Polymeric Schiff's base chelates and their precursors

Summary Various divinyl-Schiff's base ligands 3 were synthesized from 2-hydroxy-5-vinylbenzaldehyde (2) and diamines. Copolymerization of 3 with styrene directly leads to covalently polymer bound ligands 4. Introduction of Co(II) resulted in the formation of the chelates 6. Covalently polymer bound chelates show high activity for the reversible binding of dioxygen under formation of mononuclear superoxo complexes. The chelates exhibit good activities for the oxidation of 2,6-di-tert-butylphenol (9).Part 5: Ref. 1).     

Polymeric schiff base chelates and their precursors

Summary Covalently polymer bound Co(salen) 6a-c was synthesized starting from two macroporous resins 2a,b and a linear polystyrene 2c. Reaction of 2a-c with 5-chloromethylsalicylaldehyde to 3a-c, then with 1,2-diaminoethane to 4a-c and then with salicylaldehyde led to the metal free ligands 5a-c which could be metallized to 6a-c.     

Liqquid crystal polymers containing macroheterocyclic ligands

Summary The synthesis and cationic polymerization of 1-[2-methyl-4-(4-carboxybenzo-15-crown-5)phenyl]ethynyl-4-(11-vinyloxyundecan-1-yloxy)benzene (8) are described. Both 8 and poly (8) were characterized by a combination of thermal optical microscopy and differential scanning calorimetry. Both 8 and poly(8) display an enantiotropic nematic mesophase and side chain crystallization. The isotropization temperature of poly(8) is 19°C higher than that of 8.     

Alkyloxy-substituted liquid-crystalline aromatic copolyesters

Summary The synthesis and characterization of main chain liquid crystalline polyesters arising from 2,5-bispentyloxy substituted terephthalic aicd (3) and aromotic diols are described. 3 was prepared from diethyl 2,5-dihydroxyterephthalate and 1-bromopentane. The polyesters were prepared from 4,4-dihydroxybiphenyl (5), hydroquinone (6), 2,5-dimethyl hydroquinone (8) and the substituted terephthaloyl dichloride (4) in 1,1,2,2-terachloroethane. Their structures were characterized by ¹H-NMR, GPC and elemental analyses; their thermal behavior was studied by DSC measurements, microscopy under polarized light, and thermogravimetric analyses. The melting points are in the range of 130–280°C. All of them except of those with a high amount of 2,5-dimethyl hydroquinone (8) form a nematic phase above their melting point.     

Amides as Phase Modifiers for N,N′-Tetraalkylmalonamide Extraction of Actinides and Lanthanides from Nitric Acid Solutions

Abstract

The N,N′-tetraalkylmalonamides are a class of compounds under development for transuranic (TRU) separations under high nitric acid conditions. There are several issues that challenge the further development of these ligands. One is the development of improved synthetic procedures that lend themselves to commercial scale-up. Another major issue is the third-phase formation that occurs when the N,N′-tetraalkylmalonamides are contacted with medium-to-high nitric acid concentrations in hydrocarbon solvents. To address the synthesis issue we have developed a new synthetic approach for preparing these materials. Third-phase formation can be eliminated by addition of diluent modifiers such as tributylphosphate (TBP). TBP is inappropriate if a nonphosphate-containing process stream is required. Amides have been proposed as alternatives for TBP in a variety of applications because of their ease of synthesis and the variety of substituents that can be generated. We have been able to develop an amide phase-modified system that extends the working process range of alkylmalonamides (0.5 M) in dodecane (unbranched hydrocarbon) from 3.5 M to 7.5 M nitric acid and in Isopar H (branched hydrocarbon) from 4.0 M to 10.0 M nitric acid using 1.0 M di-2-ethylhexylacetamide/0.5 M alkylmalonamide. The K_d values were comparable to extraction with alkylmalonamide in Isopar H or hydrogenated tetrapropylene (TPH) solvents. The overall extraction system was more robust than the phase-unmodified system allowing for greater temperature and acid concentration fluctuations without third-phase formation.     

