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Master's Dissertation
DOI
https://doi.org/10.11606/D.46.2019.tde-29072019-160053
Document
Author
Full name
Antonio Carlos Trindade
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2000
Supervisor
Committee
Schpector, Julio Zukerman (President)
Francisco, Regina Helena Porto
Lozano, Pedro Oliver Dunstan
Title in Portuguese
Estudos cristaloquímicos por difração de raio-X
Keywords in Portuguese
Cristalografia química
Físico-química
Abstract in Portuguese
O estudo termoquímico de adutos de quelatos de acetilacetonatos com bases heterocíclicas, realizado pelo Prof. Dr. P. O. Dunstan do IQ da Unicamp, mostrou as seguinte ordem de basicidade: morfolina > piperidina> γ-picolina > piridina> quinolina> β-picolina> 4-cianopiridina> 3-cianopiridina. No caso da 3-cianopiridina e da 4-cianopiridina a ordem esperada era a inversa da obtida, entretanto no caso da piridina, quinolina, morfolina e γ-picolina a ordem obtida foi a esperada. A inversão no caso da 3 e 4-cianopiridina foi atribuída a existência de ligações de hidrogênio, que não deveriam estar presentes nas outras estruturas. Para comprovar isto foi tentada a cristalização de todos os compostos, mas somente foram obtidos cristais adequados de seis compostos e sua estrutura tridimensional determinada por difração de raios-X. Em todas as estruturas foi encontrado que o átomo de níquel está situado num centro de simetria, exceto no caso da γ-picolina no qual está numa posição de simetria m2m. O Ni(II) se encontra em todas as estruturas octaedricamente ligado a dois ânions acetilacetonato (AcAc) equatoriais e a dois ligantes em uma configuração trans. As distâncias Ni-OAcAc mostram que o poliedro de coordenação apresenta diferentes graus da chamada distorção tetragonal. Os estudos cristalográficos mostram a existência de ligações de hidrogênio em todos os compostos. Os tipos de ligações de hidrogênio encontradas são do tipo C-H...N, C-H...O e C-H...π. Mais ainda, no caso da 3 e 4-cianopiridina elas apresentam um conjunto de ligações de hidrogênio muito similares.
Title in English
X-ray diffraction crystallochemical studies
Keywords in English
Chemical crystallography
Physical chemistry
Abstract in English
The thermochemical studies of adducts of Ni(II) acetylacetonate chelate with heterocyclic bases, accomplished by Prof. Dr. P. O. Dunstan of IQ-UNICAMP, showed the following basicity order: morpholine> piperidine> γ-picoline> pyridine> quinoline> β-picoline> 4-cyanopyridine> 3-cyanopyridine. In the case of 3-cianopyridine and 4-cianopyridine the expected order was the inverse of the one obtained, and in the case of the pyridine, quinoline, morpholine and γ-picoline the order was the expected one. The inversion in the case of 3 and 4-cyanopyridine was postulated to be due to the existence of hydrogen bonds, that should not be present in the other structures. To check this hypothesis it was tried the recrystalization of all the compounds, but only suitable crystals of six of them, namely 3 and 4-cyanopyridine, pyridine, quinoline, morpholine and γ-picoline, were obtained and their three-dimensional structure determined by X-ray diffraction. In the structures the nickel atom is sited on a center of symmetry, except in the case of the γ-picoline in which it is in a position of symmetry m2m. In all the structures the Ni(II) is octahedrically bonded to two equatorial acetylacetonate (AcAc) groups and two ligands that are in a trans configuration. The Ni-OAcAc distances show that the coordination polyhedra present different degrees of the so called tetragonal distortion. The cristallographics studies show the existence of hydrogen bonds in all the compounds. The types of hydrogen bonds found are: C-H...N, C-H...O and C-H...π. Moreover, in the case of 3 and 4-cyanopyridine these compounds present a similar pattern of hydrogen bonds.
 
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Publishing Date
2019-07-29
 
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