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Abstract: Three new pentacyclic laddersiloxanes were prepared by a new method utilizing single stereoisomer of disiloxanediol as a growing unit. Thus, one diastereomer of disiloxanediol, (RS)–[i-PrPhSi(OH)]2O was isolated and treated with tetrachlorocyclotetrasiloxane, resulting in the formation of tricyclic laddersiloxanes with cis-Ph groups at terminals. All of the obtained isomers could be transformed into pentacyclic laddersiloxanes by dephenylchlorination followed by the reaction with (RS)–[i-PrPhSi(OH)]2O. The structures of new tricyclic and pentacyclic laddersiloxanes were determined by X-ray crystallography. The thermogravity properties of laddersiloxanes depending on the molecular weight and structures were summarized. [Copyright &y& Elsevier]

Cocrystallization of all-cis-tetraisopropylcyclotetrasiloxanetetraol and diisopropylsilanediol gave single crystals, which were proved to have a nano-size tube-like aggregate structure. Six molecules of the cyclic tetraol and four molecules of the diol form an asymmetric unit by means of hydrogen bonding. The structure and properties of the aggregates are discussed in detail, and also the possibility of solid-state synthesis of siloxanes is described. [ABSTRACT FROM AUTHOR]

Synthesis of novel cage and cyclic silanols bearing Tip (2,4,6-triisopropylphenyl) groups was performed. Tip-substituted silanetriol, TipSi(OH)3 (1) was prepared from TipSiCl3, and can be handled without special care in the air. The versatility of this silanol is amply demonstrated as a starting material of various silanols with novel frameworks. Thus, the condensation of 1 using 2-chloro-1,3-dimethylimidazolinium chloride as a dehydrating agent afforded (TipSi)5O7OH (2) in 45% yield. When 1 was treated with (TipSiCl2)2O, cis,trans-cyclotrisiloxanetriol (3) as well as a novel incompletely condensed silsesquioxane, (TipSi)4O5(OH)2 (4) were obtained. In addition, the dehydrochlorinative condensation of (TipSiCl2)2O and (TipSi(OH)2)2O afforded 4 as single product. The structures of all these novel silanols were determined by X-ray crystallography, and their unique structures (hydrogen-bonded aggregates or intramolecular hydrogen bonding) were demonstrated. [Copyright &y& Elsevier]

The molecular structure of the silyl-substituted octasilacubane [(t-BuMe2Si)Si]8 (1) was analyzed by X-ray crystallography, and the structural parameters (bond length and angles) were compared with those of the alkyl- and aryl-substituted octasilacubanes. A thermogravimetric analysis revealed that 1 remained stable under argon up to 300 °C, indicating that 1 is much more thermally stable than alkyl-substituted (ThexSi)8 (Thex=1,1,2-trimethylpropyl) (2), which decomposed at 200 °C. Although compound 1 is stable in the air, 1 reacted with m-chloroperoxybenzoic acid (mCPBA). Thus, treatment of 1 with fourteen equivalents of mCPBA led to the formation of octakis(tert-butyldimethylsilylsilsesquioxane) (3) in 98% yield. The structure of 3 was also established by X-ray crystallography, indicating that all the oxygen atoms inserted into the Si&z.sbnd;Si bonds of the Si8 framework and the exocyclic Si&z.sbnd;Si bonds remained intact under the conditions employed. Compound 3 is the first example of silsesquioxane with bulky silyl substituents, and shows relatively intense absorptions in the UV region. [Copyright &y& Elsevier]

Molecular recognition of dicarboxylates by a dinuclear zinc(II) complex of 2,2ʹ-binaphthalene bearing di(2-pyridyl)aminomethyl groups at 8- and 8ʹ-positions ([Zn2L]4+) by UV-vis and fluorescence spectral titrations in an aqueous solvent was investigated. In a series of α,ω-dicarboxylate, receptor [Zn2L]4+ showed the highest binding affinity for succinate and UV-vis and fluorescence changes were also largest upon the addition of this guest. In a series of phthalate derivatives, phthalate was strongly bound by [Zn2L]4+. The characteristic UV-vis and fluorescence changes strongly depend on the dihedral angle of two naphthyl groups of the complex [Zn2L]4+· dicarboxylate estimated by spectral titrations and DFT calculations. [ABSTRACT FROM AUTHOR]

Novel polyhedral structures were prepared with a butterfly‐shape composed of oligosiloxane wings and a double‐decker silsesquioxane (DDSQ) body. The compounds were synthesized in two steps from commercially available alkoxysilanes, and their structures were confirmed using spectroscopic methods and X‐ray crystallography. Not like other phenyl‐substituted cage silsesquioxanes, these butterfly cages show very good solubility in common organic solvents. The crystal structures clearly showed their unique features: a larger space with longer siloxane chains and a very flexible framework. Moreover, these compounds are thermally stable with a Td5 (5 % weight loss temperature) over 320 °C. [ABSTRACT FROM AUTHOR]

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]