Theoretical Chemistry Research Papers - Academia.edu (original) (raw)

The water-hydroxyl radical complex was prepared by irradiating peroxy radicals in hydrogen-doped argon matrices. The low water content of the matrices made it possible to observe the fundamental bands of the complexed water molecule. The experimental results are compared with the results from ab initio calculations. The complex rotates around the O-O axis in the matrix.

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- Engineering, Chemistry, Theoretical Chemistry, Chemical Physics

Hydrogenation of vegetable oils is a heterogeneous process where the process factors influence the conversion and selectivity. A Statistical study was performed on a sunflower oil (SFO) hydrogenation process using Pd-B/g-Al 2 O 3 catalyst to study the effect of the process factors, including temperature, hydrogen pressure, agitation, catalyst dose and reaction time on the iodine value and trans fatty acid content of hydrogenated SFO. It was found that each factor has a noticeable effect on the iodine value and trans fatty acid content of hydrogenated SFO. The study was also aimed to find out the optimum values for the hydrogenation factors which are capable to decline the IV to 70 (g iodine per 100 g oil) as well as produce a minimum trans fatty acid content of the hydrogenated SFO. The optimum values were found to be 431 K, 1000 kPa, 1000 kPa, 0.29 % and 42.2 min for the temperature, hydrogen pressure, agitation, catalyst dose and reaction time respectively.

- by Zahira Yaakob
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- Inorganic Chemistry, Organic Chemistry, Physical Chemistry, Theoretical Chemistry

In this paper, we associate an applicability domain (AD) of QSAR/QSPR models with the area in the input (descriptor) space in which the density of training data points exceeds a certain threshold. It could be proved that the predictive performance of the models (built on the training set) is larger for the test compounds inside the high density area, than for those outside this area. Instead of searching a decision surface separating high and low density areas in the input space, the one-class classification 1-SVM approach looks for a hyperplane in the associated feature space. Unlike other reported in the literature AD definitions, this approach: (i) is purely “data-based”, i.e. it assigns the same AD to all models built on the same training set, (ii) provides results that depend only on the initial descriptors pool generated for the training set, (iii) can be used for the huge number of descriptors, as well as in the framework of structured kernel-based approaches, e.g., chemical graph kernels. The developed approach has been applied to improve the performance of QSPR models for stability constants of the complexes of organic ligands with alkaline-earth metals in water.

- by Igor Baskin
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- Cheminformatics, Computational Chemistry, Theoretical Chemistry, Machine Learning

Computational chemistry applied to the study of polyoxometalates has achieved its maturity in the last years. During two decades, important advances have been made using theoretical tools in the comprehension and interpretation of many relevant issues. In the present minireview, we want to stress that different techniques have been incorporated to the routine of computation: from the very first Hartree-Fock LCAO-SCF calculation on the decavanadate anion, followed by numerous density functional theory-based studies on increasingly complex systems, also applying correlated ab initio techniques for magnetism and, more recently, using molecular dynamics to analyse properties in liquid media, the information provided by computational chemistry gets more and more relevant.

- by Carles Bo and +1
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- Computational Chemistry, Theoretical Chemistry, Complex System, Hartree fock method

Here, chemoinformatics is considered as a theoretical chemistry discipline complementary to quantum chemistry and force-field molecular modeling. These three fields are compared with respect to molecular representation, inference mechanisms, basic concepts and application areas. A chemical space, a fundamental concept of chemoinformatics, is considered with respect to complex relations between chemical objects (graphs or descriptor vectors). Statistical Learning Theory, one of the main mathematical approaches in structure-property modeling, is briefly reviewed. Links between chemoinformatics and its “sister” fields – machine learning, chemometrics and bioinformatics are discussed.

- by Igor Baskin
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- Cheminformatics, Computational Chemistry, Theoretical Chemistry, Chemoinformatics
- by Cina Foroutan-Nejad
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- Chemistry, Computational Chemistry, Inorganic Chemistry, Organic Chemistry
- by C. M . Cismasiu
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- Theoretical Physics, Theoretical Chemistry, Bioethics, Microbial Fuel Cells

We have analyzed the effect of external electric field on the aziridinium ion intermediate of mustine drug molecule using conceptual density functional theory based reactivity descriptors. The aziridinium ion intermediate is formed during the alkylation of DNA by mustine, a member of the nitrogen mustard family. This species experiences a field exerted by polarity of the solvent and metal ions present in body fluids (in extra- and intra-cellular fluids, blood etc.). The stability and reactivity of the aziridinium ion is monitored by studying some density based reactivity descriptors in the presence of external electric fields. Further, shifting of the reactive center (i.e., the LUMO) of the drug intermediate with variation in the electric field was observed. In addition, the maximum hardness and minimum electrophilicity principles were analyzed.► In this article, effect of external electric field on a drug intermediate is studied. ► Variation of shape of LUMO and DFT based reactivity descriptors in presence of external electric fields are observed. ► Further, the maximum hardness and minimum electrophilicity principles are analyzed.

