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| Content Provider | Royal Society of Chemistry (RSC) |
|---|---|
| Author | Robeyns, Koen Safin, Damir A. Garcia, Yann Babashkina, Maria G. |
| Copyright Year | 2016 |
| Abstract | We have studied a series of closely related N-(5-bromosalicylidene)-x-aminopyridine compounds (x = 2, 1; 3, 2; 4, 3), obtained by condensation of 5-bromosalicylaldehyde with the corresponding aminopyridine. 1H NMR spectroscopy in solution revealed a single structure, at least in CDCl3. According to single crystal X-ray diffraction it was established that the crystal structures of 1–3 each are stabilized by a linear intramolecular hydrogen bond of the O–H⋯N type, formed between the hydroxyl hydrogen atom of the phenolic ring and the imine nitrogen atom. The dihalogen C–Br⋯Br–C and halogen C–Br⋯N(Py) interactions play a crucial role for the formation of supramolecular architectures in the structures of 2 and 3, respectively. The overall geometry of each molecule in the structures of 1 and 2 was found to be almost planar, while a significantly twisted structure was found for 3. Hirshfeld surface analysis showed that the structures of all compounds are mainly characterized by H⋯X contacts as well as by a remarkable contribution from C⋯C and C⋯N contacts which is clearly observed for 1 and 2. Diffuse reflectance spectra of 1–3 each exhibit a mixture of enol, cis-keto and trans-keto forms. A major contribution of the trans-keto form is found for 1 whereas a moderate fraction is detected for 2, and only traces of the trans-keto form were observed for 3. Contrary to expectations based on dihedral angle Φ considerations, 1 exhibits negative photochromism, although it was expected to be only thermochromic. Both 2 and 3 are not photochromic, whereas 3 was expected to be photochromic (Φ > 25°). Highly favoured C⋯C, C⋯N and O⋯Br intermolecular contacts as well as the absence of Br⋯Br dihalogen interactions in the structure of 1, are presumably mainly responsible for the photochromic behaviour. Furthermore, significantly impoverished H⋯C and H⋯N contacts further support the observed negative photochromism of 1. |
| Starting Page | 53669 |
| Ending Page | 53678 |
| Page Count | 10 |
| File Format | HTM / HTML PDF |
| ISSN | 20462069 |
| Volume Number | 6 |
| Issue Number | 59 |
| Journal | RSC Advances |
| DOI | 10.1039/c6ra10094e |
| Language | English |
| Publisher | Royal Society of Chemistry |
| Access Restriction | Open |
| Subject Keyword | Dihedral angle Photochromism Enol Nuclear magnetic resonance spectroscopy Imine Nitrogen Molecular geometry Thermochromism X-ray crystallography Hydroxy group Halogen Hirshfeld Hydrogen bond |
| Content Type | Text |
| Resource Type | Article |
| Subject | Chemistry Chemical Engineering |
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