Magnetocaloric properties of dendrimer complexes of Fe(III) with substituted Schiff base

In dendrimer complexes of iron (III) with Schiff base (three complexes of iron (III) based on azomethine 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-2-aminopyridine, a significant magnetocaloric effect (MCE) and heat capacity was found the first time. It was found that the magnitude of MCE depends on the nature of the counter-ion of the complex. MCE were measured with a microcalorimeter over the temperature range of 278–320 K and in a magnetic induction of 0–1.0 T. The temperature dependences of the MCE dendrimer complexes of iron (III) with Schiff base were obtained for the first time. For all the samples studied, the existence of extreme temperature dependence of MCE in the range of temperatures 300–350 K, which is possibly the result of the magnetic phase transition, is shown. The correlation between the thermotropic mesomorphism with the magnetic phase transition in complexes has been established.     

Synthesis of spherical and hemispherical sugar‐containing poly(ornithine) dendrimers

A novel sugar‐containing poly(ornithine) dendrimer is synthesized for possible antigen delivery and related applications. The dendrimer contains an ornithine dendron as interior scaffolding and oligosaccharides on the periphery, which provide an attachment site for a peptide antigen. Maltose or lactose is bound to both hemispherical and spherical poly(ornithine) dendrimer generation 3 (G3) by reductive amination between its reducing end and the peripheral amino group of the dendrimer using a borane‐pyridine complex in a buffer solution at 50 °C. The degree of substitution of sugar is changed by varying the molar ratio of sugar to dendrimer. When the surface of spherical poly(ornithine) dendrimer G3 is modified by binding β‐alanine to the 16 amino groups, highly substituted maltose‐ or lactose‐β‐alanine‐poly(ornithine) dendrimer G3 is obtained in high yield after 7 days of reaction. The structures of these sugar‐containing dendrimers are characterized by NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analyses. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1400–1414, 2004     

SiO2–poly(amidoamine) dendrimer inorganic/organic hybrids

SiO₂–poly(amidoamine) (PAMAM) dendrimer hybrids were synthesized via (1) a Michael addition reaction between the dendrimer and 3‐(trimethoxysilyl) propyl acrylate, (2) the dissolution of the formed compound in methanol, and (3) the mixing of the latter solution with a methanol solution of partly hydrolyzed tetraethylorthosilicate (TEOS) and its casting on a glass substrate. ¹H NMR indicated that in the first step, 77% of the secondary amines were converted into tertiary amines when the fourth‐generation dendrimer was employed and 46% were converted when the second‐generation dendrimer was used. The final SiO₂–PAMAM dendrimer hybrids were obtained via the hydrolysis and condensation of the compound obtained via the Michael addition and the methanol solution of partly hydrolyzed TEOS. The compartmentalized structure of the hybrids due to the compartments of the dendrimers could be controlled by changing the dendrimer and the amount of TEOS. Scanning electron microscopy and transmission electron microscopy micrographs provided information about the structure of the hybrids. Like the PAMAM dendrimer, the SiO₂–PAMAM dendrimer hybrids exhibited a high metal ion complexing capacity because of the presence of the compartments of the dendrimer; they can be, however, much more easily handled, and, as demonstrated by thermogravimetric experiments, have much higher thermal resistance. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1443–1449, 2000     

Deep‐red light‐emitting phosphorescent dendrimer encapsulated tris‐[2‐benzo[b]thiophen‐2‐yl‐pyridyl] iridium (III) core for light‐emitting device applications

New deep‐red light‐emitting phosphorescent dendrimers with hole‐transporting carbazole dendrons were synthesized by reacting tris(2‐benzo[b]thiophen‐2‐yl‐pyridyl) iridium (III) complex with carbazolyl dendrons by DCC‐catalyzed esterification. The resulting first‐, second‐, and third‐generation dendrimers were found to be highly efficient as solution‐processable emitting materials and for use in host‐free electrophosphorescent light‐emitting diodes. We fabricated a host‐free dendrimer EL device with configuration ITO/PEDOT:PSS (40 nm)/dendrimer (55 nm)/BCP (10 nm)/Alq₃ (40 nm)/LiF (1 nm)/Al (100 nm) and characterized the device performance. The multilayered devices showed luminance of 561 cd/m² at 383.4 mA/cm² (12 V) for 15 , 1302 cd/m² at 321.3 mA/cm² (14 V) for 16 , and 422 cd/m² at 94.4 mA/cm² (18 V) for 17 . The third‐generation dendrimer, 17 (η_ext = 6.12% at 7.5 V), showed the highest external quantum efficiency (EQE) with an increase in the density of the light‐harvesting carbazole dendron. Three dendrimers exhibited considerably pure deep‐red emission with CIE 1931 (Commission International de L'Eclairage) chromaticity coordinates of x = 0.70, y = 0.30. The CIE coordinates remained very stable with the current density. The integration of rigid hole‐transporting dendrons and phosphorescent complexes provides a new route to design highly efficient solution‐processable materials for dendrimer light‐emitting diode (DLED) applications. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7517–7533, 2008     

