This paper reconstructs the relative sea level changes during the Holocene on the southeastern Brazilian coastal region (Armação dos Búzios city, at north of Rio de Janeiro state), based on the presence of rocky bottom worm snails, Vermetidae (Mollusca: Gastropoda) as bioindicators. Chronology was established by radiocarbon Accelerator Mass Spectrometry technique. Three evolutionary stages of sea level were established: sea-level lower than the current one between 8,148-6,300 cal yr BP, a rising of sea level between 6,300-4,500 cal yr BP, with a transgressive maximum of about 2.4 m above the present level at 4,700-4,500 cal yr BP, and a sea level drop from 4,500 cal yr BP until the present.

The emission of carbon dioxide in large amounts is commonly believed to be the main cause of global climate changes. Development of CO 2 capture processes is still a big current challenge. Some anions have been studied for the gas sequestration process due their great affinity to CO 2 . In this work, electronic structure calculations were performed at the MP2/aug-cc-pvtz level to compute the interaction between 20 anions and CO 2 . A CBS scheme, using extrapolated energies, was also employed for both gas phase and solvent calculations. The reactions between the anions and CO 2 were therefore studied in four different conditions (gas phase, toluene, tetrahydrofuran and water). The trends observed for the reaction thermodynamics with the MP2 method is similar to that observed previously with the B3LYP-D3 and M06-2X functionals. The reactions in the gas phase are highly exothermic and do not involve any activation energy. The solvent effect reduces the exothermicity and induces an intrinsic activation barrier. The negative charge is dispersed in the adduct, leading to a weaker interaction in a polar solvent. Then, increasing the medium polarity, the energy difference between the adduct and the reactants decreases. We also observed a limit for solvent stabilization in the low dielectric constant range. For example, the results obtained with tetrahydrofuran are closer to those obtained with water than to those obtained with toluene. Considering both the thermodynamics of the reaction and the differential solvent effects, we were able to indicate anions derived from alkyl sulfides as the most convenient for CO 2 sequestration among the set here considered.

Density functional theory (DFT) (B3LYP/6-311++G(d,p)) calculations of the interacting strength 1,2-dithiolene anionic ligands with the [M(OH 2 ) 4 ] 2+ and [M(OH 2 ) 2 ] 2+ complexes (M = Ni and Zn) were performed. Three series of ligands were studied: compounds with an aromatic ring, with an ethylene moiety and with a heterocyclic ring. The ligands have substituents electron donors and acceptors by induction and resonance. Two substitution reactions were studied: the first is the substitution of two water molecules from the [M(OH 2 ) 6 ] 2+ by a dithiolene anionic ligand (L 2− ) and the second is the substitution of two water molecules from the [M(OH 2 ) 4 L] by another dithiolene anionic ligand. Geometric, electronic and energetic properties of the substituted aquacations are correlated with the metal-ligand affinity. All the substitution processes for both metal cations are spontaneous and are modulated by the electronic effect of each substituent of the ligand. Geometric parameters and chelation angle are correlated with the interaction strength. The energy decomposition analysis (EDA) results show that the electrostatic component is the main stabilizing term for the monosubstituted complexes, while for the disubstituted complexes the covalent term is the main stabilizing component. The polarization term is the main one to describe the covalent character. Natural bond orbital (NBO) shows the acid-base interaction nature of the metal-ligand bond.DFT Study of the Interaction between the Ni 2+ and Zn 2+ Metal Cations and the 1,2-Dithiolene Ligands J. Braz. Chem. Soc. 1162

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Estudo teórico da relação dos orbitais de fronteira com eficiência de inibição de compostos modelo de derivados da 2-Aminopirazina Theoretical study of the relationship of border orbitals with compound inhibition efficiency model of derivatives from 2-Aminopirazine

