Computational & Theoretical Chemistry

Processes using supercritical fluids constitute another special separation process option other than the membrane processes which have been presented in one of the previous issues as alternative to conventional separation processes. Separation processes that ...

Metal oxides have been reported as high capacity anode materials in Lithium-ion batteries (LIBs) but lack merit of commercialization due to volume-expansion during operation and poor electronic conductivity. Nanosized metal oxide could be used to circumvent these demerits. In this work, we examined the application of tin oxide nanoclusters (Sn 3 O z , z = 0, 3-7) as anode materials in LIB using ab initio density functional theory perspective. Analysis of moderately lithiated tin oxide nanoclusters (Li x Sn 3 O z , x = 1-10) indicates a tremendous reduction in volume-expansion due to high surface area of the nanoclusters by analysis of change in Sn-Li bond length with number of lithiation by process of alloying. Structural analysis also revealed the formation of Li 2 O by conversion reaction during lithiation. Stability studies by binding energy (B.E.) during lithiation showed decreased stability as lithiation increased. The role of chemical reactivity concept on the lithiation of Sn 3 O z nanoclusters were revealed by the physicochemical properties of the nanoclusters. Electrophilicity studies reveals the capability of the nanoclusters to accept electrons from the inserted Li. Sn 3 and Sn 3 O 3 nanoclusters were the most suitable anode materials amongst other nanoclusters presented with average intercalation voltage (AIV) of 0.67 and 1.12 V respectively. The adsorption energy (E ads) and dissociation energy (E dis) obtained showed that Li dimer formation can be prevented by these nanoclusters as anode. The calculations substantiate the suitability of tin oxide nanoclusters as anode material in LIBs.

An algorithm for generating novel connectivity topological descriptors, denoted SP (subgraph property), is proposed and exemplified for P being the number of vertices N, walk degree wt'e), Randić index X, and Wiener index W. SP indices based on wt'e) and x wt'e) (Razinger's extension of x index) are tested for correlation with some physico-chemical properties of octane isomers.

By using electrospray ionization mass spectrometry (ESI-MS), it was proven experimentally that the univalent cesium cation (Cs + ) forms with meso-octamethylcalix[4]pyrrole (abbrev. 1) the cationic complex species 1 . Cs + . Further, applying quantum chemical DFT calculations, four different conformations of the resulting complex 1 . Cs + were derived. It means that under the present experimental conditions, this ligand 1 can be considered as a macrocyclic receptor for the cesium cation. ___________________________________________________________________________ The development of ditopic ion-pair receptors and calix[4]pyrrole based anion receptors * Corresponding author.

Formation of vacancy-interstitial Frenkel pairs, together with the properties of interstitials and vacancies in CdTe, ZnTe, and their alloys were investigated by first-principles calculations. Generation of Frenkel pairs on the cation sublattice strongly depends on the Fermi energy: the presence of excess free electrons reduces the energy barrier for the pair generation from 2.5 eV in intrinsic samples to 1.2 eV. Moreover, E F determines both the stability of Frenkel pairs with respect to recombination and their binding energy, which varies from ϳ0.2 to ϳ1 eV. A strong dependence on the Fermi energy, i.e., on the charge state, is also found for stable sites and barriers for diffusion of isolated interstitials. In particular, neutral interstitials have two ͑meta͒stable sites, corresponding to two local minima of energy, and diffuse by jumps between them. Positively charged interstitials have only one stable site and diffuse by twice longer and curvilinear jumps. For the relevant charge states, the barriers for diffusion range from 0.5 to 1 eV, which imply a high mobility of interstitials. Most of these properties are traced back to the defect-induced deep gap levels, their occupation, and their dependence on the defect's site. The important role of the ionicity of the host is pointed out. On the other hand, generation of Frenkel pairs on the anion sublattice requires energy of about 5 eV, and thus is nonefficient. The obtained results suggest that formation of Frenkel pairs is a microscopic origin of two effects recently observed in Schottky junctions based on CdZnTe and other II-VI alloys, namely, the reversible changes in conductivity by a few orders of magnitude, and the ferroelectric-like behavior of polarization.