- by Rahul KR
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- Theoretical Chemistry, Nitrogen, Metal ion, THEORETICAL AND COMPUTATIONAL CHEMISTRY

The influence of various all-electron basis sets and effective core potentials employed along with several DFT functionals (B3LYP, B3PW91, BLYP, BP86 and M06) on the magnitude of nucleus independent chemical shift (NICS) values in different metallic nano-clusters and hydrocarbons is studied. In general, it is demonstrated that the NICS values are very sensitive to the applied method/basis set; however, the method/basis set dependence is more prominent for computed NICS values in transition metal clusters. In hydrocarbons, medium-size basis sets perform roughly similar to large basis sets in most cases. It is also found that NICS(0) values are more sensitive to the method/basis set variation compared to the NICS values computed at 1 or 2 Å above the ring plane. However, in many cases, no broad-spectrum regulation is found for the effect of basis set/method on the magnitude of NICS values. A detailed study showed that bond length alternation in a molecule has an insignificant effect on the magnitude of NICS values so the influence of method/basis sets on the magnitude of NICS values mostly arises from the different predicted ring current intensities at various computational levels.

- by Cina Foroutan-Nejad and +2
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- Physics, Chemistry, Computational Chemistry, Inorganic Chemistry

Platinum-based heterogeneous catalysts are critical to many important commercial chemical processes, but their efficiency is extremely low on a per metal atom basis, because only the surface active-site atoms are used. Catalysts with single-atom dispersions are thus highly desirable to maximize atom efficiency, but making them is challenging. Here we report the synthesis of a single-atom catalyst that consists of only isolated single Pt atoms anchored to the surfaces of iron oxide nanocrystallites. This single-atom catalyst has extremely high atom efficiency and shows excellent stability and high activity for both CO oxidation and preferential oxidation of CO in H2. Density functional theory calculations show that the high catalytic activity correlates with the partially vacant 5d orbitals of the positively charged, high-valent Pt atoms, which help to reduce both the CO adsorption energy and the activation barriers for CO oxidation.

- by Yitao Cui
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- Biochemistry, Thermodynamics, Chemistry, Computational Chemistry

Il segno del chimico è il testo di una lettura scenica costruita con brani di Primo Levi, realizzata per incarico del Centro Internazionale di Studi Primo Levi e del Teatro Stabile di Torino. Lo spettacolo è stato allestito nel luglio 2010, per la regia e l’interpretazione di Valter MALOSTI, in occasione del convegno internazionale ESOF, EuroScience Open Forum. Nel novembre 2011 è stato portato in scena a New York da John Turturro.

- by Domenico Scarpa
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- Theoretical Chemistry, Cosmology (Physics), Jewish Studies, Italian Studies

In the present account we investigate a theoretical link between bond length, electron sharing, and bond energy within the context of quantum chemical topology theories. The aromatic stabilization energy, ASE, was estimated from this theoretical link without using isodesmic reactions for the first time. The ASE values obtained from our method show a meaningful correlation with the number of electrons contributing in the aromaticity. This theoretical link demonstrates that structural, electronic, and energetic criteria of aromaticity –ground-state aromaticity– belong to the same class and guarantees that they assess the same property as aromaticity. Theory suggests that interatomic exchange-correlation potential, obtained from the theory of Interacting Quantum Atoms (IQA), is linearly connected to the delocalization index of Quantum Theory of Atoms in Molecules (QTAIM) and bond length through a first order approximation. Our study shows that the relationship between energy-structure-electron sharing marginally deviates from the ideal linear form expected from the first order approximation. The observed deviation from linearity was attributed to a different contribution of exchange-correlation into the bond energy for the σ- and π-frameworks. Finally, we proposed two-dimensional energy-structure-based aromaticity indices in analogy to the electron sharing indices of aromaticity.

