Synthesis of diazacrown ethers with chromophores and their photoinduced charge-separation with methyl viologen

Two 4,13-diaza-18-crown-6 ethers with either two pyrenyl or two carbazolyl groups were synthesized. The two crown ethers can form complexes with methy l viologen in methanol solution. Photoirradiation of the complexes resulted in the electron transfer from the excited states of the chromophores to me thyl viologen as demonstrated by the quenching of the chromophore fluoresce nce and the detection of the absorption spectrum of the generated viologen radical cation. The back electron transfer in these systems was inhibited b y the electrostatic repulsion between the positively charged viologen radic al cation and the generated chromophore radical cation. Long-lived charge s eparation states (up to tens of min) were observed.