Peripheral substitution of a near-IR-absorbing soluble phthalocyanine using "click" chemistry

A series of near-IR-absorbing soluble phthalocyanines (Pcs) with eight alkyne moieties as side chains of the chromophore have been synthesized. One of these Pcs has been used as a scaffold for functional group modification using alkyne-azide click chemistry with various azides. This led to a small library of Pcs with photo and thermal crosslinkable, dendritic, and hydrophilic moieties starting from a single Pc molecule. A patterned thin film was fabricated by photocrosslinking one of these Pc derivatives.     

Synthesis of neoglycopolymers by a combination of "click chemistry" and living radical polymerization

The synthesis of novel well-defined alkyne side chain functional polymers featuring narrow molecular weight distributions (PDI = 1.09-1.17) by living radical polymerization is described. Grafting of protected and unprotected carbohydrates is achieved via either a C-6 or an anomeric azide (alpha or beta) onto these polymers by Cu(I)-catalyzed "click chemistry", providing a simple and efficient route to synthetic glycopolymers. The strategy provides an extremely powerful tool for the synthesis of libraries of materials that differ only in the nature of the sugar moiety presented on a well-defined polymer scaffold. A library of multivalent ligands were then prepared following a "coclicking" synthetic protocol, and the reactivity of these glycopolymers in the presence of concanavalin A and Ricinus communis agglutinin, model lectins able to selectively bind appropriate mannose and galactose derivatives, respectively, was assessed.     

Synthesis of disk-rod-disk liquid crystal trimers by using click chemistry

A series of disk-rod-disk liquid crystal trimers were synthesized.CuI-NEt3 catalyzed alkyne azide cycloaddition in toluene at room temperature connected two triphenylene discogens to a biphenyl rod-shaped mesogen.The trimers were characterized by using 1H NMR,IR,and high resolution mass spectrometry.The mesomorphic properties were investigated using polarized optical microscopy(POM) ,differential scanning calorimetry(DSC) ,and wide-angle X-ray diffraction.The results showed that the trimers exhibited rectan...     

Parallel synthesis and biological screening of dopamine receptor ligands taking advantage of a click chemistry based BAL linker

The click-chemistry-derived formyl indolyl methyl triazole (FIMT) resin 1a was evaluated for the parallel solid-phase synthesis of a series of BP-897-type arylcarboxamides. By application of a five-step sequence (including loading by reductive amination, subsequent amide coupling, deprotection, palladium-catalyzed N-arylation, and acidic cleavage), a focused library of putative dopamine D3 receptor ligands was constructed. The final products revealed good to excellent purity and were screened for binding at monoaminergic G-protein-coupled receptors when selected library members proved to show excellent binding affinity, especially toward the dopamine D3 receptor subtype.     

Synthesis of a hybrid assembly composed of titanium dioxide nanoparticles and thin multi-walled carbon nanotubes using "click chemistry"

A hybrid assembly composed of thin multi-walled carbon nanotubes (t-MWCNT) and titanium dioxide (TiO(2)) has been prepared by using "click" chemistry for photocatalytic applications. TiO(2)-decorated t-MWCNT hybrids with anatase phase TiO(2) were obtained from the reaction of an azide moiety-containing TiO(2) with alkyne-functionalized t-MWCNTs. The hybrids were systematically characterized using Fourier transform infrared spectroscopic (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDX), and X-ray diffraction (XRD) measurements. The nanohybrid has been proved to be highly active and robust for photocatalytic degradation of methyl orange. The click coupling approach is a simple and convenient route to efficiently assemble TiO(2) on the surface of carbon nanotubes, and can be extended to obtain many other nanoparticle hybrids based on carbon nanotubes.     

Different functionalization of the internal and external surfaces in mesoporous materials for biosensing applications using "click" chemistry

We report the use of copper(I)-catalyzed alkyne-azide cycloaddition reaction (CuAAC) to selectively functionalize the internal and external surfaces of mesoporous materials. Porous silicon rugate filters with narrow line width reflectivity peaks were employed to demonstrate this selective surface functionalization approach. Hydrosilylation of a dialkyne species, 1,8-nonadiyne, was performed to stabilize the freshly fabricated porous silicon rugate filters against oxidation and to allow for further chemical derivatization via "click" CuAAC reactions. The external surface was modified through CuAAC reactions performed in the absence of nitrogen-based Cu(I)-stabilizing species (i.e., ligand-free reactions). To subsequently modify the interior pore surface, stabilization of the Cu(I) catalyst was required. Optical reflectivity measurements, water contact angle measurements, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to demonstrate the ability of the derivatization approach to selectively modify mesoporous materials with different surface chemistry on the exterior and interior surfaces. Furthermore, porous silicon rugate filters modified externally with the cell-adhesive peptide Gly-Arg-Gly-Asp-Ser (GRGDS) allowed for cell adhesion via formation of focal adhesion points. Results presented here demonstrate a general approach to selectively modify mesoporous silicon samples with potential applications for cell-based biosensing.     

