Carboxylic Units Research Articles

Coordination chemistry on the surface of single-walled carbon nanotubes

A facile method to coordinate transition metal complexes (TMCs) on single-walled carbon nanotubes (SWNTs) has been developed. Reaction of Zn(OAc) 2 with carboxylic acid functionalized SWNTs (SWNT-COOH) affords SWNT complexes ‘zipped-together’ by zinc carboxylate units (termed SWNT-TMC- 1 herein). Reactions of SWNT-TMC- 1 with 2,2′-bipyridine or 4,4′-bipyridine gave two new SWNT-TMCs, the former being ‘unzipped’ (SWNT-TMC- 2), and the latter involving an additional ligand bridge between the zinc ions (SWNT-TMC- 3). Inclusion of 2,2′-bipyridine and 4,4′-bipyridine into the SWNT-TMCs was confirmed by IR spectroscopy. The microstructures of SWNT-TMC- 2 and SWNT-TMC- 3 were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (Xps), elemental mapping and linear profiles analysis.

Phosphane Copper(I) Dicarboxylates: Synthesis and Their Potential Use as Precursors for the Spin‐coating Process in the Deposition of Copper

AbstractDicopper dicarboxylates [(R3P)mCuXCu(PR3)m] (5a, X = O2CCO2, R = Ph, m = 2; 5b, X = O2CCO2, R = nBu, m = 3) were prepared by treatment of [Cu2O] (1a) with HO2CCO2H (2a) in presence of PR3 (4a, R = Ph; 4b, R = nBu). A further synthesis approach to mono‐ and dicopper dicarboxylates is given using an electrolysis cell equipped with Cu electrodes and charged with acids H2X and phosphanes R3P. Without addition of a base mononuclear [(nBu3P)mCuXH] (6a, m = 3, XH = O2CCO2H, 6b, m = 3, XH = O2CCH2CO2H, 6c, m = 3, XH = O2CCH2CH2CO2H, 6d, m = 2, XH = O2C‐2‐C5H4N‐6‐CO2H) was formed, whereas in presence of NEt3 (3), the dicopper systems [(R3P)mCuXCu(PR3)m] (5a, X = O2CCO2, R = Ph, m = 2; 5b, X = O2CCO2, R = nBu, m = 3; 5c, X = O2CCH2CO2, R = nBu, m = 3; 5d, X = O2CCH2CH2CO2, R = nBu, m = 3; 5e, X = O2C‐2‐C5H4N‐6‐CO2, R = nBu, m = 3) were produced. When 6a reacted with [(tmeda)Zn(nBu)2] (7), trimetallic [(tmeda)Zn((nBu3P)3CuO2CCO2)2] (8) was accessible. In this heterobimetallic complex the Zn(tmeda) unit spans two CuO2CCO2 entities. The molecular structures of 5a, 6a and 6d in the solid state were determined by single X‐ray structure analysis. Complexes 5a and 6a are monomers, whereas 6d creates in the solid state a linear open chain coordination polymer by hydrogen bridge formation. Characteristic for 6d is the somewhat distorted trigonal bipyrimidal arrangement around the copper atom with the nBu3P ligands in axial and the C5H3NCO2H oxygen and nitrogen atoms in equatorial positions. In 5a the oxalate connectivity binds in a μ‐1,2,3,4 fashion being part of a planar Cu2(oxalate) core. TG studies of several mono‐ and dicopper dicarboxylates were carried out. Release of the PR3 ligands is recognized and the remaining Cu‐(di)carboxylate unit decomposes to afford elemental copper and CO2. The deposition of copper onto pieces of PVD‐Cu oxidized silicon wafers by applying the spin‐coating process and using 5c and 5d as precursors is discussed.

