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In addition to seven known alkaloids (2, 6-11) and 1,2,4-trimethoxybenzene (1), three isoquinoline-derived alkaloids (3-5), namely, duguetinine (3), a compound based on an unprecedented oxahomoaporphine scaffold, and two new 8-oxohomoaporphine alkaloids, duguesuramine (4) and 11-methoxyduguesuramine (5), and a new asarone-derived phenylpropanoid (10) were isolated from the bark of Duguetia surinamensis. The isolation workflow was guided by HPLC-HRESIMS/MS and molecular networking-based analyses. Twenty-four known alkaloids were dereplicated from the D. surinamensis alkaloid-rich fraction network and were assigned by manual MS/MS interpretation. Their cytotoxic potential was evaluated.

Since the commercial introduction of Ion Mobility coupled with Mass Spectrometry (IM-MS) devices in 2003, a large number of research laboratories have embraced the technique. IM-MS is a fairly rapid experiment used as a molecular separation tool and to obtain structural information. The interpretation of IM-MS data is still challenging and relies heavily on theoretical calculations of the molecule's collision cross section (CCS) against a buffer gas. Here, a new software (HPCCS) is presented, which performs CCS calculations using high perfomance computing techniques. Based on the trajectory method, HPCCS can accurately calculate CCS for a great variety of molecules, ranging from small organic molecules to large protein complexes, using helium or nitrogen as buffer gas with considerable gains in computer time compared to publicly available codes under the same level of theory. HPCCS is available as free software under the Academic Use License at https://github.com/cepid-cces/hpccs. © 2018 Wiley Periodicals, Inc.

Hypothesis In photorheological fluids, subtle molecular changes caused by light lead to abrupt macroscopic alterations. Upon UV irradiation of an aqueous cetyltrimethylammonium bromide (CTAB) and trans-ortho-methoxycinnamic acid (trans-OMCA) solution, for instance, the viscosity drops over orders of magnitude. Multiscale modeling allows to elucidate the mechanisms behind these photorheological effects. Experiments We use time-dependent DFT calculations to study the photoisomerization, and a combination of atomistic molecular dynamics (MD) and DFT to probe the influence of both OMCA isomers on the micellar solutions. Findings The time-dependent DFT calculations show that the isomerization pathway occurs in the first triplet excited state with a minimum energy conformation closest to the after photoisomerization predominant cis configuration. In the MD simulations, with sub-microsecond timescales much shorter than the experimental morphological transition, already a clear difference is observed in the packing of the two OMCA isomers: contrary to trans-OMCA, cis-OMCA exposes notable part of its hydrophobic aromatic rings at the micelle surface. This can explain why trans-OMCA adopts rod-like micellar packing (high viscosity) while cis-OMCA spherical micellar packing (low viscosity). Moreover, lowering of the OMCA co-solute concentration allowed us to perform full simulation of the breakup process of the rod-like micelles which are stable prior to isomerization.

We report herein the first collision induced dissociation (CID) study with oxoaporphine alkaloids by electrospray ionization ion-trap mass spectrometry (ESI-IT-MS) associated with ab initio computational studies and isotope labeling experiments. Product ion spectra for a set of 11 oxoaporphine alkaloids were carefully analyzed to assign fragmentation patterns for this natural products class. All common possibilities for different arrangements of the peripheral groups, methylene dioxide bridge, methoxyl, and hydroxyl substituents, were discussed based on MS data and ab initio calculations. We observed that the most suitable protonation site generally occurs on the heterocyclic nitrogen instead of the carbonyl oxygen atom at C-7. In some special cases, a gas-phase proton transfer occurs for compounds bearing a hydroxyl group at C-3, as confirmed by isotope labeling experiments. Results point that the substitution pattern drives the dissociation behaviors of oxoaporphine alkaloids.

