Deactivation of excited 4′-dialkylamino-9-styrylacridines

Abstract

The absorption and emission spectra and deactivation of excited styrylacridines are determined by the flexibility and charge transfer properties of the donor-acceptor chromophore system. The fluorescence and excitation spectra, as well as the kinetics, vary with the excitation and emission wavelength respectively. Principal component analysis (PCA) and global analysis of the spectra and kinetics of the E isomers reveal at least two absorbing and two emitting components in fluid solution at room temperature as well as in a frozen matrix. At 77 K, the fluorescence of the Z isomer is also observed. The S n ← S 1 transition of the Z isomer is the only transient detectable from picosecond time-resolved absorption experiments in solution. The main competing deactivation channels of the S 1 state are E → Z isomerization, charge transfer-induced internal conversion and fluorescence.