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Dopamine is an important neurotransmitter belonging to the catecholamine family, which acts on the central nervous system. This catecholamine plays a key role in regulating a variety of functions, such as motor and cognitive functions. This class of neurotransmitters is important for normal neurophysiology and is also the target of a broad spectrum of therapeutic and illicit agents. Evaluating the interaction of these neurotransmitters, in particular, dopamine with water molecules, is crucial for a better understanding of the conformational preferences of dopamine in solution, which consequently assists in the design of new drugs for the treatment of diseases associated with a malfunction of the system, and direct measurement, which is particularly essential for early warning of certain diseases. In this sense, the objective of this work is to examine the effects of aqueous solvation on the geometric and electronic parameters of dopamine using Car-Parrinelo Molecular Dynamics. The Car-Parrinello Molecular Dynamics simulation was performed using the CPMD program package (Version 4.1). The results indicate that dopamine interact swith several water molecules, with the formation of hydrogen bonds. In particular, there are two hydrogen bonds (H5···Owf and N3···Hwd) with an infinite residence time that strongly suggests the protonation of these groups.

Norepinephrine, synthesized from tyrosine, is a neurotransmitter of sympathetic post-ganglion neurons. Norepinephrine regulates many critical functions which include attention, memory, learning and cardiovascular functions. This neurotransmitter has several pharmacological uses, such as adrenergic stimulants, widely used in the treatment of hypertension, cardiac surgery and in myocardial infarction. It is extremely important to study the interaction between drugs and water molecules, for a better understanding of absorption, transport and biological action. Within this context, the Car-Parrinello Molecular Dynamics, by treating the solvent explicitly, becomes ideal for the study of solvated media. In this sense, the objective of this work is to analyze the effects of aqueous solvation on the geometric and electronic parameters of norepinephrine using the Molecular Dynamics of Car-Parrinelo. The solvation dynamics was performed using the CPMD program package (version 4.1). The Radial Distribution Function of the hydrogen and oxygen atoms of the water molecules in the first solvation shell were performed for the O1, O2, O3, N7, H4, H5, H6, H8 and H9 atoms of the norepinephrine. The Radial Distribution Function analyzes indicate that most sites have a well-defined peak (N7, O1, O3, H4, H5 and H6). For the O2, H8 e H9 atoms, there are no well-defined peaks, suggesting that these sites do not interact with the atoms of the water molecules, or even the possibility of intra-molecular interactions. These criteria were considered for the next stages of this work, which are already being carried out, and they are analyzes of possible interactions of hydrogen with these sites.

In this work, we described the synthesis of 10 new fluorescent 2,1,3-benzoselenadiazole small-molecule derivatives and their chemical- and photocharacterizations. The new derivatives could, for the first time, be successfully applied as selective live cell imaging probes (at nanomolar concentrations) and stained lipid-based structures preferentially. Density functional theory (DFT) calculations were used to help in understanding the photophysical data and the intramolecular charge-transfer (ICT) processes of the synthesized dyes. Some derivatives showed impressive cellular responses, allowing them to be tested as probes in a complex multicellular model (i.e., Caenorhabditis elegans). When compared with the commercially available dye, the new fluorescent compounds showed far better results both at the cellular level and inside the live worm. Inside the multicellular complex model, the tested probes also showed selectivity, a feature not observed when the commercial dye was used to carry out the bioimaging experiments.

Accurate ab initio calculations provide the reliable information needed to study the potential energy surfaces that control the non-covalent interactions (NCIs) responsible for the formation of weak van der Waals complexes. In this work, relying on the state of the art method for NCI computations, namely symmetry adapted perturbation theory (SAPT), we calculated the potential energy curves for the interaction of noble gases (Ng = He, Ne, Ar and Kr) with methanol in three different interaction sites to account for orientational anisotropy of the interaction potential. Different levels of the SAPT and basis set were employed to disclose the nature of the stabilizing forces acting upon formation of the Ng-CH3OH adducts. SAPT-derived NCIs indicate that dispersion forces are indeed the dominating component of the total energy, but also that induction and electrostatic effects are important to counterbalance the steric repulsions. By solving the Radial Nuclear Schrodinger Equation for the complexes, we also determined the rovibrational structure of the interaction wells to extract invaluable information about the thermodynamic stability of the adducts and how different temperature conditions affect the structure of the dimers. Although SAPT calculations reveal net attractive forces, these do not afford a spontaneous complexation process even at temperatures as low as 40 K.

