Keto-enol tautomerism in new silatranes Schiff bases tailed with different substituted salicylic aldehyde

Abstract

New Schiff base-type products starting from 1-(3-aminopropyl)silatrane and three derivatives of salicylaldehyde having as substituents 3,5-dichloro- (1), 3-methoxy- (2) and 3,5-di-tert-butyl- (3), respectively were obtained and isolated with high yields (78–87%) in pure, crystalline forms and their structures were established by different methods. The molecular electronic transitions of the compounds in solvents with various polarities were investigated by UV–Vis spectral analysis. Their thermal behavior was studied by thermogravimetric analysis and differential scanning calorimetry, results of the latter highlighting thermocromism of the compounds, proved by the appearance of IR absorption bands specific for enolic form at the temperature corresponding to each sample. The moisture sorption capacity and stability of the compounds in wet environment were investigated by vapor sorption analysis in dynamic regime and IR spectroscopy. The biological activity was assessed by specific tests. All results were discussed in correlation with the nature of substituents and structures formed. The chemical handling of the silatrane tail, by using different substituents on the silicon atom would allow fine tuning of the compounds properties. Keywords: Aminopropylsilatrane, Schiff base modified silatranes, Single crystal X-ray, Azomethine, Antimicrobial activity, Surface properties