Hollow asymmetrical silica dumbbells containing a movable inner core were fabricated by a template-assisted method. Three different templates were employed for the fabrication of the hollow asymmetrical dumbbells. For the preparation of the first template, silica particles were uniformly covered with a cross-linked polymethylmethacrylate (PMMA) shell and the polymerization of styrene was conducted to induce a protrusion of polystyrene (PSt) from the PMMA shell. Anisotropic colloids composed of silica, PMMA, and PSt were used as templates, coated with a silica shell, and held at 500°C for 2 h to remove the polymer interior components of the template colloid. The heat treatment successfully produced hollow asymmetrical silica dumbbells containing an inner silica core. After being dried, approximately 50% of the inner silica particles that were originally coated with PMMA ended up in the other hollow sphere in which the PSt component existed before heat treatment, indicating that the inner silica particles could pass through the hollow asymmetrical dumbbells' necks and were free to move in the interior. In the preparation of the second and third asymmetrical dumbbell templates, magnetic silica particles and titania particles, respectively, were covered with a PMMA shell to incorporate externally responsive particles into the hollow silica shells as above. The successful syntheses demonstrated the generality of our approach. The passage of the responsive particles through the dumbbell's neck enabled active control of the position of the responsive particles inside the asymmetrical dumbbells by external fields.

Assembly and directed orientation of anisotropic particles with an external ac electric field in a range from 1 kHz to 2 MHz were studied for asymmetric composite dumbbells incorporating a silica, titania, or titania/silica (titania:silica = 75:25 vol %) sphere. The asymmetric composite dumbbells, which were composed of a polymethylmethacrylate (PMMA)-coated sphere (core-shell part) and a polystyrene (PSt) lobe, were synthesized with a soap-free emulsion polymerization to prepare PMMA-coated inorganic spheres and another soap-free emulsion polymerization to form a polystyrene (PSt) lobe from the PMMA-coated inorganic spheres. The composite dumbbells dispersed in water were directly observed with optical microscopy. The dumbbells incorporating a silica sphere oriented parallel to an electric field in the whole frequency range and they formed a pearl chain structure at a high frequency of 2 MHz. The titania-incorporated dumbbells formed chain structures, in which they contacted their core-shell parts and oriented perpendicularly to a low-frequency (kHz) field, whereas they oriented parallel to a high-frequency (MHz) field. Since the alignment of dumbbells in the chains depends not only on the interparticle forces but also on the torque that the induced dipoles in the dumbbells experience in the electric field, the orientation of dumbbells perpendicular to the electric field was the case dominated by the interparticle force, whereas the other orientation was the case dominated by the torque. The present experiments show that the incorporation of inorganic dumbbells is an effective way to control the assembled structure and orientation with an electric field.

Bicyclo[2.2.2]oct-5-en-2-ones (1) are potential compounds which are convertible into [5-5] fused-ring systems (2) by the triplet sensitized photochemical process, oxa-di-tr-methane rearrangement,1 and also into [6-6] fused-ring systems (4) via vinylation followed by the oxy-Cope rearrangement of the exoalcohols (3).2 In connection with our studies on rearrangement strategies from bridged polycyclic compounds to [m-ri\ fused-ring

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