Herein we report the first systematic investigation of the tandem mercury(ii) catalysed transvinylation/Hurd-Claisen rearrangement of MBH adducts derived from alkyl acrylates. This is the first report of E-selectivity for MBH adducts with alkyl side chains and is complementary to the previously reported Johnson-Claisen and Eschenmoser-Claisen rearrangements. The rearrangement products were obtained in good yields and could be readily converted to 2-alkenyl δ-valerolactones. Combined DFT and F-SAPT studies demonstrate that reaction rates are primarily governed by non-covalent interactions dictating the relative stability of the transition states. Our F-SAPT calculations revealed that the hyperconjugative effects are not so significant, but that electrostatic interactions, instead, are the driving forces for the relative E : Z stereoselectivity.

The electronic absorption spectrum of the neurotransmitter epinephrine (EPN) in water solution is studied, combining ab initio Car-Parrinello molecular dynamics (CPMD) with a quantum mechanical approach within the framework of the time-dependent density functional theory (TDDFT) scheme. By selecting 52 uncorrelated snapshots, the excitation modes were calculated at the LC-ωPBE/6-31+G(d) level of theory, using an optimal range-separation parameter ω, determined by means of the gap-tuning scheme in the presence of the solvent molecules. By comparing with static approaches (vacuum and implicit solvation), we show here that explicit solvation treatment dramatically enhances the photophysical properties of the EPN, especially because of the more realistic dynamic description of the molecular geometry. The agreement between the simulated and experimental spectra is demonstrated when TDDFT calculations are performed with the optimally tuned version of the DFT hybrid, not only improving the relative intensities of the absorption bands but also the λ

The current article describes the synthesis, characterization, and application of a designed hybrid fluorescent BTD–coumarin (2,1,3-benzothiadiazole-coumarin) derivative (named BTD-Lip). The use of BTD-Lip for live-cells staining showed excellent results, and lipid droplets (LDs) could be selectively stained. When compared with the commercially available dye (BODIPY) for LD staining, it was noted that the designed hybrid fluorescence was capable of staining a considerable larger number of LDs in both live and fixed cells (ca. 40% more). The new dye was also tested on live Caenorhabditis elegans (complex model) and showed an impressive selectivity inside the worm, whereas the commercial dye showed no selectivity in the complex model.

Negatively charge-tagged N-heterocyclic carbenes have been formed in solution via deprotonation of imidazolium ions bearing acid side groups and transferred to the gas phase via ESI(-)-MS. The structure of the putative and apparently stable gaseous carbenes formed in such conditions were then probed via reactions with carbon dioxide using a triple quadrupole mass spectrometer particularly optimized for ion/molecule reactions of ESI-generated ions. Complete conversion to imidazolium carboxylates was achieved, which seems to demonstrate the efficiency of the transfer, the gas-phase stability, and the long-lived nature of these unprecedented charge-tagged carbenes and their predominance in the ionic population. Comprehensive studies on the intrinsic reactivity of N-heterocyclic carbenes with silent charge tags are therefore possible. Graphical Abstract ᅟ.

The work describes the design, synthesis, characterization and biological application (bioimaging) of a new hybrid and fluorescent 2,1,3-benzothiadiazole-quinoline sensor. Both photophysical data of the designed compound and DFT calculations have indicated its high stability and have pointed to its possible efficient application as a bioprobe for bioimaging experiments. The new sensor has been designed to display lipophilic character being capable of selectively stain lipid bodies independent whether live and fixed cancer cells were used. The fluorescent sensor has also been tested as a specific bioimaging marker for C. elegans (complex multicellular model) and has showed far better selectivity in the worm than the commercially available BODIPY. A live mice has been submitted to a surgery procedure and the adipocytes (lipid-rich) cells have been differentiated from standard cells. Experiments using high fat fed mice have enabled a high-resolution 3D image reconstruction. Also, in another surgery procedure, hepatocyte cells could have been successfully followed in the blood flow using the designed sensor in a multistaining procedure alongside with a commercially available blue emitting nuclei marker.