- by Cina Foroutan-Nejad
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- Biochemistry, Chemistry, Computational Chemistry, Inorganic Chemistry

The electronic spectrum of alizarin (AZ) in methanol solution was measured and used as reference data for color prediction. The visible part of the spectrum was modelled by different DFT functionals within the TD-DFT framework. The results of a broad range of functionals applied for theoretical spectrum prediction were compared against experimental data by a direct color comparison. The tristimulus model of color expressed in terms of CIE XYZ and CIE Lab parameters was applied both to experimental and predicted spectra. It was found that the HSE03 method along with the 6-31G(d,p) basis set provides the most accurate color prediction, much better than other commonly used functionals such as B3LYP, CAM-B3LYP or PBE0. Besides, the influence of potential errors, introduced by theoretical predictions on color estimation, was examined for different wavelengths. The obtained results showed that color prediction is significantly dependent on the type of basis set and functional applied. The proposed methodology provides a simple, straightforward and more reliable way of theoretical protocols validation than just a comparison of experimental and estimated values of maximum absorbance wavelength.

- by Maciej Przybyłek
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- Chemistry, Quantum Chemistry, Physical Chemistry, Theoretical Chemistry
- by C. M . Cismasiu and +3
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- Microbiology, Biophysics, Theoretical Physics, Theoretical Chemistry

To be a combination all chemical calculation formulas concerning mole number, the dilution, concentrate mixing, acid-base, salts, reaction, gas, electron configuration and phase transition to be useful in learning chemistry

- by Soukthakhane SINGSONESACK and +1
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- Chemical Engineering, Chemistry, Analytical Chemistry, Inorganic Chemistry

The work Anatomia Magna is a research work and books research created by JoanCarles Testagorda Garcia. I explain the relation of the weather state of mind functions of the hair, thermogenesis, production of climate, mathematical union... more

- by Joancarles YoIje Martin TG
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- Physics, Theoretical Physics, Theoretical Chemistry, Rheumatology

PROGRAMA DE TECNOLOGÍA QUÍMICA JUNIO 2015

- by E Andrés Cardona Duque and +1
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- Chemistry, Analytical Chemistry, Inorganic Chemistry, Organic Chemistry
- by Eric Scerri
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- History of Science and Technology, Physics, Chemistry, Quantum Chemistry

Quantum chemical calculations using density functional theory and correlated ab initio methods of the 10 p-electron systems (N 6 H 6) 2 + and C 2 N 4 H 6 show that the planar forms are no minima on the potential energy surfaces. The twisted ring structures of the two species are energy minima, but acyclic isomers are much lower in energy. The planar geometries sustain strong diamagnetic ring current comparable with that of benzene. In contrast, the calculated multicenter normalized Giambiagi electron delocalization index I NG suggests that p-delocalization in planar (N 6 H 6) 2 + and C 2 N 4 H 6 is much weaker than in benzene. Since aromaticity is synonymous for a particular stability of cyclic delocalized systems, it may be stated that calculation or measurement of magnetic chemical shifts due to induced ring currents is not a reliable method to ascertain the aromatic character of a molecule. Aromatic compounds exhibit ring current induced magnetic shielding, but the reverse conclusion that ring current induced magnetic shielding identifies aroma-ticity is not justified. Furthermore, the 4n + 2 rule as indicator of aromatic stabilization should only be used in conjunction with the ring size; the nature of the occupied p orbitals must always be examined.

- by Cina Foroutan-Nejad
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- Chemistry, Computational Chemistry, Inorganic Chemistry, Organic Chemistry

Life is an inordinately complex unsolved puzzle. Despite significant theoretical progress, experimental anomalies, paradoxes, and enigmas have revealed paradigmatic limitations. Thus, the advancement of scientific understanding requires new models that resolve fundamental problems. Here, I present a theoretical framework that economically fits evidence accumulated from examinations of life. This theory is based upon a straightforward and non-mathematical core model and proposes unique yet empirically consistent explanations for major phenomena including, but not limited to, quantum gravity, phase transitions of water, why living systems are predominantly CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur), homochirality of sugars and amino acids, homeoviscous adaptation, triplet code, and DNA mutations. The theoretical framework unifies the macrocosmic and microcosmic realms, validates predicted laws of nature, and solves the puzzle of the origin and evolution of cellular life in the universe. Life 2012, 2 2