Cytochrome ba3 is a proton-pumping heme-copper oxygen reductase from the extreme thermophile Thermus thermophilus. Despite the fact that the enzyme's active site is buried deep within the protein, the apparent second order rate constant for the initial binding of O2 to the active-site heme has been experimentally found to be 10(9) M(-1) s(-1) at 298 K, at or near the diffusion limit, and 2 orders of magnitude faster than for O2 binding to myoglobin. To provide quantitative and microscopic descriptions of the O2 delivery pathway and mechanism in cytochrome ba3, extensive molecular dynamics simulations of the enzyme in its membrane-embedded form have been performed, including different protocols of explicit ligand sampling (flooding) simulations with O2, implicit ligand sampling analysis, and in silico mutagenesis. The results show that O2 diffuses to the active site exclusively via a Y-shaped hydrophobic tunnel with two 25-Å long membrane-accessible branches that coincide with th...

Present-day theoretical computation methods are quite effective at anticipating how corrosion inhibitors would behave on metal surfaces, conserving time and resources on laboratory testing. The present study aims to predict the inhibitory effectiveness of certain furan derivatives on surfaces of Fe (110) and Sn (111) in acidic media. To compare their fundamental attributes against corrosion as well as their behavior on iron (Fe) and tin (Sn) surfaces in an acid medium, six urea derivatives have been chosen for this purpose: Imidazolidin-2-one (Cpd A), 4-methylimidazolidine-2-one (Cpd B), Tetrahyropyrimidin-2(1H)-one (Cpd C), 1,3-dimethylimidazolidin-2-one (Cpd D), 1,1-diethylurea (Cpd E), 1,3-dimethylurea (Cpd F). The anti-corrosive characteristics of Cpds A - F were generally explored using Density Functional Theory and Monte Carlo simulations. The results indicate that the compounds had low energy gaps, the highest occupied molecular orbital energy, global hardness, as well as ionization energy and high Electron affinity, ELUMO, global softness, and number of transferred electrons, which explained their corrosion inhibition potentials. Electrostatic potential (ESP) and Fukui indices identified the reactive sites with the ability to accept and donate electrons via back-donation to the metal's d-orbital. The Monte Carlo simulation demonstrated a favorable contact between the Fe (110) and Sn (111) surfaces and inhibitory molecules in the acidic medium. In the industrial sectors, these compounds may be secured as corrosion protectors.

Schistosoma mansoni flatworm pathogen, we report further structure activity relationships (SAR) of 19 N-phenylbenzamide analogs. Our previous SAR studies, designed by selecting representative substituents from the Craig plot, identified 9 and 11 which possessed electron-withdrawing groups that benefited potency. This study sought to enhance the potency of this chemotype by incorporating other electron-withdrawing functionalities not studied previously and to overcome the potential pharmacokinetic liabilities associated with the high lipophilicity of frontrunner compounds. Compared to the most potent compound, 9 (EC 50 = 80 nM), from our previous work, the most potent compounds in the current study (32 (EC 50 = 1.17 µM), 34 (EC 50 = 1.64 µM) and 38 (EC 50 = 1.16 µM)) were less active although they retained single digit micromolar potency. Furthermore, compound 38 generated a CC 50 value of > 20 µM in counter toxicity screens using HEK 293 cells, translating to a wide selectivity index of > 17.

The aim of this research work is to develop a method to provide a reasonable "prior" electron density that can be used in the so-called "Maximum Entropy Method" (MEM) refinement of Xray diffraction (XRD) data in order to reconstruct experimental electron density at a resolution allowing its accurate topological analysis. A program was developed which build electron density on a regular grid in the "Independent Atom Model" (IAM) approach, more precisely from the knowledge of individual "spherical" atomic scattering factors of the atoms constituting the unit cell of the studied compounds. IAM X-ray structure factors of bismuth and its prior density on a grid has been generated to be tested with the MEM "Enigma" software. Preliminary accuracy and performances have been compared when such reasonable "prior" density is used instead of starting with "flat" density.

