Acid Dianion Research Articles

Late-Stage Functionalization Using a Popular Titrating Agent: Aryl-Chlorides and -Fluorides Activation by the Diphenylacetic Acid Dianion.

Aryl-chlorides and -fluorides are common building blocks, but their use in synthesis is limited by the high stability of their Ar-X bonds. The generation of aryl radicals via activation of strong Ar-X bonds is possible through the irradiation of tailor-made organic anions, which become reductants stronger than lithium metal. We report that the combination of visible light with the cheap diphenylacetic acid dianion is an even better tool, showing excellent activity across a variety of complex substrates and providing opportunities for late-stage drug modification. Ar-X bonds are chemoselectively activated in the presence of more easily reducible functions, such as Alk-Cl ones and carbonyl groups. These results pave the way to original synthetic strategies that would be otherwise considered impossible.

Binding of Glutamic Acid to Silver and Gold Nanoparticles Investigated by Surface-Enhanced Raman Spectroscopy.

Glutamate is the most important excitatory neurotransmitter, which is relevant for the study of several diseases such as amyotrophic lateral sclerosis and Alzheimer. It is the form L-glutamic acid (Glu) takes at physiologically relevant pHs. The surface-enhanced Raman spectra of Glu obtained at pH values ranging from 3.3 to 12 are collected in the presence of silver and gold colloids and on solid substrates. The observed bands are compared with the positions of calculated normal modes for free neutral glutamic acid, glutamic acid monohydrate, glutamic acid bound to gold and silver atoms, and sodium glutamate. Although gold atoms prefer to bind to the NH2 group as compared to carbonyl groups, silver atoms prefer binding to hydroxyl groups more than binding to the amino group. SERS spectra of glutamic acid solutions with a pH value of 12, in which both carboxylic groups are deprotonated, indicate a complexation of the glutamic acid dianion with the sodium cation, which was introduced into the solution to adjust the pH value. Further research towards an optimal substrate is needed.

Synthesis, Characterization and Biological Activity Evaluation of Some 1,N-bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl) Alkanes

In this paper, we present the synthesis, characterization and evaluation of antiproliferative activity for four compounds carrying the 4-amino-5-mercapto-1,2,4-triazol-3-yl scaffold. The synthesis of 1,n-bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl) alkanes was carried out using as starting reagents the dihydrazides of oxalic, malonic, succinic and adipic acids, using mercaptoacetic acid dianion as a leaving group, by a one-pot synthesis method implemented in our research group for the synthesis of 3-substituted-5-mercapto-1,2,4-triazoles. The compounds were obtained with modest yields (12–60%) but with good purity and were characterized by elemental analysis, FTIR, 1H-NMR and 13C-NMR spectroscopy. Also, the stability of the synthesized bis-triazoles was investigated under controlled thermal stress in a dynamic oxidative atmosphere. The last part of the study consisted of biological activity evaluation, by evaluating the antiproliferative activity against the A375 line (human malignant melanoma), as well as on viability of the BJ fibroblast cell line, using MTT and LDH assays.

Controlled Mechanical Actuation of Adsorbed Forisome Mechanoproteins: A Step Toward Biomolecular Devices

AbstractForisomes are giant structural plant mechanoproteins that reversibly undergo a transition from a longitudinally expanded to a contracted (dispersed) state. This transition is driven by a change in the concentration of Ca2+ ions. Artificial forisomes, expressed in yeast, have a width of 0.7 µm and a length of 4.6 µm and adsorb onto a gold surface. Scanning electrochemical microscopy imaging of the adsorbed forisomes reveales a heterogenous film in which several proteins adsorb together on the substrate surface. The adsorbed forisomes maintain their biological activity and undergo reversible contraction–expansion reactions. Infrared spectroscopy (IRS) shows that Ca2+ ions are coordinated to the carboxylate groups in the side chains of Asp and Glu affecting the 3D arrangement of the corresponding protein fragments allowing for a longitudinal contraction, dispersion of the forisome volume, and water uptake. In films, expanded forisomes accumulate small ions (ethylendiaminetetraacetic acid dianion or [Fe(CN)6]4‐) that are released upon Ca2+ driven dispersion. The properties described here make forisomes attractive for biotechnological applications.

