Terminal OH Groups Research Articles

Corrigendum: Palladium‐Supported Boron‐Doped Hollow Carbon Spheres as Catalysts for the Solvent‐free Aerobic Oxidation of Alcohols

The chemical formulae of the reactants in entries 1–6, Table 2 were missing a CH2 group adjacent to the terminal OH group and the reactant and product formulae in entry 7 were incorrect. The correct formulae can be seen in Table 2 below. The authors apologise for this oversight. Entry Reactant Product Conversion [%] t [h] Selectivity [%] 1 99 5 99 2 85 12 99 3 89 12 99 4 88 12 99 5 100 12 99 6 100 2 85 7 100 4 98

PH-responsive destabilization and facile bioconjugation of new hydroxyl-terminated block copolymer micelles

New hydroxyl-terminated amphiphilic block copolymers (HO-ABPs) having pendant t-butyl groups for pH-responsiveness and terminal OH groups for bioconjugation are reported. These HO-ABPs consist of hydrophilic poly(oligo(ethylene oxide) monomethyl ether methacrylate) and hydrophobic poly(t-butyl methacrylate) blocks and were synthesized by a consecutive atom transfer radical polymerization in the presence of an OH-terminated bromine initiator. Aqueous self-assembly of HO-ABPs resulted in colloidally stable micellar aggregates being capable of encapsulating hydrophobic guest molecules. They were nontoxic to cells and destabilized in response to low pH. A facile bioconjugation of HO-ABP micelles for active targeting is demonstrated by conjugation with biotin (vitamin H) and competitive assay exhibiting >93% ABP chains conjugated with biotin in each micelle. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

First example of bidentate coordination of the octahedral rhenium(III) cluster anion to a 3d-transition metal ion: Assembly of 2D coordination network [{Cu(NH3)3}2{Re6S8(OH)4(μ-OH)2}]·8H2O

A new 2D coordination polymer, [{Cu(NH3)3}2{Re6S8(OH)4(μ-OH)2}]·8H2O (1), has been prepared as a result of reactivity studies of the octahedral rhenium cluster anion [Re6S8(OH)6]4− in a system containing Cu2+ cations in aqueous ammonia. The compound was characterized by means of IR spectroscopy, thermal analysis, elemental analysis and single-crystal X-ray diffraction analysis. The structure determination revealed the presence of neutral layers containing Cu2+ cations surrounded by three NH3 molecules, located midway between two different [Re6S8(OH)6]4− cluster anions. The cluster anion displays an unprecedented bidentate coordination to Cu2+, occurring via the μ3-S ligand (Cu⋯S, 2.996(3)Å) and O atom of a terminal OH group (Cu–O, 1.986(7)Å). The resultant Cu(II) coordination environment can be described as a stretched octahedral geometry (4+2).

Synthesis and thiol‐responsive degradation of polylactide‐based block copolymers having disulfide junctions using ATRP and ROP

A new method to synthesize a variety of well‐controlled polylactide (PLA)‐based block copolymers having disulfide linkages at block junctions (PLA‐ss‐PATRPs) was investigated. The method uses a combination of ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP) that initiates the synthesis of a new disulfide‐labeled double‐head initiator having both terminal OH and Br groups (HO‐ss‐iBuBr). The amount of tin catalyst and polymerization time significantly influenced the control of ROP initiated with HO‐ss‐iBuBr. A series of ATRP of various methacrylates as well as acrylate and styrene in the presence of the resulting PLA‐ss‐iBuBr macroinitiators proceeded in a living manner. These well‐controlled PLA‐ss‐PATRPs were further characterized for thermal properties using differential scanning calorimetry and thiol‐responsive degradation upon the cleavage of disulfide linkages. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym. Chem. 2013, 51, 3071–3080

Role of Water in Methanol Photochemistry on Rutile TiO2(110)