Enantioselective carbonyl-directable Heck reactions using aryldiazonium salts were developed with the aim to construct chiral quaternary spiro centers in an efficient manner. Five- and six-membered spirooxindoles, spirolactones, and spirolactams (36 examples) were obtained in good to excellent isolated yields with diastereoselectivities ranging from 13:1 to >20:1, and enantiomeric excesses up to 99% in short reaction times (1.0–1.5 h) under mild conditions (40 °C). A rationale for the diastereo- and enantioselectivity based on an unprecedented non-covalent carbonyl group directing effect is also presented, and supported by computational calculations.

A technical overview of the High Performance Collision Cross Section (HPCCS) software for accurate and efficient calculations of collision cross sections for molecular ions ranging from small organic molecules to large protein complexes is presented. The program uses helium or nitrogen as buffer gas with considerable gains in computer time compared to publicly available codes under the Trajectory Method approximation. HPCCS is freely available under the Academic Use License at https://github.com/cepid-cces/hpccs .

In addition to seven known alkaloids (

S- and P-Stereogenic heterocycles were synthesized by a remarkably simple enantioselective Heck desymmetrization reaction based on the unprecedented noncovalent directing effect of S=O and P=O functionalities. Selected prochiral symmetric substrates were efficiently arylated using the recently disclosed chiral PyraBOx ligand under mild and open-flask reaction conditions. Several five-membered aryl- sulfones, sulfoxides, and phosphine oxides were synthesized in good to excellent yields, in good to high diastereoselectivity, and enantiomeric ratios up to 98:2. Theoretical calculations also support the noncovalent directing effect of the S=O and P=O functionalities during the arylation process.

Highly diastereo- and enantioselective, noncovalent, substrate-directable Heck desymmetrizations of cyclopentenyl olefins containing hydroxymethyl and carboxylate functional groups are presented. These conformationally unbiased cyclic olefins underwent effective arylations in yields of up to 97 %, diastereoselectivity up to >20:1, and enantiomeric excesses of up to 99 %. Noncovalent directing effects were shown to be prevalent in both Heck-Matsuda and oxidative Heck reactions, allowing the preferential formation of cis-substituted aryl cyclopentenes containing two stereocenters, including quaternary stereocenters. These results further validate the internal out-of-coordination-sphere ion-dipole interaction concept directing the reaction diastereoselectivity to the cis-Heck product. This approach is complementary to existing methods using bis-phosphine monoxide ligands to give the opposite trans-diastereoisomer. The applicability of the method is showcased by the straightforward synthesis of a potent phosphodiesterase 4 inhibitor in a diastereo- and enantioselective manner. The reaction is operationally simple and has broad scope with regard to the nature of the arenediazonium salt and boronic acid employed. The mechanism and origin of stereoselectivity were investigated with control experiments and DFT calculations that fully supported the stabilizing internal out-of-coordination-sphere ion-dipole interaction between the resident functional group and cationic palladium.

W1 theory is characterized by a rigorous well-defined series of ab initio calculations not explicitly including any empirical adjustment based on experimental results. To expand its applicability to large molecules, a compact effective pseudopotential was included in its computational procedure and the combination is referred to as W1CEP. The values obtained by W1CEP are very close to the original W1 theory, with a mean absolute deviation of 1.2 kcal mol −1 for W1 and of 1.4 kcal mol −1 for W1CEP. The range of the deviations with a 95% confidence interval are ±3.4 kcal mol −1 for W1 and ±4.0 kcal mol −1 for W1CEP. In addition to accuracy of the results, another important result is that the calculations using W1CEP decrease the CPU time by 13–30%.

Theoretical calculations of the binding energies of metal-polyphenols and metal-cellulose, as well as the hydration energies of metal-polyphenols were used to support the results obtained for the bioaccessibility of aluminium, cadmium, iron and zinc from four types of lettuce and one type of cole that were evaluated using an in vitro gastrointestinal digestion model and inductively coupled plasma-mass spectrometry. The bioaccessibility of Al found in the vegetables were less than 11% of the total Al content, whereas Cd exhibited average bioaccessibility of approximately 14% for the fresh samples and 41% considering the dried vegetables studied. However, the results indicated average bioaccessibility of 35% and 26% for Zn and average bioaccessibility of 19% and 21% for Fe in fresh and dried samples, respectively. The low bioaccessibility of Al is due to its strong binding with all of the vegetable components, whereas the low bioaccessibility of Fe and Zn are due to their interactions with phytates. Cd was observed to be the most bioaccessible element in the dried samples because of its weak interaction with other components in the vegetables.