According to reports, the bioactive thiourea derivative was prepared from the ethanol solutions of thiourea and chloro acetic acid in a 1:1 M ratio. DFT calculations of 2-Imino-4-oxo-1,3-thiazolidine hydrochloride (IOTH) were performed with the use of B3LYP and the 6-311+G(2d,p) basis set. Frontier molecular orbitals, mapped electrostatic potential (MEP) map, and nonlinear optical (NLO) properties of the

A new approximation formalism is applied to study the bound states of the Hellmann potential, which represents the superposition of the attractive Coulomb potential −a/r and the Yukawa potential b exp(−δr)/r of arbitrary strength b and screening parameter δ. Although the analytic expressions for the energy eigenvalues E n,l yield quite accurate results for a wide range of n, ℓ in the limit of very weak screening, the results become gradually worse as the strength b and the screening coefficient δ increase. This is because that the expansion parameter is not sufficiently small enough to guarantee the convergence of the expansion series for the energy levels.

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In an attempt to synthesize potent blockers of the influenza A M2 S31N proton channel with modifications of amantadine, we used MD simulations and MM-PBSA calculations to project binding modes of compounds 2-5, which are analogues of 1, a dual blocker. Blocking both the S31N mutant and the wild type (WT) M2, 1 is composed of amantadine linked to an aryl head group, (4-methoxy-2-hydroxy)-benzyl. Compound 6, used as control, has an 3-(thiophenyl)isoxazolyl aryl head group, and selectively blocks M2 S31N (but not WT) in an aryl head group “out” (i.e. N-ward) binding orientation. We then tested 1-6 as anti-virals in cell culture and for M2 binding efficacy with electrophysiology (EP). The new molecules 2-5 have a linker between the adamantane and amino group which can be as small as a CMe2 in rimantadine derivative 2, or longer like phenyl in 3. Alternatively, we explored the impact of expanding the diameter of adamantane with diamantyl or triamantyl in 4 and 5, respectively. Antiviral ...

This paper presents an application of the reaction class transition state theory (RC-TST) to predict thermal rate constants for hydrogen abstraction reactions of the type C 2 H 3 + alkane f C 2 H 4 + alkyl radical. The linear energy relationship (LER) was proven to hold for both noncyclic and cyclic hydrocarbons. We have derived all parameters for the RC-TST method from rate constants of 19 representative reactions, coupling with LER and the barrier height grouping (BHG) approach. Both the RC-TST/LER, where only reaction energy is needed, and the RC-TST/BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Our analysis indicates that less than 90% systematic errors on the average exist in the predicted rate constants using the RC-TST/ LER or RC-TST/BHG method, while in comparison to explicit rate calculations, the differences are within a factor of 2 on the average.

Phenothiazine sensitized solar cells: Effect of number of cyanocinnamic acid anchoring groups on DSSC performance Shivaraj Yellappa, [a,b] Whitney A. Webre, [a] Habtom B. Gobeze, [a] Anna Middleton, [a] Chandra B. KC, [a] and Francis D'Souza *[a] Dye-sensitized solar cells (DSSCs) were built to probe the effect of number of cyanocinnamic acid anchoring groups on the ring periphery of phenothiazine dyes. Two kinds of dyes, one having substitution on the N-terminal (1) and the other at the C-3 aromatic ring (2-5) have been synthesized for this purpose. Additionally the number of cyanocinnamic acid groups have been increased to two in the case of compound 6. The N-terminal in the case of compounds 2-6 was functionalized to carry either a methyl, 2-hydroxyethane, tris(ethylene oxide) and hexyl group. Evidence for charge injection from the excited singlet state of phenothiazine to TiO2 was secured from femtosecond transient absorption spectral studies wherein ultrafast charge injection process (kCI ~ 10 10-10 11 s-1) was witnessed. The DSSCs were built on nanocrystalline TiO2 using the traditional two-electrode method. Cell performance was found to be better for Cfunctionalized phenothiazine dyes compared to N-functionalized ones, and having the second cyanocinnamic group increased the efficiency to 5.8 %.

Accurate intermolecular potentials are needed for quantitative molecular simulations, but their calculation from quantum mechanics can be very demanding. We have developed several variations of a procedure, which we collectively refer to as quantum mechanical Hybrid Methods for Interaction Energies (HM-IE), to accurately estimate interaction energies from CCSD(T) calculations with a large basis set (LBS). HM-IE was tested for interaction energies of Ne 2 , (C 2 H 2) 2 , and N 2-benzene for many orientations sampling the entire potential energy surface and was found to be in excellent agreement with the CCSD(T)/LBS results while requiring considerably less computational time and resources. Furthermore, for neon, an intermolecular potential fit to interaction energies using HM-IE and a potential fit to CCSD(T)/LBS energies resulted in nearly identical predictions for densities and vapor pressures.

