STEADY-STATE AND TRANSIENT ABSORPTION-SPECTRA OF QUINHYDRONES

Picosecond time-resolved absorption spectra of crystalline quinhydrone complexes, excited at the charge transfer (CT) band, were obtained. Transient spectra weakly depend on the excitation wavelength and are similar in shape and frequency to the steady state absorption spectra within the CT band. The positive absorption at 20 000-24 000 cm-1 is assigned to radical ion species. The kinetics of induced absorption depend on the method of preparation of the crystalline complex and can be fitted to a biexponential decay with time components tau1 = 130-180 ps and tau2 > 5000 ps. Luminescence of the complexes in the range 10 000-13 000 cm-1 is observed. Its delay time increases from 300 to 1000 ps with decreasing probing frequency. Quantum chemical calculations of the absorption spectra of the complexes and intermediate radical species were carried out.