- by Erik Andrulis
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- Evolutionary Biology, Field Theory, Earth Sciences, Geology
- by Leena Sinha
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- Chemistry, Theoretical Chemistry, Density-functional theory, Ultraviolet
- by Cina Foroutan-Nejad
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- Chemistry, Computational Chemistry, Inorganic Chemistry, Organic Chemistry

The nutritional compositions of Hunteria umbellata were examined in this study. Proximate, mineral and inorganic elements of dehulled Hunteria umbellata seed (DHUS) and whole Hunteria umbellata seed (WHUS) were analyzed. The proximate composition (%) of the DHUS and WHUS seed are as follows; crude protein (13.65) and (9.0), crude
fibre (26.79) and (2.74), crude fat (2.87) and (14.97), ash (3.89) and (3.45), moisture (9.57) and (10.95) and carbohydrate (43.23) and (58.88). Hunteria umbellata are good source of macro and micro nutrient (mg/100g) with Potassium (1130) and 1150, Magnesium(180) and (189), Calcium (76) and (78), Sodium (87.5) and (90), Iron (60)
and (63), Manganese (5) and (7) also present in appreciable quantities. The result of inorganic element (mg/100g) also revealed in Hunteria umbellata; Nitrogen (7.14) and (2.11), Carbon (52.1) and (68.4), Hydrogen (4.22) and (6.11), Sulphur (2.33) and (2.26) and Oxygen (34.3) and (21.1) respectively. Nitrogen content was determined by microKjeldahl method. Total carbohydrate was calculated by the difference method while mineral analysis was carried out after acid digestion using spectrophotometer and flame photometry. The high value obtained for potassium, carbohydrate, and carbon reveal that
Hunteria umbellata seed has potential of serving as supplement for food, source of synthetic and antimicrobial drugs, and traditional herbal medicine.

- by sam olusegun and +1
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- Biochemistry, Physical Chemistry, Theoretical Chemistry, Physical Organic Chemistry

Dissipative environment/quantum dissipation QUAPI Phonon damped laser driven quantum dot qubit Tensor propagator algorithm Memory kernel a b s t r a c t This MATLAB program calculates the dynamics of the reduced density matrix of an open quantum system modeled either by the Feynman-Vernon model or the Caldeira-Leggett model. The user gives the program a Hamiltonian matrix that describes the open quantum system as if it were in isolation, a matrix of the same size that describes how that system couples to its environment, and a spectral distribution function and temperature describing the environment's influence on it, in addition to the open quantum system's initial density matrix and a grid of times. With this, the program returns the reduced density matrix of the open quantum system at all moments specified by that grid of times (or just the last moment specified by the grid of times if the user makes this choice). This overall calculation can be divided into two stages: the setup of the Feynman integral, and the actual calculation of the Feynman integral for time propagation of the density matrix. When this program calculates this propagation on a multi-core CPU, it is this propagation that is usually the rate-limiting step of the calculation, but when it is calculated on a GPU, the propagation is calculated so quickly that the setup of the Feynman integral can actually become the rate-limiting step. The overhead of transferring information from the CPU to the GPU and back seems to have a negligible effect on the overall runtime of the program. When the required information cannot fit on the GPU, the user can choose to run the entire program on a CPU.

This paper is focused on modern approaches to machine learning, most of which are as yet used infrequently or not at all in chemoinformatics. Machine learning methods are characterized in terms of the “modes of statistical inference” and “modeling levels” nomenclature and by considering different facets of the modeling with respect to input/ouput matching, data types, models duality, and models inference. Particular attention is paid to new approaches and concepts that may provide efficient solutions of common problems in chemoinformatics: improvement of predictive performance of structure–property (activity) models, generation of structures possessing desirable properties, model applicability domain, modeling of properties with functional endpoints (e.g., phase diagrams and dose–response curves), and accounting for multiple molecular species (e.g., conformers or tautomers).