2-(2-{[2-(4-Pyridylcarbonyl)hydrazinylidene]methyl}phenoxy)acetic acid

In the title compound, C15H13N3O4, the pyridine and benzene rings are nearly perpendicular [dihedral angle = 84.24 (5)°]. In the crystal structure, classical O—H⋯N hydrogen bonding between the OH group of the carboxyl unit and a neighbouring pyridine ring N atom and N—H⋯O hydrogen bonding between the imine NH group and a neighbouring O atom of an acyl unit, together with complementary non-classical C—H⋯O hydrogen bonds between carboxyl O atoms and neighbouring CH groups, link the mol­ecules into a three-dimensional system.

Interdiffusion/reaction at the polymer/polymer interface in multilayer systems probed by linear viscoelasticity coupled to FTIR and NMR measurements

This paper describes the experimental investigation of the interdiffusion/reaction mechanisms of asymmetric polymer–polymer interfaces. The study deals with the assessment of the chemical reactions occurring at the interface between two reactive polymers. A focal point of the investigation was to study these interfacial reactions by an array of techniques at very different space scales: from macroscopic viscoelastic investigations to IR and NMR spectroscopies at the molecular scale. The studied material pairs include PE-GMA/PA6 as the reactive system (RS) and PE/PA6 as the non-reactive one (NRS) – of coextruded multilayer polymers, i.e., after processing. The linear viscoelastic properties of the reactive multilayer systems were determined and the mechanisms were analyzed by NMR and FTIR measurements. Substantial reactions occurred during the rheological measurements and the results indicated the preferential formation of a copolymer at the interface, triggered by the neighboring layers. Moreover, the contribution of an interface/interphase effect was investigated along with the increase in the number of layers. The results showed that the variation in dynamic modulus of the multilayer system was a result of both diffusion and chemical reaction. Specific experiments were carried out to follow-up on the physicochemical phenomena, and the results were rationalized by comparing the obtained data with theoretical models. The effect of this interphase was quantified at a specific welding time and oscillation frequency thanks to rheological modeling. Because of the coupling between rheology and spectroscopical tools, potential reactions between the GMA functions and the amine/carboxylic polyamide chain ends were explored. The results highlighted that the main reaction mechanism was constituted by the crosslinking reaction between the GMA and carboxylic acid units, and not by that between GMA and amine end functions.

Poly[[(μ3-isonicotinato-κ3O:O:N)(triphenylphosphine-κP)silver(I)] ethanol solvate

In the crystal structure of {[Ag(C6H4NO2)(C18H15P)]·C2H6O}n, the 4-pyridylcarboxyl­ate ion binds to the phosphine-coordinated silver atoms through one of the two oxygen atoms of the carboxyl unit, and to a third phosphine-coordinate silver atom through the nitro­gen atom of the aromatic ring, giving a distorted tetra­hedral coordination at the metal atom. The μ 3-bridging mode leads to a layer motif; the disordered ethanol mol­ecules are linked to the free carboxyl oxygen atom by O—H⋯O hydrogen bonds.

Sorption−Desorption Behavior of Atrazine on Soils Subjected to Different Organic Long-Term Amendments

Sorption of atrazine on soils subjected to three different organic amendments was measured using a batch equilibrium technique. A higher K(F) value (2.20 kg(-1)(mg L(-1))(-N)) was obtained for soil fertilized with compost, which had a higher organic matter (OM) content. A correlation between the K(FOC) values and the percentage of aromatic carbon in OM was observed. The highest K(FOC) value was obtained for the soil with the highest aromatic content. Higher aromatic content results in higher hydrophobicity of OM, and hydrophobic interactions play a key role in binding of atrazine. On the other hand, the soil amended with farmyard manure had a higher content of carboxylic units, which could be responsible for hydrogen bonding between atrazine and OM. Dominance of hydrogen bonds compared to hydrophobic interactions can be responsible for the lower desorption capacity observed with the farmyard manure soil. The stronger hydrogen bonding can reduce the leaching of atrazine into drinking water resources and runoff to rivers and other surface waters.

