A new concept of photogeneration of cations: Evidence for photoejection of Ca(2+) and Li (+) from complexes with a crown-ether-linked merocyanine by picosecond spectroscopy.

Time-resolved transient absorption and gain spectra of DCM-crown and its complexes with Li(+) and Ca(2+) in acetonitrile are measured in the wavelength range 370-670 nm after subpicosecond excitation at 425 nm. The results give evidence for the fast formation of free DCM-crown from both excited complexes, with a faster rate for the Li(+) complex. A two-step mechanism is found for the initial decay (within 30 ps) of the free DCM-crown.