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Dicarboxylic Acids (dicarboxylic + acid)

Distribution by Scientific Domains
Chemistry51%
Polymers and Materials Science31%
Medical Sciences7%
Life Sciences7%
Distribution within Chemistry
Organic Chemistry31%
General & Introductory Chemistry23%
Crystallography17%
6 Other Subdomains29%

Selected Abstracts

Factors Influencing the Course of the Macrocyclization of ,,, -Diamines with Esters of ,,, -Dicarboxylic Acids

HELVETICA CHIMICA ACTA, Issue 1 2004
Dorota Gryko
The efficient synthesis of eight new macrocyclic amides (lactams) via reaction of diesters with diamines under normal dilution conditions is described. The role of intermolecular H-bond formation and steric hindrance is discussed based on 1H- and 15N-NMR studies of appropriate model compounds. Principles for the optimal choice of esters that can be efficiently transformed into diamides have been developed. [source]

Medium-Chain, Even-Numbered Dicarboxylic Acids as Novel Energy Substrates: An Update

NUTRITION REVIEWS, Issue 10 2006
Geltrude Mingrone MD
Medium-chain dicarboxylic acids are produced by higher plants and animals via fatty acid ,-oxidation or by ,-oxidation of longer-chain dicarboxylic acids. In plants, dicarboxylic acids are components of the natural protective polymers cutin and suberin; in animals, dicarboxylic acids are mainly oxidized in mitochondria, where they are transported through four different pathways. Their energy density is intermediate between glucose and fatty acids. Dicarboxylic acid administration does not require insulin or stimulate insulin secretion, and the ,-oxidation of dicarboxylic acids produces succinic acid, a gluconeogenic substrate. Therefore, dicarboxylic acids might be a suitable fuel substrate, particularly in clinical conditions in which marked insulin resistance and/or impairment of aerobic glycolysis occur. [source]

Characterization of Dicarboxylic Acids for Cellulose Hydrolysis

BIOTECHNOLOGY PROGRESS, Issue 3 2001
Nathan S. Mosier
In this paper, we show that dilute maleic acid, a dicarboxylic acid, hydrolyzes cellobiose, the repeat unit of cellulose, and the microcrystalline cellulose Avicel as effectively as dilute sulfuric acid but with minimal glucose degradation. Maleic acid, superior to other carboxylic acids reported in this paper, gives higher yields of glucose that is more easily fermented as a result of lower concentrations of degradation products. These results are especially significant because maleic acid, in the form of maleic anhydride, is widely available and produced in large quantities annually. [source]

Anthracene-Coupled Pyridine Amines: A New "Off-On" Switch for Molecular Recognition Studies on Dicarboxylic Acids.

CHEMINFORM, Issue 35 2006
Kumaresh Ghosh
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

Solid-State Chlorodecarboxylation of Mono- and Dicarboxylic Acids with the Pb(OAc)4,MCl System.

CHEMINFORM, Issue 33 2005
G. I. Nikishin
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Substituted Amides and Hydrazides of Dicarboxylic Acids.

CHEMINFORM, Issue 38 2002
Part 12.
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Facile Route to Supramolecular Structures: Self-Assembly of Dendrimers and Naphthalene Dicarboxylic Acids

CHEMISTRY - A EUROPEAN JOURNAL, Issue 23 2008
Franziska Gröhn Dr.
Cylinders and spheres can be formed by simple self-assembly of cationic dendrimers and oppositely charged small divalent organic ions in methanol (see graphic). The counterion not only controls the morphology of the nanosized assembly, but also provides functionality, such as fluorescence. The concept may lead to versatile functional supramolecular architectures. [source]

1D Ladder-like Chain and 1D Channeled 3D Supramolecular Architectures Based on Benzophenone-2,4,-dicarboxylic Acid

