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Ca(2+) binding to c-state of adenine nucleotide translocase (ANT)-surrounding cardiolipins enhances (ANT)-Cys(56) relative mobility: A computational-based mitochondrial permeability transition study

PESTANA, Cezar R.; SILVA, Carlos H. T. P.; PARDO-ANDREU, Gilberto L.; RODRIGUES, Fernando P.; SANTOS, Antonio C.; UYEMURA, Sergio A.; CURTI, Carlos
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.06%
The oxidation of critical cysteines/related thiols of adenine nucleotide translocase (ANT) is believed to be an important event of the Ca(2+)-induced mitochondrial permeability transition (MPT), a process mediated by a cyclosporine A/ADP-sensitive permeability transition pores (PTP) opening. We addressed the ANT-Cys(56) relative mobility status resulting from the interaction of ANT/surrounding cardiolipins with Ca(2+) and/or ADP by means of computational chemistry analysis (Molecular Interaction Fields and Molecular Dynamics studies), supported by classic mitochondrial swelling assays. The following events were predicted: (i) Ca(2+) interacts preferentially with the ANT surrounding cardiolipins bound to the H4 helix of translocase, (ii) weakens the cardiolipins/ANT interactions and (iii) destabilizes the initial ANT-Cys(56) residue increasing its relative mobility. The binding of ADP that stabilizes the conformation ""m"" of ANT and/or cardiolipin, respectively to H5 and H4 helices, could stabilize their contacts with the short helix h56 that includes Cys(56), accounting for reducing its relative mobility. The results suggest that Ca(2+) binding to adenine nucleotide translocase (ANT)-surrounding cardiolipins in c-state of the translocase enhances (ANT)-Cys(56) relative mobility and that this may constitute a potential critical step of Ca(2+)-induced PTP opening. (C) 2009 Elsevier B.V. All rights reserved.; FAPESP; CAPES; CNPq...

Cyclic Voltammetry and Computational Chemistry Studies on the Evaluation of the Redox Behavior of Parabens and other Analogues

Gil, Eric de S.; Andrade, Carolina H.; Barbosa, Nusia L.; Braga, Rodolpho C.; Serrano, Silvia Helena Pires
Fonte: SOC BRASILEIRA QUIMICA; SAO PAULO Publicador: SOC BRASILEIRA QUIMICA; SAO PAULO
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.13%
Parabens are antimicrobial preservatives widely used in pharmaceutical, cosmetic and food industries. The alkyl chain connected to the ester group defines some important physicochemical characteristics of these compounds, including the partition coefficient and redox properties. The voltammetric and computational analyses were carried out in order to evaluate the redox behavior of these compounds and other phenolic analogues. A strong correlation between chemical substituents inductive effects of parabens with redox potentials was observed. Using cyclic voltammetry and glassy carbon working electrode, only one irreversible anodic peak was observed around 0.8 V for methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), benzylparaben (BzP) and p-substituted phenolic analogues. The electrodonating inductive effect of alkyl groups was demonstrated by the anodic oxidation potential shift to lower values as the carbon number increases and, therefore the parabens (and other phenolic analogues) oxidation processes to the quinonoidic forms showed great dependence on the substituent pattern.

Cyclic voltammetry and computational chemistry studies on the evaluation of the redox behavior of parabens and other analogues

Gil, Eric de S.; Andrade, Carolina H.; Barbosa, Núsia L.; Braga, Rodolpho C.; Serrano, Sílvia H. P.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.06%
Parabens are antimicrobial preservatives widely used in pharmaceutical, cosmetic and food industries. The alkyl chain connected to the ester group defines some important physicochemical characteristics of these compounds, including the partition coefficient and redox properties. The voltammetric and computational analyses were carried out in order to evaluate the redox behavior of these compounds and other phenolic analogues. A strong correlation between chemical substituents inductive effects of parabens with redox potentials was observed. Using cyclic voltammetry and glassy carbon working electrode, only one irreversible anodic peak was observed around 0.8 V for methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), benzylparaben (BzP) and p-substituted phenolic analogues. The electrodonating inductive effect of alkyl groups was demonstrated by the anodic oxidation potential shift to lower values as the carbon number increases and, therefore the parabens (and other phenolic analogues) oxidation processes to the quinonoidic forms showed great dependence on the substituent pattern.

