61842-44-2Relevant articles and documents
Multiple hydrogen-bond-induced supramolecular nanostructure from a pincer-like molecule and a [60]fullerene derivative
Zhuang, Junpeng,Zhou, Weidong,Li, Xiaofang,Li, Yongjun,Wang, Ning,He, Xiaorong,Liu, Huibiao,Li, Yuliang,Jiang, Li,Huang, Changshui,Cui, Shuang,Wang, Shu,Zhu, Daoben
, p. 8686 - 8693 (2005)
A new supramolecular self-assembled system between a perylene bisimide bearing diaminopyridine-substituted isophthalamide groups (PP) and a [60]fullerene containing barbituric acid moiety (C60bar) through a complementary six-point hydrogen-bonding interaction was constructed. The formation of hydrogen bonding was confirmed by 1H NMR spectra studies in CDCl3. Fluorescence quenching experiments indicated that the fluorescence of PP was greatly quenched by the hydrogen-bonded C60bar (Ksv=2.71×104 M-1). A steady and rapid cathodic 0.15 μA cm-2 photocurrent response of the PP/C 60bar film deposited onto an ITO electrode was produced under the irradiation of 20 mW cm-2 white light, indicating the presence of photo-induced electron transfer between PP and C60bar. TEM images showed that spherical particles were fabricated by the self-assembly of PP and C60bar through hydrogen-bonding interaction.
Cooperativity and tunable excited state deactivation: Modular self-assembly of depsipeptide dendrons on a Hamilton receptor modified porphyrin platform
Gnichwitz, Jan-Frederik,Wielopolski, Mateusz,Hartnagel, Kristine,Hartnagel, Uwe,Guldi, Dirk M.,Hirsch, Andreas
supporting information; experimental part, p. 8491 - 8501 (2009/02/02)
A series of novel supramolecular architectures were built around a tin tetraphenyl porphyrin platform 6 - functionalized by a 2-fold 1-ethyl-3-3-(3-dimethylaminopropyl)carbodiimide (EDC) promoted condensation reaction - and chiral depsipeptide dendrons of different generations 1-4. Here, implementation of a Hamilton receptor provided the necessary means to keep the constituents together via strong hydrogen bonding. Characterization of all architectures has been performed, including 4 which is the fourth generation, on the basis of NMR and photophysical methods. In particular, several titration experiments were conducted suggesting positive cooperativity, an assessment that is based on association constants that tend to be higher for the second binding step than for the first step. Importantly, molecular modeling calculations reveal a significant deaggregation of the intermolecular network of 6 during the course of the first binding step. As a consequence, an improved accessibility of the second Hamilton receptor unit in 6 emerges and, in turn, facilitates the higher association constants. The features of the equilibrium, that is, the dynamic exchange of depsipeptide dendrons 1-4 with fullerene 5, was tested in photophysical reference experiments. These steady-state and time-resolved measurements showed the tunable excited-state deactivations of these complexes upon photoexcitation.
Poly(ethylene glycol)-supported nitroxyls: Branched catalysts for the selective oxidation of alcohols
Ferreira, Pedro,Phillips, Emyr,Rippon, David,Shik, Chi Tsang,Hayes, Wayne
, p. 6851 - 6859 (2007/10/03)
Nitroxyl radicals such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) are highly selective oxidation catalysts for the conversion of primary alcohols into the corresponding aldehydes. In this study, direct tethering of TEMPO units onto linear poly(ethylene glycol) (PEG) has afforded macromolecular catalysts that exhibit solubility in both aqueous and organic solvents. Recovery of the dissolved polymer-supported catalyst has been carried out by precipitation with a suitable solvent such as diethyl ether. The high catalyst activities and selectivities associated traditionally with nitroxyl-mediated oxidations of alcohols are retained by the series of "linker-less" linear PEG-TEMPO catalysts in which the TEMPO moiety is coupled directly to the PEG support. Although the selectivity remains unaltered, upon recycling of the linker-less polymer-supported catalysts, extended reaction times are required to maintain high yields of the desired carbonyl compounds. Alternatively, attachment of two nitroxyl radicals onto each functionalized PEG chain terminus via a 5-hydroxyisophthalic acid linker affords branched polymer-supported catalysts. In stark contrast to the linker-less catalysts, these branched nitroxyls exhibit catalytic activities up to five times greater than 4-methoxy-TEMPO alone under similar conditions. In addition, minimal decrease in catalytic activity is observed upon recycling of these branched macromolecular catalysts via solvent-induced precipitation. The high catalytic activities and preservation of activity upon recycling of these branched systems is attributed to enhanced regeneration of the nitroxyl species as a result of intramolecular syn-proportionation.