CHINESE JOURNAL OF CHEMISTRY, Issue 4 2008
Xiao-Gang YANG
Abstract The hydrothermal reactions of AgNO3, 2,2,-bipyridyl, and benzophenone-2,4,-dicarboxylic acid gave rise to two 3D supramolecular architectures, namely H2L·H2O (1), [Ag(bpy)2]·HL·H2O (2) (bpy2,2,-bipyridyl, H2Lbenzophenone-2,4,-dicarboxylic acid). The two compounds are extended by hydrogen bonds in two different approaches. In the case of 1, one-dimensional ladder-like structure is firstly formed through O,H···O hydrogen bonding between H2L ligands and water molecules, then extended to a 3D supramolecular architecture. Compound 2 possesses 3D supramolecular architecture containing 1D open channels, which are driven due to the strong H-bonding interactions occurring between the HL anions and water molecules; interestingly, [Ag(bpy)2]+ cations are linked together through ,-, interactions between bpy ligands and weak Ag···Ag interactions, and then reside in these channels by C,H···O hydrogen-bond. The photoluminescence properties of these compounds were also investigated, the emission maxima for 2 exhibits red-shift compared with that of free ligand and 1 due to chelating effect of the 2,2,-bipyridine ligand to the silver ion and the presence of aromatic ,-packing. [source]

ChemInform Abstract: A Novel and Facile Racemization of Chiral 1,1,-Biaryl-2,2,-dicarboxylic Acids.

CHEMINFORM, Issue 40 2001
Masanori Hatsuda
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Synthesis, Characterization, and Sensitizing Properties of Heteroleptic RuII Complexes Based on 2,6-Bis(1-pyrazolyl)pyr­idine and 2,2,-Bipyridine-4,4,-dicarboxylic Acid Ligands

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2007
Athanassios I. Philippopoulos
Abstract Starting from the Ru(bpp)Cl3 precursor (1), a family of novel heteroleptic RuII complexes of the general formulae [Ru(bpp)(dcbpyH)(X)] [X = Cl, (2a), NCS,, (3)] and Na[Ru(bpp)(dcbpy)(CN)] (4) with the ligands 2,6-bis(1-pyrazolyl)pyridine (bpp) and 2,2,-bipyridine-4,4,-dicarboxylic acid (dcbpyH2) has been synthesized, spectroscopically characterized, and attached to nanocrystalline TiO2 electrodes to be tested as solar cell sensitizers. Addition of HCl to (2a) led to the corresponding cationic derivative [Ru(bpp)(dcbpyH2)Cl]Cl (2b). All complexes were characterized by FT-IR, FT-Raman, UV/Vis, 1H NMR spectroscopy, elemental analysis, and mass spectrometry. Complex 4 and the previously reported [Ru(bdmpp)(dcbpyH2)Cl](PF6) (5) [bdmpp is 2,6-bis(3,5-dimethyl-1-pyrazolyl)pyridine] were characterized by single-crystal X-ray diffraction. The photo-electochemical properties of the dyes 2,4 were investigated and the efficiency of the corresponding dye-sensitized solar cells was compared to the sensitizing performance of the cis -[Ru(dcbpyH)2(NCS)2](NBu4)2 (N719) dye.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

The Superbase-Mediated Pairwise Substitution of the 2,2,- and 6,6,-Positions in a Biphenyl Derivative

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2004
Manfred Schlosser
Abstract The superbasic mixture of butyllithium and potassium tert -butoxide is powerful enough to enable the double proton abstraction from one ortho and one ortho, position of 4,4,-di- tert -butylbiphenyl. In this way, a series of functionalized derivatives becomes readily accessible, among them 4,4,-di- tert -butylbiphenyldiyl-2,2,-dicarboxylic acid (2a) and 4,4,-di- tert -butylbiphenyl-2,2,-diol (2d). The latter compound can be subjected again to a superbase-promoted double metalation, thus giving rise to 2,2,,6,6,-tetrasubstituted biphenyl derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Syntheses and crystal structures of triorganotin (IV) derivatives with 2,2,-bipyridine-4,4,-dicarboxylic acid