For the first time, very accurate potential energy curves (PEC) have been computed by the all electron Diffusion Quantum Monte-Carlo (DMC) and CCSD(T) methods for the ground-state of the Li 2 + , Li 2 À , LiH + and LiH À ions. In addition to the molecular moieties, Li + , Li À , H À ions have also been studied by the aforementioned methods. The employed trial wave functions for the DMC calculations are a multiplication of multi-configuration expansions which are prepared by the Complete Active Space Self-Consistent Field method (CASSCF) with the aug-cc-pVTZ and the aug-cc-pCVTZ basis sets and the Jastrow factor. The CCSD(T) computations with all electrons correlated, have been performed by the cc-pV5Z, aug-cc-pCVQZ and aug-cc-pV6Z basis sets. In addition, the correlation energies for all of the studied atomic and molecular species have been calculated. For the studied molecular species, the Hartree-Fock energies in the complete basis set limit (E CBS) have not been reported. In this work for each of the molecular systems, the most negative energy which has been computed by the cc-pV5Z or aug-cc-pCVQZ basis sets has been used. The obtained PECs by the DMC and CCSD(T) methods are used to calculate the vibrationrotation energy levels and spectroscopic constants.

Carbon-nitrogen bonds are extremely prevalent in pharmaceuticals, natural products, and other biologically relevant molecules such as nucleic acids and proteins. Intermolecular amination of C(sp3)-H bonds by catalytic nitrene transfer is a promising method for forging C-N bonds. An organocatalytic approach to nitrene transfer by way of an iminium salt offers a site-selective method for C(sp3)-H amination. Understanding of this amination mechanism including the nature of the relevant intermediates and the factors controlling the mechanism of the N-H bond formation step would aid in the design of catalysts and C(sp3)-H amination methods. In this work, the mechanism of the iminium salt-catalyzed C(sp3)-H amination via nitrene transfer was elucidated computationally using quantum mechanical methods and molecular dynamics simulations. Dispersion-corrected density functional theory (DFT) calculations provide support for an open singlet biradical species in equilibrium with the lower energy triplet species. Calculations further reveal that while the singlet biradical species undergoes N-H bond formation by a hydride transfer process, the triplet species forms the N-H bond by H-atom abstraction. Molecular dynamics (MD) simulations rule out the possibility of a fast rebound of the carbon substrate following N-H bond formation. A predictive model for mode of activation and site-selectivity that is consistent with experimental observations is presented.

We have carried out potential energy minimization searches for atomic and molecular clusters using two variants of the Ž. basin hopping strategy. We find that the significant structures basin hopping SSBH performs better than the raw structures Ž. basin hopping RSBH when both use optimized step sizes. The SSBH was able to locate previously-identified global Ž. Ž. Ž. Ž. Ž. minima for LJ n s 19, 30, 38 and benzene n s 6, 10 The benzene cluster minimum presented here is a new n n 14 result.

A novel interpretation of the chameleonic and centauric models for the Cope rearrangements of 1,5‐hexadiene (A) and different cyano derivatives (B: 2,5‐dicyano, C: 1,3,4,6‐tetracyano, and D: 1,3,5‐tricyano) is presented by using the topological analysis of the electron localization function (ELF) and Thom's catastrophe theory (CT) on the reaction paths calculated at the B3LYP/6‐31G(d,p) level. The progress of the reaction is monitorized by the changes of the ELF structural stability domains (SSD), each being change controlled by a turning point derived from CT. The reaction mechanism of the parent reaction A is characterized by nine ELF SSDs. All processes occur in the vicinity of the transition structure and corresponding to a concerted formation/breaking of C1C6 and C3C4 bonds, respectively, together with an accumulation of charge density onto C2 and C5 atoms. Reaction B presents the same number of ELF SSDs as A, but a different order appears; the presence of 2,5‐dicyano sub...

