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X-ray diffraction crystallochemical studies
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| Author(s): |
Antonio Carlos Trindade
Total Authors: 1
|
| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2000-12-12 |
| Examining board members: |
Julio Zukerman Schpector;
Regina Helena Porto Francisco;
Pedro Oliver Dunstan Lozano
|
| Advisor: | Julio Zukerman Schpector |
| Abstract | |
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. (AU) | |