HETEROATOM CHEMISTRY, Issue 1 2009
Ru-Fen Zhang
Four organotin complexes with 2,2,-bipyridine-4,4,-dicarboxylic acid, H2dcbp: (Ph3n)2(dcbp) 1, [(PhCH2)3n]2(dcbp) , 2CH3OH 2, [(Me3Sn)2(dcbp)]n3, [(Bu3Sn)2(dcbp)]n4 have been synthesized. The complexes 1,4 were characterized by elemental, IR, 1H, 13C, 119n NMR, and X-ray crystallographic analyses. Crystal structures show that complex 1 is a monomer with one ligand coordinated to two triorganotin moieties, and a 1D infinite polymeric chain generates via intermolecular CH,,,N hydrogen bond; complex 2 is also a monomer and forms a 2D network by intermolecular O,H,,,O weak interaction; both of complexes 3 and 4 form 2D network structures where 2,2,-bipyridine-4,4,-dicarboxylate acts as a tetradentate ligand coordinated to trimethyltin and tri-n-butyltin ions, respectively. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:19,28, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20506 [source]

Excitotoxic damage, disrupted energy metabolism, and oxidative stress in the rat brain: antioxidant and neuroprotective effects of l -carnitine

JOURNAL OF NEUROCHEMISTRY, Issue 3 2008
Daniela Silva-Adaya
Abstract Excitotoxicity and disrupted energy metabolism are major events leading to nerve cell death in neurodegenerative disorders. These cooperative pathways share one common aspect: triggering of oxidative stress by free radical formation. In this work, we evaluated the effects of the antioxidant and energy precursor, levocarnitine (l -CAR), on the oxidative damage and the behavioral, morphological, and neurochemical alterations produced in nerve tissue by the excitotoxin and free radical precursor, quinolinic acid (2,3-pyrindin dicarboxylic acid; QUIN), and the mitochondrial toxin, 3-nitropropionic acid (3-NP). Oxidative damage was assessed by the estimation of reactive oxygen species formation, lipid peroxidation, and mitochondrial dysfunction in synaptosomal fractions. Behavioral, morphological, and neurochemical alterations were evaluated as markers of neurotoxicity in animals systemically administered with l -CAR, chronically injected with 3-NP and/or intrastriatally infused with QUIN. At micromolar concentrations, l -CAR reduced the three markers of oxidative stress stimulated by both toxins alone or in combination. l -CAR also prevented the rotation behavior evoked by QUIN and the hypokinetic pattern induced by 3-NP in rats. Morphological alterations produced by both toxins (increased striatal glial fibrillary acidic protein-immunoreactivity for QUIN and enhanced neuronal damage in different brain regions for 3-NP) were reduced by l -CAR. In addition, l -CAR prevented the synergistic action of 3-NP and QUIN to increase motor asymmetry and depleted striatal GABA levels. Our results suggest that the protective properties of l -CAR in the neurotoxic models tested are mostly mediated by its characteristics as an antioxidant agent. [source]

Synthesis, photoluminescence, and electrochromic properties of wholly aromatic polyamides bearing naphthylamine chromophores

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2006
Guey-Sheng Liou
Abstract A series of novel polyamides with pendent naphthylamine units having inherent viscosities of 0.15,1.02 dL/g were prepared via direct phosphorylation polycondensation from various diamines and a naphthylamine-based aromatic dicarboxylic acid, 1-[N,N -di(4-carboxyphenyl)amino]naphthalene. These amorphous polyamides were readily soluble in various organic solvents and could be cast into transparent and tough films. The aromatic polyamides had useful levels of thermal stability associated with high glass-transition temperatures (268,355 °C), 10% weight loss temperatures in excess of 480 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers showed maximum ultraviolet,visible absorption at 350,358 nm and exhibited fluorescence emission maxima around 435,458 nm in N -methyl-2-pyrrolidinone solutions with fluorescence quantum yields ranging from 0.4 to 15.0%. The hole-transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple around 1.08,1.16 V (oxidation onset potential) versus Ag/AgCl in an acetonitrile solution and revealed good stability of the electrochromic characteristics, with a color change from colorless to green at applied potentials ranging from 0 to 1.6 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6094,6102, 2006 [source]