Benzophenone and zinc(II) phthalocyanine dichromophores-labeled poly (aryl ether) dendrimer: synthesis,characterization and photoinduced energy transfer

A series of benzophenone chromospheres and zinc(II) phthalocyanine dichromophores labeled poly (aryl benzyl ether) dendrimer (G_n-DZnPc(BP)_8n, n = 1?2) were synthesized. Their structures were characterized by elemental analysis, ¹H NMR, IR, UV–vis and matrix-assisted laser desorption/ionization time-of-flight spectrometry (MALDI-TOF MS). Their photophysical properties were examined by steady-state and time-resolved fluorescence methods. Both the poly (aryl benzyl ether) dendrimer and BP terminal chromophores had a significant effect on photophysical properties of the zinc(II) phthalocyanine core. Time-resolved spectroscopic measurements indicated that the lifetime of benzophenone (donor) chromophore was longer than that of the zinc(II) phthalocyanine (acceptor). The fluorescence of the peripheral benzophenone chromophores was quenched by the phthalocyanine group attached to the focal point. All of these observations suggest that an intramolecular singlet energy transfer occurs in G_n-DZnPc(BP)_8n molecules. The light-harvesting abilities of these molecules increased with generations due to an increase in the number of benzophenone chromophores. The energy transfer efficiencies were ca. 0.49 and 0.68 for generations 1 and 2, respectively, and the rate constants of the singlet-singlet energy transfer were ca. 10⁸ s^?1. The rate constants changed inconspicuously with increase of dendron generations. The intramolecular singlet-singlet energy transfer is proposed to proceed mainly via a Förster-type interaction mechanism involving the dendrimer backbone as a scaffold to hold the peripheral benzophenone chromophores and the phthalocyanine core together. This dendrimer was an effective new energy transmission complex with high efficiency and could be used as a potential light-harvesting system.     

Synthesis of dicarboxylate oligosaccharide multilayer terminal functionality upon poly(lysine) dendrimer scaffolding

A reactive three‐layered dendrimer containing carboxyl groups was synthesized by the coupling of dicarboxylic acid and a highly reactive, two‐layered glycopeptide dendrimer. Lactose, maltose, or maltotriose was reacted with the poly(lysine) dendrimer in its third and fourth generations by reductive amination and afforded two‐layered glycolysine dendrimers. The reaction was conducted in a borate buffer (pH 9.0). ¹H NMR, ¹³C NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analyses were applied for the determination of the structures of the products. When an excess amount of the oligosaccharide and a long reaction time were used, the degree of substitution increased to 1.5–2.0 against an amino group. For the preparation of highly reactive, multilayered dendrimers for an antigen carrier, C6 hydroxy groups of the oligosaccharides were selectively esterified by adipic acid and suberic acid to give 6‐O‐adipoyl oligosaccharide–poly(lysine) dendrimers and 6‐O‐suberoyl oligosaccharide–poly(lysine) dendrimers. The reactivity of these multilayered dendrimers was examined by a model reaction with phenylalanine ethyl ester. The dendrimer showed high reactivity, providing phenylalanine ethyl ester–dicarboxylate oligosaccharide–poly(lysine) dendrimers with a considerably high proportion of phenylalanine residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3622–3633, 2002     

Red‐Emitting Dendritic Iridium(III) Complexes for Solution Processable Phosphorescent Organic Light‐Emitting Diodes

Functionalization of a red phosphorescent iridium(III) complex core surrounded by rigid polyphenylene dendrons with a hole‐transporting triphenylamine surface allows to prevent the intermolecular aggregation‐induced emission quenching, improves charge recombination, and therefore enhances photo‐ and electroluminescence efficiencies of dendrimer in solid state. These multifunctional shape‐persistent dendrimers provide a new pathway to design highly efficient solution processable materials for phosphorescent organic light‐emitting diodes (PhOLEDs).     

