A study of acridine adsorption on silica by the methods of luminescence and IR spectroscopy

Abstract

Spectra of luminescence and its excitation as well as IR spectra of acridine adsorbed from the gas phase or from the solution in dichloromethane on silicon dioxide (mesoporous MCM-41 and aerosil) have been studied. The luminescence band of adsorbed acridine is shifted towards longer waves as compared with the spectrum of acridine in dichloromethane and towards short wavelengths with respect to the spectrum of protonated acridine in solution. In the IR spectrum, acridine adsorption leads to a frequency shift of the band of surface silanol groups from 3750 to 2860 cm−1 and to the appearance of absorption bands of the adsorbed acridine. Addition of SO2 results in acridine protonation with the shift of the 1624 band to 1653 cm−1. The obtained data indicate that acridine forms hydrogen bond with silanol groups of silica surface. In the case of acridine adsorption from dichloromethane, or after extended storage of the sample in acridine vapor, the luminescence band is observed at 520 nm, that is explained by self-association of acridine.