Synthesis and characterization of dendrons and dendrimers skeleton-constructed with azobenzene moiety

A series of dendrons and dendrimers skeleton-constructed with azobenzene moiety based upon 4-carboxy-4′-(1,2-propanediolether)-azobenzene as an AB₂ monomer, via a convergent approach, proceeding in a repeated stepwise growth manner starting from 4-carboxy-4′-(n-butylether)-azobenzene as a peripheral monomer, were synthesized, and characterized by NMR, FTIR, and MALDI-TOF-MS analysis. Their regular molecular architecture and thus monodispersed molecular weights were confirmed by GPC. The UV-Vis absorbance and ¹H NMR spectrum study indicated that the azobenzene moieties in CHCl₃ solution took fully trans-cis isomerization under UV irradiation, and reversely isomerization back to the trans by visible light irradiation or by heat.     

Synthesis of carbosilane dendrimers with N,N-dimethylaniline as end groups

Carbosilane dendrimers with 4-bromo-N,N-dimethylaniline as end groups were synthesized from methyltrichlorosilane, allyl chloride, magnesium and 4-bromo-N,N-dimethylaniline. All compounds were characterized by 1H NMR, IR, MS.     

A convergent route to poly(phenyl ketone ether) dendrons

A series of poly(phenyl ketone) dendrons have been constructed using a convergent strategy. An aryl fluoro-substituent is deactivated towards nucleophilic substitution by protection of a para-ketone as an acetal. This allows coupling to an activated aryl fluoride.Subsequent deprotection of the acetyl group then activates the first fluoro-substituent and allows the next generation of the dendron to be added. The synthesis of higher generations is complicated by a scrambling reaction, which lowers the yields.     

Synthesis of azide-functionalized PAMAM dendrons at the focal point and their application for synthesis of PAMAM-like dendrimers

For the first time, the divergent synthesis of azide-functionalized PAMAM dendrons using azidopropyl amine as an azide focal point and convergent synthesis of symmetric PAMAM-like dendrimers containing 1,2,3-triazole rings as connectors via click chemistry with a dialkyne core is described.     

A new way for the internal functionalization of dendrimers

The selective reaction of amines and hydrazides with only one Cl on each P(S)Cl₂ or P(O)Cl₂ end group of phosphorus dendrimers, followed by the grafting of hydroxybenzaldehyde on the remaining P-Cl functions, and the subsequent growing of the dendrimer from the aldehyde is described. Allyl and pyrene derivatives have been grafted in this way inside the dendrimers during their growing. This constitutes a new way for the internal functionalization of dendrimers.     

Chloromethylsilane functionalised dendrimers: synthesis and reactivity

Tetraallylsilane was functionalised using (chloromethyl)dimethylsilane to give the first generation chloromethyl terminated dendrimer 1. The resulting dendrimer was successfully reacted with K[CpM(CO)₂] (Cp=η⁵-C₅H₅; M=Fe, Ru) to give Si[(CH₂)₃SiMe₂CH₂MCp(CO)₂]₄ functionalised dendrimers in satisfactory yield. Reaction of dendrimer 1 with NaI in acetone gave the -SiMe₂CH₂I functionalised dendrimer, while reactions of 1 with K[CpM(CO)₃] (M=Mo, W, Re), Li[C₅Me₄H], Na[C₅Me₄H], the cobaloxime nucleophile or tert-BuLi were not successful.     

树枝化聚合物的合成研究进展

综述了近年来由树枝状大分子和线性聚合物结合而成的树枝化聚合物的合成研究进展,着重介绍了＂大分子单体＂,＂接枝到主链＂和＂从主链接枝＂等树枝化聚合物的合成路线,以及3种路线的综合应用,并对不同合成路线的特点进行了分析。     

Synthesis and photophysical properties of phenothiazine-labeled conjugated dendrimers

A novel class of conjugated dendrimers bearing phenothiazines as peripheral groups and phenylenevinylene-group as a core has been synthesized through the Wittig-Horner reaction in moderate to good yield.     

Synthesis of carbosilane dendrimers having peripheral mannose and mannobiose

The mannose monosaccharide derivative, acetylthiopropyl 2,3,4,6-tetra-O-acetyl-α-d-mannopyranoside (Man), and the mannobiose derivative, acetylthiopropyl 2,4,6-tri-O-acetyl-3-O-(2′,3′,4′,6′-tetra-O-acetyl-α-d-mannopyranosyl)-α-d-mannopyranoside (α-1,3-Man), were synthesized respectively. These mannose derivatives were introduced into carbosilane dendrimer scaffolds of the zero and first generations. As a result, six carbosilane dendrimers were functionalized by Man and α-1,3-Man. Isothermal titration microcalorimetry was done to determine binding assay between mannose moieties of carbosilane dendrimer and concanavalin A. It was found that carbosilane dendrimers bound more efficiently to concanavalin A than free mannose (Me-α-Man) and mannobiose (Me-α-1,3-Man).     

Janus carbosilane/phosphorhydrazone dendrimers synthesized by the ‘click’ Staudinger reaction

The first association of carbosilane dendrons (having a phosphine at the focal point) with phosphorhydrazone dendrons (having a thiophosphoryl azide at the focal point) has been successfully carried out by ‘Staudinger click’ reaction. The corresponding Janus dendrimers possess the characteristics of both components; they are oily as the carbosilane dendrons, and they can be easily functionalized as the phosphorhydrazone dendrons.     

Synthesis and photoresponsive study of azobenzene centered polyamidoamine dendrimers

A new series of novel polyamidoamine (PAMAM) dendrimers 4, 5 and 6 possessing azobenzene units specifically at the core were prepared and their reversible trans/cis photoisomerization properties were studied. PAMAM dendritic wedges as well as azo-based PAMAM dendrimers were fully characterized by means of FT-IR, NMR (¹H and ¹³C), mass spectrometry (MALDI-MS), thermogravimetric and elemental analysis.     