Heteroleptic Metal-Organic Frameworks of Lanthanides (Lа, Ce, and Ho) Based on Ligands of the Anilate Type and Dicarboxylic Acids

New heteroleptic metal-organic frameworks of lanthanides, units of which contain anionic organic ligands of two types, are prepared by the solvothermal synthesis in N,N-dimethylformamide (DMF). The cross-linked coordination polymer [Ho2(CA)2(Bdc)·4DMF] (I) and two scaffold derivatives [La2(pQ)2(Bpdc)·4DMF] (II) and [Ce2(CA)(Bdc)2·4DMF]·2DMF (III·2DMF), where CA is chloranilic acid dianion, pQ is 2,5-dihydroxy-3,6-di-tert-butyl-para-benzoquinone dianion, Bdc is terephthalic acid dianion, and Bpdc is 4,4'-biphenyldicarboxylic acid dianion, are synthesized. The structures of compounds I, II, and III·2DMF are studied by X-ray diffraction (XRD) (CIF file CCDC nos. 2212230, 2212231, and 2212232, respectively).

Synthesis, Crystal Structure, and Luminescent Properties of a New Holmium(III) Coordination Polymer Involving 2,5-Dihydroxy-1,4-terephthalic Acid Dianion as Ligand

A novel coordination polymer {[Ho2(DHTA)3(H2O)5]·H2O}n (1) was synthesized by hydrothermal synthesis (DHTA = 2,5-dihydroxy-1,4-terephthalic acid anion). The crystallographic data show that complex 1 crystallizes in a triclinic system with space group P1¯, with a = 9.6617(17) Å, b = 11.902(2) Å, c = 13.284(2) Å, α = 100.617(3)°, β = 92.765(2)°, γ = 106.715(2)°, V = 1429.6(4) Å3, Z = 2, C24H24O24Ho2, and Mr = 1026.290. Complex 1 contains two eight-coordinated metal centers Ho(III). The TGA results show that the weight loss can be ascribed to the removal of the organic component from 400 to 650 °C. At the temperature above 650 °C, the residue is Holmium(III) oxide (Ho2O3). The luminescent results reveal that the complex has potential application as a new green luminescence material.

Visual Hg(II) sensing in aqueous solution via a new 2,5-Bis(4-pyridyl)thiazolo[5,4-d]thiazole-based fluorescence coordination polymer

A new fluorescence coordination polymer [Zn(Py2TTz)(5-OH-IPA)]n (1) (Py2TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole, 5-OH-IPA = 5-hydroxyisophthalic acid dianion) was synthesized, which exhibited the characteristics of fluorescence quenching and bathochromic shift toward Hg(II) in aqueous solution at pH 7.00. Mechanism study showed that the interactions between Hg(II) ions and Py2TTz ligands in 1 were responsible for the fluorescence emission change. Thanks to the specific interactions between 1 and Hg(II), excellent selectivity was achieved both in aqueous solution and in solid test paper. The detection limit of 1 for Hg(II) sensing was 125.76 nmol L−1 and a linear rang was 1.00–10.00 μmol L−1. More importantly, satisfactory recovery and accuracy of 1 for Hg(II) sensing were also obtained in buffer-free real water samples.

1D and 2D Cobalt(II) coordination polymers with dipicolinic acid ligands and photocatalytic CO2 reduction

1D and 2D cobalt(II) coordination polymers, [Co(2,3-dpc)(H 2 O) 2 ] n ( 1 ), [Co(2,5-dpc)(H 2 O) 3 ] n ( 2 ) and [Co(3,5-dpc)(H 2 O) 2 ] n ( 3 ) (dpc = dipicolinic acid dianion) have been successfully synthesized by reaction of dipicolinic acid ligands with CoF 2 in aqueous methanolic solution under hydrothermal conditions. High resolution mass spectroscopy investigation reveals the forming process of CO during the photocatalytic CO 2 reduction and the plausible mechanisms are proposed.

Photoreaction of 9,10-Anthraquinone-2,6-disulfonic Acid and Ascorbic Acid Complexed at the Cationic Bilayer Interface and Consecutive Radical Dynamics

The antioxidant ability of substances such as vitamin C has attracted wide attention, and many antioxidant effects on our body are considered to act in the biomembrane interface region. However, the detailed dynamics of the radicals at the interface have not been deeply clarified. Here, we studied the reaction of photoexcited 9,10-anthraquinone-2,6-disulfonic acid dianion (AQDS2–) and ascorbic acid in the cationic vesicle solution of didodecyldimethyl ammonium bromide using time-resolved electron paramagnetic resonance (TR-EPR) and UV–vis absorption methods. The results were compared with those of micellar and aqueous systems. Analysis of UV–vis spectra revealed the formation of an intermolecular charge-transfer complex of ascorbic acid monoanion (AscH–) and AQDS2– at the cationic bilayer interface. The TR-EPR spectra revealed a hydrogen atom abstraction reaction by the excited triplet state of AQDS2– from AscH– to form an ascorbic acid monoanion radical (Asc•–) and an anthrasemiquinone dianion radical (A...