- by Igor Baskin
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- Cheminformatics, Computational Chemistry, Theoretical Chemistry, Machine Learning

This document is a Persian translation of the following papers: PCCP 2010, 12, 12630 PCCP, 2011, 13, 4576 PCCP, 2011, 13, 12655 JCC, 2011, 32, 2422 JPC A, 2011, 115, 12708 For more information also see: JPC A, 2011, 115, 12555... more

- by Cina Foroutan-Nejad
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- Chemistry, Inorganic Chemistry, Organic Chemistry, Physical Chemistry

Interatomic magnetizability provides insight into the
extent of electronic current density between two adjacent atomic
basins. By studying a number of well-known aromatic, nonaromatic,
and antiaromatic molecules, it is demonstrated that interatomic
magnetizability (bond magnetizability) not only is able to verify the
exact nature of aromaticity/antiaromaticity among different molecules,
but also can distinguish the correct aromaticity order among
sets of aromatic/antiaromatic molecules. The interatomic magnetizability
is a direct measure of the current flux between two adjacent
atomic basins and is the first QTAIM-derived index that evaluates
aromaticity based on a response property, that is, magnetizability. Bond magnetizability is easy to compute, straightforward to
interpret, and can be employed to evaluate the pure π- or σ-orbital contributions to magnetic aromaticity.

Developing a comprehensive method to compute bond orders is a problem that has eluded chemists since Lewis's pioneering work on chemical bonding a century ago. Here, a computationally efficient method solving this problem is introduced and demonstrated for diverse materials including elements from each chemical group and period. The method is applied to non-magnetic, collinear magnetic, and non-collinear magnetic materials with localized or delocalized bonding electrons. Examples studied include the stretched O 2 molecule, 26 diatomic molecules, 3d and 5d transition metal solids, periodic materials with 1 to 8748 atoms per unit cell, a biomolecule, a hypercoordinate molecule, an electron deficient molecule, hydrogen bound systems, transition states, Lewis acid–base complexes, aromatic compounds, magnetic systems, ionic materials, dispersion bound systems, nanostructures, and other materials. From near-zero to high-order bonds were studied. Both the bond orders and the sum of bond orders for each atom are accurate across various bonding types: metallic, covalent, polar-covalent, ionic, aromatic, dative, hypercoordinate, electron deficient multi-centered, agostic, and hydrogen bonding. The method yields similar results for correlated wavefunction and density functional theory inputs and for different S Z values of a spin multiplet. The method requires only the electron and spin magnetization density distributions as input and has a computational cost scaling linearly with increasing number of atoms in the unit cell. No prior approach is as general. The method does not apply to electrides, highly time-dependent states, some extremely high-energy excited states, and nuclear reactions.

- by Thomas Manz
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- Quantum Physics, Chemistry, Computational Chemistry, Quantum Chemistry

Chirped-Pulse millimetre-Wave (CPmmW) rotational spectroscopy provides a new class of information about photolysis transition state(s). Measured intensities in rotational spectra determine species-isomer-vibrational populations, provided that the rotational populations can be thermalized. The formation and detection of S 0 vinylidene is discussed in the limits of low and high initial rotational excitation. CPmmW spectra of 193 nm photolysis of vinyl cyanide (acrylonitrile) contain J ¼ 0-1 transitions in more than 20 vibrational levels of HCN and HNC, but no transitions in vinylidene or highly excited local-bender vibrational levels of acetylene. Reasons for the non-observation of the vinylidene co-product of HCN are discussed.

- by Bryan M Wong
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- Physics, Atomic, Molecular, And Optical Physics, Chemistry, Computational Chemistry

UV-induced decarboxylation of the NSAID ketoprofen, followed by activation of molecular oxygen or formation of a decarboxylated peroxide adduct, is explored using computational quantum chemistry. The excited energy surfaces reveal that the neutral species will not decarboxylate, whereas the deprotonated acid decarboxylates spontaneously in the triplet state, and with an associated 3-5 kcal/mol barrier from several low-lying excited singlet states. The observed long lifetimes of the decarboxylated anion is explained in terms of the high stability of the triplet benzoyl ethyl species with protonated carbonylic oxygen, from which there is no obvious decay channel. Mechanisms for the generation of singlet oxygen and superoxide are discussed in detail. Addition of molecular oxygen to give the corresponding peroxyl radical capable of initiating propagating lipid peroxidation reactions is also explored. The computed data explains all features of the observed experimental observations made to date on the photodegradation of ketoprofen. a Abbreviations: NSAID, nonsteroidal antiinflammatory drug; KP, ketoprofen; ROS, reactive oxygen species; ISC, intersystem crossing; DFT, density functional theory; CNDO/S, complete neglect of differential overlap-singles excitations; ZPE, zero-point vibrational energy; IEFPCM, integral equation formalism of the polarized continuum model; TD-DFT, time-dependent density functional theory; LDA, local density approximation.