A utilização da química computacional em processos químicos relacionados à ionização por electrospray; The use of computational chemistry in the studies of chemical processes involved in electrospray ionization

Lourenço, Ricardo Vessecchi
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/06/2009 PT
Relevância na Pesquisa
56.25%
Nas últimas décadas, o desenvolvimento das técnicas de ionização à pressão atmosférica impulsionou a espectrometria de massas, na caracterização e elucidação estrutural de compostos de grande massa molecular. O surgimento dessas técnicas foi o responsável pela amplitude nas aplicações e estudos de espectrometria de massas, sendo a ionização por electrospray a mais versátil dentre essas fontes de ionização. O caráter eletrolítico da fonte de ionização por electrospray permite-se obter íons provenientes de três processos químicos: i) ácido-base; ii) redox e iii) complexação. A extensão com que cada um desses processos ocorrerá dependerá de fatores relacionados à operação da fonte de ionização e grandezas termoquímicas do analito. O notável progresso em técnicas experimentais, processamento de dados e integração entre as mais diversas áreas de aplicação da química, tem estimulado e beneficiado a aplicação da química teórica em estudos de reações em fase gasosa. A aplicação da química computacional fornece uma compreensão quantitativa das variações estruturais e energéticas dos possíveis íons formados durante a ionização da amostra, permitindo também a compreensão das possíveis vias de dissociação. É neste sentido...

Implementação e analise de ferramentas de quimica computacional aplicada ao desenvolvimento de processos; Implementation and analysis of computational chemistry tools applied to the processes development

Jefferson Ferreira Pinto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/02/2006 PT
Relevância na Pesquisa
66.27%
As indústrias vêm mudando profundamente nos últimos anos, principalmente para redução de consumo energético, melhoria na qualidade dos produtos e adequação às leis ambientais. Estas mudanças podem ser auxiliadas pelas técnicas de modelagem e simulação, incluindo o detalhamento do modelo em nível atômico, quando então recebe o nome de química computacional. Diversas ferramentas abrangendo todas as áreas de química computacional, em sua maioria gratuitas ou de domínio público, foram implementadas em um microcomputador e analisadas para aplicação no desenvolvimento de processos. Foi analisado também o desempenho computacional em função do sistema operacional, que apresentou diferenças no desempenho de até 353% para cálculos de ponto flutuante, 18% para acesso a memória RAM e 67% para acesso a disco. Para melhorar o desempenho computacional, foi elaborado o projeto de um ambiente computacional paralelo de alto desempenho, no qual o custo ficou limitado à aquisição de hardware, de fácil disponibilidade no mercado, sendo que os softwares utilizados são gratuitos ou de domínio público; lndustries are changing in the last years, mainly for reduction of energy consumption, improvement in the product quality and adequacy to the environmental laws. These changes can be assisted by the modeling and simulation techniques...

Cyclic voltammetry and computational chemistry studies on the evaluation of the redox behavior of parabens and other analogues

Gil,Eric de S.; Andrade,Carolina H.; Barbosa,Núsia L.; Braga,Rodolpho C.; Serrano,Sílvia H. P.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2012 EN
Relevância na Pesquisa
56.06%
Parabens are antimicrobial preservatives widely used in pharmaceutical, cosmetic and food industries. The alkyl chain connected to the ester group defines some important physicochemical characteristics of these compounds, including the partition coefficient and redox properties. The voltammetric and computational analyses were carried out in order to evaluate the redox behavior of these compounds and other phenolic analogues. A strong correlation between chemical substituents inductive effects of parabens with redox potentials was observed. Using cyclic voltammetry and glassy carbon working electrode, only one irreversible anodic peak was observed around 0.8 V for methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP), benzylparaben (BzP) and p-substituted phenolic analogues. The electrodonating inductive effect of alkyl groups was demonstrated by the anodic oxidation potential shift to lower values as the carbon number increases and, therefore the parabens (and other phenolic analogues) oxidation processes to the quinonoidic forms showed great dependence on the substituent pattern.

