Spin Alignment of π-Conjugated Spin Systems Using the Dynamics

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In this project, we have obtained the following two representative results.(1)We have obtained the first evidence of the photo-excited quartet state with a unique dynamic electron polarization (DEP) generated through the ion-pair state (charge separated state). The ion-pair state is generated by the intramolecular photo-induced electron transfer from the anthracene moiety to the bodipy functional component. Such a unique DEP pattern has been reported only for the triplet states of the photosystems I, II and the model compounds. This is the first detection of the unique DEP pattern detected in the quartet high-spin state.(2)We have also succeeded to detect a novel lowest photo-excited triplet (S=1) state arising from four unpaired electrons. The low-lying quintet (S=2) photo-excited state was located above the photo-excited triplet state. The unique triplet state has D value reduced by the antiferromagnetic spin alignment between two radical spins through the excited triplet spin coupler. The general theoretical predictions of the spin alignment and the reduction of the fine-structure splitting of the radical-triplet-radical system are presented.In addition to the above results, we investigated several charge-transfer complexes, in which the electron donor parts are the π-radicals with the photo-excited quartet high-spin states. We also clarified the magnetic properties of the some metal complexes using the photo-excited high-spin organic molecules as ligands. Furthermore, we studied the spin dynamics of the photo-excited high-spin states of the π-radicals using a pulsed ESR technique combined with a pulsed LASER excitation.