Spectroscopic conformational study of PMS 952, a specific imidazoline ligand. Experimental results
| Autor: | Jack Huet, Marie-Hélène Baron, Edith Favre, Sabine Halut-Desportes, Hai-Fen Ye |
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| Rok vydání: | 1999 |
| Předmět: | |
| Zdroj: | Canadian Journal of Chemistry. 77:2015-2024 |
| ISSN: | 1480-3291 0008-4042 |
| Popis: | X-ray analysis of PMS 952 displays two kinds of very strong hydrogen bonds, an intramolecular one stabilizing the conformer A and an intermolecular one that associates conformers A to form two infinite chains. The 1H NMR study of vicinal coupling constants based on dihedral angle values, evidences that PMS 952 takes up an eclipsed conformation, in CCl4 and CDCl3 solutions, closely related to the conformation in solid state. Deuterium exchange in methanol-d4 points out the presence of a tautomeric form. However, as there is spectral evidence neither from NMR nor from FTIR studies for such a tautomer, this specie cannot be taken into account to explain the complexity of the FTIR spectra. NMR data also reveal that the imidazoline ring freely rotates while FTIR analysis allows characterizing two conformers (A and B), with lifetime shorter than NMR time scale. These two conformers are stabilized by two different intramolecular H-bonds. Taking into account that conformer A could exist in two states (monomer A and (A)n-chains), an equilibrium between A, (A)n, and B entities allowed the assignment of all main bands of the IR spectra, assigned to vNH, vOH, vCH, and vCN modes. The strength of hydrogen bonds is solvent dependent. Polar solvents, either proton donor or acceptor stabilized the conformer A, while CCl4 favors the conformer B.Key words: hydrogen bonds, X-ray, NMR, FTIR, imidazoline derivative. |
| Databáze: | OpenAIRE |
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