Crystal structure of aqua-trans-bis-(dimethyl sulfoxide-κO)(pyridine-2,6-di-carboxyl-ato-κ3O2,N,O6)nickel(II).

In the title complex, [Ni(C7H3NO4)(C2H6OS)2(H2O)], the NiII cation is situated on a twofold rotation axis and exhibits a distorted octa-hedral NO5 coordination environment defined by a tridentate pyridine-2,6-di-carb-oxy-lic acid dianion (dpa2-), two dimethyl sulfoxide (DMSO) mol-ecules, and a water mol-ecule. In the crystal, the complex mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into a three-dimensional network whereby DMSO mol-ecules from neighboring complexes overlap to form layers parallel to (001), alternating with layers of NiII-dpa2- moieties. The title complex is isotypic with its cobalt(II) analogue.

Guest-Induced Arylamide Polymer Helicity: Twist-Sense Bias and Solvent-Dependent Helicity Inversion.

A benzene/naphthalene alternately incorporated amide polymer was synthesized and characterized. (1) H NMR spectroscopy, fluorescence, and circular dichroism (CD) experiments indicated that, in chloroform, the polymer could be induced by the chiral l-aspartic acid dianion or one of its derivatives to form a helical tubular conformation with twist-sense bias. CD titration studies showed that the l-aspartic acid dianion (8 equiv.) could lead to a maximum Cotton effect. It was also revealed that the twist-sense bias obeyed the majority rule, and 70 % enantiomeric excess could realize the maximum helicity bias. Adding acetonitrile to the solution of chloroform caused inversion of the guest-induced helicity bias of the polymer.

Crystal structure of catena-poly[[(dimethyl sulfoxide-κO)(pyridine-2,6-di-carboxyl-ato-κ(3) O,N,O')nickel(II)]-μ-pyrazine-κ(2) N:N'

The title coordination polymer, [Ni(C7H3NO4)(C4H4N2)(C2H6OS)] n , consists of [010] chains composed of Ni(II) ions linked by bis-monodentate-bridging pyrazine mol-ecules. Each of the two crystallographically distinct Ni(II) ions is located on a mirror plane and is additionally coordinated by a dimethyl sulfoxide (DMSO) ligand through the oxygen atom and by a tridentate 2,6-pyridine-di-carb-oxy-lic acid dianion through one of each of the carboxyl-ate oxygen atoms and the pyridine nitro-gen atom, leading to a distorted octa-hedral coordination environment. The title structure exhibits an inter-esting complementarity between coordinative bonding and π-π stacking where the Ni-Ni distance of 7.0296 (4) Å across bridging pyrazine ligands allows the pyridine moieties on two adjacent chains to inter-digitate at halfway of the Ni-Ni distance, resulting in π-π stacking between pyridine moieties with a centroid-to-plane distance of 3.5148 (2) Å. The double-chain thus formed also exhibits C-H⋯π inter-actions between pyridine C-H groups on one chain and pyrazine mol-ecules on the other chain. As a result, the inter-ior of the double-chain structure is dominated by π-π stacking and C-H⋯ π inter-actions, while the space between the double-chains is occupied by a C-H⋯O hydrogen-bonding network involving DMSO ligands and carboxyl-ate groups located on the exterior of the double-chains. This separation of dissimilar inter-actions in the inter-ior and exterior of the double-chains further stabilizes the crystal structure.

Crystal structure of μ-oxalodi-hydroxamato-bis-[(2,2'-bipyrid-yl)(di-methyl sulfoxide-κO)copper(II)] bis-(perchlorate).