Facile fabrication of a novel high performance CO2 separation membrane: Immobilization of poly(amidoamine) dendrimers in poly(ethylene glycol) networks

Poly(amidoamine) (PAMAM) dendrimers showed high CO₂ separation properties and were successfully immobilized in a poly(ethylene glycol) (PEG) network upon photopolymerization of PEG dimethacrylate. The PAMAM dendrimer incorporation ratio was readily controlled, and a stable self-standing membrane containing up to 75 wt.% PAMAM dendrimer was obtained. The CO₂ separation properties over smaller H₂ were investigated by changing the PAMAM dendrimer content or generation and CO₂ partial pressure (ΔPCO₂$\mathrm{\Delta }{P}_{\text{C}{\text{O}}_2}$) under atmospheric conditions. Especially, a polymeric membrane containing 50 wt.% PAMAM dendrimer (0th generation) exhibited an excellent CO₂/H₂ selectivity of 500 with CO₂ permeability of 2.74 × 10⁻¹⁴ m³(STP)m/(m² s Pa) or 3.65 × 10³ barrer (1 barrer = 7.5 × 10⁻¹⁸ m³(STP)m/(m² s Pa)) when a mixture gas (CO₂/H₂: 5/95 by vol.) was fed at 25 °C and 100 kPa with 80% relative humidity. This polymeric materials are promising for a novel CO₂ separation membrane.     

Synthesis of Poly(amidoamine) Dendrimer with a Diphenyl Diselenide Core

Abstract

We succeeded in the synthesis of a novel poly(amidoamine) dendrimer having diphenyl diselenide at the core. Modification of the dendrimer diselenide by the reaction with glucono-δ-lactone in methanol gave a water-soluble dendrimer diselenide having chiral terminal groups. The structures of dendrimers were satisfactorily confirmed by MAIDI-TOF MS spectrometry, elemental analysis, and NMR spectroscopy. Interestingly, induced circular dichroism (ICD) of the interaction between the diphenyl diselenide core and D-gluconamide periphery of the dendrimer was observed at 300 nm.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT     

Lanthanum(III) and prasedymium(III) complexes with piperazine dithiosemicarbazones

Lanthanum(III) and praseodymium(III) complexes of the type [Ln(L)Cl(H₂O)]₂ (Ln = La(III) or Pr(III); LH₂ = dithiosemicarbazone ligands derived from piperazine dithiosemicarbazide and benzaldehyde, 4-nitrobenzaldehyde, and 2-methoxybenzaldehyde) have been synthesized in methanol in the presence of sodium hydroxide. The complexes have been characterized by elemental analyses, molecular weight, molar conductance, electronic absorption, IR, and ¹H and ¹³C NMR spectral studies. Nephelauxetic ratio, covalency parameter, and bonding parameter for these complexes have also been calculated. Thermal studies of the complexes have been carried out using TG, DTG, and DSC techniques. Kinetic parameters, such as apparent activation energy and order of reaction, were determined by the Coats-Redfern graphical method. The heats of reaction for different reaction steps were calculated from DSC curves. The article was submitted by the authors in English.     

Sequential functionalization of janus‐type dendrimer‐like poly(ethylene oxide)s with camptothecin and folic acid

Janus‐type dendrimer‐like poly(ethylene oxide)s (PEOs) of 1st, 2nd, and 3rd generation carrying terminal hydroxyl functions on one side and cleavable ketal groups on the other were used as substrates to conjugate folic acid as a folate receptor and camptothecin (CPT) as a therapeutic drug in a sequential fashion. The conjugation of both FA and CPT was accomplished by “click chemistry” based on the 1,3 dipolar cycloaddition coupling reaction. First, the hydroxyl functions present at one face of Janus‐type dendrimer‐like PEOs were transformed into alkyne groups through a simple Williamson‐type etherification reaction. Next, the ketals carried by the other face of the dendrimer‐like PEOs were hydrolyzed, yielding twice as many hydroxyls which were subsequently subjected to an esterification reaction using 2‐bromopropionic bromide. Before substituting azides for the bromide of 2‐bromopropionate esters just generated in the presence of NaN₃, an azido‐containing amidified FA derivative was reacted through click chemistry with alkyne functions introduced on the other face of the dendrimer‐like PEOs. A purposely designed alkyne‐functionalized biomolecule derived from CPT was conjugated to the azido functions carried by the dendritic PEOs by a second “click reaction.” In this case, twice as many CPT as FA moieties were finally conjugated to the two faces of the Janus‐type dendrimer‐like PEOs, the numbers of folate and CPT introduced being 2 and 4, 4 and 8, and 8 and 16 for samples of 1st, 2nd, and 3rd generation, respectively (route A). An alternate route for functionalizing the dendrimer‐like PEO of 1st generation consisted, first, in conjugating the azido‐containing CPT onto the alkyne groups present on one face of the dendritic PEO scaffold. The alkyne‐functionalized FA was further introduced by click chemistry after the bromides of 2‐bromopropionate esters were chemically transformed into azido groups. The corresponding prodrug thus contains 2 CPT and 4 FA external moieties (route B). Every reaction step product was thoroughly characterized by ¹H NMR spectroscopy. A preliminary investigation into the water solution properties of these functionalized dendritic PEOs is also presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Alkylenedithiophosphate derivatives of arsenic(III), antimony(III) and bismuth(III)

