the heme chromophore in mitochondria. The addition of extracorporeal 5ALA and its alkyl ester derivatives are in current clinical use in photodynamical diagnostics and photodynamic therapy of tumors and skin disorders. In the current study density functional theory calculations are performed on 5ALA and its methyl, ethyl, and hexyl esters, in order to explore the basic chemical properties of these species. It is concluded that even in aqueous media the zwitterionic form of 5ALA is less stable than the non-zwitterionic one, that the local environment (lipid vs water) affects the energetics of reaction considerably, and that the hexyl species is most prone to hydrolysis of the three alkyl ester derivatives.

Quantum chemical study on the population of the lowest triplet state of psoralen by Juan José Serrano-Pérez; Manuela Merchán; Luis Serrano-Andrés (107-110).
Efficient and competitive population of the reactive lowest-lying triplet state in gas-phase phototherapeutic psoralens can be achieved by combining intersystem crossing and internal conversion processes, as suggested by quantum chemical CASPT2 calculations.The efficient population of the low-lying triplet ππ* state of psoralen is studied with the quantum chemical CASPT2 method. Minima, singlet–triplet crossings, conical intersections, and reaction paths on the low-lying singlet and triplet states hypersurfaces of the system have been computed together with electronic energy gaps and spin–orbit coupling terms. A mechanism is proposed, favorable in the gas phase, for efficient deactivation of the initially populated singlet excited ππ* state, starting with an intersystem crossing with an nπ* triplet state and evolving via a conical intersection toward the final lowest-lying ππ* triplet state, protagonist of the reactivity of psoralen.

A TDDFT study on the excitation of P700 by Yuming Sun; Zhenhong Dai; Weitian Wang; Yuanping Sun (111-115).
The special chlorophyll pair P700, the ‘heart’ of the reaction center of photosynthetic system I, was studied using time-dependent density functional method to reveal the relation between its excitation and the relative use of two electron transfer branches.The excitation property of P700 has been studied using the time-dependent density functional method. It is found that the excitation of P700 is intrinsically asymmetric at its two Chla halves, and this asymmetry may be closely related to the relative use of two electron transfer branches. Based on the calculated results, we also proposed a charge separation mechanism for P700, in which the time evolution of the excited state of P700 is modulated by a quantum beat of period about 75 fs, making the electron transfer of two branches correlated, or complementary effect possible.

The triplet state decay kinetics and deactivation funnel geometry of a series of nonplanar saddle-shaped porphyrins by Vladimir S. Chirvony; Igor V. Avilov; Andrei Yu. Panarin; Vladimir L. Malinovskii; Victor A. Galievsky (116-120).
The triplet state lifetimes of the series of nonplanar saddle-shaped porphyrins are found to be much shorter than those of their planar analogs (hundreds of ns vs. a few ms). DFT calculations suggest the existence of two types of conformations in the triplet excited state: “undistorted” (characterized by triplet-ground state energy gaps ∼0.8–1 eV) and “distorted” (characterized by drastically shortened gaps ∼0.2 eV).It is found that the triplet state lifetimes of the series of nonplanar saddle-shaped porphyrins are much shorter than those of their planar analogs (hundreds of nanoseconds vs. several milliseconds). As our calculations show, two low-lying conformations with strongly different triplet-ground singlet state energy gap ΔE TS exist for each molecule in its triplet state. An energy inversion of these conformations for the most distorted porphyrin molecule is found to be responsible for the observed non-monotonic dependence of the triplet state deactivation rate on the degree of nonplanar distortion.

