A first principle photo-induced electron transfer study on a quinolin schiff base as Al3+ chemosensor using TD-DFT method

Abstract

Because of the importance and growing application of chemical sensors, mechanism of Nʹ-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido [3,2,1-ij]quinolin-9-yl)methylene)benzohydrazide (NHH) ligand activity to detect Al3+ cation in water solvent through DFT and TD-DFT methods was studied here. DFT calculations were conducted using the B3LYP function whilst TDDFT calculations were performed by using the CAM-B3LYP function and considering the solvent effect. Ground state charge transfer was calculated using the NBO analysis and the DOS graph of ligand and the complex were also obtained. The calculations on the UV–Vis absorption spectra and the fluorescence emission indicate that the emitted spectra showed a considerable Red-Shift after the complex being formed. The reason of such change was about the geometry of the ligand after the formation of the [Al·NHH]3+ complex. The phenomenon of photo-induced electron transfer and photo-induced charge transfer were studied using the theory of hole-electron and it was revealed that the reason for increase of the emitted wavelength was about a PET cut off (break) after formation of a complex in three states of excitation, with absorbing wavelength of 272.33, 248.54 and 235.91 nm, toward fluorophore, respectively.