Tailor made liquid crystalline networks exhibiting a chiral smectic C (S C * ) mesophase via living cationic copolymerization

Summary Living cationic copolymerization of (2S, 3S)-(+)-2-chloro-3-methylpentyl 4-(8-vinyloxyoctyloxy)biphenyl-4-carboxylate (15-8) with 2-vinyloxyethyloxy methacrylate (16-2) leads to reactive copolymers poly[(15-8)-co-(16-2)]X/Y (where X/Y is the mol ratio between the two monomers in the copolymer) containing methacryloyl side groups. The thermally crosslinked copolymers with X/Y=5/5 to 9/1 display an enantiotropic chiral smectic C (S _C ^* ) mesophase.This paper is part 28 in the series: Molecular engineering of liquid-crystalline polymers by living polymerization. Part 27: V. Percec, Q. Zheng: Polym. Bull., previous paper in the issue     

Molecular engineering of liquid crystalline polymers by living polymerization

Summary This paper describes the synthesis and characterization of poly{3-[4-cyano-4-biphenyl)oxy]propyl vinyl ether} [poly(6-3)] macromonomers obtained by the functionalization of the growing chain end of the corresponding living polymer obtained by the initiation of the cationic polymerization of 3-[4-cyano-4-biphenyl)oxy]propyl vinyl ether with CF₃SO₃H/S(CH₃)₂, with 2-hydroxy ethyl methacrylate [poly(6-3)-I], 2-[2-(2-allyloxyethoxy)ethoxy]ethanol [poly(6-3)-II] and 10-undecen-1-ol [poly(6-3)-III].Part 20: V. Percec and M. Lee, J. Mater. Chem., submitted     

Thermoplastic elastomers by sequential monomer addition

The living carbocationic polymerization (LC Pzn) of p-methylstyrene (pMeSt) was achieved by the use of the 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl₄ initiating system in the presence of triethylamine (Et₃N) electron donor in CH₃Cl/nC₆H₁₄ mixed solvent at-80°C. Next, the synthesis, characterization, and some physical-mechanical characteristics of a series of poly (p-methylstyrene-b-isobutylene-b-p-methylstyrene) (PpMeSt-PIB-PpMeSt) triblocks is described. The latter synthesis involved two steps in one reactor: 1) The generation of diliving polyisobutylene dications (PIB) by the dicumyl chloride (DiCumCl)/TiCl₄ system under similar conditions followed by 2) The addition of pMeSt and growth of living PpMeSt cations. The PpMeSt-PIB-PpMeSt triblocks are soft thermoplastic elastomers (TPEs).Paper L in the series Living Carbocationic Polymerization     

Polymeric bound porphyrines and their precursors

Summary The solid state synthesis of a monosubstituted phthalocyanine 6 is described. 4-(4-Hydroxyphenoxy)-1,2-benzenedicarbonitrile is polymer bound to a chloromethylated macroreticular polystyrene, yielding polymer 3. Reaction of 3 with 4-phenoxy-1,2-benzenedicarbonitrile in the presence of zinc salt results in the formation of covalently bound polymeric phthalocyanine 5. 6 is obtained by cleavage with HBr/acetic acid.Part 1: Ref. 1     

An ultrafast synthesis method of LiNi1/3Co1/3Mn1/3O2 cathodes by flash/field‐assisted sintering

LiNi_1/3Co_1/3Mn_1/3O₂ as a promising cathode material in lithium‐ion batteries was synthesized by flash/field‐assisted sintering technique for the first time. This study showed that the current‐limited synthesis of LiNi_1/3Co_1/3Mn_1/3O₂ could be carried out at temperatures less than 400°C for only 8 minutes, compared with the conventional pressureless sintering at 850°C for 12 hours. X‐ray diffraction results showed the phase evolution from precursor mixtures to the final LiNi_1/3Co_1/3Mn_1/3O₂ products during flash/field‐assisted sintering process and a well‐layered structure without undesirable cation mixing in the as‐formed LiNi_1/3Co_1/3Mn_1/3O₂. Combined with the lowered sintering temperatures and reduced sintering time, the excellent electrochemical performance of flash/field‐assisted sintered LiNi_1/3Co_1/3Mn_1/3O₂ materials suggested that this technique could be an energy‐efficient approach for the synthesis of lithium‐ion battery cathode materials and other materials requiring high‐temperature heat treatment.     