The interest for novel chalcone-based materials in nonlinear optics is dependent on strong second harmonic generation in organic systems. Chalcones are α,β-unsaturated ketones that can be easily obtained by Claisen–Schmidt condensation between ketones and aromatic aldehydes. A new 2-amino-chalcone was synthesized and its crystal molecular structure was elucidated using the single crystal X-ray diffraction technique. This compound, C15H12BrNO2, crystallizes in monoclinic centrosymmetric space group C2/c with cell parameters a = 29.47(7) A; b = 6.97(5) A, c = 13.59(1) A, β = 112.52(6)° and V = 2581.2(2) A3. In addition to the crystal structure, the analysis of Hirshfeld surfaces indicates the presence of hydrogen bonds of types N–H⋯O and O–H⋯O that stabilize two independent centrosymmetric dimers, and also indicates the presence of π–π stacking interactions that stabilize a supramolecular trimeric system. Being a push–pull chromophore we investigated the NLO properties of the 2-amino-chalcone asymmetric unit using the supermolecule approach in combination with an iterative electrostatic polarization scheme. The calculations were performed using the CAM-B3LYP/6-311+G(d) level of theory for both dynamic and static situations. In the presence of the embedding charges, the γ value is increased by 20% for the dynamic calculation but only 8% for the static limit. In contrast to the crystal form, when in solution the 2-amino-chalcone lacks an inversion center so that second order NLO properties do not vanish. Following this idea we computed the NLO properties using the implicit solvation approach IEF-PCM. The solvent effect on the NLO properties was to augment its values as the solvent polarity increases. We obtained for the in-crystal and in DMSO 2-amino-chalcone, γ(−2ω;ω,ω,0) = 144.12 × 10−36 esu and 260.163 × 10−36 esu, respectively, and therefore interesting materials for third order NLO applications.

In the present contribution, we develop an adapted theoretical approach based on DFT calculations (B3LYP functional) and solution of the nuclear Schrodinger equation by using the Discrete Variable Representation method to model the interaction of ammonia with metallo-phthalocyanines (MPcs, where M = Fe2+, Co2+, Ni2+, Cu2+ or Zn2+). This approach is intended to be a general protocol for the rational design of chemical sensors. The as-obtained binding energy curves, obtained from ab initio points, permitted us to calculate rovibrational energies and spectroscopic constants, as well as to establish the relative population of rovibrational states in different types of MPc–NH3 thermodynamic systems. Simulated binding energy curves show that the binding energy in MPc–NH3 systems is dependent on the type of M central ion, decreasing in the order FePc > ZnPc > CoPc > CuPc > NiPc, with values spanning from −170 to −16 kJ mol−1. Also, MPc–NH3 systems have at least 16 rovibrational levels, which confirms that they are all bound systems (chemically or physically). Despite that, only the interaction between ammonia and FePc, CoPc or ZnPc is spontaneous within the studied temperature range (200–700 K). NiPc and CuPc show a change between spontaneous and non-spontaneous behaviours at ∼400 K and ∼500 K, respectively. Less bound systems should more efficiently guarantee the sensors' signal reset, while they are also less specific than sensors built with medium to strongly bound systems. Moreover, the intermediate energy and spontaneous binding of ammonia to NiPc and CuPc at operation temperatures, as determined with our theoretical approach, suggests that these MPcs are most promising for ammonia sensors.

We calculated the nonlinear optical properties of 24 azo-enaminone derivatives, incorporating solvent effects on their geometric and electronic structure, to assess the impact of the environment on these properties. Namely, we incorporated chloroform, tetrahydrofuran, acetone, ethanol, methanol, and dimethyl sulfoxide in our calculations and compared our results incorporating solvent effects with our gas-phase calculations. To account for the electron correlation effects on NLO properties, we performed the calculations at MP2/6-31G(p)//MP2/6-31G(d) level set. The polarizable continuum model was used to simulate the presence of the solvent. The exponents of p extra functions added to heavy atoms were obtained, imposing the maximization of the first hyperpolarizability. Two structural configurations (Z and E) of azo-enaminones were investigated to assess the isomeric effects of the electric properties. Our results show that both solvent polarity and relative strength of the donor groups have a significant i...