Electric field effects on the reactivity of heme model systems by Pablo M. De Biase; Fabio Doctorovich; Daniel H. Murgida; Dario A. Estrin (121-126).
Proteins integrated or transiently bound to membranes are subject to strong electric fields. High electric fields are also present in protein-based electrochemical devices. We report DFT calculations of the electric field effects on ligand binding and on redox potentials of porphyrin models representing the active sites of typical heme proteins.Proteins integrated or transiently bound to membranes are subject to strong electric fields. However, the role of these fields on tuning the reactivity of redox proteins is still an open issue. High electric fields are also present in protein-based electrochemical devices. In this work we report DFT calculations of the electric field effects on ligand binding and on the redox potentials of porphyrin models representing the active sites of typical heme proteins such as cytochrome c, cytochrome c oxidase, cytochrome c peroxidase and cytochrome P450.

Near infrared photo-induced DNA damage in the presence of copper-dppz complex: Evidence for the involvement of singlet oxygen by Angela Fortner; Shuguang Wang; Gopala Krishna Darbha; Anandhi Ray; Hongtao Yu; Paresh Chandra Ray; Rajamohan R. Kalluru; Chan Kyu Kim; Vinita Rai; Jagdish P. Singh (127-132).
Long-standing challenge is the development of a photo-sensitizer with a very good DNA damage efficiency in (700–800) nm region, which satisfies the basic requirements of photodynamic therapy. This Letter demonstrates for the first time that 99% DNA damage activity above 700 nm is possible in the presence of copper (II) complex and shows a nice trend between DNA damage efficiency and singlet oxygen quantum yield.We present the effect of the DNA damage efficiency by excitation wavelengths above 700 nm within d–d transition bands of (l-lysine) (dppz) Cu(II) complexes. Our results show significant DNA cleavage between 700 and 755 nm. The efficiency of photosensitized DNA cleavage and quantum yield of singlet oxygen production at different excitation wavelengths have been determined to gain insight into the involvement of the d–d band in the DNA damage process. Time-dependent density functional (TD-DFT) calculations were performed to understand the influence of the metal to l-lysine transition on the d–d bands of the Cu(II) complex-DNA moiety. It is found that the involvement of d–d transition in the reaction pathway of singlet oxygen formation seems to play an important role in the DNA cleavage efficiency using light of wavelength above 700 nm.

Hybridization energies of double strands composed of DNA, RNA, PNA and LNA by Takayuki Natsume; Yasuyuki Ishikawa; Kenichi Dedachi; Takayuki Tsukamoto; Noriyuki Kurita (133-138).
The electronic properties of double strands involving LNA, PNA, DNA and RNA were investigated by density-functional theory calculations. The computed hybridization energies are comparable to the experimental finding that PNA and LNA single strands display high affinity toward a complementary DNA or RNA strand.The electronic properties of double strands composed of trimeric LNA, PNA, DNA and RNA single strands were investigated by density-functional molecular orbital calculations. The computed hybridization energies for the double strands involving PNA or LNA are larger than those for DNA–DNA and RNA–RNA. The larger stability is attributed to the presence of a larger positive charge of the hydrogen atoms contributing to the hydrogen bonds in the PNA–DNA and LNA–DNA double-strands. These results are comparable to the experimental finding that PNA and LNA single strands display high affinity toward a complementary DNA or RNA single strand.

On the magnetic field and isotope effects in enzymatic phosphorylation by Anatoly L. Buchachenko; Nikita N. Lukzen; J. Boiden Pedersen (139-143).
Our calculations of the rate of ATP production, based on the shown, previously proposed, reaction mechanism, agree with the experimentally observed magnesium isotope effect. We predict that a magnetic field will increase the rate of ATP formation by 60% for samples enriched by the magnetic magnesium isotope .A huge magnesium isotope effect on the rate of enzymatic synthesis of adenosine triphosphate (ATP) has recently been reported. This indicates that the reaction involves an intermediate ion-radical pairs and should be sensitive to external magnetic fields. We have calculated the rate of ATP production based on a previously proposed molecular reaction mechanism. The calculated maximum isotope effect is in agreement with experiment. Magnetic field is predicted to increase the rate of ATP formation by 60% for samples enriched by magnetic magnesium (25Mg) while decreasing the rate by 9% for naturally occurring samples.