Cationic ring-opening polymerization of 2-phenyl-1,2-oxaphospholane (deoxophostone)

Summary The ring-opening polymerization of deoxophostone 5, a five-membered cyclic phosphinite, has been studied. Some cationic initiators gave polymer whereas anionic and radical initiators as well as metal chloride (Lewis acid) catalysts did not yield polymer. The polymer consisted of a phosphine oxide repeating unit 6. The polymerization proceeded via the Arbuzov-type reaction. The reduction of polymer 6 with a HSiCl₃/Et₃N system gave polyphosphine 7.     

A spin-frustrated (4, 12)-connected metal-organic framework with unusual {Co8(μ4-OH)6}10 + cubes

A novel (4, 12)-connected metal-organic framework, {(NH₄)₂·[Co₁₁(μ₄-OH)₆(CN)₆(trz)₁₂]}_n, was solvothermally constructed from unusual Co^II₈ cubes, octahedral Co^II₁ subunits, and μ₃-N1,N2,N4-triazolate (trz) connectors. Strong antiferromagnetic coupling between the neighboring Co^II ions results in an absence of long-range magnetic ordering, leading to a strong spin-frustration with f > 62.     

Synthesis and polymerization of p-bromomethylstyrene and p-lodomethylstyrene

Summary Synthesis of p-bromomethylstyrene (3) and p-iodome-thylstyrene (4) is reported. 3 was obtained by the bromomethylation of 2-phenylethyl bromide followed by dehydrobromination of the resultant p-(2-bromoethyl) benzyl bromide (2) with t-BuOK, as well as by cleaving p-vinyl-benzyl methanosulfonate with LiBr in the presence of 18--crown-6. 4 was obtained from p-chloromethylstyrene (1) via the Finkelstein reaction. 3 was polymerized successfully in the presence of free-radical initiators, but 4 was found to be too unstable to give a well-defined polymer.     

Preparation and characterization of Co/SiO2, Co-Mg/SiO2 and Mg-Co/SiO2 catalysts and their activity in CO hydrogenation

Co/SiO₂, Mg-Co/SiO₂ and Co-Mg/SiO2 catalysts were prepared from acetate, nitrate or carbonyl precursors. The catalysts were characterized by XRD, XPS, SIMS and TGA. The steady-state activity and product distribution of the catalysts were evaluated in synthesis gas reactions at 0.5 MPa and 235-290°C using 3 : 1 : 3 molar ratio of Ar : CO : H₂. The activity in CO hydrogenation decreased in the precursor order Co₂(CO)₈>Co(NO₃)₂> Co(CH₃COO)₂, and the probability of chain growth decreased in the precursor order Co(NO₃)₂>Co₂(CO)₈>Co(CH₃COO)₂. Alcohol yields were highest with Co₂(CO)₈, and lowest with Co(NO₃)₂, Magnesium promotion influenced the catalyst activity and decreased the CO₂ formation, but the promotion effects were less profound than those of the precursor. Surface studies on partially magnesium covered cobalt foil model catalysts suggested that magnesium promotes CO dissociation and chain growth, neither of which were, however, observed in the supported catalysts.     

Preparation of Cobalt Nitride from Co–Al Hydrotalcite and its Application in Hydrazine Decomposition

Alumina supported cobalt nitride [Co₄N–Al₂O₃ (HT)] with high cobalt loading has been prepared for the first time from Co–Al hydrotalcite precursors. The formation of the Co₄N phase was confirmed by XRD, H₂-TPR, and XPS. Compared with Co₄N/Al₂O₃ (IMP) prepared by conventional impregnation and nitriding, the hydrotalcite derived catalyst exhibited a much better activity for hydrazine decomposition as consequence of higher dispersion of active species.     

