NEW EPR METHODS FOR INVESTIGATING PHOTOPROCESSES WITH PARAMAGNETIC INTERMEDIATES

Some of the significant advances in time-resolved multifrequency elect ron paramagnetic resonance (EPR) methods are reviewed, with the explic it focus on studies of light-driven processes and photoreactions in re al time. Prominent examples are excited state electron transfer reacti ons with transient charge-separated radical pairs playing a central ro le. Paramagnetic intermediates and products are key functional states; thus EPR is the method of choice for their characterization. Photogen erated spin polarization and coherences as process-inherent features a dd the practical advantage of compensation in the trade-off between se nsitivity and time resolution. Additionally, they provide detailed str uctural and dynamic information on the photoreactive system. Significa nce and specificity of the results achieved for charge separation in p hotosynthetic reaction centers and donor-acceptor model complexes indi cate highly promising perspectives in photochemical research.