Lithiosilanes and their application to the synthesis of polysilane dendrimers

An account is given of the preparation and structural investigations of silyllithium compounds, including X-ray and NMR data. This review covers the chemistry of lithiosilanes with alkyl, aryl, functional substituents and lithiooligosilanes with Si---Si bonds. Application of lithiosilanes for the synthesis of polysilane dendritic molecules is also described.     

"A posteriori" modification of carbosilane dendrimers and dendrons: their activation in core and branch positions

The introduction of phenyl groups at different points on carbosilane dendrimers allows their acidolytic conversion to highly reactive triflato groups which in turn are readily substituted by anionic nucleophiles. Core phenylated first-fourth generation dendrimers were synthesized from tri(allyl)phenylsilane by an alternating sequence of hydrosilylation and allylation steps. Similarly, carbosilane dendrimers containing phenyl-Si groups at the branching points and in the periphery were prepared from tetraallylsilane which was hydrosilylated with PhHSiCl2. Reaction of the phenylated dendrimers with triflic acid in toluene cleanly gave the silyl triflate derivatives, provided that the correct stoichiometry of the reagents was used. In the presence of a large excess of triflic acid the SiMe3-end groups are slowly converted to SiMe2(OTf)-units. The proof of concept was provided by the fixation of a {Ph2PCH2} group using the lithiated diphenylphosphinomethanide Ph2PCH2Li, obtained by cleavage of Ph3SnCH2PPh2 with PhLi, as well as a lithiated ether-alcohol functionalized triphos derivative to the core of a third generation carbosilane dendrimer.     

Synthesis, characterization, and electroluminescent properties of star shaped donor-acceptor dendrimers with carbazole dendrons as peripheral branches and heterotriangulene as central core

Luminescent and redox-active heterotriangulene-based dendrimers (G1 and G2) of first and second generation have been synthesized, and their photophysical properties, oxidation behaviors, and applications in organic light emitting diodes (OLEDs) have been investigated. The dendrimers show efficient aggregation-induced emissions originated from the carbazole dendrons, heterotriangulene core, intramolecular charge-transfer (ICT), and intermolecular aggregation absorptions. Highest-occupied molecular orbital and lowest-unoccupied molecular orbital (HOMO and LUMO) values were acquired using UV-vis spectroscopy and cyclic voltammetry. The OLEDs fabricated with G1 and G2 as non-doping emitters exhibit exclusive aggregation-induced luminescence peaking at 600 and 630 nm, respectively, and demonstrate a good performance with maximum luminance of 1586 cd m⁻² at current efficiency of 5.3 cd A⁻¹ for G1 and 827 cd m⁻² at current efficiency of 6.9 cd A⁻¹ for G2.     

Synthesis and properties of dumbbell-shaped dendrimers containing 9-phenylcarbazole dendrons

We report the synthesis and structural characterization of two dumbbell-shaped dendrimers incorporating 9-phenylcarbazole units as dendrons, as well as their thermal, morphological, photophysical, and electrochemical properties.     

Synthesis of 1,2,4-triazole dendrimers

A convergent synthetic strategy towards novel 1,2,4-triazole dendrimers, in which 3,5-dichloro-4-(4-methoxyphenyl)-4H-1,2,4-triazole was used as the heterocyclic building block, was successfully explored. Nucleophilic aromatic substitution at this novel AB₂-monomer was used as the key step in the propagation of the heterocyclic dendrons and these dendrons were attached to both a 1,3,5-triazine and a methylene core. The peripheral 1,2,4-triazole could be varied not only by nucleophilic aromatic substitution but also by Suzuki cross-coupling. The presented dendrimers are promising candidates to be used in applications where the large number of heteroatoms can be exploited or a better resistance to the applied conditions is required.     

Synthesis and rheological properties of star-shaped polydimethylsiloxanes based on carbosilane dendrimers

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Continuous intra- and intermolecular energy transfer in light-harvesting gels from natural amino acids-based dendrons

The gels and co-gels from glycine (Gly) and glutamic acid (Glu)-based dendrons with either tyrosine (Tyr) or tryptophan (Trp), two of the luminescent amino acid residues in natural proteins, at the focal point were prepared (Tyr-AB₄ and Trp-AB₄). It was found that such gels, especially the co-gels from Tyr-AB₄/Trp-AB₄, showed a high efficient energy transfer (ET) and light-harvesting behaviors. Moreover, luminescent gels with tunable emission ranging from blue to green were also observed owing to the cascade intra- and intermolecular ET from dendritic gelators to the guest molecules (PDNS) in the host-guest gel sample (co-gel with PDNS as the guest molecule), which mimicked the natural light-harvesting systems.     

Synthesis and DSSC application of novel dendrimers with benzothiazole and triazole units

Synthesis of novel dendrimers with benzothiazole as surface group and triazole as branching unit is achieved through click chemistry. The presence of more number of benzothiazole and triazole units increases the molar absorption coefficient and alters the fluorescence as well as electrochemical behaviors in the dendrimers. Dye-sensitized solar cell (DSSC) studies reveal that dendrimers with more number of benzothiazole and triazole groups exhibit better current generating capacity than the dendrimers with lesser number of benzothiazole and triazole groups. Dendrimer 2b shows the maximum current conversion efficiency (η) of 7.1%.     

Synthesis of thioether-containing carbosilane dendrimers with sterically shielded sulfur atoms

Russian Chemical Bulletin - Carbosilane thiols were synthesized as the first- and second-generation (in silicon) dendrons. It was demonstrated that the resulting bulky thiols successfully undergo...