Commodity cluster computing for computational chemistry

Hawick, K.; Grove, D.; Coddington, P.; Buntine, M.
Fonte: Internet Journal of Chemistry Publicador: Internet Journal of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2000 EN
Relevância na Pesquisa
76.34%
Access to high-performance computing power remains crucial for many computational chemistry problems. Unfortunately, traditional supercomputers or cluster computing solutions from commercial vendors remain very expensive, even for entry level configurations, and are therefore often beyond the reach of many small to medium-sized research groups and universities. Clusters of networked commodity computers provide an alternative computing platform that can offer substantially better price/performance than commercial supercomputers. We have constructed a networked PC cluster, or Beowulf, dedicated to computational chemistry problems using standard ab initio molecular orbital software packages such as Gaussian and GAMESS-US. This paper introduces the concept of Beowulf computing clusters and outlines the requirements for running the ab initio software packages used by computational chemists at the University of Adelaide. We describe the economic and performance trade-offs and design choices made in constructing the Beowulf system, including the choice of processors, networking, storage systems, operating system and job queuing software. Other issues such as throughput, scalability, software support, maintenance, and future trends are also discussed. We present some benchmark results for the Gaussian 98 and GAMESS-US programs...

Estimation of Free Radical Polymerization Rate Coefficients using Computational Chemistry

Bebe, Siziwe
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 752417 bytes; application/pdf
EN; EN
Relevância na Pesquisa
56.13%
Acrylic free radical polymerization at high temperature proceeds via a complex set of mechanisms, with many rate coefficients poorly known and difficult to determine experimentally. This problem is compounded by the large number of monomers used in industry to produce coatings and other materials. Thus, there is a strong incentive to develop a methodology to estimate rate coefficients for these systems. This study explores the application of computational chemistry to estimate radical addition rate coefficients for the copolymerization of acrylates, methacrylates and styrene. The software package Gaussian is used to calculate heats of reaction (ΔHr) values for monomer additions to monomeric and dimeric radicals, using minimum energy structures identified and characterized for the reactants and products. The Evans-Polanyi relationship is applied to estimate reactivity ratios from the relative differences in ΔHr. The validity of this methodology is tested through a comparison of calculated monomer and radical reactivity ratios for acrylate, methacrylate, vinyl acetate, ethene and styrene systems to available experimental data for copolymerization systems. The methodology is found to work for some systems while there is computational breakdown in others due to steric crowding and/or breakdown of the Evans-Polanyi relationship.; Thesis (Ph.D...

Computational analysis of quinoxalines N,N-Dioxide and ITS Derivates

Pereira, Joana
Fonte: Instituto Politécnico do Porto. Escola Superior de Tecnologia da Saúde do Porto Publicador: Instituto Politécnico do Porto. Escola Superior de Tecnologia da Saúde do Porto
Tipo: Dissertação de Mestrado
Publicado em //2013 ENG
Relevância na Pesquisa
56.13%
A quinoxalina e seus derivativos são uma importante classe de compostos heterocíclicos, onde os elementos N, S e O substituem átomos de carbono no anel. A fórmula molecular da quinoxalina é C8H6N2, formada por dois anéis aromáticos, benzeno e pirazina. É rara em estado natural, mas a sua síntese é de fácil execução. Modificações na estrutura da quinoxalina proporcionam uma grande variedade de compostos e actividades, tais como actividades antimicrobiana, antiparasitária, antidiabética, antiproliferativa, anti-inflamatória, anticancerígena, antiglaucoma, antidepressiva apresentando antagonismo do receptor AMPA. Estes compostos também são importantes no campo industrial devido, por exemplo, ao seu poder na inibição da corrosão do metal. A química computacional, ramo natural da química teórica é um método bem desenvolvido, utilizado para representar estruturas moleculares, simulando o seu comportamento com as equações da física quântica e clássica. Existe no mercado uma grande variedade de ferramentas informaticas utilizadas na química computacional, que permitem o cálculo de energias, geometrias, frequências vibracionais, estados de transição, vias de reação, estados excitados e uma variedade de propriedades baseadas em várias funções de onda não correlacionadas e correlacionadas. Nesta medida...