- by Jon Matxain
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- Chemistry, Organic Chemistry, Theoretical Chemistry, Medicinal Chemistry

The influence of electron density on the magnitude of non-nuclear magnetic shielding, NICS, is
studied in detail by scanning the electron density vs. NICSzz (the out-of-plane component of
NICS). This study sheds new light on the role of electron density on the magnitude of NICS.
Scanning the electron density vs. NICSzz not only helps to discriminate the electronic ring
currents operative in aromatic, nonaromatic and antiaromatic species, but also yields a measure
to compare the strength of diatropic/paratropic currents in molecules with different ring sizes or
different number of p electrons without relying on the methods of sigma–pi separation.

A one-dimensional local bend model is used to describe the variation of electronic properties of acetylene in vibrational levels that embody large amplitude local motions on the S 0 potential energy surface. Calculations performed at the CCSD(T) and MR-AQCC levels of theory predict an approximately linear dependence of the dipole moment on the number of quanta in either the local bending or local stretching excitation. In the local mode limit, one quantum of stretching excitation in one CH bond leads to an increase of 0.025 D in the dipole moment, and one quantum of bending vibration in the CCH angle leads to an increase of 0.068 D. The use of a one-dimensional model for the local bend is justified by comparison to the well-established polyad model which reveals a decoupling of the large amplitude bending from other degrees of freedom in the range of N bend ) 14-22. We find that the same one-dimensional large amplitude bending motion emerges from two profoundly different representations, a one-dimensional cut through an ab initio, seven-dimensional Hamiltonian and the three-dimensional (l ) 0) pure-bending experimentally parametrized spectroscopic Hamiltonian.

The potential enzyme evaluation of the acidophilic, chemolitotrophic and heterotrophic bacteria specific to the mining biotope is of high interest in the solubilization, recovery and / or removal of platinum metals from industrial waste car tires. The obtained data show that the formation of extracellular polymeric substances plays an important role in the attachment of the chemolithotrophic bacteria on the surface of minerals, as well as sulphur. In this sense, a direct interaction between the bacterial cells and the solid surface is mandatory for an efficient mobilization of platinum metals from waste car tires. These occur at two levels: (a) physical sorption due to electrostatic forces with low pH in the leaching media; (b) chemical sorption is carried out only in the type of chemical bonds between the bacterial cell disulphide bond and minerals. The optimization of the technological process such as solubilization and the recovery of platinum metal ions contained in ferrous and non-ferrous industrial waste was materialized through a series of laboratory experiments based mainly on the affinity of bacterial cells for certain organic and / or inorganic surfaces. It is based on the results of the physical-chemical characterization of the liquid samples taken. This study deals with the optimization of the solubilization process of metal ions contained in such samples.

- by C. M . Cismasiu
- •
- Biochemistry, Microbiology, Theoretical Physics, Theoretical Chemistry

Determination of the ground-and excited-state unimolecular decomposition mechanisms of 1,2-dioxetanedione gives a level of insight into bimolecular decomposition reactions of this kind for which some experimental results are reported. Although a few studies have put some effort to describe a biradical mechanism of this decomposition, there is still no systematic study that proves an existence of a biradical character. In the present study, state-of-the-art high-level multistate multiconfigurational reference second-order perturbation theory calculations are performed to describe the reaction mechanism of 1,2-dioxetanedione in detail. The calculations indicate that the decomposition of this four-membered ring peroxide containing two carbonyl carbon atoms occurs in concerted but not simultaneous fashion, so-called " merged " , contrary to the case of unimolecular 1,2-dioxetane and 1,2-dioxetanone decompositions where biradical reaction pathways have been calculated. At the TS of the ground-state surface, the system enters an entropic trapping region, where four singlet and four triplet manifolds are degenerated, which can lead to the formation of triplet and singlet excited biradical species. However, these excited species have to overcome a second activation barrier for C−C bond cleavage for excited product formation, whereas the ground-state energy surface possesses only one TS. Thus our calculations indicate that the unimolecular decomposition of 1,2-dioxetanedione should not lead to efficient excited-state formation, in agreement with the lack of direct emission from the peroxyoxalate reaction.