Synthesis and properties of novel soluble polyamides having ether linkages and laterally attached p -terphenyl units

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2004
Sheng-Huei Hsiao
Abstract A new ether-bridged aromatic dicarboxylic acid, 2,,5,-bis(4-carboxyphenoxy)- p -terphenyl (3), was synthesized by the aromatic fluoro-displacement reaction of p -fluorobenzonitrile with 2,,5,-dihydroxy- p -terphenyl in the presence of potassium carbonate, followed by alkaline hydrolysis. A set of new aromatic polyamides containing ether and laterally attached p -terphenyl units was synthesized by the direct phosphorylation polycondensation of diacid 3 with various aromatic diamines. The polymers were produced with high yields and moderately high inherent viscosities (0.44,0.79 dL/g). The polyamides derived from 3 and rigid diamines, such as p -phenylenediamine and benzidine, and a structurally analogous diamine, 2,,5,-bis(4-aminophenoxy)- p -terphenyl, were semicrystalline and insoluble in organic solvents. The other polyamides were amorphous and organosoluble and could afford flexible and tough films via solution casting. These films exhibited good mechanical properties, with tensile strengths of 91,108 MPa, elongations to break of 6,17%, and initial moduli of 1.95,2.43 GPa. These polyamides showed glass-transition temperatures between 193 and 252 °C. Most of the polymers did not show significant weight loss before 450 °C, as revealed by thermogravimetric analysis in nitrogen or in air. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4056,4062, 2004 [source]

Synthesis and properties of organosoluble poly(amide imide imide)s based on tetraimide dicarboxylic acid condensed from 4,4,-(hexafluoroisopropylidene)diphthalic anhydride, 4,4,-oxydianiline, and trimellitic anhydride and various aromatic diamines

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2002
Chin-Ping Yang
Abstract A novel tetraimide dicarboxylic acid was synthesized with the ring-opening addition of 4,4,-(hexafluoroisopropylidene)diphthalic anhydride, 4,4,-oxydianiline, and trimellitic anhydride in a 1/2/2 molar ratio in N -methyl-2-pyrrolidone followed by azeotropic condensation to tetraimide dicarboxylic acid. A series of poly(amide imide imide)s (PAIIs) with inherent viscosities of 0.8,1.1 dL/g were prepared from tetraimide dicarboxylic acid with various aromatic diamines by direct polycondensation. Most of the PAIIs were readily soluble in a variety of amide polar solvents and even in less polar m -cresol and pyridine. Solvent-cast films had tensile strengths ranging from 99 to 106 MPa, elongations at break ranging from 8 to 13%, and initial moduli ranging from 2.0 to 2.3 GPa. The glass-transition temperatures of these PAIIs were recorded at 244,276 °C. They had 10% weight losses at temperatures above 520 °C in air or nitrogen atmospheres. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1092,1102, 2002 [source]

Synthesis and Investigation of Submicrometer Spherical Indium Oxide Particles

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2008
Sung-En Lin
Spherical indium (In) oxide in submicrometer size is considered as a practical material in photonic bandgap applications. To obtain narrow size distribution, systematic studies of different conditions such as precursor concentration, reaction temperature, and other parameters have been carried out and are reported here. Tri- or dicarboxylic acid of citric acid (CA), malic acid, and tartaric acid were introduced into the reaction system and In-precipitates of spherical shape were produced. The particle size and internal morphology were observed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction and thermal analysis were performed. The reaction kinetics analysis shows that the reaction rate depends on the reaction temperature, urea, and In concentration rather than on CA. [source]

Poly[bis(,3 -5,-carboxy-2,2,-bipyridine-5-carboxylato-,4O:N,N,:O,)lead(II)]