Novel derivatives of methyl hexahydro-3-methyl-6-thioxo-1,2,4,5-tetrazine-3-nonanoate

Methyl hexahydro-3-methyl-6-thioxo-1,2,4,5-tetrazine-3-nonanoate (I) on treatment with reagents such as chloroacetic acid, 1,2-dibromoethane and 2-mercaptoethanol under different reaction conditions afforded methyl 3,4,6,7-tetrahydro-3-methyl-6-oxo-2H-thiazolo[3,2-b]-1,2,4,5-tetrazine-3-nonanoate (II), methyl 3,4,6,7-tetrahydro-3-methyl-2H-thiazolo[3,2-b]-1,2,4,5-tetrazine-3-nonanoate (III) and methyl 8-methyl-1-oxa-4-thia-6,7,9,10-tetraazaspiro-[4.5]-decane-8-nonanoate (IV) in good yields. The structures of compounds II–IV were established by elemental analysis, infrared (IR), nuclear magnetic resonance (NMR), and mass spectral data.     

Influence of the termonomer on the synthesis and properties of ethylene-propylene polymers

EPDM elastomers have been synthesized by the Ziegler-Natta oatalytic system VOCl₃/Al₂Et₃Cl₃ with the objetive of verifying the influence of termonomers on terpolymer synthesis and on the properties of peroxide-vulcanized terpolymer compositions. Two groups of termonomers have been studied. Dienes, i.e., dicyclopentadiene (DCP), 5-ethylidene-2-norbornene (ENB) and limonene, and aromatic compounds, i.e., indene (IND) and styrene (ST). The influence on the synthesis has been verified by yield, termonomer incorporation, and molecular weight distri bution. The vulcanizate properties have included mechanical and electrical properties.     

NO Reduction with Hydrogen over Cobalt Molybdenum Nitride and Molybdenum Nitride: A Comparison Study

Cobalt molybdenum nitride (Co₃Mo₃N) and molybdenum nitride (Mo₂N) were investigated for the catalytic reduction of NO with H₂. The latter deactivated rapidly with time on stream, whereas the former remained active and stable over a test period of 30 h. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H₂-temprature-programmed reduction (H₂-TPR) characterization indicated that the deactivation of Mo₂N was due to the bulk oxidation of Mo₂N to MoO₂. As for the Co₃Mo₃N catalyst, despite partial decomposition into Mo₂N and Co, it remained resistant to oxidation. The results suggest that compared to the monometallic nitride, the bimetallic one is more suitable for NO reduction with H₂.     

Co(II) coordinated metal-organic framework: An efficient catalyst for heterogeneous aerobic olefins epoxidation

An 8-connected, linear trinuclear cluster-based microporous metal organic framework (NH₄)₂[Co₃(Ina)(BDC)₃(HCOO)] (denoted as Co₃InaBDC₃, Ina = isonicotinate and BDC = 1,4-benzenedicarboxylate, CCDC is 935147) had been successfully synthesized by a facile hydrothermal synthesis method. The compound was extended through BDC linkers breadthwise and Ina linkers lengthways to the highly-connected framework. The Co₃InaBDC₃ was characterized through FT-IR, N₂ adsorption, XRD, TGA and SEM, and its characteristic structure was elucidated by single crystal X-ray diffraction. Using O₂ as oxidant, the Co₃InaBDC₃ was investigated as a good performed heterogeneous catalytic material for cyclooctene epoxidation. An extremely high turnover frequency (1370 h^− 1) for epoxycyclooctane was achieved, and Co₃InaBDC₃ exhibited excellent stabilities in 5 recycles without any loss of its catalytic performance.     

Freestanding Co3N thin film for high performance supercapacitors

Suitable electrode materials play a decisive role in the performance of supercapacitors. In recent years, transition metal nitrides come into view because of their advantages of superior electrical conductivity exceeding the corresponding metal oxides and higher specific capacitance compared with carbon-based materials. Herein, we have successfully synthesized the binder-free Co₃N thin films for high-efficiency supercapacitor by reactive magnetron sputtering. Remarkedly, the Co₃N thin film electrodes can reach a high specific capacity of 47.5 mC cm^?2 at a current density of 1.0 mA cm^?2 along with reasonable cycling stability (78.1% remaining after 10,000 cycles). These findings have proved that the Co₃N thin films have great potential applications for supercapacitors or other electrochemical energy storage devices.