Mellitate Anions Research Articles

In Situ and Ex Situ Luminescence Investigation of Rare Earth Layered Double Hydroxides Intercalated with Mellitate Anion

In Situ and Ex Situ Luminescence Investigation of Rare Earth Layered Double Hydroxides Intercalated with Mellitate Anion

Solid-state supramolecular structure formed between the 1-(diaminomethylene)thiourea and mellitic acid

The single crystals of hexakis(1-(diaminomethylene)thiouron-1-ium) benzene-1,2,3,4,5,6-hexacarboxylate (mellitate(6-)) tetrahydrate suitable for the X-ray analysis were grown using a solution growth technique at room temperature. The compound crystallises in centrosymmetric space group of the triclinic system. The conformation of six crystallographically independent 1-(diaminomethylene)thiouron-1-ium cations is not strictly planar, but twisted. Both planar arms of the cations are oppositely rotated by 6.1(1) ÷ 20.9(1)o around the CN bonds involving the central N atom. All of the carboxylate groups of mellitate(6-) anion are inclined to the plane of aromatic six-membered carbon ring by 43.0(1) ÷ 72.0(1)o. Oppositely charged components i.e. 1-(diaminomethylene)thiouron-1-ium cations and mellitate(6-) anion interact each other via NH⋯O hydrogen bonds forming hexakis(1-(diaminomethylene)thiouron-1-ium) mellitate units that further interact with the water molecules forming hexakis(1-(diaminomethylene)thiouron-1-ium) mellitate tetrahydrate supramolecular architecture. Hirshfeld surface and the analysis of 2D fingerprint plots are used for illustrate both qualitatively and quantitatively interactions between the units governing the supramolecular assemblies. The compound was also characterised by vibrational spectroscopy. The vibrational assignment have been supported by the isotopic frequency shift.

Mellitate: A multivalent anion with extreme charge density causes rapid aggregation and misfolding of wild type lysozyme at neutral pH.

Due to its symmetric structure and abundance of carboxyl groups, mellitic acid (MA–benzenehexacarboxylic acid) has an uncommon capacity to form highly ordered molecular networks. Dissolved in water, MA dissociates to yield various mellitate anions with pronounced tendencies to form complexes with cations including protonated amines. Deprotonation of MA at physiological pH produces anions with high charge densities (MA5- and MA6-) whose influence on co-dissolved proteins has not been thoroughly studied. As electrostatic attraction between highly symmetric MA6- anions and positively charged low-symmetry globular proteins could lead to interesting self-assembly patterns we have chosen hen egg white lysozyme (HEWL), a basic stably folded globular protein as a cationic partner for mellitate anions to form such hypothetical nanostructures. Indeed, mixing of neutral HEWL and MA solutions does result in precipitation of electrostatic complexes with the stoichiometry dependent on pH. We have studied the self-assembly of HEWL-MA structures using vibrational spectroscopy (infrared absorption and Raman scattering), circular dichroism (CD), atomic force microscopy (AFM). Possible HEWL-MA6- molecular docking scenarios were analyzed using computational tools. Our results indicate that even at equimolar ratios (in respect to HEWL), MA5- and MA6- anions are capable of inducing misfolding and aggregation of the protein upon mild heating which results in non-native intermolecular beta-sheet appearing in the amide I’ region of the corresponding infrared spectra. The association process leads to aggregates with compacted morphologies entrapping mellitate anions. The capacity of extremely diluted mellitate anions (i.e. at sub-millimolar concentration range) to trigger aggregation of proteins is discussed in the context of mechanisms of misfolding.

Hydrothermal Synthesis, Crystal Structure and Magnetic Properties of Lithium Manganese Complex of Benzene-Hexacarboxylic Acid (Mellitic Acid)

A new mellitate complex LiMn[C6(COO)6]0.5(H2O)2 (1) has been synthesized by the reaction of mellitic acid and Mn(OAc)2·4H2O in the presence of LiOH·H2O. 1 was characterized by the elemental analyses, IR spectra, TGA and the single crystal X-ray diffraction. X-ray crystal structural analysis revealed that the Li cation has a distorted tetrahedral geometry, coordinated by three carboxylic oxygen atoms and one water molecule. The Mn cation is coordinated to one water molecule and five carboxylic oxygen atoms in a slightly distorted octahedral coordination geometry. The mellitate anions behave as a bridging ligand and link six lithium ions and eight manganese ions repeatedly to form an interesting three-dimensional metal–organic coordination polymer. Variable-temperature magnetic susceptibility measurements indicate the presence of antiferromagnetic behavior. A new mellitate complex LiMn[C6(COO)6]0.5(H2O)2 has been synthesized. X-ray crystal structural analysis revealed that the mellitate anions behave as the bridging ligand and link six lithium ions and eight manganese ions repeatedly to form an interesting three-dimensional metal–organic coordination polymer. Its magnetic behavior was studied.