Photochemistry of the molecularly and dissociatively adsorbed forms of methanol on the vacuum-annealed rutile TiO2(110) surface was explored using temperature-programmed desorption (TPD) both with and without coadsorbed water. Methoxy, and not methanol, was confirmed as the photochemically active form of adsorbed methanol on this surface. UV irradiation of methoxy-covered TiO2(110) led to depletion of the methoxy coverage and to formation of formaldehyde and a surface OH group. Coadsorbed water did not promote either molecular methanol photochemistry or thermal decomposition of methanol to methoxy. However, terminal OH groups (OHt), prepared by coadsorption of water and oxygen atoms, thermally converted molecularly adsorbed methanol to methoxy at 120 K thus enabling photoactivity. While chemisorbed water molecules had no influence on methoxy photochemistry, water molecules hydrogen-bonded in the second layer to bridging oxygen (Obr) sites inhibited methoxy photodecomposition to formaldehyde. From this, we...

Rheology and Crystallization of Long-Chain Branched Poly(l-lactide)s with Controlled Branch Length

A series of long-chain branched poly(l-lactide)s (LCB-PLAs) with controlled branch length were prepared by a simple and efficient method through a combination of ring-opening polymerization (ROP) of l-lactide and a coupling reaction between the terminal OH groups of the PLA prepolymers and the NCO groups of HDI. The influences of reaction conditions on the synthesis of the LCB-PLAs were investigated, and the structures of the resultant LCB-PLAs were characterized by 1H NMR spectroscopy and SEC-MALLS. By adjusting the degree of polymerization and the composition of the prepolymers, LCB-PLAs with different branch densities and molecular weights between branch points were obtained. The effect of macromolecular chain branching on the rheology and crystallization of PLA was also investigated. The LCB structure contributed to the enhancement of the zero-shear viscosity, complex viscosity, storage modulus, melt strength, and strain hardening under elongational flow. Thermal behavior indicated that the branch structure resulted in a short nucleation induction period and more rapid crystallization, which can be a guarantee of high-strength foams.

Radiolysis of Water on ZrO2 Nanoparticles

The radiolysis of water adsorbed on the surface of ZrO2 nanoparticles has been examined using a variety of spectroscopic techniques. Irradiations were performed with fast electrons, γ rays, and 5 MeV helium ions. Infrared spectroscopic analysis of the surface reveals little change in the surface stoichiometry, which probably indicates the relative insensitivity of this technique to the doses given. X-ray photoelectron spectroscopy reveals a loss in the relative number of terminal OH groups on the surface with radiolysis. The maximum production of excess H2 is found when a single water layer or less is adsorbed on the terminal OH surface layer. Little or no H2 seems to come from the surface-bound OH groups.

Heteronuclear alkali metal bis(μ-trihydroxyglutarato)dihydroxodigermanates(IV): The crystal and molecular structure of K4[Ge2(μ-Thgl)2(OH)2] · 4H2O

Heterometallic potassium and sodium trihydroxyglutaratogermanates of the formulas K4[Ge2(μ-Thgl)2(OH)2] · 4H2O (I) and Na4[Ge2(μ-Thgl)2(OH)2] · 5H2O (II) (H5Thgl is trihydroxyglutaric acid) were obtained for the first time and characterized by elemental analysis, X-ray powder diffraction, thermogravimetry, and IR spectroscopy. Complex I was examined by single-crystal X-ray diffraction. The crystals are triclinic; a = 7.5933(15) A, b = 7.628(4) A, c = 10.516(4) A, α = 104.01(3)°, β = 101.041(17)°, γ = 97.50(3)°, V = 570.0(3) A3, Z = 1, space group \(P\bar 1,R\bar 1 = 0.0479\) for 2848 reflections with I > 2σ (I). Complex I is made up of the centrosymmetric dimeric complex anions [Ge2(μ-Thgl)2(OH)2]4−, the potassium cations, and water molecules of crystallization. In the anion, the two Ge atoms are bridged by two fully deprotonated ligands Thgl5−. The coordination polyhedron of the Ge(IV) atom is a distorted trigonal bipyramid. Its equatorial plane is made up of the O atom of the terminal OH group (Ge-O…OH, 1.760(2) A) and the O atoms of two alcohol groups of two ligands Thgl5− (av. Ge-Oalc, 1.797(2) A; the angles OeqGe(1)Oeq, 110.12°–137.11°). The axial positions are occupied by the O atom of the alcohol group (Ge-Oalc, 1.853(2) A) and the carboxyl O atom of one carboxylate group (Ge-Ocarb, 1.944(2) A) of two symmetry-related ligands Thgl5−. The angle OaxGeOax is 163.68(10)°. The second carboxylate group of the ligand Thgl5− is not coordinated to the Ge atom. The coordination numbers of the cations K(1)+ and K(2)+ are seven and nine, respectively (K(1)-O, 2.685–2.889 A; K(2)-O, 2.675–3.262 A). In the crystal, the structural units are united into a three-dimensional framework.