The centrosymmetric binuclear complex, [Cu2(C2H2N2O4)(C10H8N2)2(C2H6OS)2](ClO4)2, contains two copper(II) ions, connected through an N-deprotonated oxalodi-hydroxamic acid dianion, two terminal 2,2'-bi-pyridine ligands, and two apically coordinating dimethylsulfoxide mol-ecules. Two non-coordinating perchlorate anions assure electrical neutrality. The copper(II) ions in the complex dication [Cu2(C10H8N2)2(μ-C2H2N2O4)(C2H6SO)2](2+) are in an O2N3 square-pyramidal donor environment, the Cu-Cu separation being 5.2949 (4) Å. Two hydroxamate groups in the deprotonated oxalodi-hydroxamic acid are located trans to one each other. In the crystal, O-H⋯O and C-H⋯O hydrogen bonds link the complex cations to the perchlorate anions. Further C-H⋯O hydrogen bonds combine with π-π contacts with a centroid-to-centroid separation of 3.6371 (12) Å to stack the mol-ecules along the a-axis direction.

Copper inorganic-organic hybrid coordination compound as a novel L-cysteine electrochemical sensor: Synthesis, characterization, spectroscopy and crystal structure

Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2] ⋅2H2O, where pydc = pyridine-2,6-dicarboxylic acid (dipicolinic acid) and pz = pyrazine has been synthesized and characterized by elemental analysis, spectra (IR, UV-Vis), thermal (TG/DTG) analysis, magnetic measurements and single crystal X-ray diffraction. In the dimeric structure, the planar tridentate pyridine-2,6-dicarboxylic acid dianion coordinates to a Cu(II) ion in a meridional fashion and defines the basal plane of the complex. The fourth equatorial coordination site is then occupied by a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. The axial positions of each Cu(II) complex are occupied by one water molecule to form a distorted square pyramidal geometry. The complicated hydrogen bonding network accompanied with C–O ⋯π and C–H ⋯π stacking interactions assemble the crystal structure of 1 into a fascinating supramolecular architecture. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] (Cu-PDAP) on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) is described. Oxidation of cysteine on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the Cu-PDAP/CNTs film displays excellent electrochemical catalytic activities towards L-cysteine oxidation. Dinuclear coordination compound of Cu(II), namely, [Cu2(pydc)2(pz)(H2O)2].2H2O, has been synthesized and characterized by elemental analysis, spectral (IR, UV-Vis), thermal (TG/DTG) analysis as well as single crystal X-ray diffraction. Electrochemical behavior of [Cu2(pydc)2(pz)(H2O)2] on the surface of carbon nanotube (CNTs) glassy carbon electrode (GCE) was described and oxidation of cysteine on the surface of modified electrode was investigated.

Syntheses, crystal structures, and luminescent properties of three metal coordination polymers based on adipic acid and 2-(pyridine-3-yl)-(1H)-benzimidazole

Three new metal coordination polymers constructed from adipic acid and 2-(pyridin-3-yl)-(1H)-benzimidazole ligands, [M(ADP)(3PBI)2(H2O)2]·2H2O (M = Ni and Co for 1 and 2, respectively) and [Cd(ADP)(3PBI)(H2O)] (3) [ADP = adipic acid dianion; 3PBI = 2-(pyridin-3-yl)-(1H)-benzimidazole], have been synthesized by hydrothermal reactions and were characterized by X-ray single-crystal diffraction, elemental analyses, IR, powder X-ray diffraction, and thermogravimetry. Complexes 1 and 2 are isostructural. Both form a 1-D linear chain structure, which is further assembled into a 3-D supramolecular framework by π⋯π stacking and hydrogen bonding interactions. Complex 3 possesses a binuclear unit and displays a 2-D layer which is further extended to a 3-D supramolecular architecture via hydrogen bonding and other weak packing interactions. The luminescent properties of 3 were investigated in the solid state at room temperature.

Synthesis, structure and thermolysis of Ba(II)–M(II) (M = Co, Zn) bimetallic 3D-polymers as precursors of complex oxides

The Ba–Co and Ba–Zn heterometallic 3D-polymers [BaM(H2O)5(Me2mal)2]n, where Me2mal2− is the dimethylmalonic acid dianion, MII=Co (1), Zn (2), were synthesized by the reactions of CoSO4 or Zn(OAc)2, respectively, with Ba(OH)2 in water. The thermal dehydration of 1 and 2 occurs in one step. A kinetic model for the dehydration of complexes 1 and 2 is proposed. Crystalline BaCoO3−x and BaZnO2 were formed as a result of solid state thermolysis of 1 and 2 under the following conditions: air flow rate 60ml/min, heating rate 10°C/min up to t=800°C (1) or 750°C (2), followed by storage for 12h at the same temperatures.

