In the experimental part of my master’s thesis, I reacted a copper(II) or zinc(II) starting compound, [Cu(quin)2(H2O)] or [Zn(quin)2(H2O)], with 2-hydroxypyridine or 2-hydroxymethylpyridine under different reaction conditions. In the solid state, 2-hydroxypyridine exists in keto tautomeric form, known as 2-pyridone. In the reaction with the copper starting material, 2-pyridone coordinated to copper(II) ion, forming a coordination species with the [Cu(quin)2(2-pyridone)] composition. I carried out numerous reactions in the reaction system of the copper starting compound and 2-hydroxymethylpyridine, but most of these were unsuccessful, as I only isolated the unreacted starting compound. The only successful reaction occurred at a higher temperature and in the presence of a base, resulting in the formation of turquoise crystals of a new compound. Unfortunately, the quality of the crystals did not allow for single-crystal X-ray structural analysis, which would have enabled their unequivocal identification. Nevertheless, the results of the analyses suggest that the new compound contains both the quinaldinate and the 2-hydroxymethylpyridine ligands. I also carried out many reactions in the reaction system of the zinc starting material and 2-hydroxypyridine/2-pyridone, where I managed to isolate the polymer [Zn2,5(quin)4(2-piridon)(2-Py-O)]n. The polymeric complex contains both 2-pyridone and 2-pyridonate, the anionic form of 2-pyridone. The presence of 2-pyridonate is surprising, as no strong base was added to the reaction mixture to deprotonate 2-pyridone. Equally interesting is the product from the reaction system of the zinc starting compound and 2-hydroxymethylpyridine, [Zn(quin)(2-HmpyO)(2-HmpyOH)].Et2O. In this case as well, the anionic, deprotonated form of the ligand is bound to the zinc(II) ion, despite the absence of a strong base in the reaction mixture. The reaction products were characterized by infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray structural analysis.
|
