Theoretical calculations involving magnetic systems low-dimensional

Autor: Silva Junior, Henrique de Castro
Přispěvatelé: Guedes, Guilherme Pereira, Florencio, Antonio da Silva, Silva, Clarissa Oliveira da, Neves, Amanda Porto, Cassaro, Rafael Alves All?o
Jazyk: portugalština
Rok vydání: 2016
Předmět:
Zdroj: Biblioteca Digital de Teses e Dissertações da UFRRJ
Universidade Federal Rural do Rio de Janeiro (UFRRJ)
instacron:UFRRJ
Popis: Submitted by Leticia Schettini (leticia@ufrrj.br) on 2021-11-04T15:42:11Z No. of bitstreams: 1 2016 - Henrique de Castro Silva Junior.pdf: 10051524 bytes, checksum: 0ba6947a8323a7c340b693418e4e21a9 (MD5) Made available in DSpace on 2021-11-04T15:42:12Z (GMT). No. of bitstreams: 1 2016 - Henrique de Castro Silva Junior.pdf: 10051524 bytes, checksum: 0ba6947a8323a7c340b693418e4e21a9 (MD5) Previous issue date: 2016-07-25 This study has evaluated the magnetic properties of seven novel coordination compounds by using Density Functional Theory as a tool. In order to obtain a more accurate description of spin topologies and coupling constants (JAB), an extensive review of theory levels proposed by available literature was held and allowed to establish that the combination PBE/TZVP/Def2 Def2-SVP and TPSS/Def2-TZVP//Def2-SVP led to better, qualitative, results by the Broken-symmetry technique. All molecular structures were solved by X-ray diffraction by single-crystal and structural parameters used for the calculations. In the monomeric systems [CuCl2(L1)2] and [Fe(L2)2(OH2)4], the FPBU approach was used to evaluate the main distances between metal centers that could be important for the magnetic coupling. With these results it was possible to show that the copper(II)-based compound behave like a supramolecular magnetic chain, while a paramagnetic behavior was observed for the iron(II) containing complex. DFT Studies of the magnetic properties of two isostructural polymers with the formula 1?[M(L3)2(bipy)(H2O)2] (M = CuII or CoII) made it possible to compare how magnetic couplings of a molecule are influenced by a change in metal centers, revealing the importance of the anisotropic component in cobalt(II) ions. Also, polymeric systems containing carboxylate bridges led to structures whose calculations predicted entirely different magnetic identities: 1?[Cu2(L3)4(phen)2] is predicted to form a dimeric ferromagnetic system, with J(AB) above 200 cm-1 and 2?[Cu(L3)4] with the antiferromagnetic paddle-wheel structure. A careful analysis of the magnetostructural correlation for the polymers containing carboxylate bridges allowed to understand the magnitude of the magnetic couplings expected as well as the confirmation by results found in literature, that the calculated values are consistent. The complicated network of magnetic couplings in the hexamer [Cu(OMe)(fta)]6 was streamlined based on geometric parameters, showing that the entire system could be represented as a combination of three individual dimeric systems. A subsequent comparison with the literature and experimental data confirmed that the assumptions made to decompose the hexameric system in three smaller dimeric systems where correct. Neste trabalho estudaram-se as propriedades magn?ticas de sete novos compostos de coordena??o atrav?s da Teoria do Funcional de Densidade. A fim de se obter descri??es mais acuradas das topologias de spin e das constantes de acoplamento, realizou-se uma extensiva revis?o dos n?veis de teoria propostos em literatura, o que permitiu estabelecer que a combina??o PBE/Def2-TZVP//Def2-SVP e TPSS/Def2-TZVP//Def2-SVP levava a resultados de n?vel qualitativo para as constantes de acoplamento (JAB) obtidas pela t?cnica de Broken-symmetry. Todas as estruturas moleculares foram resolvidas por difra??o de raios X por monocristal e os par?metros estruturais foram utilizados para a realiza??o de c?lculos. Nos sistemas monom?ricos [CuCl2(L1)2] e [Fe(L2)2(OH2)4], o processo FPBU foi utilizado para se avaliar as principais dist?ncias entre os centros met?licos que seriam importantes para o acoplamento magn?tico. Com estes resultados foi poss?vel mostrar que o complexo de cobre comporta-se como um cadeia magn?tica supramolecular, enquanto que um comportamento paramagn?tico foi observado para o compostos de ferro(II). Os estudos das propriedades magn?ticas por DFT de pol?meros isoestruturais de f?rmula 1?[M(L3)2(bipy)(H2O)2] (M = CuII ou CoII) permitiu comparar como os acoplamentos magn?ticos de uma mol?cula s?o influenciados pela troca dos centros met?licos revelando a import?ncia da componente anisotr?pica do cobalto(II). Os sistemas polim?ricos contendo pontes carboxilato levaram a estruturas cujos c?lculos previram identidades magn?ticas completamente diferentes: o 1?[Cu2(L3)4(phen)2] formando um sistema dim?rico ferromagn?tico, com J acima de 200 cm-1 e o 2?[Cu(L3)4] que forma a popular estrutura do tipo paddle-wheel antiferromagn?tica. Uma cautelosa an?lise da correla??o magnetoestrutural para os pol?meros contendo pontes carboxilato permitiu compreender a magnitude dos acoplamentos magn?ticos esperados bem como a confirma??o, por valores dispon?veis em literatura, de que os valores calculados s?o consistentes. A complicada rede de acoplamentos magn?ticos no sistema hexam?rico do [Cu(OMe)(fta)]6 foi racionalizada com base em par?metros geom?tricos, mostrando que todo o sistema poderia ser representado como a combina??o de tr?s sistemas dim?ricos individuais e uma posterior compara??o com valores da literatura e dados experimentais corroboram que acoplamentos magn?ticos da mesma ordem dos acoplamentos calculados s?o esperados.
Databáze: OpenAIRE
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