Small molecules-photoencapsulation and magnetic properties of fullerene-shaped polyoxometalates

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In our discovery of the photochemical control (photoencapsulation) of the structural variety of the polyoxovanadate clusters which serve as hosts for neutral and charged species with vastly different cavity requirements, both spherical and layred clusters were prepared and crystallographically characterized. The sodium cation-encapsulating species [V_<12>B_<32>O_<84>(Na_4)]^<15->, isolated as H_7[V_<12>B_<32>O_<76>(OH)_8(Na)_4]・13H_2O by the photolysis of the [V_4O_<12>]^<4->/MeOH/Na_3BO_3 system, was novel and greatly fantastic : [V_<12>B_<32>O_<76>(OH)_8(Na_4)]^<7-> consists of the edge-sharing(VO)_<12>O_<24> array ring of VO_5 square-pyramids sandwiched by two B_<16>O_<20>(OH)_4 rings to form a cyclic doughnut-shaped framework, and the central cavity in the cyclic anion is occupied by Na^+ cations. other cation (Li^+ or K^+)-encapsulated species could be prepared by the modified procedure. In a trial of the preparation of V/W-mixed-clusters, the egg-shape cluster [V^V_<14>V^<IV>_8O_ … More <54>(MoO_4)]^<8-> and superkeggin structural clusters [V_<16>W_2O_<42>(VO_4)]_<6-> and [V_6W_<12>O_<42>(VO_4)]^<5-> were also found. furthermore, the template-exchange reaction was established for the above spherical clusters.the chemically induced dynamic electron polarization (CIDEP) spectroscopy of the [V_4O_<12>]^<4->/MeOH system revealed that the reaction precursor involved in the photoredox reaction of all the polyoxometalates is the O*M LMCT triplet states which undergoes the hydrogen abstraction from alcohols to yield one-protonated polyoxometalate and alpha-hydroxyalkyl radicals. All the spherical clusters obtained were paramagnetic, and most of them showed the antiferromagnetic exchange interaction which was explained by the nearest V・・・V distances in the anion. However, a layred cluster NaV_2P_2O_<10>・4H_2O was unique from a standpoint of its weak ferromagnetic property which was demonstrated by the uncoupled spin exchange-interaction due to the overlapping between the two vanadyl orbitals.The photoencapsulation reaction provides an essentiality for constructing molecular devices as well as photochemically designing nanocomposites Less