Among four-atom processes, the reaction OH + HBr → H2O + Br is one of the most studied experimentally: its kinetics has manifested an unusual anti-Arrhenius behavior, namely, a marked decrease of the rate constant as the temperature increases, which has intrigued theoreticians for a long time. Recently, salient features of the potential energy surface have been characterized and most kinetic aspects can be considered as satisfactorily reproduced by classical trajectory simulations. Motivation of the work reported in this paper is the investigation of the stereodirectional dynamics of this reaction as the prominent reason for the peculiar kinetics: we started in a previous Letter ( J. Phys. Chem. Lett. 2015 , 6 , 1553 - 1558 ) a first-principles Born-Oppenheimer "canonical" molecular dynamics approach. Trajectories are step-by-step generated on a potential energy surface quantum mechanically calculated on-the-fly and are thermostatically equilibrated to correspond to a specific temperature. Here, refinements of the method permitted a major increase of the number of trajectories and the consideration of four temperatures -50, +200, +350, and +500 K, for which the sampling of initial conditions allowed us to characterize the stereodynamical effect. The role is documented of the adjustment of the reactants' mutual orientation to encounter the entrance into the "cone of acceptance" for reactivity. The aperture angle of this cone is dictated by a range of directions of approach compatible with the formation of the specific HOH angle of the product water molecule; and consistently the adjustment is progressively less effective the higher the kinetic energy. Qualitatively, this emerging picture corroborates experiments on this reaction, involving collisions of aligned and oriented molecular beams, and covering a range of energies higher than the thermal ones. The extraction of thermal rate constants from this molecular dynamics approach is discussed and the systematic sampling of the canonical ensemble is indicated as needed for quantitative comparison with the kinetic experiments.

This paper describes the synthesis, structure, photophysical properties, and bioimaging application of a novel 2,1,3-benzothiadiazole (BTD)-based rationally designed fluorophore. The capability of undergoing efficient stabilizing processes from the excited state allowed the novel BTD derivative to be used as a stable probe for bioimaging applications. No notable photobleaching effect or degradation could be observed during the experimental time period. Before the synthesis, the molecular architecture of the novel BTD derivative was evaluated by means of DFT calculations to validate the chosen design. Single-crystal X-ray analysis revealed the nearly flat characteristics of the structure in a syn conformation. The fluorophore was successfully tested as a live-cell-imaging probe and efficiently stained MCF-7 breast cancer cell lineages.

The work describes the use of ionophilic indium complex bearing a task-specific ionic liquid as the ligand with hydrophilic chlorides. The new luminescent complex was designed to be completely water-soluble aiming at cell-imaging application. The indium derivative was also characterized by single-crystal X-ray analysis and the molecular arrangement could be compared in the condensed phase with aqueous solutions. An alternative methodology had to be employed to an accurate analysis of the photophysical properties determined by DFT calculations to describe the experimental results. The complex stabilizes from the excited state through a charge transfer process which was depicted as a ligand-to-ligand transfer (from a chlorine atom to the imidazolium ring) as indicated by the theoretical investigation. EPR experiments could be conducted at −196 °C to evaluate the charge transfer process and it proved to be in accordance with the predicted result from DFT calculations. The luminescent properties of the complex allowed it to be used as a bioprobe during cell-imaging experiments with several live cells lineages.

A study of the spectroscopic properties of the buckyball dimer (C70)2 was performed, which involved mapping the potential energy curve of this system. The spectroscopic constants of the system were obtained using theoretical Dunham and discrete variable representation methods, as well as the Rydberg analytical function expanded to the sixth degree. Because the fullerenes in the dimer have both hexagonal and pentagonal faces, the properties of (C70)2 were examined for different system configurations. The fullerene dimerization process involves a weak interaction, possibly mediated by short-range components such as van der Waals forces. The differences between the spectroscopic constants of the various (C70)2 configurations and between their dissociation energies De were found to be rather small, which can be attributed to the dominant influence of the hexagonal faces of the fullerenes on the interaction between the fullerenes. These results should aid our understanding of the process of fullerene dimer formation and hopefully facilitate the development and application of new materials based on these dimers. Graphical Abstract Comparison of the potential energy curve and a schematic representation for the all (C70)2 fullerenes dimers configurations.

A study of the spectroscopic properties of the buckyball dimer (C

Well-defined structure–property relationships offer a conceptual basis to afford a priori design principles to develop novel π-conjugated molecular and polymer materials for nonlinear optical (NLO) applications. Here, we introduce the bond ellipticity alternation (BEA) as a robust parameter to assess the NLO characteristics of organic chromophores and illustrate its effectiveness in the case of streptocyanines. BEA is based on the symmetry of the electron density, a physical observable that can be determined from experimental X-ray electron densities or from quantum-chemical calculations. Through comparisons to the well-established bond-length alternation and π-bond order alternation parameters, we demonstrate the generality of BEA to foreshadow NLO characteristics and underline that, in the case of large electric fields, BEA is a more reliable descriptor. Hence, this study introduces BEA as a prominent descriptor of organic chromophores of interest for NLO applications.