To address the title question, the relative intrinsic acidities of phenol and benzoic acid as well as the isomeric family of ortho-, meta-, and para-hydroxybenzoic acids were compared. Dissociation of the [PhCO2···H···OPh]– proton-bound dimer showed slightly greater acidity for benzoic acid. Using traveling-wave ion mobility mass spectrometry (TWIM-MS) with CO2 as the drift gas and post-TWIM collision-induced dissociation, the gaseous deprotonated molecules of the isomeric hydroxybenzoic acids were properly separated and characterized. For the para isomer, an intrinsic gas-phase acidity order inverse to that in solution was found, as before, that is, the phenol site of para-hydroxybenzoic acid was found to be considerably more acidic than its benzoic acid site, whereas the opposite was observed in solution, regardless of the solvent. However, for the ortho and meta isomers, the inversion in acidity order upon going from solution to the gas phase was not observed, and gaseous carboxylate anions were still found to predominate over phenoxide anions. Actually, for the ortho isomer, an even greater acidity as estimated from proton affinity values for the benzoic acid site relative to that of the phenol site was predicted, and accordingly, only a single isomer was sampled by TWIM-MS. Rationales for these contrasting trends based on interfering inductive effects, charge delocalization by resonance, and intraionic H-bonds that govern the acidity of benzoic acid relative to that of phenols are presented.

Three guaianolide sesquiterpenes, denoted guatterfriesols A-C, and four aporphine alkaloid derivatives were isolated from the stem bark of the Amazonian plant Guatteria friesiana. Thus far, sesquiterpene lactones have not been described in Annonaceae. Structures of the previously undescribed compounds were established by using 1D and 2D NMR spectroscopy in combination with MS. The absolute stereochemistry was assigned via NOE NMR experiments, ECD spectroscopy, and theoretical calculations using the TDDFT approach. Among the isolated compounds, the alkaloid guatterfriesidine showed anti-glycation activity by inhibiting the formation of advanced glycation end-products (AGEs) through the prevention of oxidation in both BSA/methylglyoxal and BSA/fructose systems.

The effect of selenate and selenite enrichment on mineral composition of a red type of lettuce cv. “Veneza roxa” was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP OES), molecular modeling and principal component analysis (PCA). Both Se species did not show toxicity, while selenate promoted the greatest Se accumulation by the plant. There was an increase of 886 µg of Se per 100 g of fresh sample at different concentrations of selenate, but for selenite the maximum variation was only of 114 µg per 100 g. Selenate promoted the absorption of Mo and S and the reduction of K, Mn and P, meanwhile selenite increased Mn and decreased Mo accumulation. Copper and Fe absorption was negatively affected, Ca and Mg showed a slight increase, and Na and Zn were not affected by Se species. Despite the changes in the nutritional balance, Se-enriched lettuce can still be considered a potential dietary source of this essential element.

Ion mobility spectrometry (IMS) separates ions while they travel through a buffer gas under the influence of an electrical field. The separation is affected by mass and charge but most particularly by shape (collision cross section). When coupled to MS, IMS-MS offers therefore a powerful tool for structural elucidation and isomer separation. Systematic studies aimed to compare and quantitate the effects of structural changes on drift time such as length and ramification of carbon chain, unsaturation, geometrical isomerism (cis/trans isomers for instance), cyclization and ring size are, however, scarce. Herein we used traveling wave ion mobility mass spectrometry (TWIM-MS) to systematically evaluate the relationship between structure and drift time. For that, a series of deprotonated carboxylic acids were used as model ions with a carboxylate “charge tag” for gas phase MS manipulation. Carboxylic acids showed a near linear correlation between the increase of carbon number and the increase of collision cross section (CCS). The number of double bonds changes slightly the CCS of unsaturated acids. No differences in drift time and no significant differences in CCS of cis- and trans-double bond of oleic and elaidic acids were observed. Cyclization considerably reduces the CCS. In cyclic carboxylic acids, the increase of double bonds and aromatization significantly reduces the CCS and the drift times. The use of a more polarizable drift gas, CO2, improved in some cases the separation, as for biomarker isomers of steranoic acids. The β-isomer (cis-decaline) has smaller CCS and therefore displayed lower drift time compared to the α-isomer (trans-decaline). Structural changes revealed by calculations were correlated with trends in drift times.