Tris(alkylenedithiophosphates) of arsenic(III), antimony(III) and bismuth(III),

have been synthesized by the reactions of alkylenedithiophosphoric acids with metal oxides and chlorides and of their ammonium salts with metal chlorides in suitable solvents. Mixed chloride alkylenedithiophosphates of arsenic(III) and antimony(III),

have been obtained by the reactions of metal chlorides with ammonium alkylenedithiophosphates at 1 : 1 and 1 : 2 molar ratios or alternatively by the co-disproportionations reactions of metal chlorides with metal tris(alkylenedithiophosphates) at different (2 : 1 and 1 : 2) molar ratios. These new compounds have been characterized by elemental analyses, molecular weight measurements and spectroscopic (IR, and ¹H and ³¹P NMR) data. Chelated structures with bidentate alkylenedithiophosphate groups have been proposed for all these derivatives.     

Poly(amidoamine) dendrimer‐coated magnetic nanoparticles for the fast purification and selective enrichment of glycopeptides and glycans

Glycosylated proteins modulate various important functions of organisms. To reveal the functions of glycoproteins, in‐depth characterization studies are necessary. Although mass spectrometry is a very efficient tool for glycoproteomic and glycomic studies, efficient sample preparation methods are required prior to analyses. In the study, poly(amidoamine) dendrimer‐coated magnetic nanoparticles were presented for the specific enrichment and fast purification of glycopeptides and glycans. The enrichment and purification performance of the developed method was evaluated both at the glycopeptide, and the glycan level using several standard glycoprotein digests and released glycan samples. The poly(amidoamine) dendrimer‐coated magnetic nanoparticles not only showed selective affinity (Immunoglobulin G/Bovine Serum Albumin, 1/10 by weight) to glycopeptides and released glycans but also good sensitivity (0.4 ng/µL for Immunoglobulin G) for glycoproteomic and glycomic applications. Thirty‐five glycopeptides of Immunoglobulin G were detected after enrichment with poly(amidoamine) dendrimer‐coated magnetic nanoparticles. In addition, 55 ¹⁸O tagged deamidated glycopeptides belonging to human plasma glycoproteome were confirmed. Finally, fifty 2‐aminobenzoic acid, and 30 procainamide‐labelled human plasma N‐glycans released from human plasma glycoproteins were determined after purifications. The results indicate that the proposed enrichment and purification method using poly(amidoamine) dendrimer‐coated magnetic nanoparticles could be simply adjusted to sample preparation methods.     

Synthesis of cationic gold(III) complexes using iodine(III)

Abstract

We report the synthesis and characterization of cationic Au(III) complexes supported by nitrogen-based ligands. The syntheses are achieved by reacting Au(I) complexes [Au(N-Me-imidazole)₂]⁺ and [Au(pyridine)(NHC)]⁺ with iodine(III) reagents PhI(OTf)(OAc) and [PhI(pyridine)₂]²⁺ yielding a series of cationic gold(III) complexes. In contrast, reactions of phosphine ligated gold(I) complexes with iodine(III) reagents results in the oxidation of the phosphine ligand.     

