Synthesis, characterization and photophysical properties of polyfunctional phenylsilsesquioxanes: [o-RPhSiO1.5]8, [2,5-R2PhSiO1.5]8, and [R3PhSiO1.5]8. compounds with the highest number of functional units/unit volume
[PhSiO1.5]8 promotes self-bromination to produce [o-BrPhSiO1.5]8: further bromination gives crystalline [2,5-Br2PhSiO1.5]8 with a density of 2.32 g cm−3 and a calculated refractive index of 1.7 or the tetraicosa bromo compound [Br3PhSiO1.5]8
[PhSiO<sub>1.5</sub>]<sub>8,10,12</sub>as nanoreactors for non-enzymatic introduction of ortho, meta or para-hydroxyl groups to aromatic molecules
作者:Mozhgan Bahrami、Xingwen Zhang、Morteza Ehsani、Yousef Jahani、Richard M. Laine
DOI:10.1039/c7dt00373k
日期:——
the traditional electrophilic reactions provide selective functionalization at each position on the aromatic ring. Furthermore, halogenation serves as a starting point for the synthesis of two structuralisomers of practical utility, i.e. in drug prospecting. The o-bromo and p-iodo compounds are easily modified by catalytic cross-coupling to append diverse functional groups. Thereafter, F−/H2O2 treatment
传统的电溴化沿用已久的“规则”:吸电子事业溴化选择性的取代基元的位置,而电子取代基的青睐邻位和对位溴化。相比之下,在[PhSiO 1.5 ] 8,10,12倍半硅氧烷中,笼子起着相当于CF 3的庞大的吸电子基团的作用。然而,在温和条件下进行溴化反应却没有催化剂,极大地促进了邻位取代。令人惊讶的是,没有催化剂的ICl碘化有利于(> 90%)对位取代[ p -IC 6 H 4 SiO 1.5] 8,10,12。最后,硝化和Friedel-Crafts酰化和磺酰化是高度间选择性的,> 80%。原则上,两种卤化形式与传统的亲电反应相结合,可在芳环的每个位置提供选择性官能化。此外,卤化用作合成两种具有实际用途的结构异构体的起点,即在药物勘探中。的Ô溴和p碘化合物易于通过催化交叉偶联追加多种多样的官能团改性。此后,F - / H 2 ö 2处理使Si-C键断裂,用OH代替Si。这代表了将羟基引入芳环的
Synthesis, characterization and photophysical properties of polyfunctional phenylsilsesquioxanes: [o-RPhSiO1.5]8, [2,5-R2PhSiO1.5]8, and [R3PhSiO1.5]8. compounds with the highest number of functional units/unit volume
作者:Santy Sulaiman、Jin Zhang、Theodore Goodson, III、Richard M. Laine
DOI:10.1039/c1jm11701g
日期:——
The availability of pure samples of o-Br8OPS, 2,5-Br16OPS, and Br24OPS provides a rare opportunity to synthesize sets of corresponding stilbene derivatives: o-RStyr8OPS, RStyr16OPS, and RStyr24OPS where R = 4-methyl (Me), Boc-protected 4-amino (NBoc), or 4-acetoxy (Ace). These derivatives show unique UV-Vis absorption and photoluminescent behavior that points to interesting interactions between the organic tethers and the silsesquioxane cage. o-RStyr8OPS shows blue-shifts in the absorption spectra compared to p-MeStyr8OPS, suggesting that the stilbene groups sit over and interact with the face of the electrophilic silsesquioxane cage as is the case with the parent molecule, o-Br8OPS. The emission spectra of o-RStyr8OPS are similar to p-MeStyr8OPS indicating similar excited states involving the core LUMO. RStyr16OPS exhibits absorption and emission spectra as well as ΦPL similar to 1,4-distyrylbenzene, pointing to disruption in conjugation with the silsesquioxane cage because of steric interactions. RStyr24OPS offers absorption maxima that are blue-shifted and emission maxima that are red-shifted relative to RStyr16OPS. We speculate that RStyr24OPS is so sterically hindered that interactions with the cage face must occur. NBocStyr24OPS and AceStyr24OPS show moderate ΦPL and high two photon cross-section values, leading us to conclude that there are two excited states of nearly equivalent energy in these molecules with similar decay rates: a normal radiative π–π* transition and charge transfer involving the silsesquioxane cage. These same functional groups can be anticipated to offer much greater two photon absorption if different methods can be found for protecting the free amine from oxidation or replacing the acetoxy group (e.g. perhaps using alkyl or aryl groups).
[PhSiO1.5]8 promotes self-bromination to produce [o-BrPhSiO1.5]8: further bromination gives crystalline [2,5-Br2PhSiO1.5]8 with a density of 2.32 g cm−3 and a calculated refractive index of 1.7 or the tetraicosa bromo compound [Br3PhSiO1.5]8
作者:Mark F. Roll、Priyanka Mathur、Kunio Takahashi、Jeffrey W. Kampf、R. M. Laine
DOI:10.1039/c1jm11536g
日期:——
We describe here the synthesis and characterization of the octa-, hexadeca- and tetraicosa-brominated derivatives of octaphenylsilsesquioxane, [PhSiO1.5]8 or OPS, which offer high 3-D symmetry. Surprisingly OPS catalyzes its own bromination in refluxing CH2Cl2, in the absence of a traditional Lewis acid catalyst, leading unexpectedly and with high selectivity (â¥85%) to the ortho-bromo product, [o-BrPhSiO1.5]8. It appears that the electrophilic character of the cage polarizes the Br2 molecule promoting bromination at the ortho position. Thereafter, with the introduction of a Lewis acid catalyst or simply through prolonged bromination without a catalyst, it is possible to double the number of Br's to produce primarily crystalline [2,5-Br2PhSiO1.5]8 in yields of 80+%. Extended catalytic bromination provides the disordered tetraicosa-brominated compound [Br3PhSiO1.5]8 in low yields. The latter two compounds have bromine densities of 9.5 and 8.4 Br per nm3, respectively, some of the highest densities of Br compounds found in the literature. Crystalline [2,5-Br2PhSiO1.5]8 offers single crystal densities of 2.32 g cmâ3 and a calculated refractive index of 1.7 where sapphire is 1.76. The brominated compounds were characterized using NMR, FTIR, TGA and single crystal X-ray diffraction. This set of compounds offers the potential viacatalytic cross-coupling reactions to produce spherical molecules with some of the highest degrees of functionality possible for any first generation star/hyperbranched cores.