Synthesis and properties of starch-g-poly(maleic anhydride-co-vinyl acetate)

Starch-g-poly(maleic anhydride-co-vinyl acetate) (SMV) was synthesized via the esterification reaction of starch with the copolymer of maleic anhydride and vinyl acetate. The carboxylic unit percentage (CUP) of SMV was tailored with reaction conditions, and it ranged from 29.8 to 46.9%. The structure and the morphology of the copolymers were character- ized with Fourier Transform Infrared spectroscopy and X-ray diffraction analysis. It was found that SMV could form com- plex with some metal cations such as Ca 2+ , Pb 2+ and Hg 2+ or cationic polyelectrolyte chitosan, and precipitate from the solution. The weight of precipitation increases with an increase of the CUP of SMV. In addition, a physically cross-linked hydrogel of SMV/poly(vinyl alcohol) (PVA) was obtained by freeze/thaw technique. Scanning electron microscopy exhib- ited the hydrogel was uniform. The gel exhibited pH-responsive re-swelling. The maximum swelling-ratio values of SMV/PVA (9:1, wt/wt) gel were 3.29 and 5.34 in HCl (pH 1.0) and phosphate-buffer saline (PBS) (pH 12) respectively.

Coordination polymers containing ferrocene backbone. Synthesis, structure and electrochemistry

The reaction of 1,1'-ferrocenedicarboxylic acid (LH(2)) with bis(triphenyltin) oxide afforded a molecular heterobimetallic compound [(Ph(3)Sn)(2)L]. In the latter the two carboxylate units of [L](2-) are involved in an anisobidentate chelating coordination mode to two triphenyl tin units. The reaction of LH(2) with trimethyltin hydroxide or bis(tri-n-butyltin) oxide afforded 2D-coordination polymers [(Me(3)Sn)(2)L](n) and [(n-Bu(3)Sn)(2)L](n) which are formed as a result of anisobidentate bridging coordination action of the two carboxylate units of [L](2-). Interestingly the 2D-coordination polymers contain 24-membered macrocycles each of which is comprised of four trialkyl tin units. The coordination unsaturation of [(Ph(3)Sn)(2)L] can be utilized to form coordination polymers. Accordingly the reaction of LH(2) with bis(triphenyltin) oxide in the presence of ditopic nitrogen ligands such as 4,4'-bipyridine, 4,4'-trimethylenebipyridine or 4,4'-vinylenebipyridine afforded one-dimensional coordination polymers which contain in their backbone three distinct structural components viz., two triorganotin units, a ferrocenyl unit and a bridging nitrogen ligand unit. The coordination polymers, however, do not retain their structural integrity in solution and fall apart to their monomeric units. Electrochemical studies on these hybrid orgaonotin/ferrocene systems reveal that most of them exhibit a single quasi-reversible oxidation peak.

2-(2,4-Dichloro-phen-yl)acetic acid.

In the title compound, C8H6Cl2O2, the dihedral angle between the C—C(=O)—OH carboxyl unit and the benzene ring is 70.70 (4)°. In the crystal, mol­ecules are linked into inversion dimers by pairs of O—H⋯O hydrogen bonds. The dimers are linked into chains extending along [001] by weak C—H⋯Cl inter­actions.

2-Mesitylacetic acid

In the title compound, C11H14O2, the dihedral angle between the CCOO carboxyl unit and the benzene ring is 85.37 (7)°. In the crystal, the mol­ecules are linked into inversion dimers by pairs of O—H⋯O hydrogen bonds.