- by Pooria Farahani and +1
- •
- Theoretical Chemistry, Chemiluminescence

In this work, a new partitioning method is presented which allows one to calculate properties of radicals, in particular, atomic spin populations. The method can be seen as an extension of the Hirshfeld-I method [Bultinck, P. et al. J. Chem. Phys. 2007, 126, 144111], in which the atomic weight functions, defining the atoms-in-molecules, are constructed by means of an iterative scheme in which the charges of the atoms-in-molecules are altered but the spin remains fixed. The Hirshfeld-I method is therefore not suitable for the calculation of atomic spin populations of open-shell systems. The new fractional occupation Hirshfeld-I (FOHI) uses an iterative scheme in which both the atomic charge and spin are optimized, resulting in a self-consistent method for the calculation of atomic spin populations. The results obtained with the FOHI method are compared with experimental results obtained using polarized neutron diffraction, thus serving as a validation of the FOHI method as well as the Hirshfeld definition of atoms-in-molecules in general.

- by Davy Geldof and +2
- •
- Computational Chemistry, Quantum Chemistry, Physical Chemistry, Theoretical Chemistry
- by C. M . Cismasiu
- •
- Microbiology, Theoretical Physics, Theoretical Chemistry, Art

3 Institutul National de Cercetare-Dezvoltare pentru Metale si Resurse Radioactive -ICPMRR Bucureşti, tomnic90@yahoo.fr MASA ROTUNDĂ CENTIREM 24 NOIEMBRIE 2017 IMPLICAŢII TEHNOLOGICE ALE ORGANISMELOR SPECIFICE ECOSISTEMELOR CONTAMINATE INDUSTRIAL DIN NORDUL OLTENIEI Harta judeţului Gorj cu delimitarea termocentralelor Rovinari şi Turceni (Cismasiu si colab., 2017)

Evaluarea potentialului enzimatic al bacteriilor acidofile, chemolitotrofe si heterotrofe, specifice biotopului minier este de mare interes in solubilizarea, recuperarea si/sau indepartarea metalelor platinice din deseuri industriale auto uzate. Datele obtinute au evidentiat faptul ca formarea substantelor polimerice extracelulare joaca un rol important in atasarea bacteriilor chemolitotrofe pe suprafata mineralelor, precum si de sulf. In acest sens, interactiunea directa intre celula bacteriana si suprafata solida este obligatorie pentru o mobilizare eficienta a metalelor platinice din deseuri auto uzate. Acestea au loc la doua niveluri: (a) sorbtia fizica din cauza fortelor electrostatice datorita pH-ului scazut din mediile de lesiere; (b) sorbtia chimica in care se realizeaza numai legaturi chimice de tip legaturi bisulfide intre celula bacteriana si minerale. Activitatea de optimizare a procesului tehnologic de solubilizare si recuperare a ionilor metalici platimici continuti in deseuri industriale feroase si neferoase s-a concretizat printr-o serie de experimente de laborator care se bazeaza in principal pe afinitatea unor celule bacteriene pentru anumite suprafete de natura organica si/sau anorganica. Pe baza rezultatelor caracterizarii fizico-chmice a probelor lichide prelevate s-a considerat important studiul de fata privind optimizarea procesului de solubilizare a ionilor metalici continuti in acestea. Cercetarile in domeniul ecologiei microbiene a mediilor extreme de acide s-au intensificat in ultimii ani pe linia cercetarilor fundamentale cat si applicative. Datele din literature de specialitate reflecta faptul ca rolul bacteriilor chemolitotrofe, cat si a celor heterotrofe, este si continua sa fie de mare interes practic pentru procesele de solubilizare a metalelor sau de sorbtie a acestora din efluenti lichizi. Metodele de mobilizare bacteriana a metalelor platinice sunt urmatoarele: (1) includerea in materiale inerte de natura organica si anorganica; (2) absorbtia pe un material solid; (3) mobilizarea prin legaturi de afinitate intre molecule biologice; (4) mobilizarea metalelor platinice si celulelor prin legaturi covalente sau coordinative cu alte materiale decat cele inerte. Rezumatul reprezinta o contributie la cercetarea si dezvoltarea proceselor tehnologice bazate pe activitatea bacteriilor chemolitotrofe acidofile cu aplicatii eficiente in bioremedierea mediilor poluate cu substante anorganice reziduale cat si pentru recuperarea unor cantitati de ioni metalici.