Control of Molecular Packing in the ET Based Conductor by Supramolecular Mellitate Networks (ET = Bis(ethylenedithio)tetrathiafulvalene)

Electrochemical oxidation of bis(ethylenedithio)terathiafulvalene (ET) with mellitic acid and pyridine in methanol produces a partially oxidized salt of [ET]3[C6(COO)6H42-]2[C5H5NH+]2·CH3OH·2H2O (1). In the crystal of 1, mellitate anions form a two-dimensional hydrogen-bonding double-sheet layer with pyridinium, methanol, and water. ET molecules are packed between the layers, forming a two-dimensional conducting sheet. The ET arrangement in the sheet resembles that in α-ET2I3, which has a metal-to-insulator transition. The transition into insulating states is completely suppressed in 1 due to the close packing of ET molecules in the supramolecular mellitate network.

Poly[[bis[pentaaquagadolinium(III)]-μ4-benzene-1,2,3,4,5,6-hexacarboxylato] tetrahydrate

The title compound, {[Gd2(C12O12)(H2O)10]·4H2O} n , consists of an extended network of Gd ions coordinated by the mellitate anions and water molecules. In this complex, each Gd atom involves a dodecahedral coordination environment comprising five water molecules and three O atoms from two separate mellitate anions. The center of mass of the hexaanion [C6(COO)6]6− coincides with a crystallographic inversion center.

Mellitate Anions: Unique Anionic Component with Supramolecular Self‐Organizing Properties

AbstractFor Abstract see ChemInform Abstract in Full Text.

Mellitate anions: unique anionic component with supramolecular self-organizing properties

Mellitate obtained by deprotonation of mellitic acid (benzene hexacarboxylic acid) is a unique anion; the negative charge and the hydrogen-bonding network pattern in the crystal structure vary with the number of sites deprotonated. Structural studies on a number of organic ammonium salts have revealed that the formation of an infinite network of mellitate anions occurs preferentially even in conditions in which proton donors co-exist in solution. The advantage of utilizing mellitate as an anionic component is that the cationic component is packed in the space provided by the anionic network. This scheme can be applied even when attractive forces, such as π–π stacking of π-radicals, operate between the cations. The combination with mellitate has been determined to lead to novel assembly structures of such cationic species.

Crystal design of cation-radical salts based on the supramolecular self-organizing arrangement of mellitate anions

Mellitate anions form hydrogen-bonding infinite networks in the salts with pyridinium cations. The network pattern depends on the number of deprotonation (n) from the mellitic acid; for n = 3, triangular hydrogen-bond units form a two-dimensional sheet, while for n = 2, dual hydrogen-bond units induce one-dimensional belts or two-dimensional grids. These self-organizing properties have been utilized for the crystal design of the TTF-type radical cation salts. Crystallization with TMTTF gave two kinds of crystals. One of the radical cation salt crystals consists of a channel network of the anions and one-dimensional columns of TMTTF in the channels. In the other TMTTF salt, the anions with n = 1 form a two-dimensional sheet with methanol molecules. The TMTTF radicals are packed between the sheets with their molecular planes parallel to the anion planes.

Hydrothermal synthesis and structural investigation of silver magnesium complex of benzenehexacarboxylic acid (mellitic acid), Ag 2Mg 2[C 6(COO) 6] · 8H 2O with two-dimensional layered structure

Crystal and molecular structure of silver magnesium mellitate, Ag 2Mg 2[C 6(COO) 6] · 8H 2O, was synthesized hydrothermally and characterized by X-ray structure analysis. The complex crystallizes in the monoclinic system, space group P2/ n, with unit cell dimensions of a=7.4347(2), b=9.9858(2), c=14.4248(3) Å, β=99.2429(5)°, V=1055.01(4) Å 3, and Z=2. The structure was solved and refined to R=0.036 ( R w=0.045) for 1707 independent reflections [ I o>2 σ( I o)]. The Ag cations are coordinated by six carboxylic oxygen atoms of mellitate anions with composition of [C 6(COO) 6] 6− on the (1 0 1) plane; each mellitate anion linking three neighboring Ag distorted trigonal prisms produces a two-dimensional layered structure parallel to (1 0 1). The Mg cations, which are coordinated by four water molecules and two carboxylic oxygen atoms, are intercalated between the two-dimensional layer stacks. The carboxylate group coordinated to Mg and Ag cations serve as a tridentate ligand in that structure. The number of water molecules incorporated into the mellitate compound is controlled mainly by ionic radii of metal cation in the structure. Furthermore, the ionic radii of metal cations in the mellitate compound play an essential role in arrangement of mellitate anions in the structure, whether as a one-dimensional infinite chain, a two-dimensional layered structure, or a three-dimensional framework structure.