Pd(ITMe)2(PhCCPh) acts as a highly reactive pre-catalyst in the unprecedented homogenous catalyzed diboration of terminal and internal alkynes, yielding a number of novel and known syn-1,2-diborylalkenes in a 100% stereoselective manner. DFT calculations suggest that a similar reaction pathway to that proposed for platinum phosphine analogues is followed, and that destabilization of key intermediates by the NHCs is vital to the overall success for the palladium-catalyzed B–B addition to alkynes.

Composite methods using ONIOM and different basis sets have been used to calculate proton and electron affinities for a set of alcohols at QCISD(T)/6-311++G(2df,p) level of theory. The study was carried out considering HF, MP2 and DFT (25 exchange correlation functional) methods. The calculation performed at ONIOM2(QCISD(T)/6-311++G(2df,p):HF/6-31G(d))//ONIOM2(O3LYP/6-31G(d):HF/6-31G(d)) resulted in the smallest average absolute deviation for AP and AE, 4,75 kJ/mol e 0,43 eV, respectively.

Orientador: Nelson Henrique Morgon Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química Resumo: Simulações de Dinâmica Molecular Atomística e cálculos TDDFT e DFT foram realizados para estudar o efeito da fotoisomerização do ânion trans/cis-OMCA em micelas formadas pelo surfactante catiônico CTAB em solução aquosa. Cálculos TDDFT mostraram que o processo de isomerização ocorre via o primeiro estado excitado tripleto. O mínimo de energia, para este estado, ocorre próximo a conformação cis, o que explica a maior presença desse isômero após o processo de fotoisomerização. Nas simulações de dinâmica molecular sem OMCA, as micelas originalmente em forma de haste se dividiram em várias micelas esféricas. Na presença de OMCA, os ânions auxiliaram na estabilização das micelas do tipo haste através da migração para dentro da micela. Enquanto suas partes hidrofílicas ficam na região do grupo de cabeça do surfactante, o empacotamento dos grupos hidrofóbicos difere entre trans e cis-OMCA. Para cis é possível notar que parte de grupo hidrofóbico está exposto na superfície da micela. Para trans-OMCA esta porção penetra no interior da micela. Em ambos os casos, micelas em forma de haste demonstraram ser estáveis. As estimativas para o parâmetro crítico de empacotamento (CPP) encontradas nas simulações mostram a tendência de empacotamento preferencial em micelas esféricas e haste para CTAB + cis-OMCA (0,34) e CTAB + trans-OMCA (0,48), respectivamente, em boa concordância com as evidências experimentais Abstract: Atomistic Molecular Dynamics Simulations and TDDFT and DFT calculations were carried out to study the effect of trans/cis-OMCA anion photoisomerization into micelles formed by the cationic surfactant CTAB in aqueous solution. TDDFT calculations were showed that the isomerization process occurs via the first triplet excited state. The minimum energy for this state, occurs closer to the cis conformation, which explains the greater presence of this isomer after photoisomerization process. In the molecular dynamics simulations without OMCA, rod-like micelles were divided into multiple spherical micelles. Micelles formed from CTAB in the presence of either OMCA isomer are stable in a rod-like micellar structure throughout the entire simulation (80 ns).The fact that even with the cis-OMCA anions, the micelles remain rod-like is due to different timescales between the MD simulation (submicro second) and the experimental transition that takes minutes. Despite this discrepancy, the simulations already show a clear difference in the packing of the two OMCA isomers in the micelles: while in both cases the hydrophilic groups are in the surfactant head group area, the hydrophobic aromatic rings pack in different ways. For trans-OMCA, the hydrophobic group is fully embedded in the micelle, whereas for cis-OMCA a notable part is on the micelle surface. Estimations for the Critical Packing Parameter (CPP) values corresponding to these configurations explain the tendencies for the micelles to pack into spheres with cis-OMCA and into rods with trans-OMCA, in good agreement with experiment Doutorado Físico-Química Doutor em Ciências CNPQ 140910/2011-5