Synthesis of tadpole polymers via triple click reactions: Copper-catalyzed azide-alkyne cycloaddition, diels-alder, and nitroxide radical coupling reactions

We designed a trifunctional initiator (3) containing anthracene, bromide, and OH functionalities and subsequently used as an initiator in atom transfer radical Polymerization (ATRP) of styrene to yield linear polystyrene (PS) with α-anthracene, OH, and ω-bromide terminal groups, of which bromide is later transformed into azide to result in the linear anthracene-, OH-, and azide-terminated PS (l-α-anthracene-OH-ω-azide-PS). The copper-catalyzed azide–alkyne cycloaddition reaction between l-α-anthracene-OH-ω-azide-PS and α-furan-protected-maleimide-ω-alkyne linkage, 4 afforded the linear anthracene-, OH-, and maleimide-terminated PS. The cyclization via intramolecular Diels–Alder click reaction of this linear PS and the subsequent conversion of the hydroxyl into bromide resulted in the cyclic PS with one bromide located on the ring, (c-PS)-Br. Finally, the c-PS-Br was clicked with either well-defined tetramethylpiperidine-1-oxyl-terminated poly(ethylene glycol) (PEG) or poly(ε-caprolactone) (PCL) yielding the tadpole polymer, (c-PS)-b-PEG or (c-PS)-b-PCL. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Effect of the degree of branching on the glass transition temperature of polyesters

Glass transition temperature dependence on the branching degree can be empirically estimated by excluding additional effects on this parameter as molecular weight distribution, end group interactions or crystallization. In this communication aliphatic–aromatic polyesters with a well defined degree of branching between 0% (linear) and 50% (hyperbranched) are investigated by differential scanning calorimetry. The hydrogen bonding effect of the OH-terminal groups was successfully extracted from the pure branching effect by protection of the end-functionalities. Fractionation of samples with variation of the branching degree and end-functionalities led to series of narrowly distributed molar masses. The dependence of the molecular weight on the glass transition temperature for different branching degrees was calculated and compared for polar and non-polar end groups.

Characteristics of the charge transfer surface complex on titanium(iv) dioxide for the visible light induced chemo-selective oxidation of benzyl alcohol

This paper deals with the oxidation of benzyl alcohol by O2 on pure TiO2 under visible light irradiation, and it was found that the benzyl alcohol is converted into benzaldehyde with high selectivity (>99%). In order to understand the origins of the visible light induced photocatalysis, surface characterizations of the charge transfer complex formed by the interaction of benzyl alcohol with the TiO2 was extensively performed by investigating the effect of heat-treatment on TiO2 or its chemical modification with hydrofluoric acid. Moreover, the study of the kinetic isotope effect (KIE) for the oxidation of benzyl alcohol showed that the α-deprotonation from benzyl alcohol is the rate determining step (RDS), the process of which is assisted by the terminal OH groups of TiO2. Photo-electrochemical investigations were also incorporated to demonstrate the reaction mechanism behind the visible light induced photocatalytic reaction.

