Luiz Guilherme M. de Macedo

A Structure-Activity Relationship (SAR) Study of Neolignan Compounds with Anti-schistosomiasis Activity

A set of eighteen neolignan derivative compounds with anti-schistosomiasis activity was studied by using the quantum mechanical semi-empirical method PM3 and other theoretical methods in order to calculate selected molecular properties (variables or descriptors) to be correlated to their biological activities. Exploratory data analysis (principal component analysis, PCA, and hierarchical cluster analysis, HCA), discriminant analysis (DA) and the Kth nearest neighbor (KNN) method were employed for obtaining possible relationships between the calculated descriptors and the biological activities studied and predicting the anti-schistosomiasis activity of new compounds from a test set. The molecular descriptors responsible for the separation between active and inactive compounds were: hydration energy (HE), molecular refractivity (MR) and charge on the C19 carbon atom (Q19). These descriptors give information on the kind of interaction that can occur between the compounds and their respective biological receptor. The prediction study was done with a new set of ten derivative compounds by using the PCA, HCA, DA and KNN methods and only five of them were predicted as active against schistosomiasis.

An accurate relativistic universal Gaussian basis set for hydrogen through Nobelium without variational prolapse and to be used with both uniform sphere and Gaussian nucleus models.

An accurate relativistic universal Gaussian basis set (RUGBS) from H through No without variational prolapse has been developed by employing the Generator Coordinate Dirac–Fock (GCDF) method. The behavior of our RUGBS was tested with two nuclear models: (1) the finite nucleus of uniform proton‐charge distribution, and (2) the finite nucleus with a Gaussian proton‐charge distribution. The largest error between our Dirac–Fock–Coulomb total energy values and those calculated numerically is 8.8 mHartree for the No atom.

A polynomial version of the generator coordinate Dirac–Fock method

A polynomial version of the Generator Coordinate Dirac–Fock (p‐GCDF) method is introduced and applied to develop Adapted Gaussian Basis Sets (AGBS) for helium‐ and beryllium‐like atomic species (He, Ne+8, Ar+16, Sn+48, Be, Ne+6, Ar+14, and Sn+46) and for Kr and Xe atoms. The Dirac–Fock–Coulomb and Dirac–Fock–Breit energies obtained with these basis sets are in excellent agreement with numerical finite‐difference calculations. Moreover, the sizes of the AGBS generated here with the p‐GCDF method are significantly smaller than the size of previous relativistic Gaussian basis sets.

Fully relativistic calculations on the potential energy surfaces of the lowest 23 states of molecular chlorine

The electronic structure and spectroscopic properties (R(e), omega(e), omega(e)x(e), beta(e), and T(e)) of the ground state and the 22 lowest excited states of chlorine molecule were studied within a four-component relativistic framework using the MOLFDIR program package. The potential energy curves of all possible 23 covalent states were calculated using relativistic complete open shell configuration interaction approach. In addition, four component multireference configuration interaction with single and double excitation calculations were performed in order to infer the effects due to dynamical correlation in vertical excitations. The calculated properties are in good agreement with the available experimental data.The electronic structure and spectroscopic properties (R(e), omega(e), omega(e)x(e), beta(e), and T(e)) of the ground state and the 22 lowest excited states of chlorine molecule were studied within a four-component relativistic framework using the MOLFDIR program package. The potential energy curves of all possible 23 covalent states were calculated using relativistic complete open shell configuration interaction approach. In addition, four component multireference configuration interaction with single and double excitation calculations were performed in order to infer the effects due to dynamical correlation in vertical excitations. The calculated properties are in good agreement with the available experimental data.

Synthesis, structure, electronic and vibrational spectra of 9-(diethylamino)-benzo(a)phenoxazin-7-ium-5-N- methacrylamide

The electronic and vibrational spectra of 9-(Diethylamino)-benzo(a)phenoxazin-7-ium-5-N-methacrylamide (Nile Blue-5-N-methacrylamide) are measured, and the results are compared with the theoretical values obtained by quantum chemical calculations. The geometry, electronic transitions, charge distribution, and the IR normal modes of this new dye and of its precursor Nile Blue have been computed by using Density Functional Theory (DFT) method with the functional B3LYP and the 6-31G(d) Gaussian basis set. The molecular properties of the two dyes, predicted and observed, are very similar in the electronic ground state. In the excited state, however, the longer lifetime and larger fluorescence quantum yield of the Nile Blue-5-methacrylamide is ascribed to an inhibition of the twisted intramolecular charge transfer (TICT) process, when the NH2 is substituted by the methacrylamide in the 5-position of the aromatic extended ring of the dye. The change in charge density of the N atom in 5-position, as well as the difference in dipole moment and ionization potential of the two dyes molecules, explain the attenuation of TICT process. The vibration spectra of both dyes are simulated properly by using the DFT method.