Structural analysis of poly(amidoamine) dendrimer immobilized in crosslinked poly(ethylene glycol)

Polymeric membranes comprised of poly(amidoamine) (PAMAM) dendrimer immobilized in a poly(ethylene glycol) (PEG) network exhibit an excellent CO₂ separation selectivity over H₂. The CO₂ permeability increases with PAMAM dendrimer concentration in the polymeric membrane and becomes 500 times greater than H₂ permeability when the dendrimer content was 50 wt % at ambient conditions (5 kPa of CO₂ partial pressure). However, the detailed morphology of the membrane has not been discussed. The immiscibility of PAMAM dendrimer and PEG matrix results in phase separation, which takes place in a couple of microns scale. Especially, laser scanning confocal microscope captures a 3D morphology of the polymeric blend. The obtained 3D reconstructions demonstrate a bicontinuous structure of PAMAM dendrimer‐rich and PEG‐rich phases, which indicates the presence of PAMAM dendrimer channel penetrating the polymeric membrane, and CO₂ will preferentially pass through the dendrimer channel. In addition, Fourier transform of the 3D reconstructions indicates the presence of a periodic structure. An average size of the dendrimer domain calculated is 2–4 μm in proportion to PAMAM dendrimer concentration. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Silsesquioxane Modified with PAMAM Dendrimer and a Bimetallic Complex for Electrochemical Detection of Ascorbic Acid

Octakis(3-chloropropyl)octasilsesquioxane (S) was organofunctionalized with the PAMAM Dendrimer G.0 (SPD). After functionalization, silsesquioxane interacts with copper chloride and subsequently with potassium hexacyanoferrate (III) to produce the structure CuHSPD. The silsesquioxane functionalized with the PAMAM dendrimer (SPD) and the obtained novel hybrid composite (CuHSPD) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The CuHSP voltammogram showed two well-defined redox pairs with E^θ′= 0.27 and 0.74 V, that are assigned to the Cu^I/Cu^II and Fe^II(CN)₆/Fe^III(CN)₆ redox pairs, respectively. The graphite paste electrode containing CuHSPD allowed the electrocatalytic determination of ascorbic acid using various electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, and chronoamperometry.     

Polarographic studies of catalytic reduction of hydrogen in Cr(VI)−As(III) and Cr(III)—As(III) systems

In the presence of traces of Cr(VI) or Cr(III) ions in ammonia or borate buffers containing the As(III) ions a catalytic hydrogen wave arises in the dc polarogram. It was established that the complex Cr(H₂AsO₃)_n^+3?n is formed in the solution, and that its reduced form adsorbed at DME is of catalytic activity. The wave can be employed for the determination of low concentrations (2×10^?8×10^?7M) of Cr(VI) and Cr(III) ions.     

Iron(III) dihydrogenphosphate(I)

The structure of rhombohedral (R) iron(III) tris­[di­hydrogen­phosphate(I)] or iron(III) hypophosphite, Fe(H₂PO₂)₃, has been determined by single‐crystal X‐ray diffraction. The structure consists of [001] chains of Fe³⁺ cations in octa­hedral sites with symmetry bridged by bidentate hypophosphite anions.     

基于双“click”反应的树枝状化合物的一锅法合成

将叠氮和炔基之间Cu(I)催化的“click”反应以及蒽和马来酰亚胺之间的Diels-Alder反应相结合, 采用“一锅法”技术合成出结构完美且外围含有亲水性寡聚乙二醇(OEG)链段的树枝状化合物4, 产率为75%. 利用核磁共振氢谱、碳谱、紫外、荧光光谱以及MALDI-TOF质谱等对产物进行了表征与分析, 并利用凝胶渗透色谱(GPC)对其纯度进行了测试.     

Preparation and adsorption properties of crosslinked polystyrene-supported low-generation diethanolamine-typed dendrimer for metal ions

Two novel chelating resins, polystyrene supported G1.0 diethanolamine-typed dendrimer (PS-DEA) and G2.0 diethanolamine-typed dendrimer (PS-(DEA)₂), were prepared by anchoring low-generations diethanolamine-typed dendrimer into crosslinked polystyrene in this paper. Fourier transform-infrared spectra (FTIR), scanning electron microscopy (SEM) and elemental analysis were employed to character their structures. The results of adsorption for metal ions showed that the resins had good adsorption capacities for Cu²⁺, Ag⁺ and Hg²⁺, especially PS-DEA for Cu²⁺. The adsorption kinetics and adsorption isotherms of PS-DEA for Cu²⁺ and PS-(DEA)₂ for Hg²⁺ were studied. The results showed that the adsorption kinetics of the two resins can be modeled by pseudo second-order rate equation wonderfully and Langmuir and Freundlich equations could well interpret the adsorption of PS-(DEA)₂ for Hg²⁺ and PS-DEA for Cu²⁺, respectively. The adsorption mechanism of the resins for Cu²⁺ was confirmed by X-ray photoelectron spectroscopy (XPS).