Synthesis, structure, solution and DFT studies of a pyrazine-bridged binuclear Cu(II) complex: On the importance of noncovalent interactions in the formation of crystalline network

A pyrazine-bridged binuclear Cu(II) complexes with formulae of [Cu2(chel)2(pyz)(H2O)4], (1, pyz=pyrazine, H2chel=chelidamic acid), has been synthesized and characterized by elemental analyses, IR spectroscopy and solution studies. The crystal structure of the binuclear Cu(II) complex has been determined by X-ray single-crystal diffraction technique. Both copper(II) metal centers are bridged by pyrazine. The coordination environment around each copper(II) atom can be described as a distorted octahedral geometry. The axial positions of each Cu(II) complex are occupied by two water molecules and equatorial positions are occupied by a tridentate chelidamic acid dianion and a pyrazine molecule that functions as a linear bidentate ligand bridging two Cu(II) complexes to form a dimer. Hydrogen bonding and CO⋯π interactions link the binuclear Cu(II) complex generating the 3D infinite network. These assemblies are described and analyzed by means of density functional theory (DFT) calculations since they play an important role in the construction of three-dimensional supramolecular frameworks. The protonation constants of pyrazine and chelidamic acid as the building blocks of the proton transfer systems (H2chel-pyz) and their corresponding stability constants were determined by potentiometric studies. The stoichiometry and stability constants of H2chel-pyz complex with Cu2+ was investigated by potentiometric technique in aqueous solution. The results from solution studies were compared with the solid state data, in details.

Magnetically active coordination polymers containing VO2+ and Na+ cations linked by substituted malonic acid anions

The interaction of vanadyl sulfate VOSO4·3H2O and dimethylmalonic (H2Me2mal = = C3H6(CO2H)2), butylmalonic (H2Bumal = C4H10(CO2H)2), and cyclobutane-1,1-dicarboxylic (H2cbdc = C4H6(CO2H)2) acids with Na2CO3 at pH ∼4 in aqueous solutions gives crystals of compounds [Na4(VO)2(Me2mal)4(H2O)]n (1), {[Na6(VO)3(Bumal)6(H2O)15]· ·3H2O}n (2), and [Na2(VO)(cbdc)2(H2cbdc)(H2O)3]n (3), whose structures were determined by X-ray diffraction analysis. The formation of 3D (for 1) and 2D (for 2 and 3) polymer networks occurs in crystals of the compounds. These networks are constructed of mononuclear bis-chelate dianionic fragments [VOL2]2− (L is the corresponding dicarboxylic acid dianion) linked by the Na atoms. The magnetic properties of the obtained compounds were studied. The solid samples and solutions of complexes 1–3 were characterized by ESR spectroscopy.

Synthesis, structure and properties of three isostructure polymer networks based on mixed ligands

Three isostructure coordination polymers with a general formula: [ML(bbi)(H2O)2]n (M=Co, 1; Zn, 2; Cd, 3) {L=fumaric acid dianion, bbi=1,4-bis(1H-imidazol-1-yl)butane} have been successfully prepared by adopting liquid diffusion method. Their structures have been determined by single-crystal X-ray diffractions, and further characterized by elemental analysis, FT-IR spectra, Powder X-ray diffractions and thermogravimetric (TGA) studies. The results show that they all possess a three-dimensional (3D) framework constructed by the double helical chains and L dianions and reveal a 3-fold interpenetrating net with a uninodal 4-connected Diamond-related topology. In addition, the photoluminescent properties of 2 and 3 have also been investigated at room temperature.

Bis(3,5-diamino-4H-1,2,4-triazol-1-ium) 3,4-dioxocyclobutane-1,2-diolate

The asymmetric unit of the title compound, 2C2H6N5 +·C4O4 2−, contains two 3,5-diamino-4H-1,2,4-triazolium cations and one squarate dianion. The squaric acid mol­ecule donated one H atom to each of the two 3,5-diamino-1,2,4-triazole mol­ecules at their N atoms. The squaric acid dianion has four C—O bonds which are shorter than a normal single C—O bond (1.426 Å) and are slightly longer than a normal C=O bond (1.23 Å), which indicates the degree of electron delocalization in the dianion. In the crystal, the cations and dianions are linked by N—H⋯N and N—H⋯O hydrogen bonds into a three-dimensional network.