Patterned conductive polyaniline films fabricated using lithography and in situ polymerization

AbstractIn this article, we describe a novel bottom‐up technique for the preparation of transparent conductive films of polyaniline (PANI). A UV‐curable photoresist was formulated containing an acrylate‐endcapped urethane oligomer [UA(PPG400)], acrylic acid, a photoinitiator, and a reactive diluent (tripropylene glycol diacrylate), and the lithography techniques were used to pattern the structure with line widths/spaces of 100 μm/100 μm, 10 μm/10 μm, and 5 μm/5 μm on a polyethylene terephthalate substrate. The carboxylic acid units on the surface of the patterned photoresist interacted with the aniline monomer units to form anilinium complexes; using ammonium persulfate as a chemical oxidant, we then synthesized a layer of conductive PANI on the surface of the patterned resist through in situ polymerization. The optimal conductivity of the PANI conductive film was ca. 10 S/cm. The thin film was characterized, and its physical properties investigated using Fourier transform infrared spectroscopy, UV–Vis spectroscopy, differential scanning calorimetry, optical and atomic force microscopy, and four‐point probe conductivity measurements. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Dimethylthiazolidine Carboxylic Acid as a Rigid P3 Unit in Inhibitors of Serine Proteases: Application to Two Targets†

Serine proteases are a very large class of enzymes, many of which represent important targets for therapeutic agents against a wide variety of disease states. The similarity in active site architecture for these proteases has often allowed inhibitor design strategies for a particular target to be successfully applied to other enzymes in the class. In many cases, the presence of a bulky P3 amino acid residue in peptide-based inhibitors is central to conferring an extended peptide conformation, critical to binding of the ligands to serine protease active sites. The dimethylthiazolidine carboxylic acid 'residue' was found to be effective as a novel P3 replacement in peptidomimetic inhibitors of two distinct serine proteases, the hepatitis C NS3 protease and the human cytomegalovirus maturational protease. An array of NMR methods was used to confirm that the dimethylthiazolidine carboxylic acid unit indeed confers conformational and dynamic properties very similar to that of the rigidified parent structures.

Reproducibility and Efficiency of Carbon Nanotube End‐Group Generation and Functionalization

AbstractIn a systematic fashion, several methods for esterification and amidation of single‐walled carbon nanotubes have been evaluated with focus on efficiency and reproducibility in forming covalently functionalized products soluble in organic media. The outcome of transformations was determined using IR, Raman and NMR spectroscopy and by thermogravimetric analysis (TGA). Amidation proceeding via a SWNT‐(COCl)n intermediate yielded the expected covalent product, whereas carboxylate salt formation dominated with other attempted methods. Esterification was achieved via the acyl chloride method and via alkylation of SWNT‐(COO–)n, the latter being the more efficient method. A non‐covalent solubilizing interaction was obtained for RNH2 but not for ROH (R = octadecyl), proving that the most important non‐covalent interaction between oxidatively cleaned SWNTs and octadecylamine is a salt formation. The outcome of the secondary functionalization of carboxyl units is highly reproducible for experiments carried out on the same batch of SWNT‐(COOH)n. Normalization of the outcome of the secondary functionalization to the composition of the different batches of starting materials reveals an overall high reproducibility of the secondary functionalizations. The differences in outcome related to different commercial SWNT batches from the same synthetic procedure is negligible compared to that resulting from differences in overall carboxyl content after the primary HNO3 oxidative cleaning step. Hence, the composition of purified SWNT starting materials always needs to be assessed, in particular before drawing any conclusions concerning differences in outcome from reaction systems involving different sources of SWNT material. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Dimethyl 1-cyanomethyl-1H-pyrazole-3,5-dicarboxylate

The title mol­ecule, C9H9N3O4, syhthesized from 1H-pyrazole-3,5-dicarboxylic acid and 2-bromo­acetonitrile, is approximately planar; the inter­planar angles between the pyrazole ring and the mean planes of the two carboxylate units and the cyanomethyl unit are 4.49 (10), 5.56 (9) and 5.03 (19)°, respectively. In the crystal, inversion dimers linked by pairs of weak C—H ⋯O bonds occur, and the packing is further stabilized by aromatic π–π stacking [centroid–centroid separation = 3.793 (4) Å].

