Synthesis, characterization and catalytic function of a B12-hyperbranched polymer

Tahara, Keishiro; Shimakoshi, Hisashi; Tanaka, Akihiro; Hisaeda, Yoshio

doi:10.1039/b923924c

Cited by 14 publications

(20 citation statements)

References 37 publications

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“…50% of the entire weight of 3, as well as the fact that the solubility of 3 in organic solvents is different from that of the unmodified HBP, but similar to that of the monomeric B 12 1. 29,30 The peak currents of 3 increased in proportion to the square root of the scan rate over a range of scan rates from 20 to 500 mV s ¹1 as shown in Figure 1b. This good reversibility clearly indicates that a fast electron transfer proceeds by the diffusion of B 12 HBP to the electrode.…”

Section: Resultsmentioning

confidence: 94%

“…30 3: HBP having OH groups with a 1:1 composite of 2-(N,N-diethyldithiocarbamoyl)ethyl methacrylate (EMA-DC) and 2-hydroxyethyl methacrylate (HEMA) (M w = 98400, M w /M n = 7.69 determined by GPC-MALS (multi-angle light scattering)) was covalently functionalized by esterification with a vitamin B 12 General Analyses and Measurements. The UVvis absorption spectra were measured on a Hitachi U-3300 spectrometer at room temperature.…”

Section: Methodsmentioning

confidence: 99%

“…In the previous work, our interest in the immobilization of redox-and coordination-rich metal complexes on a soluble dendritic support has motivated us to prepare a covalently functionalized hyperbranched polymer with a vitamin B 12 derivative (B 12 HBP) as shown in Scheme 2. 29,30 Using a recent advanced technique for polymer syntheses followed by a modification procedure, the catalytic sites of B 12 were effectively introduced along the highly branched polymeric backbone to afford the multimetallic catalytic nanomaterial with a high density of cobalt centers.…”

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confidence: 99%

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Redox Behavior and Electrochemical Catalytic Function of B12–Hyperbranched Polymer

Tahara

Shimakoshi

Tanaka

et al. 2010

Bulletin of the Chemical Society of Japan

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The electrochemical behavior of a covalently functionalized hyperbranched polymer with a vitamin B 12 derivative (B 12 HBP) was investigated by cyclic voltammetry and UVvis spectroscopy combined with bulk electrolysis in N,Ndimethylformamide. The B 12 HBP showed excellent properties for a homogeneous catalyst such as the good accessibilities of the cobalt centers in B 12 HBP to an electrode and substrates and the maintained supernucleophilicity of the Co(I) species to alkyl halides. The cobalt-methylated B 12 HBP was newly synthesized, and its electrochemical behavior was also investigated by cyclic voltammetry. Furthermore, B 12 HBP was used as an electrochemical degradation catalyst for 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT). This work presents the first electrocatalysis study of a catalytically active transition-metal complex on a homogeneous dendritic support and investigates the suitability of the present B 12 HBP system for electrochemical dehalogenation.There has been increasing attention to the use of soluble polymers for homogeneous catalyst supports as a potential alternative to traditional solid-phase syntheses in recent years. 14 In particular, soluble branched polymers, such as dendrimers and hyperbranched polymers (HBPs), have been widely investigated as homogeneous supports for catalytically active transition-metal complexes, which are either covalently attached to the core/periphery moiety or noncovalently incorporated. 5,6 These microscopically heterogeneous and dendritic polymers offer several advantages such as their ready removal from the products, 7 good accessibilities to catalytic centers, 8 and dendritic effects on the catalyst activity/selectivity. 9,10 In other words, they can combine the advantages of homogeneous and heterogeneous catalysis as promising scaffolds which effectively organize catalytic sites on their nanosized structure but do not hinder the catalytic process. However, the application of these branched polymers to electrochemical molecular transformations represents an almost unexplored area, although the electrochemical activation of the transition-metal catalysts is a beneficial method to develop good redox catalysis systems. 11Vitamin B 12 and derivatives can acquire three formal oxidation states of cobalt, and each oxidation state has quite difference ligand accepting abilities (i.e., octahedral, square pyramidal, or square planar for Co(III), Co(II), or Co(I), respectively).12,13 Such a redox-and coordination-rich chemistry plays a critical role in the cobalamin-dependent enzymatic reactions in vivo 14,15 and in a number of chemical trans-

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Section: Resultsmentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Redox Behavior and Electrochemical Catalytic Function of B12–Hyperbranched Polymer

Tahara

Shimakoshi

Tanaka

et al. 2010

Bulletin of the Chemical Society of Japan

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“…The Helmholtz free energy minimization, on the other hand, is used when compressibility of the system is of concern. In both cases the condition of chemical equilibrium ensues: (12) In case of Helmholtz free energy the optimization yields the additional condition of mechanical equilibrium. This condition is trivial for the Gibbs energy, because it depends directly on the pressure and not on the volume.…”

Section: Phase Equilibrium Calculationsmentioning

confidence: 99%

“…Due to their architecture, HBP show a lower viscosity in melt and solution compared to their linear analogue and the rich amount of various functional groups offers a tuneable solubility in different solvents. Based on these advantages of HBP different applications have been suggested, for instance possible implementations of HBP are discussed in the field of medicine [1][2][3][4][5][6][7][8], catalysis [9][10][11][12][13], membrane materials [14][15][16][17][18][19][20], chemical engineering [21][22][23][24], sensors [25][26][27][28], thermosets [29][30][31] or as rheological modifier [32,33]. Polymeric drug delivery systems offer great opportunities to effectively control the drug release in human body [34][35][36][37][38][39][40][41][42][43][44].…”

Section: Introductionmentioning

confidence: 99%

Phase Diagrams for Systems Containing Hyperbranched Polymers

et al. 2012

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Abstract:Hyperbranched polymers show an outstanding potential for applications ranging from chemistry over nanotechnology to pharmacy. In order to take advantage of this potential, the underlying phase behaviour must be known. From the thermodynamic point of view, the modelling of these phase diagrams is quite challenging, because the thermodynamic properties depend on the architecture of the hyperbranched polymer as well as on the number and kind of present functional end groups. The influence of architecture can be taken into account via the lattice cluster theory (LCT) as an extension of the well-known Flory-Huggins theory. Whereas the Flory-Huggins theory is limited to linear polymer chains, the LCT can be applied to an arbitrary chain architecture. The number and the kind of functional groups can be handled via the Wertheim perturbation theory, applicable for directed forces between the functional groups and the surrounding solvent molecules. The combination of the LCT and the Wertheim theory can be established for the modelling or even prediction of the liquid-liquid equilibria (LLE) of polymer solutions in a single solvent or in a solvent mixture or polymer blends, where the polymer can have an arbitrary structure. The applied theory predicts large demixing regions for mixtures of linear polymers and hyperbranched polymers, as well as for mixtures made from two hyperbranched polymers. The introduction of empty lattice sites permits the theoretical investigation of pressure effects on phase behaviour. The calculated phase diagrams were compared with own experimental data or to experimental data taken from literature. OPEN ACCESSPolymers 2012, 4 73

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Applications of Electron Paramagnetic Resonance

Karunakaran¹,

Murugesan²

2018

Spin Resonance Spectroscopy

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Synthesis, characterization and catalytic function of a B12-hyperbranched polymer

Cited by 14 publications

References 37 publications

Redox Behavior and Electrochemical Catalytic Function of B12–Hyperbranched Polymer

Redox Behavior and Electrochemical Catalytic Function of B12–Hyperbranched Polymer

Phase Diagrams for Systems Containing Hyperbranched Polymers

Applications of Electron Paramagnetic Resonance

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