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2009
Cheng-Zhi Xie
The title compound, [Pb(C12H7N2O4)2]n, obtained by reaction of Pb(NO3)2 and 2,2,-bipyridine-5,5,-dicarboxylic acid (H2bptc) under hydrothermal conditions, has a structure in which the unique PbII cation sits on a twofold axis and is octa-coordinated by four O-atom donors from four Hbptc, ligands and four N-atom donors from two Hbptc, ligands in a distorted dodecahedral geometry. With each PbII cation connected to six Hbptc, ligands and each Hbptc, ligand bridging three PbII cations, a three-dimensional polymeric structure is formed. From a topological point of view, the three-dimensional net is binodal, with six-connected (the PbII cation) and three-connected (the Hbptc, ligand) nodes, resulting in a distorted rutile (42.8)2(4489122) topology. [source]

Structural effects on the solid-state photodimerization of 2-pyridone derivatives in inclusion compounds

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2009
Marina Telzhensky
The structures of six crystalline inclusion compounds between various host molecules and three guest molecules based on the 2-pyridone skeleton are described. The six compounds are 1,1,-biphenyl-2,2,-dicarboxylic acid,2-pyridone (1/2), C14H10O4·2C5H5NO, (I,a), 1,1,-biphenyl-2,2,-dicarboxylic acid,4-methyl-2-pyridone (1/2), C14H10O4·2C6H7NO, (I,c), 1,1,-biphenyl-2,2,-dicarboxylic acid,6-methyl-2-pyridone (1/2), C14H10O4·2C6H7NO, (I,d), 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol,1-methyl-2-pyridone (1/2), C30H22O2·2C6H7NO, (II,b), 1,1,6,6-tetraphenyl-2,4-hexadiyne-1,6-diol,4-methy-2-pyridone (1/2), C30H22O2·2C6H7NO, (II,c), and 4,4,,4,,-(ethane-1,1,1-triyl)triphenol,6-methyl-2-pyridone,water (1/3/1), C20H18O3·3C6H7NO·H2O, (III,d). In two of the compounds, (I,a) and (I,d), the host molecules lie about crystallographic twofold axes. In two other compounds, (II,b) and (II,c), the host molecules lie across inversion centers. In all cases, the guest molecules are hydrogen bonded to the host molecules through O,H...O=C hydrogen bonds [the range of O...O distances is 2.543,(2),2.843,(2),Å. The pyridone moieties form dimers through N,H...O=C hydrogen bonds in five of the compounds [the range of N...O distances is 2.763,(2),2.968,(2),Å]. In four compounds, (I,a), (I,c), (I,d) and (II,c), the molecules are arranged in extended zigzag chains formed via host,guest hydrogen bonding. In five of the compounds, the guest molecules are arranged in parallel pairs on top of each other, related by inversion centers. However, none of these compounds underwent photodimerization in the solid state upon irradiation. In one of the crystalline compounds, (III,d), the guest molecules are arranged in stacks with one disordered molecule. The unsuccessful dimerization is attributed to the large interatomic distances between the potentially reactive atoms [the range of distances is 4.027,(4),4.865,(4),Å] and to the bad overlap, expressed by the lateral shift between the orbitals of these atoms [the range of the shifts from perfect overlap is 1.727,(4),3.324,(4),Å]. The bad overlap and large distances between potentially photoreactive atoms are attributed to the hydrogen-bonding schemes, because the interactions involved in hydrogen bonding are stronger than those in ,,, interactions. [source]

The crucial role of C,H...O and C=O..., interactions in the building of three-dimensional structures of dicarboxylic acid,biimidazole compounds