Wormlike micelles formed by the addition to cetyltrimethylammonium bromide (CTAB) of a range of aromatic cosolutes with small molecular variations in their structure were systematically studied. Phenol and derivatives of benzoate and cinnamate were used, and the resulting mixtures were studied by oscillatory, steady-shear rheology, and the microstructure was probed by small-angle neutron scattering. The lengthening of the micelles and their entanglement result in remarkable viscoelastic properties, making rheology a useful tool to assess the effect of structural variations of the cosolutes on wormlike micelle formation. For a fixed concentration of CTAB and cosolute (200 mmol L(-1)), the relaxation time decreases in the following order: phenol > cinnamate> o-hydroxycinnamate > salicylate > o-methoxycinnamate > benzoate > o-methoxybenzoate. The variations in viscoelastic response are rationalized by using Mulliken population analysis to map out the electronic density of the cosolutes and quantify the barrier to rotation of specific groups on the aromatics. We find that the ability of the group attached to the aromatic ring to rotate is crucial in determining the packing of the cosolute at the micellar interface and thus critically impacts the micellar growth and, in turn, the rheological response. These results enable us for the first time to propose design rules for the self-assembly of the surfactants and cosolutes resulting in the formation of wormlike micelles with the cationic surfactant CTAB.

Traveling wave ion mobility mass spectrometry (TWIM-MS) is shown to be able to separate and characterize several isomeric forms of diterpene glycosides stevioside (Stv) and rebaudioside A (RebA) that are cationized by Na(+) and K(+) at different sites. Determination and characterization of these coexisting isomeric species, herein termed catiomers, arising from cationization at different and highly competitive coordinating sites, is particularly challenging for glycosides. To achieve this goal, the advantage of using CO2 as a more massive and polarizable drift gas, over N2, was demonstrated. Post-TWIM-MS/MS experiments were used to confirm the separation. Optimization of the possible geometries and cross-sectional calculations for mobility peak assignments were also performed.