First-principles density functional theory study of sulfur oxide chemistry on transition metal surfaces; 1st-principles density functional theory study of sulfur oxide chemistry on transition metal surfaces

Lin, Xi, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 310 p.; 9412825 bytes; 9412627 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.27%
In this thesis, the chemistry of sulfur oxides on transition metals is studied extensively via first-principles density functional theory (DFT) computations, focusing on the chemical reactivity and selectivity in sulfur poisoning chemical processes that address environmental concerns. The systematic approach we establish can be extended to general computational studies of small gas-phase molecules interacting with extended surfaces or finite-size clusters. The thesis starts with a theoretical presentation of modem quantum many-body theory that brings together mean-field theory, DFT, and Green's function quantum Monte Carlo theory. The essence of chemical reactivity theory in the framework of DFT is emphasized. The thesis continues with an extensive survey of the current status of sulfur oxide chemistry and an overall presentation of our computational approaches towards a detailed understanding of chemical reactivity and selectivity. The basic guidelines in chemical reactivity are systematically constructed by computed comprehensive thermodynamic data of surface S, O, SO, SO2, SO3, and S04 species as a function of coverage at low and intermediate temperatures. Under these basic guidelines, experimentally measured surface spectra are interpreted...

Recent advances in 1,4-benzoquinone chemistry

Abraham,Ignatious; Joshi,Rahul; Pardasani,Pushpa; Pardasani,R.T
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 EN
Relevância na Pesquisa
56.07%
1,4-Benzoquinones are ubiquitous in nature and can be synthesized by diverse strategies. Recent developments on their synthetic methodologies, cycloaddition reactions, computational chemistry and pulse radiolytic studies are reported in this review. Their chemical and biological significance as well as their derivates' are also covered.

Application of computational chemistry methods to obtain thermodynamic data for hydrogen production from liquefied petroleum gas

Sousa,J. A.; Silva,P. P.; Machado,A. E. H.; Reis,M. H. M.; Romanielo,L. L.; Hori,C. E.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2013 EN
Relevância na Pesquisa
66.2%
The objective of this study was to estimate thermodynamic data, such as standard enthalpy, entropy and Gibbs free energy changes of reaction and, consequently, chemical equilibrium constants, for a reaction system describing the hydrogen production from Liquefied Petroleum Gas (LPG). The acquisition of those properties was made using computational chemistry methods and the results were compared with experimental data reported in the literature. The reaction system of steam reforming of LPG was reported as a set of seven independent reactions involving the chemical species n-C4H10, C3H8, C2H6, C2H4, CH4, CO2, CO, H2O, H2 and solid carbon. Six computational approaches were used: Density Functional Theory (DFT) employing Becke's three parameter hybrid exchange functional, and the Lee-Yang-Parr correlation functional (B3LYP) using the 6-31G++(d,p) basis set and the composite methods CBS-QB3, Gaussian-1 (G1), Gaussian-2 (G2), Gaussian-3 (G3) and Gaussian-4 (G4). Mole fractions of the system components were also determined between 873.15 and 1173.15 K, at 1 atm and a feed with a stoichiometric amount of water. Results showed that the hybrid functional B3LYP/6-31G++(d,p), G3 and G4 theories were the most appropriated methods to predict the properties of interest. Gaussian-3 and Gaussian-4 theories are expected to be good thermodynamic data predictors and the known efficient prediction of vibrational frequencies by B3LYP is probably the source of the good agreement found in this study. This last methodology is of special interest since it presents low computational cost...