The joint use of the topological analysis provided by the electron localization function (ELF) and catastrophe theory (CT), at the B3LYP/6-31G(d) calculation level, allows us to examine the Lewis acid (protonation H + and presence of BH 3) and the role of an electron donor substituent (-OCH 3) at R and positions along the course of the molecular mechanism for the Nazarov rearrangement of penta-1,4-dien-3-one and eight derivatives. The progress of the reaction is monitored by the changes of the ELF structural stability domains (SSDs), each change being controlled by a turning point derived from CT. These SSDs and the corresponding turning points are associated with a sequence of elementary chemical steps. Along the cyclization path of penta-1,4-diene-3-one, four SSDs as well as three turning points (cusp1-fold1-cusp2) have been characterized. The first and second SSDs correspond to a polarization of the CO bond and electronic redistribution among the CC bonds, respectively, and they can be associated with the formation of an oxyallyl structure. The third and fourth SSDs can be assigned to the ring closure process. Protonation of the oxygen atom shifts the reactive directly into the second SSD, greatly reducing the activation and reaction energies. The electronic effects due to Lewis acids and electron donor substituents have been rationalized in terms of calculations of mesomeric structures from ELF basin populations. The combination of Lewis acids together with R and-OCH 3 substitutions renders a cooperative and competitive effect on activation and reaction free energies, respectively.

Density functional theory and molecular orbital theory are used to calculate the fukui function and the condensed fukui function for several enolate ions in order to carry out an analysis of the different effects that have an influence on the chemical reactivity at the carbon and oxygen atoms. It is shown that substituent, substrate, and solvent effects may be explained in a unified way in terms of the values of the condensed fukui function when these are analyzed through a local version of the hard and soft acids and bases principle. The results suggest that it could be interesting to carry out experimental work that may confirm the importance of the hardness and softness parameters to get a better understanding of enolate ion chemistry.

A calculation of the simplest part of the second-order electron self-energy (loop after loop irreducible contribution) for hydrogen-like ions with nuclear charge numbers 3 ≤ Z ≤ 92 is presented. This serves as a test for the more complicated second-order self-energy parts (loop inside loop and crossed loop contributions) for heavy one-electron ions. Our results are in strong disagreement with recent calculations of Mallampalli and Sapirstein for low Z values but are compatible with the two known terms of the analytical Zαexpansion.

S1. GC/MS methodology and table S2. Kinetic model for thermal decomposition of PFOS table S3. Predicted (model) and experimental thermal decomposition of PFOS concentration graphs for 200 mL/min and 300 mL/min S4. Micro GC and FT-IR C 2 F 4 concentration comparison S5. Atomic coordinates for species relevant in PFOS decomposition S6. NASA thermochemical coefficients for Chemkin modelling S7. PFOS concentration calculation example

The structure and function of a new class of host molecules for the supramolecular complexation of anionic guest species are analysed within the context of other recent advances in the field. In particular, organometallic hosts based upon the calixarenes, and the related macrocycle cyclotriveratrylene (CTV), are examined. X-Ray crystallographic results clearly demonstrate the inclusion of anionic guest species such as BF4-, I-, CF3S03-, Re04-etc. within the ostensibly electron-rich bowl-shaped cavities of both types of host as a result of cooperative effects arising from the presence of two or more metal centres arranged around a common binding pocket. Solution radiochemical studies show that hosts based upon CTV in particular are selective for large tetrahedral anions such as M04-(M = Tc, Re). It is anticipated that the ability to discriminate between anions on a size and shape selective basis by means of manipulation of host cavity dimensions will pave the way towards new sensor devices and methods of environmental waste remediation.

In this article we look at the question of the security of Data Encryption Standard (DES) against non-linear polynomial invariant attacks. Is this sort of attack also possible for DES? We present a simple proof of concept attack on DES where a product of 5 polynomials is an invariant for 2 rounds of DES. Furthermore we present numerous additional examples of invariants with higher degrees. We analyse the success probability when the Boolean functions are chosen at random and compare to DES S-boxes. For more complex higher degree attacks the difficulties disappear progressively and up to 100 % of all Boolean functions in 6 variables are potentially vulnerable. A major limitation for all our attacks, is that they work only for a fraction of the key space. However in some cases, this fraction of the key space is very large for the full 16-round DES.