1.42-fold enhancement of formate selectivity by linker conversion on the Zn-based metal organic framework catalyst

Electro-reduction of carbon dioxide(ERCO₂) is considered an effective method to alleviate the greenhouse effect and produce value-added chemicals.Achieving the dominant selectivity of Zn-based catalysts for formate remains a challenge.In this article,the ZnIn-E₁₂ catalyst is successfully prepared by solvent assisted ligand exchange(SALE) method to convert organic ligands,achieving a Faradaic efficiency of 72.28% for formate at-1.26 V vs.RHE(V_RHE),which is 1.42 ti...     

"Thiol-ene" click chemistry: a facile and versatile route for the functionalization of porous polymer monoliths

The preparation of porous polymer monoliths with dodecyl and zwitterionic functionalities via the "thiol-ene" click chemistry of thiol-containing monoliths with both hydrophobic and polar methacrylate "ene" monomers has been demonstrated. Selected separations confirmed the excellent potential of these monoliths in chromatography.     

Stepwise "click" chemistry for the template independent construction of a broad variety of cross-linked oligonucleotides: influence of linker length, position, and linking number on DNA duplex stability

Cross-linked DNA was constructed by a "stepwise click" reaction using a bis-azide. The reaction is performed in the absence of a template, and a monofunctionalized oligonucleotide bearing an azido-function is formed as intermediate. For this, an excess of the bis-azide has to be used compared to the alkynylated oligonucleotide. The cross-linking can be carried out with any alkynylated DNA having a terminal triple bond at any position of the oligonucleotide, independent of chain length or sequence with identical or nonidentical chains. Short and long linkers with terminal triple bonds were introduced in the 7-position of 8-aza-7-deaza-2'-deoxyguanosine (1 or 2), and the outcome of the "stepwise" click and the "bis-click" reaction was compared. The cross-linked DNAs form cross-linked duplexes when hybridized with single-stranded complementary oligonucleotides. The stability of these cross-linked duplexes is as high as respective individual duplexes when they were ligated at terminal positions with linkers of sufficient length. The stability decreases when the linkers are incorporated at central positions. The highest duplex stability was reached when two complementary cross-linked oligonucleotides were hybridized.     

Orthogonal approaches to the simultaneous and cascade functionalization of macromolecules using click chemistry

The development of selective chemistries that are orthogonal to the diverse array of functional groups present in many polymeric systems is becoming an important tool for the synthesis and use of macromolecules in fields ranging from biomedical devices to nanotechnology. By combining copper-catalyzed cycloaddition chemistry with other synthetic transformations such as esterification, amidation, etc., highly efficient and modular simultaneous and cascade functionalization strategies have been developed. These single-step strategies for preparing multifunctional macromolecules represent a significant advance as compared to traditional multistep approaches, and the utility of these concepts is demonstrated by selective preparation of a diverse range of orthogonally functionalized vinyl polymers.     

Diversity-oriented synthesis of a library of substituted tetrahydropyrones using oxidative carbon-hydrogen bond activation and click chemistry

Eighteen (2RS,6RS)-2-(4-methoxyphenyl)-6-(substituted ethyl)dihydro-2H-pyran-4(3H)ones were synthesized via a DDQ-mediated oxidative carbon-hydrogen bond activation reaction. Fourteen of these tetrahydropyrans were substituted with triazoles readily assembled via azide-alkyne click-chemistry reactions. Examples of a linked benzotriazole and pyrazole motif were also prepared. To complement the structural diversity, the alcohol substrates were obtained from stereoselective reductions of the tetrahydropyrone. This library provides rapid access to structurally diverse non-natural compounds to be screened against a variety of biological targets.     

Toward the syntheses of universal ligands for metal oxide surfaces: controlling surface functionality through click chemistry

A new means for functionalizing metal oxide surfaces, specifically nanoparticles, is demostrated. This process involves the design of stable ligands that bind strongly to the surface of metal oxides and can undergo further chemical modification via click chemistry, with both small molecules as well as polymers, to yield metal oxide surfaces with tailored functionality. The nanoparticles are stable and easily dispersed in both polar and nonpolar solvents, a property that is controlled by the ligand. The resultant nanoparticles were characterized by TEM, TGA, FTIR, and NMR.     