- by C. M . Cismasiu
- •
- Biochemistry, Microbiology, Theoretical Physics, Theoretical Chemistry

Despite the outstanding scintillation performance characteristics of cerium tribromide (CeBr 3 ) and cerium-activated lanthanum tribromide, their commercial availability and application are limited due to the difficulties of growing large, crack-free single crystals from these fragile materials. This investigation employed aliovalent doping to increase crystal strength while maintaining the optical properties of the crystal. One divalent dopant (Ca 2þ ) was used as a dopant to strengthen CeBr 3 without negatively impacting scintillation performance. Ingots containing nominal concentrations of 1.9% of the Ca 2þ dopant were grown, i.e., 1.9% of the CeBr 3 molecules were replaced by CaBr 2 molecules, to match our target replacement of 1 out of 54 cerium atoms be replaced by a calcium atom. Precisely the mixture was composed of 2.26 g of CaBr 2 added to 222.14 g of CeBr 3 . Preliminary scintillation measurements are presented for this aliovalently doped scintillator. Ca 2þ -doped CeBr 3 exhibited little or no change in the peak fluorescence emission for 371 nm optical excitation for CeBr 3 . The structural, electronic, and optical properties of CeBr 3 crystals were studied using the density functional theory within the generalized gradient approximation. Calculated lattice parameters are in agreement with the experimental data. The energy band structures and density of states were obtained. The optical properties of CeBr 3 , including the dielectric function, were calculated. V C 2014 AIP Publishing LLC.

- by Bryan M Wong
- •
- Materials Engineering, Physics, Theoretical Physics, Materials Science
- by Cina Foroutan-Nejad
- •
- Chemistry, Computational Chemistry, Organic Chemistry, Theoretical Chemistry

A correlation has been developed for corrected experimental C1s XPS binding energies of polymers vs. calculated partial charges of carbon atom in model oligomers. Representative polymers containing a wide variety of heteroatoms such as Cl, F, O, N, Si have been selected. Molecular geometry was determined with the semiempirical valence orbital AM1 method, and Mulliken population analysis was applied to calculate partial atomic charges. The resulting charge-potential model equation can be used to predict core electron binding energies in polymers and deconvolute XPS spectra.

- by Zoltan Fekete and +2
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- Computational Chemistry, Physical Chemistry, Theoretical Chemistry, Polymer science

Bridgehead imine substituted cyclopentadithiophene structural units offer the opportunity to modify the electronic properties, in particular, the HOMO−LUMO energy levels of donor−acceptor polymers with unprecedented precision. Utilizing a common synthetic pathway, copolymers with high average molecular weights, a variety of functionality, and properties suitable for solar cell incorporation can be generated. The fabrication of organic photovoltaic devices with these new materials is demonstrated.

- by Bryan M Wong
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- Materials Engineering, Physics, Materials Science, Solid State Physics

The quantum theory of angular momentum and the associated Racah-Wigner algebra of the Lie group SU(2) have been widely used in many branches of theoretical and applied physics, chemical physics, and mathematical physics. This paper starts with an account of the basics of such a theory, which represents the most exhaustive framework in dealing with interacting many-angular momenta quantum systems. We then outline the essential features of this algebra, that can be encoded, for each fixed number N = (n ? 1) of angular momentum variables, into a combinatorial object, the spin network graph, where vertices are associated with finite-dimensional, binary coupled Hilbert spaces while edges correspond to either phase or Racah transforms (implemented by 6j symbols) acting on states in such a way that the quantum transition amplitude between any pair of vertices is provided by a suitable 3nj symbol. Applications of such a combinatorial setting-both in fully quantum and in semiclassical regimes-are briefly discussed providing evidence of a unifying background structure.

A series of 2-hydroxy-5-bromo-4-methoxy-N-(substituted phenyl) chalconeimine was synthesized, characterized and tested for their antimicrobial activity. These new derivative was achieved by treating 2-hydroxy-5-bromo-4-methoxy chalcone with substituted aniline at reflux temperature using ethanol as solvent in presence of H2SO4. Structures of the synthesized compounds were characterized using IR, 1H-NMR and mass spectroscopy. The synthesized compounds were screened for their in vitro antibacterial activity against bacteria S. aureus, E. coli, P. aeruginosa and S. Pyogenes. And antifungal activity against C. Albicans and A.Clavatus some of these compounds exhibited moderate to good activity.