In order to account for the deviations from the Arrhenius rate law for the effect of temperature on food processes, we adopt an alternative approach inspired by the deformed exponential based on the Euler limit. The non-enzymatic browning of onions and the growth of bacteria were chosen to validate our proposal, which provides a better description than other formulas previously tested for these systems. These results show that the deformed Arrhenius rate law is suitable for describing the effect of rate-temperature on different food systems and suggest a relationship between the kinetic behavior of food processes and classical collective phenomena.

A task-specific ionic liquid constituted by a Bronsted acid (1-(3-sulfopropyl)-3-methyl-imidazolium hydrogen sulfate) as the cation, namely MSI, and by [PW12O40]3− as the triply charged counter-anion, namely PW (a heteropolyacid derivative), was used as an efficient catalyst for the condensation reaction between aldehydes and o-phenylenediamines.

In this paper, we propose a new alternative analytical function aiming to better describe the potential energy curves of the doubly charged diatomic molecules. To achieve this goal, we modified an existing potential function in the literature to describe dicationic diatomic molecules using the deformed exponential function. We generated the potential energy curve of the testing group of dicationic diatomic molecules $$ \mathrm{B}{\mathrm{e}}_2^{2+} $$ , BH2+, $$ \mathrm{H}{\mathrm{e}}_2^{2+} $$ and NH2+ by means of the CCSD(T)/aug-cc-pVQZ level of theory. To validate this new function, we also calculated the spectroscopic constants and the rovibrational spectra for the electronic state $$ {X}^1{\varSigma}_g^{+} $$ of the $$ \mathrm{B}{\mathrm{e}}_2^{2+} $$ and $$ \mathrm{H}{\mathrm{e}}_2^{2+} $$ systems using the Dunham and discrete variable representation methods. For BH2+ and NH2+ molecules, despite exhibiting a local minimum in the potential energy curve, no vibrational levels are supported, so the spectroscopic constants for these poorly bound systems are invalidated. The fitting accuracy had a better performance over the original potential for describing dicationic diatomic systems, considering that the discrete variable representation method resulted in a similar vibrational structure described in the literature. This fact can be explained due to the deformed function’s flexibility.

A series of new rationale designed 2,1,3-benzothiadiazole (BTD) fluorescent derivatives has been synthesized and applied for cellular selective staining of cancer cells in cell-imaging experiments. Four new synthesized BTD derivatives showed only poor or reasonable cellular selection, but with excellent fluorescence intensity and almost no background signal emitting at the blue or green channels. The knowledge gained by analysing their molecular architecture, however, allowed the planning and synthesis of a fluorescent BTD, which was then successfully tested and showed superior mitochondrial selection with outstanding results in bioimaging experiments in living cells. The new marker (named Splendor) was then compared with the commercially available MitoTracker Red (also through co-staining experiments) and showed far better mitochondrial selection, fluorescence intensity and chemical stability. Mitochondrial imaging and tracking (dynamic changes) was possible using Splendor during the whole cellular division cycle. DFT calculations were performed to offer insights into the origin of the chemical- and photostability of BTD derivatives. In addition, molecular docking calculations hint at a potential molecular target for the BTD derivatives in the mitochondrial protein adenine nucleotide translocase, which may explain the mitochondrial selectivity of Splendor versus the other four BTD derivatives.

The ability of the chalcone, C18H18O4, to form solvates was theoretically and experimentally investigated. The unit cell with Z′ > 1, composed of two independent chalcone molecules (α and β), shows the formation of a stable molecular complex which is related with the presence of methanol in this crystal lattice. Aiming to understand the process of crystal lattice stabilization, a combination of techniques was used, including X-ray diffraction (XRD), computational molecular modeling, and an ab initio molecular dynamic. The results show that α and β molecules are sterically barred from forming a direct hydrogen bond with one other. In addition, the presence of the methanol molecule stabilizes the crystal structure by a bifurcated O—H···O interaction acting as a bridge between them. The theoretical thermodynamic parameter and the rigid potential energy surface scan describe the role of methanol in the energy stabilization of the crystal. The absence of the methanol compound in the asymmetric unit destabilize...