An approach for the surface functionalized gold nanoparticles with pH-responsive polymer by combination of RAFT and click chemistry

In this report, we demonstrated a novel efficient post-modification route for preparation of smart hybrid gold nanoparticles with poly(4-vinylpyridine) (P4VP) based on RAFT and click chemistry. A new azide terminated ligand was first synthesized to modify gold nanoparticles by ligand exchange reaction, and then click reaction was used to graft alkyne terminated P4VP which was prepared by RAFT onto the surface of gold nanoparticles. The functionalized hybrid gold nanoparticles were characterized by TEM, FTIR, and XPS etc. The results indicated that the P4VP was successfully grafted onto the surface of gold nanoparticles by click reaction. The surface grafting density was calculated to be about 6 chains/nm²_. In addition, the hybrid gold nanoparticles showed a pH responsive phenomenon as the pH value changed around 5.     

Novel approach to the design of potential bioactive alkaloid anabasine conjugates using click chemistry methodology

Anabasine‐containing azides and acetylenes were used as building blocks in copper(I)‐catalyzed 1,3‐dipolar cycloaddition reactions with a series of acetylenes and azides via click methodology to provide a range of anabasine conjugates being potential ligands for neuronal nicotinic acetylcholine receptors.     

Fast, easy, clean chemistry by using water as a solvent and microwave heating: the Suzuki coupling as an illustration

Water is an excellent solvent for organic chemistry and microwave heating offers a very efficient way of heating reaction mixtures. In this article, by focusing on the Suzuki reaction, it is shown how these two methods, used alone or together, can impact modern synthetic chemistry, making reactions faster, easier and cleaner.     

Lowering of the detection limit in atomic absorption spectroscopy using ensemble summation of signals obtained by means of a microsample technique

Summary The software for the ensemble summation of signals in atomic absorption spectroscopy combined with injection dosation of liquid microsamples is developed. The average of 16 realizations provides a 4-fold lowering of the detection limit of the elements as a result of improved reproducibility. The method is illustrated by the trace content determination of Cd, Mn, Ni, Ag, Zn, Fe, Se, Pb and Na.

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Herabsetzung der Nachweisgrenze In der Atomabsorptions-Spektroskopie Durch Anwendung der Ensemblesummierung im Zusammenhang mit der Mikroproben-Technik

Zusammenfassung Es wurde die Software für eine Ensemblesummierung von Signalen bei der Injektionsdosierung von flüssigen Mikroproben in der Atomabsorptions-Spektroskopie entwickelt. Bei der Ensemblesummierung von 16 einzelnen Fällen (Injektionen) wird 4mal die Nachweisgrenze herabgesetzt, was auf Grund der Verbesserung der Reproduzierbarkeit erfolgt. Die Herabsetzung der Nachweisgrenze wird am Beispiel der Elemente Cd, Mn, Ni, Ag, Zn, Pb, Fe, Se und Na gezeigt.

     

Synthesis of highly modified DNA by a combination of PCR with alkyne-bearing triphosphates and click chemistry

We report the combination of "click chemistry" with PCR by using alkyne-modified triphosphates for efficient and homogeneous labeling of DNA. A series of modified PCR products of different lengths (300, 900, and 2000 base pairs) were prepared by using a variety of alkyne- and azide-containing triphosphates and different polymerases. After intensive screening of real-time PCR methods, protocols were developed that allow the amplification of genes by using these modified triphosphates with similar efficiency to that of standard PCR. The click reaction on the highly modified PCR fragments provided conversion rates above 90 % and resulted in the functionalization of hundreds of alkynes on large DNA fragments with superb selectivity and efficiency.     

Synthesis of a [2]rotaxane incorporating a "magic sulfur ring" by the thiol-ene click reaction

The mild and highly efficient thiol-ene click reaction has been used to construct a rotaxane incorporating dibenzo-24-crown-8 (DB24C8) and a dibenzylammonium-derived thread in high yield under the irradiation of UV light. A rotaxane containing a disulfide linkage in the macrocycle was also synthesized by the thiol-ene click reaction. It has been demonstrated that the formation of the [2]rotaxane with the disulfide bond in the macrocycle occurs by a mechanism that is different to the threading-followed-by-stoppering process. The successful construction of a rotaxane directly from its constituent components, the macrocycle containing a disulfide linkage and the dibenzylammonium hexafluorophosphate salt, suggests that the space within the macrocycle incorporating the disulfide linkage is smaller than the phenyl unit and a plausible reaction mechanism has been proposed as follows: A small amount of the initiator forms two radicals upon the absorption of UV irradiation; the radicals act as a "key" to "unlock" the disulfide bond in the macrocycle. The resulting crown ether like moiety in the macrocycle is clipped around the ammonium ion center in the dumb-bell-shaped compound. The [2]rotaxane is generated upon recombination of the disulfide linkage.