Heteroaryl chalcone allied triazole conjugated organosilatranes: synthesis, spectral analysis, antimicrobial screening, photophysical and theoretical investigations

Abstract

A series of heteroaryl tethered triazole conjoined organosilatranes were synthesized following an archetypal click reaction. The reaction sequence follows the initial generation of acetylinic Schiff bases (3a–3c, 4a–4c) which undergo 3 + 2 cycloaddition with 3-azidopropyltriethoxysilane (3-AzPTES) to give organotriethoxysilanes (5a–5c, 6a–6c) which were ultimately amended into their five-membered organosilatrane descendants (7a–7c, 8a–8c). The synthesized compounds were fully characterized by IR, ¹H, ¹³C, mass spectrometry techniques and elemental analysis. Also, the complete structure elucidation of 7a and 8a was achieved via X-ray crystallography. The photophysical studies of the entire sequence of organosilatranes were performed in solvents of varying polarity to gain an insight into their solvatochromic behaviour. The results reveal that the molecules display trivial positive solvatochromism suggesting a high dipole moment of the excited state that has also been concurrently supported by the results derived from the Lippert–Mataga equation. Further, the molecular structures and photophysical properties of the organosilatranes were also studied theoretically by applying the IEFPCM model that mimics the desired solvent in combination with the TDDFT approach. Theoretical results were found to be in absolute accord with the experimental values. Additionally, several DFT based reactivity descriptors are reported presenting a meticulous view into the relative stability and reactivity of the chalcone linked organosilatranes. Further, all the organosilatranes were screened for their physiochemical and pharmacokinetic delineation by computational analysis and then investigated for their antimicrobial activities against different strains of bacteria and fungi. Compounds 8b and 8c were found to be the most potent antibacterial and antifungal agents, respectively.