Network formation of mellitate anions ([C6(COO)6H6−n]n−) in the salts with piperidinium derivatives and o-phenylenediammonium

Single crystals of mellitate anion ([C6(COO)6H6−n]n−) with piperidinium [C5H10NH2+]3[C6(COO)6H33−] (1) and [C5H10NH2+]2[C6(COO)6H42−]·CH3OH·3H2O (2), with 1-methylpiperidinium [C5H10NHCH3+]2[C6(COO)6H42−]·2H2O (3), and with o-phenylenediammonium [C6H4(NH3)22+]2[C6(COO)6H24−]·2CH3OH (4) have been prepared and structurally characterized. In all of the salts, two-dimensional (2D) networks of mellitate anions were formed due to the strong self-organization of the anion. In 1, a 2D hexagon-type network of hydrogen-bond has been observed to form among the anions. This is characteristic of the mellitate anions with n = 3 (n: deprotonation number from the acid). In other salts, a 2D anion network containing either water molecules or –NH3 groups commonly formed. Since the network pattern occurs with different cation species, this hydrogen-bonding unit was determined to be dominant in the n = 2 anion with water and the n = 4 anion with –NH3 species.

Hydrogen-Bond Networks of Mellitate Anions ([C6(COO)6H6−n]n−) in Salts with Pyridine Derivatives

Abstract Single crystals of mellitate anion ([C6(COO)6H6−n]n−) salts with 3-aminopyridinium, [3-NH2C5H4NH+]3[C6(COO)6H33−] (1), 4-methylpyridinium, [4-CH3C5H4NH+]2[CH3C5H4N]2[C6(COO)6H42−] (2), [4-CH3C5H4NH+]2[C6(COO)6H42−]·2CH3OH (3), pyridinium, [C5H5NH+]2[C6(COO)6H42−]·2H2O (4), 3-methylpyridinium, [3-CH3C5H4NH+]2[C6(COO)6H42−] (5), [3-CH3C5H4NH+]5[C6(COO)6H33−][C6(COO)6H42−]·CH3OH (6), and isoquinolinium, [C9H7NH+]2[C6(COO)6H42−]·CH3OH (7), [C9H7NH+]2[C9H7NH0.50.5+][C6(COO)6H3.52.5−]·CH3OH (8) have been structurally characterized. In these crystals, strong hydrogen-bonds between the mellitate anions are formed. Various arrangements that depend on the deprotonation number, n, have been found. All hydrogen-bonds found between the anions are combinations of a carboxy and a carboxylato group. The “triangular hydrogen-bond” unit between the anions, in which three anions are connected by the three hydrogen-bonds to form a triangle, in the salt with n = 3, induces the two dimensional (2-D) sheet self-organizing structure in this crystal. “Dual hydrogen-bond” units between the anions, in which two pairs of the hydrogen-bonds connect the neighboring anions, have been found in the salts with n = 2 or 2.5. The repetition of the co-planer “dual hydrogen-bond” induces the anion one-dimensional (1-D) belt structure, while the combination of the standing and co-planer “dual hydrogen-bond” units induces the 2-D grid structure. These 2-D grids are further linked by hydrogen-bonds to form a channel. In all the salts (n = 3, 2, 2.5), the counter cation molecules are arranged in the space defined by the anion network.

Synthesis, crystal structures and magnetic behavior of polymeric lanthanide complexes with benzenehexacarboxylic acid (mellitic acid)

Three lanthanide complexes with mellitic acid [Ce 2{C 6(COO) 6}(H 2O) 8]·H 2O ( 1), [Eu 2{C 6(COO) 6}(H 2O) 8]·H 2O ( 2) and [Yb 2{C 6(COO) 6}(H 2O) 10]·2H 2O ( 3), have been synthesized and structurally characterized by X-ray crystallography and magnetic properties. The three compounds crystallize in the monoclinic space space P2 1/ n, with unit cell dimensions of: a = 8.627(2), b = 13.218(2), c = 9.650(1) A ̊ , β = 95.93(1)° and Z = 2 for 1;a = 8.505(2), b = 13.145(1), c=9.536(2) A ̊ , β=94.73(2)° and Z=2 for 2; a = 8.420(1), b = 9.224(4), c = 16.229(1) A ̊ , β = 100.267(9)° and Z = 2 for 3. All three structures consist of an extended network of metal ions, coordinated to mellitate anions and water molecules linked by a complex hydrogen bonding. 1 and 2 are isomorphous with near isostructural [M 2{C 6(COO) 6}(H 2O) 8] units in which the metal ion is coordinated by four water molecules and five oxygen atoms of the mellitate anions, and each mellitate group involves a tetrakis(bidentate) and bis(unidentate) coordination mode bridging six metal ions forming a three-dimensional framework. In 3 the ytterbium atom is bound with five water molecules and three oxygen atoms of the mellitate anion, and each mellitate moiety bridges four dodecahedral Yb(III) ions yielding a two-dimensional sheet structure. The magnetic susceptibility of 1 and 3 as a function of temperature (5.0–300 K) exhibits a sharp maximum at 6.0 K for both compounds.