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2009
Xiao-Li Gao
The supramolecular architectures of three dicarboxylic acid,biimidazole compounds, namely, 2,2,-biimidazolium malonate, C6H8N42+·C3H2O42,, (I), 2,2,-bi(1H -imidazole) succinic acid, C6H6N4·C4H6O4, (II), and 2,2,-biimidazolium 2,2,-iminiodiacetate chloride, C6H8N42+·C4H6NO4,·Cl,, (III), are reported. The crystal structures are assembled by the same process, namely double conventional N,H...O or O,H...N hydrogen bonds link the dicarboxylates and biimidazoles to form tapes, which are stacked in parallel through lone-pair,aromatic interactions between carbonyl O atoms and biimidazole groups and are further linked via weak C,H...O interactions. The C=O..., interactions involved in stacking the tapes in (II) and the C,H...O interactions involved in linking the tapes in (II) and (III) demonstrate the crucial role of these interactions in the crystal packing. There is crystallographically imposed symmetry in all three structures. In (I), two independent malonate anions have their central C atoms on twofold axes and two biimidazolium dications each lie about independent inversion centres; in (II), the components lie about inversion centres, while in (III), the unique cation lies about an inversion centre and the iminiodiacetate and chloride anions lie across and on a mirror plane, respectively. [source]

Rat Liver Microsomal Lipid Peroxidation Produced during the Oxidative Metabolism of Ethacrynic Acid

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 4 2001
Kyoko Yamamoto
Two oxidative metabolites of ethacrynic acid with dicarboxylic acid and hydroxylated ethyl group, respectively, were formed in the reaction mixture. The oxidative metabolism of ethacrynic acid was inhibited by cytochrome P450 inhibitors. The formation of TBARS was remarkably depressed by inhibitors like diethyldithiocarbamate and disulfiram. These results indicate that lipid peroxidation occurred in rat liver microsomes through the oxidative metabolism of ethacrynic acid. [source]

Characterization of Dicarboxylic Acids for Cellulose Hydrolysis

BIOTECHNOLOGY PROGRESS, Issue 3 2001
Nathan S. Mosier
In this paper, we show that dilute maleic acid, a dicarboxylic acid, hydrolyzes cellobiose, the repeat unit of cellulose, and the microcrystalline cellulose Avicel as effectively as dilute sulfuric acid but with minimal glucose degradation. Maleic acid, superior to other carboxylic acids reported in this paper, gives higher yields of glucose that is more easily fermented as a result of lower concentrations of degradation products. These results are especially significant because maleic acid, in the form of maleic anhydride, is widely available and produced in large quantities annually. [source]

Photoisomerization of a Maleonitrile-Type Salen Schiff Base and Its Application in Fine-Tuning Infinite Coordination Polymers

CHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2010
Chun-Wei Lin
Abstract Strategically designed salen ligand 2,3-bis[4-(di- p -tolylamino)-2-hydroxybenzylideneamino]maleonitrile (1), which has pronounced excited-state charge-transfer properties, shows a previously unrecognized form of photoisomerization. On electronic excitation (denoted by an asterisk), 1Z*,1E isomerization takes place by rotation about the C2C3 bond, which takes on single-bond character due to the charge-transfer reaction. The isomerization takes place nonadiabatically from the excited-state (1Z) to the ground-state (1E) potential-energy surface in the singlet manifold; 1Z and 1E are neither thermally inconvertible at ambient temperature (25,30,°C), nor does photoinduced reverse 1E*,1Z (or 1Z*) isomerization occur. Isomers 1Z and 1E show very different coordination chemistry towards a ZnII precursor. More prominent coordination chemistry is evidenced by a derivative of 1 bearing a carboxyl group, namely, N,N,-dicyanoethenebis(salicylideneimine)dicarboxylic acid (2). Applying 2Z and its photoinduced isomer 2E as building blocks, we then demonstrate remarkable differences in morphology (sphere- and needlelike nanostructure, respectively) of their infinite coordination polymers with ZnII. [source]

Biosynthesis of New Indigoid Inhibitors of Protein Kinases Using Recombinant Cytochrome P450 2A6