The paper collects the answers of the authors to the following questions: • What is the significance of the topological approach? • Can new chemical concepts be found by a topological approach? • What is the status of a chemical concept within a topological approach? • Should topological approaches provide measurable quantities? • Is it possible to predict the outcome of a topological approach without performing a calculation on a computer? • What are new domains for which topological approaches would be useful?

Magnetic ionic liquids (MILs) show clear superiority over conventional ionic liquids suitably nested in many applications, particularly in medicine and drug delivery engineering. The easy way of collecting them using an external magnet and separating them from the reaction mixture is a favorable and unique technique. A magnetic imidazolium-based IL, including iron coordinated with −NO and chloride ligands ([BMIm][Fe(NO) 2 Cl 2 ]) (BMIm = 1-n-butyl-3-methyl-imidazolium), has been studied using density functional theory. Such dinitrosyl iron compounds are significant as NO-saving sources and carriers because of their longer physiological lifetime compared with molecular NO. The dependability of the calculations was examined and elucidated at three different methods (M06-2X, B3LYP, and B3LYP-D3) to unravel the importance of noncovalent interactions, including dispersion and H-bonding. Also, the effect of a large basis set on different features of this MIL was assessed. This research is a pioneer in theoretically characterizing the type of −NO moiety of this openshell dinitrosyl iron compound. The complicated structure of the dinitrosyliron unit was determined by the geometrical parameters, stretching frequencies, and magnetic moment calculation. Based on these fingerprint data, the predominant form of two NO's in this MIL is the nitroxyl anion NO − , rather than ṄO or NO +. Unraveling that one of the NO ligands structurally is dangling enhances the application of this MIL as a NO-saving and source compound. Consequently, Fe 3+ is identified as the major oxidation state of the iron atom, leading to the MIL with a strong magnetic moment (of 5.22μ B).

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used as analgesics, antipyretics, anti-clotting, and anti-inflammatory agents. One such NSAID, ketoprofen (KTP), is prescribed to treat pain, sprains, menstrual irregularities, osteoarthritis (OA), and rheumatoid arthritis (RA). By inhibiting cyclooxygenase, it halts prostaglandin synthesis. However, it exhibits significant side effects in humans and other living things. Herein, the chemical structure of KTP has been modified to search for improved chemical and medicinal effects. Density functional theory (DFT) has been employed for geometry optimization. Molecular docking and molecular dynamics (MD) simulations were conducted to investigate the binding affinity and stability of the protein-drug complex with prostaglandin synthase protein. ADMET predictions were carried out to calculate and compare the pharmacokinetic behavior of KTP and its new analogs. Spectral and chemical results support the structural conformation of the new analogs, all of which exhibit improved physicochemical, and binding properties compared to the parent drug. After a 100 ns MD simulation, the drugs remained tightly bound to the binding site of the receptor protein, showing significant interactions with shorter distances among the new analogs. The ADMET predictions confirmed better pharmacokinetic properties of novel analogs compared to KTP. The study compares several KTP metabolites using thermo-chemical, spectral, biological, and toxicological analysis. Results showed the reactivity and stability, with spectral data evaluating all KTP analogs. ADMET predicts that all KTP derivatives are less toxic and have better pharmacokinetic features than KTP. Most KTP analogs exhibit excellent oral bioavailability and significant analgesic, antipyretic, and anti-inflammatory functions. These findings support the potential use of these drugs in the future drugs.

In this paper we present real space analyses of the nature of the dihalogen‐water cage interactions in the 512 and 51262 clathrate cages containing chlorine and bromine, respectively. Our Quantum Theory of Atoms in Molecules and Interacting Quantum Atoms results provide strong indications that halogen bonding is present even though the lone pairs of water molecules are already engaged in hydrogen bonding interactions.

Radiative and non-radiative processes of excited CT slates of Rut tl) and Pt(I1) compounds and excited d-d states of Rh(l!l) compounds in the solid state and at higher temperatures are examined, A rapid non-radiative transition of a metal-to-ligand charge tra,~sfer excited state to the ground state does not occur over a wide temperature range (77-300 K) for [Ru(bpy)3](PF6) 2 and [Pt2(tpy)2(guanidinato)]{ClO4)3. Srx.ctral simulations of the d-d emissions of Rh(llI) compounds in the range 77-536 K are carried out by assuming a simple configuration coordinate. The large Huang-Rhys factors indicate that t~e lowest arid second lowest d-d excited states of Rh (Iti) compounds are s;rong!y coupled to the exci~ed vibratimml state of the ground state. The frequency factors of non-radiative decay are 10 ~ ~-t0' 2s-~ for the excited triplet state.

