The crystal structure and IR spectra of μ-(bipyrimidine-N1,N1′,N5,N5′)-bis[(azido-N1)(methanol)(bipyrimidine-N1,N1′)copper(II)] bis(triflate) bis(methanol)

The structure of the title compound [Cu₂(bipym)₃(N₃)₂(CH₃OH)₂](CF₃SO₃)₂(CH₃OH)₂ has been determined by X-ray diffraction. The crystals are triclinic, space group P1, with a = 8.1844(5), b = 11.0253(6), c = 12.9089(7) Å, = 80.249(4), , = 74.933(5), = 74.001(4)°, and Z = 1. The structure consists of a dinuclear Cu(II) unit formed of two didentate bipym ligands, one bis-didentate bipym ligand, two azido anions, and two coordinating methanol molecules. The Cu(II) atom is elongated tetragonally surrounded by two nitrogens of the didentate bipym ligand, one nitrogen of the bis-didentate ligand, and one nitrogen of the azido anion forming the equatorial plane with one nitrogen of the bis-didentate ligand and an oxygen atom of the methanol molecule as the axial atoms. A noncoordinating triflate anion and an additional methanol molecule are also in the crystal lattice and have a hydrogen bond distance of 2.801(3) Å with an angle of 157(4)°. The cations link by O – H ··· N bonds into infinite chains running in the c-direction.     

Designing Injectable,Covalently Cross‐Linked Hydrogels for Biomedical Applications

Hydrogels that can form spontaneously via covalent bond formation upon injection in vivo have recently attracted significant attention for their potential to address a variety of biomedical challenges. This review discusses the design rules for the effective engineering of such materials, and the major chemistries used to form injectable, in situ gelling hydrogels in the context of these design guidelines are outlined (with examples). Directions for future research in the area are addressed, noting the outstanding challenges associated with the use of this class of hydrogels in vivo.

     

Molecular Weight Control in Emulsion Polymerization by Catalytic Chain Transfer: A Reaction Engineering Approach

Summary: For the application of catalytic chain transfer in (mini)emulsion polymerization, catalyst partitioning and deactivation are key parameters that govern the actual catalyst concentration at the locus of polymerization and consequently the final molecular weight distribution. A global model, based on the Mayo equation, catalyst partitioning and deactivation was developed. The influence of several reaction parameters on the instantaneous number average molecular weight was quantified.     

Graft modification of starch nanoparticles with pH-responsive polymers via nitroxide-mediated polymerization

The grafting to approach and nitroxide-mediated polymerization (NMP) were used to graft modify starch nanoparticles (SNP) with pH-responsive polymers. SG1-capped poly(2-(dimethylamino)ethyl methacrylate-co-styrene), P(DMAEMA-co-S), and poly(2-(diethylamino)ethyl methacrylate-co-styrene), P(DEAEMA-co-S), with relatively low dispersity and high degree of livingness was synthesized in bulk via NMP using a commercial available alkoxyamine. These macroalkoxyamines were then grafted to vinyl benzyl-functionalized SNP (SNP-VBC) to obtain pH-responsive materials. The grafted SNP were characterized by proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis confirming the successful synthesis of these new materials. Low grafting efficiencies (~6%) were observed for both SNP-grafted materials with pH-responsive polymers, as expected when using the grafting to approach. The pH-responsiveness of SNP-g-P(DMAEMA-co-S) and SNP-g-P(DEAEMA-co-S) was confirmed by measuring the ζ-potential at different pH values. At acidic conditions (pH 3–6) the grafted materials were protonated and exhibited positive ζ-potential, whereas at basic conditions (pH 10–13) the same grafted materials were deprotonated and exhibited negative ζ-potential.     

High‐Silica Zeolite SSZ‐61 with Dumbbell‐Shaped Extra‐Large‐Pore Channels

The synthesis of the high‐silica zeolite SSZ‐61 using a particularly bulky polycyclic structure‐directing agent and the subsequent elucidation of its unusual framework structure with extra‐large dumbbell‐shaped pore openings are described. By using information derived from a variety of X‐ray powder diffraction and electron microscopy techniques, the complex framework structure, with 20 Si atoms in the asymmetric unit, could be determined and the full structure refined. The Si atoms at the waist of the dumbbell are only three‐connected and are bonded to terminal O atoms pointing into the channel. Unlike the six previously reported extra‐large‐pore zeolites, SSZ‐61 contains no heteroatoms in the framework and can be calcined easily. This, coupled with the possibility of inserting a catalytically active center in the channel between the terminal O atoms in place of H⁺, afford SSZ‐61 intriguing potential for catalytic applications.