Chromophore-Labeled Dendrons as Light Harvesting Antennae
摘要:
A novel series of polyether dendrimer segments (dendrons) end-clipped with pyrenyl, naphthyl, or methyl groups has been prepared by a convergent growth method. Steady-state fluorescence measurements indicate the absence of intramolecular naphthalene excimer in the naphthyl-capped dendrons. However, in the pyrenyl-capped dendrons, excimer emission predominates. Fluorescence from both the naphthyl monomer and pyrenyl excimer are quenched when a suitable electron donor (e.g., a 3-[dimethylamino]phenoxy group) is covalently attached at the dendron focal point. No sensitized emission from the dendron backbone is observed in the chromophore-labeled dendrons, although the control methyl-capped dendron fluoresces weakly at 310 nn when excited at 284 nm. Absorption and fluorescence spectra, fluorescence quantum yields, and fluorescence lifetimes for the chromophore-labeled dendrons are reported.
(OsO42−) core dendrimers was prepared by an ion-exchange technique through the mixing of K2OsO4 and a bis(quaternary ammonium bromide) core dendrimer, which consisted of poly(benzyl ether) dendron. By employing an osmate core dendrimer as a homogeneous catalyst, dihydroxylation reactions of olefins proceeded rapidly, and the dendritic osmium catalyst was recovered by reprecipitation and then reused. Furthermore
通过离子交换技术,通过混合K 2 OsO 4制备了一系列渗透酸(OsO 4 2-)核心树枝状大分子双(季铵溴化)核心树状聚合物,其由聚(苄基醚)树突组成。通过使用渗透性核树枝状聚合物作为均相催化剂,烯烃的二羟基化反应迅速进行,并且通过再沉淀回收树枝状催化剂,然后再使用。此外,观察到树枝状对催化剂的可循环性的影响。在不对称二羟基化反应的情况下,以高化学收率得到适当的对映体过量(ee)的相应的二醇。在这种情况下,不仅树状的catalyst催化剂,而且手性配体也可以通过再沉淀而回收,并且可以有效地重复使用多达五次。
Synthesis and Characterization of 2,3,9,10-Tetradendronized Pentacene
A new pentacene dendrimer was synthesized in 81% yield through the aromatization of a dihydropentacene derivative having benzyl ether dendrons at the C2, C3, C9, and C10 positions. The dendrimer is very soluble in various organic solvents such as toluene, benzene, chloroform, dichloromethane, acetone, and ethyl acetate. The half-life of the dendrimer reaches 22.4 min upon photoirradiation in air. Interestingly, regiospecific [4 + 2] cycloaddition reactions proceeded at the central ring of the pentacene.
Photochromic dendrimer diarylethenes with a C-2-connected bisbenzothienylethene core were synthesized; the most notable feature of them is the strong memory effect of cyclizable conformation of the open form when generated from the closed form by visible light irradiation in polycarbonate films.
Synthesis of Novel Dendritic 2,2‘-Bipyridine Ligands and Their Application to Lewis Acid-Catalyzed Diels−Alder and Three-Component Condensation Reactions
作者:Takahito Muraki、Ken-ichi Fujita、Masato Kujime
DOI:10.1021/jo070767a
日期:2007.10.1
dendritic Cu(OTf)2 catalysts were used for Diels−Alder and three-component condensationreactions. The dendritic Cu(OTf)2-catalyzed Diels−Alder reaction proceeded smoothly, and these dendritic catalysts could be recycled without deactivation by reprecipitation. Three-component condensationreactions such as Mannich-type reactions also proceeded not only in dichloromethane but also in water. Furthermore
Facile Synthesis of Aldehyde-focal Fréchet Type Dendrons and Dendrimers via Staudinger/Aza-Wittig Reactions
作者:Seung-Choul Han、Sung-Ho Jin、Jae-Wook Lee
DOI:10.5012/bkcs.2011.32.10.3624
日期:2011.10.20
Fr$\acutee}$chet-type dendritic benzaldehydes were efficiently synthesized using 3,5-dihydroxybenzaldehyde as an aldehyde focal point functionalized unit by adding a generation to the existing dendron or direct oxidation of Fr$\acutee}$chet-type dendritic benzyl alcohols. These dendritic benzaldehydes were applied for the construction of dendrimers containing secondary amines as connectors via Staudinger/aza-Wittig Reactions with $\alpha}$,$\alpha}'$,-diazidop-xylene core.