Using a set of different techniques, which included single crystal X-ray, NMR, UV–vis, conductivity measurements, SAXS (small angle X-rays), ESI-MS(/MS) (electrospray (tandem) mass spectrometry), and theoretical calculations, an ample study of the structural organization and supramolecular interaction of the task-specific ionic liquid 1-methyl-3-carboxymethylimidazolium chloride (named MAI.Cl) was conducted. All techniques allowed for comprehensive investigation in the solid state, solution, and gas-phase behavior of MAI.Cl. Most relevant interactions are demonstrated showing the importance of hydrogen bonding to supramolecular organization of MAI.Cl in different states and its tendency to aggregate in aqueous solutions.

A task-specific ionic liquid with a Bronsted acid (1-(3-sulfopropyl)-3-methylimidazolium hydrogen sulfate, namely MSI ) bearing an anionic heteropolyacid derivative ([PW 12 O 40 ] 3− , namely PW ) were used as an efficient catalyst for the three-component Mannich and Hantzsch reactions. Using ( MSI ) 3 PW as the catalyst supported in imidazolium-based ionic liquids allowed these multicomponent reactions to take place in good to excellent yields. The Mannich reaction, performed at room temperature, was also evaluated by means of electrospray (tandem) mass spectrometry—ESI-MS(/MS). ESI-MS data pointed to the origin of the ionic liquid effect, i.e., formation of ion pairs with the charged reaction intermediates and furthers association into larger supramolecular aggregates. DFT calculations revealed the strength of the supramolecular interactions between the charged species detected by ESI-MS and the spontaneity association of these ion pairs affording larger supramolecular aggregates.

Neste trabalho, apresentaram-se resultados de cálculos das energias e constantes espectroscópicas rovibracionais do sistema molecular Cl2 em diferentes estados eletrônicos. Foram realizados cálculos de 20 estados eletrônicos, utilizando as funções de Rydberg e Bond Order generalizadas como formas analíticas para ajustar as curvas de energia potencial, geradas a partir das energias eletrônicas. Com essas formas analíticas, as energias rovibracionais e as constantes espectroscópicas foram determinadas, combinando as energias obtidas via solução da Equação de Schrödinger Nuclear com uma equação espectroscópica e via método de Dunham. As constantes espectroscópicas obtidas estão em excelente acordo com os dados experimentais disponíveis para alguns estados eletrônicos.

A series of rationally designed, non-symmetrical, 4,7-π-extended-2,1,3-benzothidiazole derivatives had their electronic and geometrical properties evaluated by means of DFT calculations. The data obtained from the calculated 2,1,3-benzothiadiazole (BTD) intermediates allowed the design and synthesis of a final structure bearing a fluorine-containing aromatic group on one side of the BTD ring and a C≡C spacer linking a long chain-containing (C8) aromatic group on the other side. This specific molecular architecture is expected to display liquid crystalline behavior. The new designed structure was therefore synthesized in good overall yield using cross-coupling reactions (Suzuki and Sonogashira reactions). Copyright © 2013 John Wiley & Sons, Ltd.

No final da década de 60, Richard Wolfgang já alertava sobre a necessidade de inserir uma distribuição de não equilíbrio na descrição teórica da constante cinética em substituição à distribuição de Maxwell Boltzmann. Somente, 20 anos depois, surge uma proposta consistente, capaz de atender às necessidades previstas por Wolfgang: a distribuição de Tsallis. Esta distribuição é baseada na termodinâmica não extensiva de Tsallis, obtendo como caso particular a termodinâmica convencional Gibbs-Boltzmann. Neste artigo, serão apresentados detalhes, acerca desse modelo e a evolução da descrição da constante cinética à luz da distribuição de Tsallis.

Bronsted and Lewis acid catalysts with ionic tags under homogeneous and heterogeneous conditions have been tested to perform the Biginelli synthesis of 3,4-dihydropyrimidin-2(1H)-one (DHPMs). Metal-containing ionic liquids were evaluated as the catalysts with reasonable results (homogeneous systems). Heterogeneous catalysts (zeolite β and H3PW12O40 supported on zeolite β) have been tested, as well, with good to excellent results. The use of a functionalized acid ionic liquid with a heteropolyacid in the anion moiety (homogeneous system) gave the best results using no excess of the three reagents. The preferred mechanistic pathway was investigated by electrospray ionization (tandem) mass spectrometry in both positive and negative ion modes with very elucidative results. The ionic liquid effect and its origin were also investigated using mass spectrometry and DFT calculations.