Bis(citrato)hydroxogermanic(IV) acid dimer [H5O2][Ge(H2Cit)(H2.5Cit)(OH)]2 · 2CH3COOH · 2H2O: Synthesis, properties, and crystal and molecular structure

Bis(citrato)hydroxogermanic(IV) acid was obtained for the first time in the complex [H5O2][Ge(H2Cit)(H2.5Cit)(OH)]2 · 2CH3COOH · 2H2O (H4Cit is citric acid). The complex was characterized by chemical analysis, X-ray powder diffraction, TGA, and IR spectroscopy. Complex I was studied by X-ray crystallography. The crystals are triclinic; a = 10.0651(4) A, b = 10.1918(4) A, c = 10.5838(4) A, α = 85.0110(10)°, β = 85.2170(10)°, γ = 86.7670(10)°, V = 1076.50(7) A3, Z = 1, space group \(P\bar 1\), R1 = 0.0353 for 5709 reflections with I > 2σ(I). Complex I is composed of centrosymmetric dimeric complex anions [Ge2(H2Cit)2(H2.5Cit)2(OH)2]−, dioxonium cations [H5O2]+, and acetic acid and water molecules of crystallization. The coordination polyhedron of the Ge atom is a trigonal bipyramid. Its equatorial plane comprises two O atoms of the deprotonated alcohol groups of two ligands H2Cit (A) and H2.5Cit (B) and the O atom of the terminal OH group (Ge-O, 1.7585–1.7754 A; OeqGe(1)Oeq, 116.26°–127.64°). The axial positions are occupied by the carboxy O atom of the deprotonated carboxylate group of the α branch of ligand A (α-Ge-O(C)(carb), 1.8882(12) A)) and the carbonyl O atom of the hemiprotonated acetate α branch of ligand B (α-Ge-O(C) 1.9615(12) A, O(1)Ge(1)O(8) 170.47(5)°). In structure I, the complex dianion, the cation, and acetic acid and water molecules are united through hydrogen bonds into a three-dimensional framework.

Chain extension of adipic acid and (or) succinic acid/butanediol polyesters with 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoylbiscaprolactamate combined chain extenders

AbstractThis paper provided an easy and flexible method to synthesize high molecular weight polyesters by polycondensation and chain extension. Low molecular weight polybutylene adipate, polybutylene succinate, and poly(butylene succinate‐co‐butylene adipate) (PBSA) were synthesized through melt condensation polymerization from adipic acid and/or succinic acid with butanediol. The prepolyesters obtained had different amount of COOH and OH terminal groups. Chain extension of them was carried out at 180–240°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The influencing factors of the chain extension were studied. At the optimal conditions, chain‐extended polybutylene adipate with Mn up to 39,100, polybutylene succinate with intrinsic viscosity of 0.99 dl/g, and PBSA with intrinsic viscosity from 0.73 to 0.81 dl/g were synthesized. The chain‐extended polyesters were characterized by IR spectrum, 1H NMR spectrum, differential scanning calorimetry, thermogravimetric analysis (TGA), wide angle X‐ray scattering, and tensile test. The thermal analysis showed that chain extension often led to slight decrease of the regularity, the crystallinity, and the melting point. This deterioration of the properties is not harmful enough to impair their thermal properties and obstruct them from being used as biodegradable thermoplastics. The TGA showed that the chain‐extended polyesters were stable with initial decomposition temperature over 354.7°C. The tensile strength of the chain extended PBS and PBSAs with butylene adipate units less than 20 mol% was in the range of 18.95–31.22 MPa. Copyright © 2010 John Wiley & Sons, Ltd.

