Synthesis, Structure and Magnetic Differences of Two a-Nitronyl Nitroxide Isomers
The two isomeric organic nitronyl nitroxide free radicals2-(2-hydroxyl-3-methoxy-phenyl)-4, 4, 5, 5-tetramethyl-4, 5-dihydro-1H-imidazoyl-1-oxyl-3-oxide, 1, and 2-(3-hydroxyl-4-methoxyphenyl)-4, 4, 5, 5-tetramethyl-4, 5-dihydro-1H-imidazoyl-1-oxyl-3-oxide, 2, have been synthesized and their stru...
| Autores: | , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2008 |
| País: | México |
| Institución: | Universidad Autónoma de Nuevo León |
| Repositorio: | Redalyc-UANL |
| OAI Identifier: | oai:redalyc.org:47552108 |
| Acceso en línea: | https://www.redalyc.org/articulo.oa?id=47552108 |
| Access Level: | acceso abierto |
| Palabra clave: | Química isomers structure ferromagnetism Organic radicals phase transition |
| Sumario: | The two isomeric organic nitronyl nitroxide free radicals2-(2-hydroxyl-3-methoxy-phenyl)-4, 4, 5, 5-tetramethyl-4, 5-dihydro-1H-imidazoyl-1-oxyl-3-oxide, 1, and 2-(3-hydroxyl-4-methoxyphenyl)-4, 4, 5, 5-tetramethyl-4, 5-dihydro-1H-imidazoyl-1-oxyl-3-oxide, 2, have been synthesized and their structures determined byX-ray diffraction. Structure 1 has three dimensional, strong, intramolecularhydrogen bonds in addition to intermolecular interactionsfavoring sheets. The structure of radical 2 also shows strong hydrogenbonds both intra- and intermolecular. Some of these bonds are with alattice water molecule, yielding a three-dimensional crystal structure.An important structural difference between both radicals is that incompound 1, one of the nitrogen atoms of the radical shows smallerangles than the other atom in the same radical and than both nitrogenatoms in compound 2. This suggests that in 1, one of the nitrogenatoms has a higher sp3 character than the other. This proposal is supportedby the N-O bond length which is significantly longer in the sp3nitrogen side. Both isomers show quite different magnetic behavior.In 1 there are both ferromagnetic (JF/k = + 0.11 ± 0.01 K) and antiferromagnetic(JAF/k = - 0.81 ± 0.10 K) interactions, whereas 2 onlyshows antiferromagnetism (JAF/k = - 1.60 ± 0.02 K) with a phasetransition at Tc = 2.48 K. |
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