Composite methods adapted to the ONIOM approach were used in the description of proton (PA) and electron (EA) affinities for a group of 50 molecules (alcohols, ketones, radicals and alkenes). The electronic energy was described considering the scaling ZPE (λ) and higher level (HLC) corrections. The optimal value for λ was obtained from the PA data. The EA calculations were used for optimization of the terms in HLC. Different performances of exchange-correlation functionals were considered. The methodology ONIOM2(QCISD(T)/6-311++G(2dF,p):HF/6-31G(d))//ONIOM2(B3LYP/6-31G(d):HF/6-31G(d)) provided the smallest median absolute deviation (MAD) for PA and EA, 5.38 kJ mol-1 and 0.11 eV, respectively, in comparison to the experimental data. Métodos compostos adaptados ao método ONIOM foram utilizados no cálculo teórico de afinidades por próton (PA) e eletrônica (EA) para um grupo de 50 moléculas (álcoois, cetonas, radicais e alcenos). A energia eletrônica foi descrita considerando-se o escalonamento de ZPE (λ) e a correção de alto nível (HLC). O valor ótimo para λ foi obtido através dos dados de PA. Os cálculos de EA foram utilizados na otimização dos termos presentes em HLC. Foram explorados diferentes tipos de funcionais de troca-correlação. A metodologia ONIOM2(QCISD(T)/6-311++G(2dF,p):HF/6-31G(d))//ONIOM2(B3LYP/6-31G(d):HF/6-31G(d)) forneceu os menores desvios absolutos médios para PA e EA, 5,38 kJ mol-1 e 0,11 eV, respectivamente, em comparação com dados experimentais.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior The Norcoclaurine Synthase enzyme is known to be the Pictet-Spenglerase responsible for catalyzing the condensation of dopamine and 4-hydroxyphenylacetaldehyde, leading to the formation of s-norcoclaurine, the first metabolite in the biosynthesis of benzylisoquinoline alkaloids. Recently, the Norcoclaurine Synthase has shown great promiscuity towards many aldehyde and ketone substrates, raising great interest in further understandings. In this work, we computationally investigate the structural aspects of this enzyme regarded to the substrate (S)-citronellal, a long-chain aliphatic aldehyde that contrasts with the natural aldehyde, 4-hydroxyphenylacetaldehyde. Furthermore, we also investigated the mechanism of a condensation reaction between dopamine and (S)citronellal catalyzed by the Norcoclaurina Synthase. For that, we employed molecular docking methodologies, classical molecular dynamics simulation, and density functional theory. We demonstrate through molecular docking and molecular dynamics simulations that the preferential enzyme-substrate binding mode presents the dopamine more deeply anchored in the active site, interacting with the amino acid LYS122 in a conformation considered active, meaning it will favor the occurrence of the reaction. Also, the (S)citronellal occupies the cavity entrance, having part of its chain solvent-exposed, which may be indicative of the promiscuity of the enzyme concerning the carbonylated compounds. From a mechanistic aspect, through density functional theory and cluster methodology, we showed that the reaction path has three fewer intermediates than the previously published one. Furthermore, we also found that the conformational constraints experienced by the substrates considerably alter the activation energy barrier for the cyclization step. A enzima Norcoclaurina Sintase é conhecida por ser a Pictet-Spenglerase responsável por catalisar a condensação da dopamina e do 4-hidroxifenilacetaldeído, levando à formação da s-norcoclaurina, o primeiro metabólito na biossíntese dos alcalóides benzilisoquinolínicos. Recentemente, estudos mostraram que a Norcoclaurina Sintase possui alta promiscuidade frente a muitos aldeídos e cetonas, despertando grande interesse para seu uso. Neste trabalho, investigamos computacionalmente os aspectos estruturais dessa enzima em relação ao substrato (S)citronelal, um aldeído alifático de cadeia longa que contrasta com o aldeído natural, o 4-hidroxifenilacetaldeído. Além disso, investigamos também o mecanismo de reação de condensação entre a dopamina e o (S)citronelal catalisado pela Norcoclaurina Sintase. Para tanto, empregamos metodologias de ancoramento molecular, simulação de dinâmica molecular clássica e teoria do funcional da densidade. Demonstramos através do ancoramento molecular e de simulações de dinâmica molecular que o modo de ligação preferencial enzima-substrato apresenta a dopamina mais profundamente ancorada no sítio ativo, interagindo com o amino ácido LYS122 em uma conformação considerada ativa, o que significa que irá favorecer a ocorrência da reação, enquanto que o (S)citronelal ocupa a entrada da cavidade, tendo uma parte de sua cadeia exposta ao solvente, o que pode ser um indicativo da promiscuidade da enzima em relação aos compostos carbonilados. Do ponto de vista mecanístico, utilizando a teoria do funcional da densidade e a metodologia de cluster, mostramos que o caminho da reação possui três intermediários a menos em relação ao previamente publicado. Além disso, também descobrimos que as restrições conformacionais experimentadas pelos substratos alteram consideravelmente a barreira de energia de ativação para a etapa de ciclização.

CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico A fim de projetar racionalmente novos materiais moleculares com propriedades ópticas lineares desejáveis, tais como índice de refração ou birrefringência, foi investigado como a polarizabilidade atômica e de grupos funcionais de moléculas prototípicas respondem aos efeitos de campo cristalino. Ao construir agregados finitos de ureia, ácido succínico, p-nitroanilina, 4-mercaptopiridina e metilbenzoato, e particionando a densidade eletrônica do agregado, usando a teoria quântica de átomos em moléculas, podem-se extrair os átomos e grupos funcionais e estimar o aumento de polarizabilidade em relação aos valores calculados para moléculas isoladas. A polarizabilidade isotrópica e a anisotropia dos grupos funcionais foi utilizada na compreensão das contribuições de tais grupos para as propriedades ópticas nesses sistemas modelo; o que pode ajudar o químico sintético a fabricar materiais eficientes. Esta análise é complementada por um ranqueamento das polarizabilidades dos grupos funcionais calculadas a partir de trinta funcionais DFT em fase gasosa, bem como comparando os resultados de índice de refração obtidos a partir de um gás orientado, com aqueles obtidos sob condições periódicas de contorno ou experimentais, quando possível. Estimaram-se ainda as propriedades ópticas das moléculas e dos grupos funcionais nos agregados finitos a partir de um modelo clássico de interação eletrostática baseado nos momentos de dipolo atômicos. Ainda, a fim de mostrar extensivamente a eficiência do modelo clássico em reproduzir os resultados opto-eletrônicos de cálculos puramente quânticos, utilizaram-se agregados de butano, benzeno, piridazina, m-nitrofenol e p-nitrofenol, além de blocos construtores covalentemente ligados, isto é, polímeros verdadeiros. Com isto, o modelo clássico se mostrou eficiente em diversos tipos de ambientes químicos, dos mais fracamente ligados, como aqueles que apresentam somente interações dispersivas e também daqueles fortemente conectados, como o caso de ligações covalentes. In order to rationally design new molecular materials with desirable linear optical properties, such as refractive index or birefringence, it was investigated how atomic and functional-group polarizability tensors of prototypical molecules respond to crystal field effects. By building finite aggregates of urea, succinic acid, p-nitroaniline, 4-mercaptopyridine or methylbenzoate, and by partitioning the cluster electronic density using quantum theory of atoms in molecules, it was possible to extract atoms and functional groups from the aggregates and estimate their polarizability enhancements with respect to values calculated for molecules in isolation. The isotropic polarizability and its anisotropy for the molecular building blocks are used to understand the functional-group sources of optical properties in these model systems, which could help the synthetic chemist to fabricate efficient materials. This analysis is complemented by benchmarking density functionals for atomic distributed polarizabilities in gas phase, by comparing the results with refractive-index calculations under periodic boundary conditions, and by estimating functional-group optical properties from a classical electrostatic atom dipole interaction model. In order to show extensively the efficiency of the classical model in reproducing the optoelectronic results of purely quantum calculations, it was used aggregates of butane, benzene, pyridazine, m-nitrophenol and p-nitrophenol, besides truly polymeric chains built from covalently connected building blocks. Herewith, the classical model proved to be efficient in several types of chemical environments, from the most weakly connected, such as those that present only dispersive interactions and also those strongly linked, as the case of covalent bonds.