CHEMISTRY & BIODIVERSITY, Issue 1 2005
Zhongliu-Liu Wu
Glycogen synthase kinase-3 (GSK-3) is a potential drug target for a number of human diseases. Some indigoids have been found to be potent inhibitors of GSK-3, and individual compounds with better activity, specificity, and solubility are desired. In this work, a new disubstituted indigoid generation system was developed with a tryptophanase-deficient Escherichia coli strain as a host to express the human cytochrome P450 2A6 mutant L240C/N297Q, which catalyzes the oxidation of indole to isatin and indoxyl, which in turn react to generate indigoids. Forty-five substituted 1H -indoles from commercial sources were used as substrates in the system, and indigoid mixtures were tested as potential inhibitors of GSK-3. After preliminary screening, cell extracts with high inhibitory activity towards GSK-3,/, were fractionated, and the IC50 values of twelve individual indigoids were measured for GSK-3,/, as well as the protein kinases CDK1/cyclinB and CDK5/p25. Several indigoids, including an indigo, showed stronger inhibition than found in previous work. The most potent towards GSK-3,/,, dimethyl indirubin 5,5,-dicarboxylate (IC50 of 51,nM), was modified by chemical reactions. One product, indirubin 5,5,-dicarboxylic acid 5-methyl ester, inhibited GSK-3,/, with an IC50 of 14,nM and selectivity nearly 40-fold over CDK1 and CDK5. Indirubin-5-5,-dicarbonitrile was also modified to the corresponding 3,-oxime, which had low specificity but showed very high inhibition of all three kinases with IC50 values of 5, 13, and 10,nM towards GSK-3,/,, CDK1, and CDK5, respectively. Thus, this system has the potential to generate new indigoids with therapeutic potential. [source]

Analysis of Single-Molecule Fluorescence Spectroscopic Data with a Markov-Modulated Poisson Process

CHEMPHYSCHEM, Issue 14 2009
Mark Jäger Dr.
Abstract We present a photon-by-photon analysis framework for the evaluation of data from single-molecule fluorescence spectroscopy (SMFS) experiments using a Markov-modulated Poisson process (MMPP). A MMPP combines a discrete (and hidden) Markov process with an additional Poisson process reflecting the observation of individual photons. The algorithmic framework is used to automatically analyze the dynamics of the complex formation and dissociation of Cu2+ ions with the bidentate ligand 2,2,-bipyridine-4,4,dicarboxylic acid in aqueous media. The process of association and dissociation of Cu2+ ions is monitored with SMFS. The dcbpy-DNA conjugate can exist in two or more distinct states which influence the photon emission rates. The advantage of a photon-by-photon analysis is that no information is lost in preprocessing steps. Different model complexities are investigated in order to best describe the recorded data and to determine transition rates on a photon-by-photon basis. The main strength of the method is that it allows to detect intermittent phenomena which are masked by binning and that are difficult to find using correlation techniques when they are short-lived. [source]

Synthesis, Crystal Structures and Thermal Stabilities of [Cu(bpp)2(bpdc)(H2O)2]n·2nH2O and [Cu(bpp)2]n·n (tdc) ·7.5nH2O

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2008
Jing-Hua YU
Abstract Two novel copper(II) coordination polymers [Cu(bpp)2(bpdc)(H2O)2]n·2nH2O (1) and [Cu(bpp)2]n·n(tdc)·7.5nH2O (2) (H2bpdc=biphenyl-4,4,-dicarboxylic acid, bpp=1,3-di(4-pyridyl)propane and H2tdc=thiophene-2,5-dicartboxylic acid) have been synthesized by the reactions of Cu(NO3)2 and bpp with the H2bpdc or H2tdc, respectively at room temperature. In the complexes 1 and 2, their Cu atoms have a distorted octahedral geometry, and two water molecules coordinate weakly to the Cu atom in the long axial direction. Both complexes have one-dimensional linear polymer structures. In complex 1, both carboxylate groups of the bpdc can coordinate to Cu atom, while both carboxylate groups of the tdc dianion in complex 2 do not coordinate to the Cu atom, which only balance the charge. In the both complexes, the bpp ligand has different conformation: trans - trans in complex 1 and trans - gauche in complex 2. The thermal gravimetric analyses indicate that both complexes are stable under 110 and 160 °C, respectively. [source]

1D Ladder-like Chain and 1D Channeled 3D Supramolecular Architectures Based on Benzophenone-2,4,-dicarboxylic Acid

