Synthesis, Structures, and Thermal Properties of Symmetric and Janus "Lantern Cage" Siloxanes.

Symmetric and asymmetric (Janus‐type) new "lantern cage" siloxanes (PhSiO1.5)4(Me2SiO)4(RSiO1.5)4 (R=Ph or iBu) were synthesized through reaction of all‐cis‐[PhSi(OSiMe2Br)O]4 with all‐cis‐[RSi(OH)O]4 (R=Ph or iBu). These precursors were obtained by facile two or three‐step reactions from commercially available compounds. The spectroscopic properties of the resulting products were fully characterized and they showed high thermal stability and sublimation without decomposition. The crystal structures clearly indicated that the internal vacancy volumes of the lantern cages are considerably larger than that of octaphenylsilsesquioxane (PhSiO1.5)8. DFT calculations of the lantern cage showed a distinctly different electronic state from that of octasilsesquioxane. These results suggest that lantern cage siloxanes have a characteristic "field" in the molecule. Lantern cage silsesquioxane: Symmetric and novel asymmetric (Janus‐type) new "lantern cage" siloxanes that contains a large interior space were synthesized, and structure and electronic properties were investigated. [ABSTRACT FROM AUTHOR]