Made available in DSpace on 2018-12-11T16:43:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Apoio à Pesquisa do Distrito Federal Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A prolapse-free basis set for Eka-Actinium (E121, Z = 121), numerical atomic calculations on E121, spectroscopic constants and accurate analytical form for the potential energy curve of diatomic E121F obtained at 4-component all-electron CCSD(T) level including Gaunt interaction are presented. The results show a strong and polarized bond (≈181 kcal/mol in strength) between E121 and F, the outermost frontier molecular orbitals from E121F should be fairly similar to the ones from AcF and there is no evidence of break of periodic trends. Moreover, the Gaunt interaction, although small, is expected to influence considerably the overall rovibrational spectra. Faculdade de Biotecnologia Instituto de Ciências Biológicas Universidade Federal Do Pará (UFPA) Laboratório de Estrutura Eletrônica E Dinâmica Molecular (LEEDMOL) Instituto de Química Universidade de Brasília (UnB), P.O. Box 04478 Departamento de Matemática Universidade Estadual Paulista (UNESP), P.O. Box 473 Instituto de Física Universidade de Brasília (UnB), P.O. Box 04455 Departamento de Matemática Universidade Estadual Paulista (UNESP), P.O. Box 473 CNPq: 157843/2015-7 FAPESP: 2013/19289-0 FAPESP: 2016/07476-9

A formulation is presented for the application of tools from quantum chemistry and transition-state theory to phenomenologically cover cases where reaction rates deviate from Arrhenius law at low temperatures. A parameter d is introduced to describe the deviation for the systems from reaching the thermodynamic limit and is identified as the linearizing coefficient in the dependence of the inverse activation energy with inverse temperature. Its physical meaning is given and when deviation can be ascribed to quantum mechanical tunneling its value is calculated explicitly. Here, a new derivation is given of the previously established relationship of the parameter d with features of the barrier in the potential energy surface. The proposed variant of transition state theory permits comparison with experiments and tests against alternative formulations. Prescriptions are provided and implemented to three hydrogen transfer reactions: CH4 + OH → CH3 + H2O, CH3Cl + OH → CH2Cl + H2O and H2 + CN → H + HCN, widely investigated both experimentally and theoretically. © 2016 Wiley Periodicals, Inc.

The main goal of this paper is to present the rovibrational energies and spectroscopic constants of the Cl2 molecular system in the relativistic states $$ {\text{X}}:(1)0_g^{ + } $$ , A′:(1)2 u , A:(1)1 u , $$ {\text{B}}\prime :(1)0_u^{ - } $$ and $$ {\text{B}}:(1)0_u^{ + } $$ . More precisely, we have evaluated the Cl2 ω e , ω e x e , ω e y e , α e , γ e and B e rovibrational spectroscopic constants using two different procedures. The first was obtained by combining the rovibrational energies, calculated through solving Schrodinger’s nuclear equation and the diatomic rovibrational energy equation. The second was obtained by using the Dunham method. The calculated properties are in good agreement with available experimental data.

Chalcones are α,β-unsaturated aromatic ketones which can present a wide range of biological activities. Here, the structure of the chalcone (E)-1-(4-biphenyl)-3-(3,4,5-trimethoxyphenyl)prop-2-en-1-one was determined by single crystal X-ray diffraction technique and compared to those of similar compounds whose crystal structures are available in the Cambridge Structural Database. These comparisons have allowed us to conclude that electron delocalization is abrogated through the biphenyl and carbonyl moieties, while resonance effects are increased through the trimethoxyphenyl group and the olefin carbons. Single-molecule calculations of the asymmetric unit using the DFT method have strengthened these structural relationships, since experimental and theoretical molecular geometries were similar. For instance, the global minimum for the optimized structure occurs when one of the four dihedral angles on the bridge between the two rings of biphenyl is 40.25°, a value close to that of the corresponding torsion determined by single crystal X-ray diffraction analysis [41.7(3)°]. Our theoretical approaches further suggest another stable conformer for different torsions around this bridge, although this conformer was not found in the crystal phase because C–H···π intermolecular interactions contributing to assemble the supramolecular architecture of the studied compound keep only the conformer observed. Other face-to-face π···π stacking interactions and C–H···Ο contacts are also responsible for the crystal assembly.