SYNTHESIS AND STRUCTURE OF A THREE-DIMENSIONAL LANTHANUM(III) COORDINATION POLYMER WITH MELLITATE, {La2[C6(COO)6](H2O)9} · 2H2O

Abstract The crystal and molecular structure of a lanthanum(III) mellitate, La2C12H22O23, has been determined by X-ray structural analysis using a combination of direct and heavy atom methods. The complex crystallizes in the monoclinic space group P21/n with unit-cell dimensions of a = 6.723(4), b = 11.368(5), c = 29.813(4) Å and β = 95.851(3)°. Block-diagonal least-squares refinement using automated diffractometer-collected data resulted in R = 2.5 and Rw = 3.4. The crystal structure consists of layers perpendicular to the a axis. Each layer is formed by an extended network of lanthanum ions coordinated with mellitate anions and water molecules, and linked through a complex three-dimensional hydrogen-bonding network. Among the six carboxylate groups of the mellitate anion, five form coordination bonds to six lanthanum atoms. The two independent lanthanum ions are both nine-coordinate and the configuration around lanthanum is a tricapped trigonal prism with the La-O bond distances ranging from 2.457 Å to 2.704 Å.

Unendliche Y2(H2O)10[C6(COO)6]-Ketten in Y2[C6(COO)6] · 14H2O / Infinite Chains of Y2(H2O)10[C6(COO)6] in Y2[C6(COO)6] · 14 H2O

Colourless monoclinic single crystals of Y2[C6(COO)6]· 14H2O were grown in aqueous silica gel (space group P21/n, a = 847.5(1), b = 923.4(2), c = 1632.0(3) pm, β = 100.33(1)°, Ζ = 2, 223 parameters, 1784 reflections, Rg = 0.0357). Y3+ is coordinated by 5 water molecules and 3 oxygen atoms of the mellitate anion in a dodecahedral fashion. Y3+ and [C6(COO)6]6- ions are linked by coordinative bonds, yielding infinite chains of composition Y2(H2O)10[C6(COO)6] extending parallel to [100]. Hydrogen bonds connect adjacent chains.

Crystal structures and Mössbauer studies of NpO +2 complexes with polycarboxylic acids

Complexes of neptunyl ( 237NpO + 2 ) with pyromellitic (benzene tetracarboxylic) and mellitic (benzene hexacarboxylic acids were prepared; their formula is: (Na 3NpO 2C 10O 8H 2) 2·11H 2O and Na 4(NpO 2) 2C 12O 12·8H 2O respectively. These solids were studied by X-ray diffraction, Mössbauer spectroscopy ( 237Np) and magnetic susceptibility measurements. ▪ ▪ ▪Fig. 3. Cation-cation complex of NhO 2 + The crystal structure of the Na 3NpO 2 pyromellitate was refined to R = 0,027 and R w = 0.040 for 6793 independent reflexions. Crystal data are: P 1 , a = 14.46(1) Å, b = 9.404(8) Å, c = 6.768(4) Å, α = 95.08°, β ] 103.23°, γ = 87.47°, Z = 1. In this structure (Fig.1), the NpO + 2 ions are bonded to four pyromellitate anions whose carboxyl oxygens form the base of a pentagonal bipyramid surrounding the Np atom. The Mössbauer spectrum recorded at 4.2 K and shown in Fig. 2, exhibited a magnetic hyperfine splitting attributed to paramagnetic relaxation phenomena [1, 2]. The crystal structure of the Na 4(NpO 2) 2 mellitate was solved by classical methods. R = 0.044 and R w = 0.056 for 2372 independent reflexions. a = 12.53(1) Å, b = 11.58(2) Å, c = 17.81(2) Å, β = 105.79°, Z = 4, space group C 2/c. Two NpO + 2 ions are connected to each other and coordinated to four mellitate anions. Figure 3 shows the ‘cationcation’ complex of NpO + 2 . The χ curve for this complex follows the Curie-Weiss law. A magnetic transition occurs at about 10 K. The Mössbauer spectrum ( 237Np) recorded at 4.2 K and then fitted [3] leads to the following hyperfine parameters: H eff = 5490(10) k0e, e 2qQ = 97(2) mm s −1. The isomer shift (δ = −19.2(5) mm s −1 ref. NpAl 2 [4]) corresponds to that of Np(V). Two Np atoms are at a distance shorter than 3.5 Å in this complex and this could explain the magnetic transition observed.