New Insight into the Formation of Nitrogen Sulfide: A Quantum Chemical Study

We studied the chemical mechanism for the formation of (2)NS in the interstellar medium was by using the CCSD/6-311++G(d,p) and CCSD(T)/6-311++G(3df,3pd) levels of theory. To the best of our knowledge, this is the first detailed study of the chemical mechanism for the formation of (2)NS. Several reactions proposed in this article are spin-forbidden. They were treated with the Landau-Zener theory and by the MRCI methodology. The following reactions paths proposed in this article are energetically favorable: (1) (1)NH + (2)SH --> cis-(2)HNSH --> TS1 --> trans-(2)HNSH --> TS2 --> (2)H(2)NS --> TS3 --> (2)NS + H(2) and (2) (4)N + (1)SH --> (1)NSH --> TS13 --> (1)HNS --> (2)NS + (2)H. However, the latter reaction, (4)N + (1)SH --> (1)NSH, is spin-forbidden, and its probability of occuring (p(sh)) is zero. The chemical mechanism for the formation of (2)NS in the interstellar medium is now presented in more detail, which is of great importance.

Fully relativistic prolapse-free Gaussian basis sets: The actinides and Tl81–Ra88

In this work, four-component prolapse-free Gaussian-type functions (GTFs) suitable for molecular calculations were generated for elements from Tl (Z=81) up to No (Z=102). In order to obtain compact, stable, and reliable basis sets, the absolute values of the energy difference between the Dirac–Fock–Roothan (DFR) total energy E(DFR) and the corresponding numerical values E(NDF) obtained by Visscher and Dyall [At. Data Nucl. Data Tables67, 207 (1997)] are at millihartree order of magnitude and prolapse to be smaller than (or close to) 1mH. The resulting GTFs are the most compact explicit prolapse-free basis sets for these elements.

On the Angular Distribution of the H+Li2 Cross Sections: a Converged Time-Independent Quantum Scattering Study

A thorough time-independent quantum scattering study is performed on a benchmark potential energy surface for the H+Li2 reaction at the fundamental electronic state. Integral and differential cross sections are calculated along with thermal rate coefficients until convergence is reached. Our findings show that vibrational and rotational excitations of the reactant hinder reactivity, though for the latter a considerable reaction promotion was spotted as we increase the reactant rotational quantum number until the critical value of j = 4. Such a promotion then begins to retract, eventually becoming an actual inhibition for larger j. In a straightforward manner, the concept of time-independent methods implemented in this study allowed this accurate state-to-state analysis. Furthermore, a nearly isotropic behaviour of the scattering is noted to take place from the angular point of view. Remarkably, our computational protocol is ideally suited to yield converged thermal rate coefficients, revealing a non-Arrhenius pattern and showing that J-shifting approach fails to describe this particular reaction. Our results, when compared to previous and independent ones, reinforce the latest theoretical reference for future validation in the experimental field.

Estudo Teórico dos 23 Estados Covalentes da Molécula F 2 através da Metodologia Relativística MRCI de 4 Componentes

Apesar de estado fundamental do F2 ser bem caracterizado, seus estados excitados sao pouco compreendidos devido as dificuldades experimentais e teorico/computacional. Neste trabalho obtivemos todos os 23 estados excitados covalentes da molecula F2 com o benchmark para inclusao dos efeitos de correlacao eletronica, o metodo multireferencial de interacoes de configuracoes (MRCI), e dos efeitos relativisticos, o metodo de 4 componentes resolvendo a equacao de Dirac. A equacao de Dirac se faz necessaria para tratar o efeito de spin-orbita para obter os 23 estados covalentes possiveis de forma variacional. Este trabalho e um dos primeiros da literatura a gerar as curvas de energia potencial de todos os estados covalentes possiveis de uma molecula utilizando o MRCI de 4 componentes. DOI: 10.5935/1984-6835.20160030