Synthesis, Crystal Structure, and Spectral and Magnetic Properties of Chloro-Bridged Chain Complex of Dinuclear Ruthenium(II,III) 3,4,5-Triethoxybenzoate

A chloro-bridged chain complex constructed from paddlewheel-type dinuclear ruthenium(II,III) carboxylate units, [Ru2{3,4,5-(C2H5O)3C6H2CO2}4Cl]n·1.2nC2H5OH (1·1.2nC2H5OH), was synthesized and characterized by elemental analysis and IR and UV-vis spectroscopies. The single-crystal X-ray analysis showed that the complex forms a zig-zag chain structure, in which the chloroligands bridge the dinuclear units at the axial positions with the Ru1–Cl–Ru2 angle of 120.38(7)°. A broad band around 1144 nm and a band at 475 nm were observed in the diffused reflectance spectra and ascribed to a δ→δ* and a π(RuO, Ru2)→π*(Ru2) transitions, respectively. Temperature dependence of magnetic susceptibility showed that the antiferromagnetic interaction between the dinuclear units is weak (zJ = −0.8 cm−1) with D value of 60 cm−1.

Characterizing the chelatable/labile iron pool in mammalian cells

Iron shuttling in and out of cellular proteins and compartments comprises a chelatable or labile pool. Attempts at characterizing this pool have been largely unsuccessful. Using 3h labeling with tracer 59Fe, we identified a 1600 Da component in ultrafiltrates of cultured cell lysates that degraded to 600 Da over time (if not separated from the bulk of the cellular protein) and could be converted from 1600 to 600 Da with proteinase K. Both the 1600 and 600 Da components were negatively charged at pH 7+ and separated from cellular 59Fe‐labeled ferritin (Ft) in native PAGE. 59Fe in the unknown versus Ft varied inversely with total cellular Fe. However, analysis of Centricon 10 ultrafiltrates from human HepG2 and Caco2 cells showed that the Fe content did not vary appreciably with cellular Fe status (pretreatment with 180 uM Fe or 30 uM DFO for 24h, or untreated). Concentrations in this pool were 90‐ 200 ng/mg cell protein, with total iron contents ranging from 200 to1600 ng/mg. Mass spectrometry after laser fragmentation released multiple units of 44 Da (consistent with COO‐). We conclude that the cellular labile Fe pool stays quite constant despite changes in Fe status and may primarily consist of a complex of Fe with a small peptide plus carboxylate units. Supported in part by PHS Grant No. RO1 HD 46949.

Prospectives and surgical usefulness of perioperative parathyroid hormone assay in thyroid surgery

Hypocalcemia is the most frequent complication after thyroid surgery. The incidence varies and has been reported as ranging from 1.2 to 40%. Permanent hypoparathyroidism occurs in less than 3% of patients, whereas transient postoperative hypocalcemia is much more common. Postoperative hypoparathyroidism is traditionally detected by serial measurement of serum calcium concentrations and requires multiple venepunctures and, potentially, several days of hospitalization following the procedure. The parathyroid hormone (PTH) molecule is a polypeptide composed of an 84-amino acid sequence with an active amino terminal on one end and an inactive carboxyl unit on the other. Measurement of the intact PTH (iPTH) is an accurate representation of the true parathyroid state. In recent years, iPTH assay has been under investigation for thyroid surgery in many centers as an early iPTH measurement may be of value for prediction of postoperative symptomatic hypocalcemia, guiding the surgeon for parathyroid autotransplatation, and selection of patients requiring onset of calcium substitution or safe discharge home. This paper reviews the relevant medical literature published regarding the influence of PTH assay technology on the quality of thyroid surgery, as well as on the prevention of postoperative symptomatic hypocalcemia. Searches were last updated in April 2008.

{5,5′-Bis(methoxycarbonylmethoxy)-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}copper(II)

The title compound, [Cu(C22H22N2O8)], is a tetra­dentate Schiff base complex. The CuII ion has a nearly square-planar geometry, being coordinated by two N atoms and two O atoms. The two chemically equivalent halves of the mol­ecule are crystallographically independent. One of the carboxylic acid methyl ester units is located in the main plane of the mol­ecule and the other is rotated by 65.3 (5)° with respect to this unit. In the crystal structure, there are π–π stacking inter­actions between adjacent six-membered chelate rings, with centroid-to-centroid distances of 3.602 (2) Å.