A series of B3LYP/6-311+G(d,p) calculations of the affinity of monodentate ligands for [Cd(HO)] are performed. Three types of ligands containing O (phosphine oxide, lactam, amide, carboxylic acid, ester, ketone, aldehyde, ether, halohydrin, enol, furan), N (thiocyanate, amine, ammonia, azide), and S (thioester, thioketone, thiol, thiophene, disulfide) interacting atoms are investigated. The results show that phosphine oxide has the largest affinity for the cadmium cation due to the polarization of the P=O bond. As the P atom has a large atomic radius, the O atom can polarize the electronic cloud enhancing its amount of electronic charge and favoring the interaction with Cd. The affinity order found is phosphine oxide > thioester > lactam > amide > carboxylic acid > ester > thioketone > ketone > thiocyanate > amine > ammonia > aldehyde > ether > thiol > thiophene > enol > halohydrin > disulfide > azide > furan ligands. These results were also corroborated by the functional M06-2X. The electronic effects (resonance and induction) of neighboring groups of the interacting atom modulate the strength of metal-ligand binding. For almost all the O-donor ligands the electrostatic component has the same magnitude as the covalent term, while for the N- and S-donor ligands the covalent term is predominant. The polarization term accounts for twice the exchange term as part of the covalent component. The dispersion term varies less than 2 kcal mol for the complexes analyzed. The Pauli repulsion term is correlated with the metal ligand distance, increasing in the compounds with decreased metal-ligand bond length. The charge between the interacting atoms is also strongly correlated with both the interacting strength and the electrostatic interaction component. The natural bond orbital analysis highlights correlations of the bond order, and S and P contributions of the interacting metal-ligand orbital with the coordination strength. Graphical abstract The affinity of 20 monodentate ligands with different functional groups for the [Cd(HO)] cation is calculated based on the interaction enthalpy and Gibbs free energy for the substitution of one water molecule from the fully hydrated cation. The affinity is correlated with geometric, electronic, and energetic parameters of the ligands and the complexes as well as with energy decomposition and natural bond order analyses results.

A corrosão é um problema mundial que promove um grande impacto econômico, devido aos custos diretos e indiretos, afetando tanto países desenvolvidos quanto os países em desenvolvimento. Diversos métodos são usados na indústria com intuito de evitar e/ou reduzir a taxa de deterioração de materiais metálicos. Os inibidores de corrosão têm sido amplamente utilizados como agentes de tratamento. Inibidores de corrosão são adicionados a meios corrosivos para mitigar a deterioração do metal versus soluções às quais estão expostos; como é sabido, eles são compostos orgânicos contendo grupos polares, como átomos de nitrogênio em sua estrutura molecular, enxofre e/ou oxigênio; compostos heterocíclicos com grupos funcionais polares e ligações duplas. Para o aperfeiçoamento do processo anticorrosivo, novos materiais têm sido investigados experimentalmente e através de cálculos teóricos.  O estudo do mecanismo de atuação dos inibidores de corrosão assim como os fatores que influenciam a eficiência de inibição tem sido o alvo de muitos trabalhos teóricos. Entre eles, destacam-se os estudos com baseados na a teoria do funcional da densidade (TFD). O objetivo deste artigo é apresentar uma breve revisão da utilização de cálculos teóricos, destacando o método da Teoria do Funcional de Densidade (TFD) como ferramenta na análise de propriedades das moléculas orgânicas com possíveis aplicações como inibidores de corrosão. Esta revisão apresenta as propriedades eletrônicas e índices de reatividade mais importantes relacionados à eficiência de inibidores de corrosão orgânicos, tais como: as energias dos orbitais de fronteira, diferença de energia (HOMO/LUMO), momento de dipolo, eletronegatividade, potencial químico, dureza, maciez, fração de elétrons transferidos, índice global de eletrofilicidade Além disso, descritores químicos quânticos locais, como carga, função de Fukui e suavidade, também foram explorados. Como conclusão, pode-se considerar que os cálculos DFT fornecem fortes evidências para complementar as investigações experimentais ou mesmo para prever com segurança algumas propriedades experimentalmente desconhecidas relacionadas aos inibidores de corrosão.

The emission of carbon dioxide in large amounts is commonly believed to be the main cause of global climate changes. Development of CO2 capture processes is still a big current challenge. Some anions have been studied for the gas sequestration process due their great affinity to CO2. In this work, electronic structure calculations were performed at the MP2/aug‐cc‐pvtz level to compute the interaction between 20 anions and CO2. A complete basis set scheme, using extrapolated energies, was also employed for both gas phase and solvent calculations. The reactions between the anions and CO2 were therefore studied in four different conditions (gas phase, toluene, tetrahydrofuran and water). The trends observed for the reaction thermodynamics with the MP2 method is similar to that observed previously with the B3LYP‐D3 and M06‐2X functionals. The reactions in the gas phase are highly exothermic and do not involve any activation energy. The solvent effect reduces the exothermicity and induces an intrinsic activation barrier. The negative charge is dispersed in the adduct, leading to a weaker interaction in a polar solvent. Then, increasing the medium polarity, the energy difference between the adduct and the reactants decreases. We also observed a limit for solvent stabilization in the low dielectric constant range. For example, the results obtained with tetrahydrofuran are closer to those obtained with water than to those obtained with toluene. Considering both the thermodynamics of the reaction and the differential solvent effects, we were able to indicate anions derived from alkyl sulfides as the most convenient for CO2 sequestration among the set here considered.