Isoprenoid glycerol dialkanol diethers: A series of novel archaeal lipids in marine sediments

We report a new series of archaeal lipids, widespread in marine sediments and tentatively assigned as isoprenoid glycerol dialkanol diethers (GDDs). They are structural analogs of isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs), with one glycerol unit missing and with each biphytanyl moiety possessing a terminal OH group. Identification is based on molecular formulae determined from accurate mass measurement and interpretation of mass spectral fragmentation patterns. Acetylation of GDD-0 confirmed the presence of three OH groups, and ether cleavage and reduction of the products afforded two biphytanyl chains. Tests of different protocols for both extraction and acid hydrolysis indicate that GDDs were not formed during sample preparation. The co-existence of GDDs and GDGTs in 12 selected marine sediment samples of varying origin showed that the ring distribution in these two ether lipid pools is related and implies that the two compound classes share a common biological source. The presence of isoprenoid GDDs is possibly linked to the occurrence of biphytane diols in marine sediments, where both GDD and diol can be either biosynthetic intermediates or degradation products, and supports the recently proposed fossil lipid recycling by benthic archaea (Takano, Y., Chikaraishi, Y., Ogawa, O.N., Nomaki, H., Morono, Y., Inagaki, F., Kitazato, H., Hinrichs, K.-U., Ohkouchi, N., 2010. Sedimentary membrane lipids recycled by deep-sea benthic archaea. Nature Geoscience 3, 858–861). GDD core lipid was detected in a culture of Methanothermococcus thermolithotrophicus, suggestive of a potential biological function for these compounds, but no intact polar lipids (IPLs) containing GDDs as core lipids have been detected to date.

Biodegradable Block Copolymer Micelles with Thiol-Responsive Sheddable Coronas

Novel sheddable micelles having hydrophilic coronas capable of being shed from biodegradable polylactide (PLA) cores by the cleavage of disulfide linkages in response to thiols were prepared by aqueous micellization of PLA-based amphiphilic block copolymers functionalized with disulfides at block junctions. These well-defined copolymers were synthesized by a combination of ring-opening polymerization and atom transfer radical polymerization in the presence of a new disulfide-functionalized double-head initiator having both terminal OH and Br groups. (1)H NMR and GPC results indicate that both polymerizations were well-controlled with molecular weight distribution as low as M(w)/M(n) < 1.2. Aqueous micellization to form core/shell micelles with disulfides at the interface of PLA cores and hydrophilic coronas and their thiol-responsive degradation were investigated. In the presence of water-soluble thiols, disulfide linkages in the micelles were cleaved and hydrophilic coronas were lost, causing PLA cores to precipitate due to the loss of colloidal stability. In a biomedical perspective, the new sheddable micelles were not cytotoxic and hence biocompatible.

Gas–Surface Scattering Dynamics of CO2, NO2, and O3in Collisions with Model Organic Surfaces

High-energy (70 kJ/mol) molecular beams of CO(2), NO(2), and O(3) were scattered from long-chain methyl (CH(3)-), hydroxyl (OH-), and perfluoro (CF(3)(CF(2))(8)-, or F-) ω-functionalized alkanethiol self-assembled monolayers (SAMs) on gold to study the dynamics of energy exchange and thermal accommodation of atmospherically important triatomic molecules on model organic surfaces. Overall, the extent of energy transfer in gas collisions with all of the surfaces studied was substantial. Specifically, the triatomics scatter from each surface only after dissipating greater than 80% of their incident energy. Furthermore, although the OH-SAM is a more rigid surface, the extent of energy transfer and accommodation of these molecules to the CH(3)- and OH-SAMs were approximately the same. The similar scattering dynamics are likely due to significant gas-surface attractive forces between the triatomics and the OH terminal groups, which compensate for the rigidity of this monolayer. In contrast to the OH- and CH(3)-SAMs, the dominant pathway in collisions of the gases with the F-SAM was impulsive scattering. The portion of molecules that accommodated (<40%) to the F-SAM was about half of the amount that accommodated (∼70%) to the CH(3)- and OH-SAMs. Although differences in the surface properties had a significant effect on the dynamics, variances in the chemical and physical properties of the three gases, CO(2), NO(2), and O(3), were found to have little effect on the extent of energy transfer and accommodation for collisions with any one surface.