Two novel heteroleptic Ru[3+2+1] sensitizers, 1 and 2, with unsymmetrical bipyridine as ancillary ligand and electron donating 4-methylstyryl group in the anchoring p-extended terpyridyl ligand were synthesized and characterized. DFT studies reveal that the lowest unoccupied molecular orbital (LUMO) is distributed over the terpyridine. The two new sensitizers showed an improvement in the molar extinction coefficient compared to reference standard N749 dye. Among the two new sensitizers, 1 exhibited maximum solar to electric conversion efficiency (g) of 5.19% with short circuit current density of 14.032 mA cm À2 , open circuit voltage of 0.520 V and fill factor of 0.712, under Air Mass (AM) 1.5 sunlight, while the reference N749 sensitized solar cell exhibited g-value of 6.44%.

We report an extensive high-level ab initio theoretical investigation of the interaction electric properties of the weakly bound complexes of water with rare gases, H 2 O • • • Rg (Rg) He, Ne, Ar, Kr and Xe). Our approach relies on finite-field many-body perturbation theory (MP) and coupled-cluster (CC) calculations with flexible, carefully designed basis sets of Gaussian-type functions (GTFs). We have obtained estimates of the electron correlation effects on the reference self-consistent field (SCF) values at all levels of theory employed in this work. For the planar equilibrium configuration (C s symmetry) of the complexes, at the CCSD(T) level of theory, the interaction mean first hyperpolarizability is positive (SCF values in parentheses): j int / e 3 a 0 3 E h-2 (H 2 O-Rg)) 0.72 (0.56), 1.20 (0.79), 7.04 (4.28), 9.88 (5.34), and 15.52 (6.68) for Rg) He, Ne, Ar, Kr, and Xe, respectively. For the interaction mean second hyperpolarizability, we have obtained (SCF values in parentheses): γ j int /e 4 a 0 4 E h-3 (H 2 O-Rg))-18.93 (-14.19),-37.78 (-24.35),-83.16 (-72.42),-102.92 (-125.70), and-206.45 (-286.83) for Rg) He, Ne, Ar, Kr, and Xe. In addition to the equilibrium values of the interaction electric properties, we have also extracted information for their dependence on the variation of the distance of the rare gas atom from the center of mass of the water molecule (without changing direction). The gradient of the interaction mean second hyperpolarizability at the equilibrium configuration is determined as (dγ j int /dR) e /e 4 a 0 3 E h-3 (H 2 O-Rg)) 9.89 (He), 25.42 (Ne), 73.71 (Ar), 144.71 (Kr), and 324.68 (Xe).

The photophysical properties of a multicomponent array consisting of a free-base aryl-porphyrin and a gold(III) aryl-porphyrin, assembled via a central bis(terpyridine) ruthenium(II) complex, PH 2-Ru-PAu, have been studied in low-temperature glassy media by steady state and time-resolved methods. Comparison of the photophysical properties of this triad with those of the reference molecular models and of the related dyads (Ru-PH 2 , Ru-PAu) allows the photoinduced processes occurring in PH 2-Ru-PAu to be elucidated. The photoinduced processes in glassy media in the dyads Ru-PH 2 and Ru-PAu are basically similar to those occurring at room temperature where the absorbed energy is transferred with 100% efficiency to the pertinent porphyrin lowest triplet state. For Ru-3 PAu the decay to the ground state is similar to the model 3 PAu and displays double-exponential behavior, while in the case of Ru-3 PH 2 some perturbing effect of the ruthenium center in accelerating the inter-system crossing to the ground state by the heavy atom effect can be noticed. In the triad PH 2-Ru-PAu the primary photoinduced steps are similar to those occurring at room temperature and, by energy-transfer steps, populate both triplets of peripheral porphyrins. In contrast with room-temperature events, a further energy-transfer step from PH 2-Ru-3 PAu to the spatially opposed 3 PH 2-Ru-PAu (center to center distance) 2.1 nm) occurs in glassy media with a rate constant of 2.5 × 10 7 s-1 , as probed by transient absorption spectroscopy. This process, which occurs by an exchange mechanism, is mediated by the interposed Ru(II) bisterpyridine complex, which acts as an electron relay.

