Estrutura cristalina e refinamento de deformação em sais de ácido piromelítico

Detalhes bibliográficos
Ano de defesa: 2012
Autor(a) principal: Leonardo Humberto Rezende dos Santos
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Federal de Minas Gerais
UFMG
Programa de Pós-Graduação: Não Informado pela instituição
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Link de acesso: http://hdl.handle.net/1843/SFSA-8TJQWV
Resumo: Four organic salts derived of 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) have been synthesized: bis(3-aminopyridinium) 1,4-dihydrogen 1,2,4,5- benzenetetracarboxylate tetrahydrate (1), bis(3-carboxyphenilammonium) 1,4- dihydrogen 1,2,4,5-benzenetetracarboxylate dihydrate (2), bis(4-carboxyphenilammonium) 1,4-dihydrogen 1,2,4,5-benzenetetracarboxylate (3) andbis(3-carboxypyridinium) 1,4-dihydrogen 1,2,4,5-benzenetetracarboxylate (4a,b). Crystal structures of all compounds were determined by single-crystal X-ray diffraction at 120 K. Compound 1 crystallizes in the space group P21/c while compounds 2 and 3 crystallize in the group Pi. Compound 4 has been observed in two polymorphic formswhich crystallize in the space groups Pi (4a) and P21/c (4b). Intermolecular hydrogen bonds are particularly important to building uncommon supramolecular arrays. Additionally, crystallographically asymmetric intramolecular short O-H···O hydrogen bonds are observed in 2, 4a and 4b. The O···O distances are 2.387(1), 2.423(1) and2.385(1) A respectively. 4a also presents an intermolecular short O-H···O hydrogen bond in which the O···O distance is 2.513(2) A. Electron deformation refinement has been carried out in 4a by using multipolar atomic nucleus-centered deformation functions and the electron density distribution has been interpreted using Quantum Theory of Atoms in Molecules, which has given evidence of partly covalent character ofshort hydrogen bonds in this polymorphic modification