Star-shaped Dendrimers Research Articles

Synthesis and Biological Studies of Cationic Organoiron Star-Shaped Dendrimers with Attached Ketoprofen and Mefenamic Acid at the Peripheries

Synthesis and Biological Studies of Cationic Organoiron Star-Shaped Dendrimers with Attached Ketoprofen and Mefenamic Acid at the Peripheries

Electrochemical Biosensor Based on Polyelectrolyte Complexes with Dendrimer for the Determination of Reversible Inhibitors of Acetylcholinesterase

An acetylcholinesterase biosensor has been developed based upon a fourth generation poly(amidoamine) dendrimer with terminal amino groups. The immobilization of acetylcholinesterase was performed by physical adsorption onto the polyelectrolyte complex consisting of dendrimer and poly(styrene sulfonate) or deoxyribonucleic acid as counter ions. The efficiency of immobilization was evaluated by surface plasmon resonance that indicated a twofold increase of the quantity of enzyme on the surface in comparison with similar biosensors with no dendrimer. This property can be attributed to higher roughness of the underlying surface and its possible porosity caused by the star-shaped dendrimer molecules. The influence of the polyelectrolytes used on the biosensor performance as well as kinetic characteristics of enzymatic hydrolysis of thiocholine were assessed. The calibration curves of reversible inhibitors used in the therapy of neurodegenerative diseases (Huperzine A and galantamine) were ascribed with a four-parametrical logistic model. The 15% inhibition levels varied from 9.4 to 65 nM Huperzine A and 90 to 107 nM galantamine depending on the content of the polyelectrolyte complex. The biosensors were tested on example artificial and real urine samples and provided recoveries from 95 to 110%.

Star-shaped tetra- and octa-arylamine triptycene-based dendrimers: modular building blocks for blue emission materials

The divergent synthesis of star-shaped oligophenylene dendrimers is described. These latter consist of a triptycene central core decorated with various peripheral tetra- and octa-arylamine derivatives. The target compounds were prepared via a convenient [4 + 2] Diels–Alder cycloaddition reaction followed by palladium-catalyzed Buchwald–Hartwig Cross-Coupling reactions in very good overall yields. The dendritic structures were confirmed by 1H- and 13C-nuclear magnetic resonance, high resolution mass spectrometry, and thermogravimetric analysis. Photophysical studies of these star-shaped dendrimers revealed their violet and blue fluorescent properties, thus, promoting them as promising materials for emission applications.

Convenient Synthesis and Characterization of Star-Shaped Dendrimers: 2,4,6-Trisubstituted 1,3,5-Triazine Derivatives

A serial of novel star-shaped 2,4,6-trisubstituted 1,3,5-triazine (s-triazine) dendrimers were synthesized via step-by-step nucleophilic substitution starting from 2,4,6-trichloro-1,3,5-triazine, and were characterized by 1H, 13C NMR, FT-IR and ESI-MS spectra. The crystal structures for 2b, 2d and 4c have been determined by X-ray diffraction analysis, which indicate that there are hydrogen bonding and short contact interactions existing in intermolecules result in forming three-dimensional network architecture. D NMR experiments demonstrate that symmetrical trialkylamino-s-triazine shows correlated rotations of its N(2-ethoxy-2-oxoethyl) groups, while unsymmetrical 2-R-4,6-bis(dialkylamino)-s-triazines display two non-equivalent N(2-ethoxy-2-oxoethyl) groups, issued from the restricted rotation about the created C(s-triazine)-N bonds, and was conformed by crystallographic data.