Linear aliphatic polyesters are degradable thermoplastic polymers, which can be obtained by ring-opening polymerization (ROP) of cyclic esters through a coordination-insertion mechanism. Aluminum based organometallic complexes have a leading position as efficient catalysts for this polymerization process. Aluminumalkyl complexes bearing salicylaldiminato ligands, although less explored, have been shown to be efficient and versatile catalysts for the ROP of various cyclic esters. These species have the potential to function as active catalysts in the ROP because of their less coordinatively saturated nature with respect to analogous SALEN-type complexes. They have been used as efficient catalysts in the ROP of commercially available cyclic esters, such as ε-caprolactone, L-lactide, rac-lactide, and glycolide. Moreover, they resulted in efficient catalysts for the ROP of cyclic esters with large ring-size and for the ROP of functionalized lactide. Furthermore, they have been used in the co-and ter-polymerization of various cyclic esters affording well controlled polymerization and a plethora of microstructural architectures, ranging from random to block to multiblock.

Structure, dynamics, and electron delocalization of Al 4 2and Al 4 4based clusters are investigated. Gradient-corrected Density-Functional Born-Oppenheimer Molecular Dynamics simulations indicate that Al 4 2based clusters have a rigid planar Al framework, while the Al 4 4based moieties show large distortions from planarity. The induced magnetic field analysis of these species indicates that both systems have diatropic σ-systems, while the π-system is diatropic for Al 4 2and paratropic for Al 4 4-. The total magnetic response is diatropic for Al 4 2-, while Al 4 4is "bitropic": it has typical antiaromatic long-range cones, while the magnetic field in the Al 4 4ring plane is similar to that of aromatic annulenes.

This article deals with the different types of the hydrogen storage process, its thermochemistry, adsorption process, and binding energy, in the light of the computational approach using the conceptual density functional theory (CDFT). This article expresses the view that lithium iodide (LiI) is a viable template for hydrogen storage at low temperatures. The density functional theory (DFT) has been used to investigate the structure and chemical reactivity of the resulting templates. The adsorption process is found to be quasi-sorption in nature. The molecular hydrogen interacts with building blocks (with Li centre) through electrovalent interaction and a single LiI molecule is capable of absorbing 10 H 2 with a high gravimetric wt% value (13.07 wt%) which is found to be a promising system as per standard. The changes in Gibbs free energy indicate that hydrogen adsorption can occur spontaneously at cryogenic temperatures.

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It is found that electron delocalization indices can be efficiently used as a sorting tool for the classification of bonds between iodine atoms in a wide range of various covalent and noncovalent I…I/I-I interactions. The characteristics of bonds in a symmetrical triiodide anion can serve as benchmarks allowing to distinguish the I…I halogen bond from the I-I covalent bond.

The hydrogen bonding in the guanine-cytosine nucleotide base pair has been examined via Rayleigh-Schrödinger perturbation theory. Correlation of the molecular orbitals for the free bases and for the hydrogen bonded complex shows that thea molecular orbitals become delocalized as the base pair is formed, whereas then molecular orbitals are only slightly perturbed. The results suggest that, as regards the a molecular orbitals delocalized over both units, two polarization mechanisms play major roles. The first is by in-group mixing in a second order polarization effect; the second is accounted for by intermolecular and unsymmetrical charge transfer. Thus, the first order contribution to the perturbed orbital energies of the a and π molecular orbitals localized on the same unit of the base pair, is predominantly from exchange (due to antisymmetrization) repulsion energy, whereas the second order contributor is mainly polarization energy. Both molecular orbital correlation and perturbation energy show that the molecular orbitals of cytosine become stabilized as the base pair is formed. An atom-atom bond index per molecular orbital has been introduced in order to understand the observed behaviour in the light of the population analysis. The results presented constitute a reasonable theoretical description of the elementary molecular interactions involved in nucleic acids and nucleic acid-nucleic acid associations.