Memory and Thread Placement Effects as a Function of Cache Usage: A Study of the Gaussian Chemistry Code on the SunFire X4600 M2

Yang, Rui; Antony, Joseph; Janes, Pete; Rendell, Alistair
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
56.11%
In this work we study the effect of cache blocking and memory/thread placement on a modern multicore shared memory parallel system, the SunFire X4600 Ml, using the Gaussian 03 computational chemistry code. A protocol for performing memory and thread place

Scope of computational organometallic chemistry. Structure, reactivity and properties

Ortuño Maqueda, Manuel Ángel
Fonte: [Barcelona] : Universitat Autònoma de Barcelona, Publicador: [Barcelona] : Universitat Autònoma de Barcelona,
Tipo: Tesis i dissertacions electròniques; info:eu-repo/semantics/doctoralThesis; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2015 ENG
Relevância na Pesquisa
46.32%
La química organometálica se define como el área de conocimiento que une el mundo orgánico (ligando) con el inorgánico (metal), aprovechando lo mejor de ambos. Un aspecto interesante de los compuestos con metales de transición es la capacidad de realizar transformaciones químicas que no se pueden llevar a cabo fácilmente usado química convencional. Entre los retos que la química organometálica puede abordar se incluyen energías renovables, nuevos materiales y síntesis de compuestos de alto valor añadido. En este contexto, la química computacional juega un papel muy importante a la hora de entender los fenómenos químicos. La inmensa cantidad de técnicas disponibles permite analizar distintos tipos de enlace, proponer mecanismos de reacción, mejorar procesos catalíticos e incluso estimar propiedades espectroscópicas. En resumen, esta tesis cubre diferentes aspectos de la química organometálica desde un punto de vista computacional. El grueso de resultados se divide en tres capítulos: Estructura, Reactividad y Propiedades. En Estructura (i) se analiza la geometría de compuestos paramagnéticos de Pt(III) con el objetivo de distinguir entre estructuras plano-cuadradas y de tipo balancín, y (ii) se estudia la presencia de interacciones agósticas en especies insaturadas de Pt(II). En Reactividad (i) se evalúan los efectos estéricos y electrónicos de carbenos N-heterocíclicos en reacciones de activación C–H mediadas por platino...

The Semantics of Chemical Markup Language (CML) for Computational Chemistry : CompChem

Phadungsukanan, Weerapong; Kraft, Markus; Townsend, Joe A; Murray-Rust, Peter
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Article; Published Version
EN
Relevância na Pesquisa
46.27%
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.; AbstractThis paper introduces a subdomain chemistry format for storing computational chemistry data called CompChem. It has been developed based on the design, concepts and methodologies of Chemical Markup Language (CML) by adding computational chemistry semantics on top of the CML Schema. The format allows a wide range of ab initio quantum chemistry calculations of individual molecules to be stored. These calculations include, for example, single point energy calculation, molecular geometry optimization, and vibrational frequency analysis. The paper also describes the supporting infrastructure, such as processing software, dictionaries, validation tools and database repositories. In addition, some of the challenges and difficulties in developing common computational chemistry dictionaries are discussed. The uses of CompChem are illustrated by two practical applications.

The use of CML and CML in Computational Chemistry and Physics Programs

Wakelin, Jon; Garcia, A; Murray-Rust, Peter
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
66.25%
Proceedings of the 2004 e-Science All Hands Meeting, 31st August - 3rd September, Nottingham UK; This work addresses problems associated with data exchange and data representation in the computational chemistry and physics communities. Recent computational developments, such as Condor and the Grid, have paved the way for new kinds of simulations that demand more rigorous data handling. To this end, the paper discusses the use of XML and the Chemical Markup Language (CML) in theoretical chemistry and physics. Extensions to the core CML language, known as CMLComp, are also discussed. However, the majority of atomic scale simulation software is written in Fortran. Fortran's lack of XML support represents a potential barrier to the adoption of CML in these fields. This has prompted the authors to develop XML and CML processing tools for Fortran, including native SAX and DOM implementations, as well as libraries for generating well formed XML and CML. These libraries have been used to extend existing simulation packages to work with the CML and CMLComp languages. Finally, we give a practical example that highlights how these XML aware applications can be effectively used as workflow components in complex chemical and physical simulations.