Poly-dioxybiphenyl phosphazene random copolymers with pendant 3-hydroxy-propyl groups and polycaprolactone branches

The polyphosphazenes {[NP(O 2C 12H 8)] 0.75[NP(O–C 6H 4–CH 2–CH 2–CH 2–OH)(O–C 6H 5)] 0.25} n and {[NP(O 2C 12H 8)] 0.75[NP(O–C 6H 4–(CH 2–CH 2–CH 2–OH)) 2] 0.25} n , having pendant –OH groups, have been synthesized by the direct reaction of the intermediate {[NP(O 2C 12H 8)] 0.75[NP(Cl) 2] 0.25} n with the heterobifunctional reagent HO–C 6H 4–(CH 2) 3OH in the presence of Cs 2CO 3 which specifically activates the phenolic OH in the presence of the alkylic hydroxyl. The Sn(Oct) 2 promoted ring-opening polymerization of ɛ-caprolactone at 110 °C on the terminal OH groups gave well defined polycaprolactone (P-CL) branched polyphosphazenes in good yield. The effects of the branching on the crystallization behaviour as well as the thermal stability of the new polymers have been studied.

Dissociation of methanol on hydroxylated TiO 2-B (1 0 0) surface: Insights from first principle DFT calculation

The adsorption of methanol on hydroxylated TiO 2-B (1 0 0) surface with bridging and terminal hydroxyl groups has been studied by first principle calculations. On both clean and hydroxylated surfaces with bridging OH group (OH br), the O–H bond scission is the most favorable dissociation of methanol and the C–O bond scission is also feasible. This indicates the OH br has little influence on the adsorption of methanol. The terminal OH group (OH t) plays a major role in the C–H scission of methanol, which is important for the applications associated with the direct use of hydrogen, such as in situ hydrogenation, and hydrogen generation via the photocatalytic reaction. The dissociative adsorption of methanol via C–H scission, which is an endothermic adsorption on other TiO 2 surfaces, is identified as exothermic adsorption with adsorption energy in the range of −1.54 eV to −1.91 eV around OH t on TiO 2-B (1 0 0) surface. The lowest activation barrier for C–H scission is ∼0.80 eV, which is lower than the release heat of molecular adsorption. Moreover, the hydrogen atoms in methanol are easily transferred to the OH t and then move to nearby O 2c sites to regenerate the hydroxyl group. This proton migration process could result in extra stable chemi-sorption of methanol with an adsorption energy as low as −2.23 eV, which is above twice that of methanol molecularly adsorbed on the surface. Thus, the proton channel feature of OH t on the surface is borne out by our calculations.

A liquid-crystalline fullerene–oligophenylenevinylene dyad which displays columnar mesomorphism

The design, synthesis and liquid-crystalline properties of a family of hybrid compounds which are built from rod-like (oligophenylenevinylene) and disc-like [poly(benzyl ether)] units are reported. All compounds form columnar phases within broad temperature ranges; the mesophases are stable even below room temperature. Weak photovoltaic effect was observed for the C60–OPV dyad. For the molecule having a terminal OH group, frustration of the hexagonal packing was observed and gave rise to a rare phase sequence. For this material, a columnar phase with trigonal symmetry and doubling of the crystallographic lattice was found below the hexagonal columnar phase.

Phase behaviour of hyperbranched polyesters and polyethers with modified terminal OH groups in supercritical solvents

Hyperbranched polyethers and polyesters have been synthesized, and their phase behaviour in carbon dioxide and light hydrocarbons explored as a function of concentration and temperature. The synthesis includes modifications of the terminal OH groups with aliphatic carboxylic acids derivatives, trimethylchlorosilane, and trifluoroacetic acid anhydride. Modified polyesters show good solubility in carbon dioxide, ethane and propane. The comparison with the literature data shows that the silane and fluorinated derivatives of the hyperbranched polyesters are soluble in carbon dioxide to the same extent as the most CO 2-philic polymeric materials synthesized till now. It seems that the nature of the end groups is an important factor that influences phase equilibria of hyperbranched macromolecules in supercritical solvents. However, the nature of the interior of the macromolecule is also significant. The results obtained show that in general hyperbranched polyesters are better soluble in carbon dioxide than hyperbranched polyethers. In light hydrocarbons as solvents the opposite effect is observed.