The synthesis of complexes using precursor complexes with ferrocenyl carboxylate units as building blocks

Using ferrocenyl carboxylates as functional ligands, we synthesized a mononuclear complex [Zn(η 2-OOCCH CHFc) 2(CH 3OH) 2] ( 1) and a binuclear complex [Cd(bafca) 2(H 2O) 2] 2 ( 2) (bafca − = α-benzamido-β-ferrocenylacrylic carboxylate) as precursor complexes. Investigation on the substitution reaction of precursor complexes as building blocks in solution-state, four complexes [Zn(OOCCH CHFc) 2(bbbm)] n ( 1a), {[Zn(OOCCH CHFc)(ntb)](CH 3OH)} ( 1b), [Cd(bafca) 2(2,2′-bpy)] 2 · 9H 2O ( 2a) and {[Cd(bafca) 2(bbbm)(CH 3OH) 2] · 6CH 3OH} n ( 2b) were obtained (bbbm = 1,1-(1,4-Butanediyl)bis-1H-benzimidazole, ntb = N,N-bis(1H-benzimidazol-2-ylmethyl)-1H-Benzimidazole-2-methanamine and 2,2′-bpy = 2,2′-bipyridine). As anticipated, the structural integrity of precursor complexes can be maintained in these four complexes. It indicates that we can synthesize the desired complexes with the destination structures by using precursor complexes as building blocks and choosing appropriate auxiliary ligands. In addition, the electrochemical properties of all complexes were investigated, and it can be seen from the results that half-wave potentials of these complexes are slightly higher than that of the corresponding ligand.

Copper(I) Carboxylates of Type [(nBu3P)mCuO2CR] (m = 1, 2, 3) – Synthesis, Properties, and their Use as CVD Precursors

AbstractCopper(I) carboxylates of type [(nBu3P)mCuO2CR] (m = 1: 3a, R = Me; 3b, R = CF3; 3c, R = Ph; 3d, R = CH=CHPh. m = 2: 4a, R = Me; 4b, R = CF3; 4c, R = Ph; 4d, R = CH=CHPh. m = 3: 8a, R = Me; 8b, R = CF3; 8c, R = CH2Ph; 8d, R = (CH2OCH2)3H; 8e, R = cC4H7O) are accessible by following synthesis methodologies: the reaction of [CuO2CR] (1a, R = Me; 1b, R = CF3; 1c, R = Ph; 1d, R = CH=CHPh) with m equivalents of nBu3P (2) (m = 1, 2, 3), or treatment of [(nBu3P)mCuCl] (5a, m = 1; 5b, m = 2) with [KO2CCF3] (6). A more straightforward synthesis method for 8a – 8e is the electrolysis of copper in presence of HO2CR (7a, R = Me; 7b, R = CF3; 7c, R = CH2Ph; 7d, R = (CH2OCH2)3H; 7e, R = cC4H7O) and 2, respectively. This method allows to prepare the appropriate copper(I) carboxylate complexes in virtually quantitative yield, analytically pure form, and on an industrial scale.IR spectroscopic studies reveal that the carboxylic units in 4, 5, and 8 bind in a unidentate, chelating or μ‐bridging fashion to copper(I) depending on m and R.The thermal properties of 4, 6, and 8 were determined by TG and DSC studies. Based on TG‐MS experiments a conceivable mechanism for the thermally induced decomposition of these species is presented.Hot‐wall Chemical Vapor Deposition experiments (CVD) with precursor 4b showed that copper could be deposited at 480 °C onto a TiN‐coated oxidized silicon substrate. The copper films were characterized by SEM and EDX studies. Pure layers were obtained with copper particles of size 200 – 780 nm.