Computational chemistry

Truhlar, Donald G.; McKoy, Vincent
Fonte: IEEE Publicador: IEEE
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /11/2000
Relevância na Pesquisa
46.3%
Computational chemistry has come of age. With significant strides in computer hardware and software over the last few decades, computational chemistry has achieved full partnership with theory and experiment as a tool for understanding and predicting the behavior of a broad range of chemical, physical, and biological phenomena. The Nobel Prize award to John Pople and Walter Kohn in 1998 highlighted the importance of these advances in computational chemistry. With massively parallel computers capable of peak performance of several teraflops already on the scene and with the development of parallel software for efficient exploitation of these high-end computers, we can anticipate that computational chemistry will continue to change the scientific landscape throughout the coming century. The impact of these advances will be broad and encompassing, because chemistry is so central to the myriad of advances we anticipate in areas such as materials design, biological sciences, and chemical manufacturing.

Computational chemistry on Fujitsu vector-parallel processors: Development and performance of applications software

Rendell, Alistair; Bliznyuk, Andrei; Huber, Thomas; Nobes, Ross H; Akhmatskaya, Elena V; Fruchtl, Herbert A; Kung, Paul W-C; Milman, Victor; Lung, Han
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.25%
In this and a preceding paper, we provide an introduction to the Fujitsu VPP range of vector-parallel supercomputers and to some of the computational chemistry software available for the VPP. Here, we consider the implementation and performance of seven popular chemistry application packages. The codes discussed range from classical molecular dynamics to semiempirical and ab initio quantum chemistry. All have evolved from sequential codes, and have typically been parallelized using a replicated data approach. As such they are well suited to the large-memory/fast-processor architecture of the VPP. For one code, CASTEP, a distributed-memory data-driven parallelization scheme is presented.

Computational chemistry on Fujitsu vector-parallel processors: Hardware and programming environment

Nobes, Ross H; Rendell, Alistair; Nieplocha, Jarek
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
66.13%
In this and the following paper, we provide an introduction to the Fujitsu VPP range of vector-parallel supercomputers and to some of the computational chemistry software available for the VPP. Here, we consider the hardware and the design of software to

Structure of coordination complexes: The synergy between NMR spectroscopy and computational chemistry

Conradie,Jeanet
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
66.2%
Illustrative examples of how NMR spectroscopy and computational chemistry data can be used in synergy to gain information on structure, coordination mode, bonding, symmetry and isomeric distribution of transition metal complexes, is presented. Isomer distribution and the most stable structures in a series of Ti(/3-diketonato)2Cl2 and Ti(β-diketonato)2(biphen) complexes as determined by density functional theory (DFT) methods and the application of the Boltzmann equation, are in agreement with crystal structures and variable temperature NMR results. Secondly, the DFT determined coordination mode of the 4-amino-3,5-bis(pyridine-2-yl)-1,2,4-triazole, (bpt-NH2) which has the appropriate chemical geometry to behave as anionic or neutral bidentate chelating group to form a 5- or 6-membered complex, is shown to be in agreement with ¹Ή NMR shifts for [Rh(bpy)2(bpt-NH)]2+, [Rh(phen)2(bpt-NH)]2+, [Rh(bpt-NH)(cod)] and [Ir(bpt-NH)(cod)] (cod = 1,5-cyclooctadiene, phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine). The oxidative addition of CH3I to [Rh(/3-diketonato)(CO)(PPh3)] complexes consist of three reaction steps and involves isomers of two different RhIII-alkyl and two different RhIII-acyl species. For this reaction experimental ¹Ή NMR techniques complement the stereochemistry of reaction intermediates and products as calculated by density functional theory. NMR properties...