Surface stabilized layer of a surface drying phase by G. Barbero; L.R. Evangelista; I. Lelidis (144-148).
Surface stabilized phases in the case of ordered media with two competing order parameters. If the lower temperature phase is destabilized at the substrate, and if there is a coupling between the order parameters, the surface drying phase might form a layer close to the substrate.Surface stabilized phases in the case of ordered media with two competing order parameters describing two distinct phases, stable in different temperature ranges, are investigated. If the lower temperature phase is destabilized at the substrate, and if there is a coupling between the two order parameters, we show that the surface drying phase might form a layer close to the substrate. This behavior is investigated for a semi-infinite sample and for a sample in the shape of a slab of thickness d. It is shown that one of the order parameters presents a maximum close to the surface.

Effective simulation of biological systems: Choice of density functional and basis set for heme-containing complexes by Chunying Rong; Shixun Lian; Dulin Yin; Aiguo Zhong; Ruiqin Zhang; Shubin Liu (149-154).
Using ferric-S-methyl-porphyrin as the prototype, the issue of how to effectively simulate systems of biological importance is addressed in regard to the selection of density functionals and basis sets. Accurate structural and electronic properties including DFT reactivity indices have been obtained and significant gain in computational efficiency has been achieved.Using ferric-S-methyl-porphyrin as the prototype of heme-containing complexes, we address how to accurately and efficiently carry out density functional studies for systems of biological importance. Our results indicate that GGA and meta-GGA functionals bias the lower spin state by producing levitated frontier orbitals and often fail to provide a correct description of the ground spin state. Also, we propose composite double and triple zeta quality basis sets with polarization functions applied only to the transition metal and electronegative atoms. Accurate structural and electronic properties including DFT reactivity indices have been obtained and significant gain in computational efficiency has been achieved.

The comparison of experimental and theoretical electronic absorption spectra obtained from TD-DFT calculations has allowed the determination of the preferential complexing site in the Al(III)-protocatechuic acid system.In acidic aqueous medium and in methanol, the formation of a 1:1 complex between Al(III) and protocatechuic acid (PCAH) was highlighted by electronic absorption spectroscopy. The ground and low-lying excited electronic states of the possible structures of the 1:1 complex were studied using DFT approach. Molecular and electronic properties were calculated using the VSXC functional, while excited singlet states were examined using TD-DFT methodology. A very good agreement in wavelengths was found between the theoretical electronic spectrum of a chelate involving the catechol group and the 1:1 complex experimental spectrum.

The standard heat of formation ( Δ H f ∘ ) of corannulene (C20H10) is calculated based on 40 hyperhomodesmotic reactions constructed based on different schemes, under which resonance energy and/or nonplanar strain energy are considered.The standard heat of formation ( Δ H f ∘ ) of corannulene (C20H10) is calculated based on 40 hyperhomodesmotic reactions and compared with the existing experimental result. We found that: (1) the reliability of hyperhomodesmotic reactions depends on the construction scheme and the reference molecules; (2) both resonance energy and nonplanar strain energy should be considered during the construction of hyperhomodesmotic reactions. Two principles are proposed for the selection of reference molecules: (i) structurally similar to the object molecule; (ii) simple and small. Due to structural similarity, the above knowledge obtained from C20H10 is of great reference for polycyclic aromatic hydrocarbons and fullerenes.

A new population analysis: Dipole-moment-conserving charge-set by Hirofumi Sato; Shigeyoshi Sakaki (165-169).
By using the first-order moment of the integral, a new population analysis is developed. The analysis computes the gross charge population that exactly reproduces total dipole moment of linear molecules.A modified version of the Mulliken population analysis is developed. In the original Mulliken population analysis, the overlap density is equivalently partitioned into the two concerning atoms. In the present version, this trivial assumption is uprated by using the first-order moment of the integral, i.e. dipole moment integral. The modified version of the analysis computes the gross charge population that exactly reproduces total dipole moment of linear molecules.