The present manuscript describes the synthesis of two novel 2,1,3-benzothiadiazole (BTD) derivatives containing an excited state intramolecular proton transfer (ESIPT) site. Photophysical properties, X-ray analysis, ESIPT and intramolecular charge-transfer (ICT) of these novel fluorescent monosubstituted BTD derivatives were investigated. It is also shown that ESIPT and ICT can take place concomitantly. Theoretical calculations (ab initio and DFT) corroborate the high stability of these derivatives in the excited state due to efficient ESIPT and ICT processes. Also, the optimized calculated geometries of these new structures allowed a better understanding of the different behaviour of the dyes in a wide pH range (1–13). Finally, the new compounds exhibit impressive cellular selectivity and stain only mitochondria in different cell lines and are far better than the commercially available MitoTracker-red.

In this paper the accuracy of the q -Integral method is evaluated in several molecular properties of the H 2 system using the Density Functional Theory (DFT). The q -Integral method is an alternative approach to evaluate two-electron integrals where the CPU time is substantially less than usual. For this purpose, we evaluated potential energy curves, rovibrational spectroscopy constants, rovibrational spectra, interatomic equilibrium distance and longitudinal static hyper (polarizability). All calculations were carried out through the STO-3G, STO-6G and double- ξ (DZV) atomic basis set. The results, using DFT methodology, are in good agreement with those obtained through the usual procedure of calculating the two-electron integrals, and show some of the same tendency as the previous results using HF, MP2 and Coupled Cluster methods. All calculations were performed in the general ab initio quantum chemistry package GAMESS, where we implemented the q -Integral method in the source code.

In this work, we introduce a new analytical form based on the q-exponential function to build three-dimensional reactive surfaces. The quality of this new function is tested by fitting the ab initio potential energy surface (PES) to the ground state Na+HF reaction. The thermal rate constant and reactive probabilities were determined considering this new PES. The obtained properties agree with those found for other PES available in literature.

O conhecimento das propriedades térmicas é de grande importância para simulação da variação da temperatura em sistemas de transporte, estocagem e dimensionamento industrial, principalmente na indústria de alimentos. Neste trabalho nós propomos uma metodologia teórica-experimental para a predição da difusividade e condutividade térmica de alimentos baseada em um procedimento híbrido entre um aparato experimental muito simples e o método de otimização Levenberg-Marquardt. Para validar esta metodologia nós utilizamos pasta de tomate comercial. A difusividade e a condutividade térmica obtidas foram 0,093cm2 /min e 0,544 W/m.K, respectivamente. Estes resultados estão de acordo com a literatura.

O estudo de propriedades moleculares vem se tornando uma forte ferramenta na análise de diversos tipos de processos químicos e físicos, como: desenvolvimento de novos materiais, sistemas catalíticos, sistemas moleculares excitados, entre vários outros. Para a análise dessas propriedades, do ponto de vista teórico, o caminho mais promissor tem sido via equações da Mecânica Quântica. Entretanto, a resolução analítica para sistemas moleculares polietrônicos é inviável surgindo a necessidade de aproximações que supra este problema. Atualmente, os métodos mais promissores na descrição de sistemas moleculares, são Hartree – Fock e Teoria do Funcional de Densidade. Estes métodos serão descritos em detalhes neste artigo dentro da necessidade de descrever propriedades moleculares. Será abordado também, um método de correção para o cálculo da energia de ligação devido ao erro da superposição de bases atômicas (BSSE), conhecido como método de Counterpoise.

The q-Integral method, based on the q-Exponential function, has been recently introduced as an alternative approach to calculate the two-electron integrals which appear in ab initio atomic and molecular quantum mechanical calculations. The advantage of this procedure is that the CPU time for calculating of two-electron integrals is substantially reduced when compared with the usual one. The objective of this work is to investigate the accuracy of the q-Integrals as a function of the internuclear distance for molecular systems. To this purpose we employed the q- Integrals to construct the potential energy surface (PES) for the H2 molecule and used the PES to determine the rovibrational levels and spectroscopic constants of the molecule, which are properties very sensitive to the form of the PES. The results obtained are in good agreement with the ones obtained through the standard procedure of calculating the two-electron integrals, implying that the q-Integral method is accurate enough to be used in any molecular quantum mechanical calculation. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem 108: 2540 -2549, 2008