O presente trabalho apresenta um estudo DFT e ab initio da modelagem de sistemas formados pela adsorção de átomos, íons e clusters de lítio (Lin0/+, n = 1 → 4) sobre diferentes regiões de estruturas de grafenos hidrogenados pristines (PG) e com o defeito Stone-Wales (SWG). Foram utilizadas diferentes combinações funcionais de densidade e funções de base para os cálculos de estrutura eletrônica de clusters Li. Dentre os níveis de teoria empregados, o nível B97-D/6-31G(d,p) apresentou os melhores resultados em comparação com os dados disponíveis da literatura recente. Em alguns casos, os funcionais B3LYP e SVWN falharam consideravelmente em representar os parâmetros termodinâmicos e eletrônicos de alguns clusters de Li estudados. Realizou-se um processo de mapeamento da adsorção do íon Li+ sobre um dos modelos PG e SWG com o foco em simular o funcionamento de Baterias de Íon Lítio (BIL). Como observado em outros trabalhos da literatura, os mapeamentos mostraram que o íon Li+ é adsorvido de forma mais estável nas extremidades de ambas as estruturas de PG e SWG por meio de uma interação eletrostática. Os cálculos de distribuição de carga ChelpG, análise dos orbitais de fronteira e dos espectros Raman e UV-Vis simulados indicaram a perturbação do caráter metálico e eletrônico dos grafenos isolados após a adsorção das espécies de Li0/+. Os espectros Raman e UV-Vis calculados revelaram variações de intensidade e deslocamentos das bandas de absorção típicas do grafeno. Essas variações podem contribuir para novos experimentos de caracterização espectroscópica de sistemas Li0/+-Grafenos. Os resultados do mapeamento realizado com as espécies de Li0/+ serviram ainda de ponto de partida para a adsorção dos clusters Lin0/+ (n = 2 → 4) sobre a superfície dos grafenos. A presença do clusters nas nanoestruturas revelaram uma redução nos valores de gap HOMO-LUMO, potenciais de ionização adiabático e vertical (PiA e PiV, respectivamente) e função trabalho (Φ) para todos os sistemas. Porém, uma considerável diminuição dos valores de tensão elétrica da BIL teórica (VBIL) para os sistemas contendo o defeito Stone-Wales parece sugerir uma grande desvantagem ao se usar nanoestruturas defeituosas na concepção de materiais anódicos para BIL. A presença do defeito Stone-Wales proporciona aos sistemas maior reatividade a ponto de se obter sistemas Li0/+-SWG termodinamicamente mais estáveis que sistemas Li0/+-PG. Dessa forma, o funcionamento de BIL pode ser prejudicado ao se utilizar apenas sistemas SWG na construção do material anódico. The present work has dealt with the DFT and ab initio methodologies applied for studying the adsorption of atoms, ions and clusters of Lithium (Lin0/+, n = 1 → 4) on different regions of hydrogenated pristine graphene (PG) structures and with the Stone-Wales (SWG) defect. Different combinations of density functionals and basis sets were used for calculating the electronic structure of Li clusters. Among the levels of theory employed, the level B97-D/6-31G(d,p) demonstrated the best results compared with data available from recent literature. The functionals B3LYP and SVWN failed considerably to represent the thermodynamic and electronic parameters of some studied Li clusters. A Li+ ion adsorption mapping process was carried out on one of the PG and SWG models with the focus on simulating the operation of Lithium-Ion Batteries (BIL). As previously observed in the literature, the mappings showed that the Li+ ion is more stable adsorbed on the edges of both PG and SWG structures through an electrostatic interaction. The ChelpG charge distribution calculations, analysis of the boundary orbitals, and the simulated Raman and UV-Vis spectra indicated interference of the metallic and electronic character of the isolated graphenes after the adsorption of the Li0/+ species. The calculated Raman and UV-Vis spectra revealed variations in intensity and displacements of the absorption bands that are typically observed on graphene systems. These variations may contribute to propose new experiments for spectroscopic characterization of Li0/+-Graphenes systems. The results of the mapping carried out with the Li0/+ species were used as a starting point for the adsorption of the Lin0/+ clusters (n = 2 → 4) on the graphene models’ surfaces. The presence of the clusters in the nanostructures revealed a reduction in the values of HOMO-LUMO gap, adiabatic and vertical ionization potentials (PiA e PiV, respectively) and work function (Φ) for all systems. However, a considerable decrease in the electrical voltage values of the theoretical BIL (VBIL) for the systems containing the Stone-Wales defect seems to suggest a great disadvantage when using defective nanostructures in the design of anodic materials for BIL applications. The presence of the Stone-Wales defect provides the systems with greater reactivities to the point of obtaining Li0/+-SWG systems thermodynamically more stable than Li0/+-PG systems. Thus, the working process of BIL can be compromised by using only SWG systems in the construction of the anodic material.