Synthesis of multi-porphyrin dendrimer as artificial light-harvesting antennae

To mimic bacterial light-harvesting antenna complexes, a series of dendritic multiporphyrin arrays, n PZn-PFB (n = 2, 4; cone-shaped dendrimers, n = 8, 16; star-shaped dendrimers), were synthesized and characterized by 1H NMR and MALDI-TOF-MS spectroscopy. Photoinduced energy-transfer efficiency (ΦET) from peripheral Zn porphyrin ( PZn ) units to an inner core free-base porphyrin ( PFB ) in the dendrimers was evaluated by fluorescence measurement. Both star- and cone-shaped multi-porphyrin arrays exhibited significantly high efficiency energy transfer from the photoexcited PZn units to the energy-accepting PFB , where the star-shaped dendrimers, 8PZn-PFB (94%) and 16PZn-PFB (88%), had a slightly higher efficiency than those of the cone-shaped dendrimers, 2PZn-PFB (92%) and 4PZn-PFB (80%), respectively.

Time–frequency two-dimensional mapping of rapid energy transfer in light-harvesting star-shaped dendrimers

Rapid energy transfer dynamics in light-harvesting small dendrimers (star-shaped stilbenoid phthalocyanine: SSS1-Pc) having oligo ( p-phenylenevinylene) peripheries was studied by real-time pump-probe imaging spectroscopy implemented on a single-shot basis. Using this method, we could successfully map the time–frequency two-dimensional (2D) image of the transient absorption of SSS1-Pc with a very short accumulation time. Under the selective excitation of the peripheries, the 2D image obtained clearly shows the transient absorption as well as the ground-state bleaching due to the energy transfer to the core with a fast rise time of ∼0.3 ps. This fast rise implies that the rapid energy transfer from the peripheries to the core takes place through the short-range interactions due to the overlap of wave functions between the excited states of the peripheries and the core.

Facile Synthesis of Polyamide Dendrimers from Unprotected AB2 Building Blocks: Dumbbell-Shaped Dendrimer, Star-Shaped Dendrimer, and Dendrimer with a Carboxylic Acid at the Core

A fast, inexpensive, and highly efficient synthesis of aromatic polyamide dendrimers, without the need for protection and deprotection steps, has been developed. Dendrons and various types of polyamide dendrimers were easily prepared by a convergent approach involving activation of a carboxylic acid at the focal point using a small excess of thionyl chloride as the activating agent, followed by condensation with an unprotected AB2 building block, 3,5-bis(4-aminophenoxy)benzoic acid. A third generation dendrimer with a molecular weight of 8197 Da was prepared in a high yield, using 1,3,5-tris[N-(4-aminophenyl)]benzenetricarboxamide as a core molecule. A dendrimer with a carboxylic acid group at its core (molecular weight: 10 700 Da) could be prepared from the third generation dendron with 3,5-bis(3,5-diaminobenzoylamino)benzoic acid as the core molecule. All the above products purified only by precipitation revealed a high purity, assessed using matrix assisted laser desorption ionization time-of-flight m...

Synthesis of a novel star-shaped dendrimer by radial-growth polymerization of sarcosine N-carboxyanhydride initiated with poly(trimethyleneimine) dendrimer

Synthesis of a novel star-shaped dendrimer by radial-growth polymerization of sarcosine N-carboxyanhydride initiated with poly(trimethyleneimine) dendrimer

Synthesis of a novel star-shaped dendrimer by radial-growth polymerization of sarcosineN-carboxyanhydride initiated with poly(trimethyleneimine) dendrimer

A novel ABn-type dendrimer/linear polymer block copolymer, i.e., poly(trimethyleneimine) dendrimer-block-(polysarcosine)64 (1), was synthesized by ring-opening polymerization of sarcosine N-carboxyanhydride initiated with the 64-NH2-terminal poly(trimethyleneimine) dendrimer as a macroinitiator. 1 has narrow molecular weight distributions (Mw/Mn = 1.01–1.03, by size exclusion chromatography) and controlled polysarcosine chain lengths (by varying the monomer/dendrimer feed molar ratios). Small-angle neutron scattering (SANS) data obtained in D2O solution of 1 (DP's of polysarcosine = 2.0 and 24) fitted well with a Guinier plot of a spherical particle, and gave diameters of 44 and 100 Å, respectively.