CHINESE JOURNAL OF CHEMISTRY, Issue 4 2008
Xiao-Gang YANG
Abstract The hydrothermal reactions of AgNO3, 2,2,-bipyridyl, and benzophenone-2,4,-dicarboxylic acid gave rise to two 3D supramolecular architectures, namely H2L·H2O (1), [Ag(bpy)2]·HL·H2O (2) (bpy2,2,-bipyridyl, H2Lbenzophenone-2,4,-dicarboxylic acid). The two compounds are extended by hydrogen bonds in two different approaches. In the case of 1, one-dimensional ladder-like structure is firstly formed through O,H···O hydrogen bonding between H2L ligands and water molecules, then extended to a 3D supramolecular architecture. Compound 2 possesses 3D supramolecular architecture containing 1D open channels, which are driven due to the strong H-bonding interactions occurring between the HL anions and water molecules; interestingly, [Ag(bpy)2]+ cations are linked together through ,-, interactions between bpy ligands and weak Ag···Ag interactions, and then reside in these channels by C,H···O hydrogen-bond. The photoluminescence properties of these compounds were also investigated, the emission maxima for 2 exhibits red-shift compared with that of free ligand and 1 due to chelating effect of the 2,2,-bipyridine ligand to the silver ion and the presence of aromatic ,-packing. [source]

Role of the charge in continuous beds in the chiral separation of hydroxy acids by ligand-exchange capillary electrochromatography

ELECTROPHORESIS, Issue 17 2003
Oliver Lecnik
Abstract This paper deals with the chiral separation of hydroxy acids using diallyl-dimethylammonium chloride as a positive charge-providing agent in the continuous bed. The chiral continuous bed was prepared by in situ copolymerization of monomers, including an L -4-hydroxyproline derivative as a chiral selector. This phase was applied to the chiral separation of hydroxy monocarboxylic acids and hydroxy dicarboxylic acids, respectively. The influence of both the selector concentration and the charge-providing agent on retention and separation was investigated. [source]

Silicon-Assisted Direct Covalent Grafting on Metal Oxide Surfaces: Synthesis and Characterization of Carboxylate N,N,-Ligands on TiO2

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010
Henri Arzoumanian
Abstract The easy covalent bonding of an OH-bearing molecule onto a metal oxide surface can be done by transesterifying a trimethylsilylated hydroxy function with the surface OH groups. This results in the grafting of the organic molecule directly on the matrix, accompanied by the formation of trimethylsilanol, which can easily be eliminated as volatile hexamethyldisiloxane and water. This was accomplished on a TiO2 matrix with three carboxylic acids: acetic, isonicotinic, and 2,2,-bipyridyl-4,4,-dicarboxylic acids. The N,N,-immobilized ligand was then used for a dioxidomolybdenum entity and tested as such at room temperature and under atmospheric pressure O2 oxidation of ethylbenzene. All intermediates and grafted species were fully characterized by 13CMAS NMR spectroscopy, and thermogravimetric and elemental analysis. [source]

Equilibrium and kinetic investigation of the interaction of model palladium(II) complex with biorelevant ligands

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2010
Mohamed M. Shoukry
Pd(DME)Cl2 complex was synthesized and characterized, where DME is 2-{[2-(dimethylamino)ethyl]-methylamino}ethanol. Stoichiometry and stability constants of the complexes formed between various biologically relevant ligands (amino acids, peptides, DNA constituents, and dicarboxylic acids) and [Pd(DME)(H2O)2]2+ are investigated at 25°C and at constant 0.1 M ionic strength. The effect of dielectric constant of the medium on the stability constant of Pd(DME)-CBDCA complex, where CBDCA is cyclobutanedicarboxylate, is also reported. The concentration distribution diagrams of the various species formed are evaluated. The kinetics of base hydrolysis of amino acid esters coordinated to Pd(DME)2+ complex is investigated. The effect of the temperature on the kinetics of base hydrolysis of glycine methyl ester complex is studied. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 608,618, 2010 [source]