Hydrogen Maleate Anion Research Articles

Design, Preparation and Characterization of the Adducts of the Bis‐Amido Cobalticinium Complex [CoIII(η5‐C5H4CONHC5H4N)2][PF6] with Fumaric and Maleic Acids

AbstractThe supramolecular hydrogen‐bonded adducts obtained by treating the cationic bis‐amido complex [CoIII(η5‐C5H4CONHC5H4N)2]+ with fumaric and maleic acid are investigated and their modes of aggregation in the solid state are explored. It is shown that the bis‐amido organometallic complex can be mono‐ and di‐protonated in the reaction with the dicarboxylic acids, leading to the formation of complex, mixed‐anion supramolecular salts containing either the dication [CoIII(η5‐C5H4CONHC5H4N)(η5‐C5H4CONHC5H4NH)]2+, [1H]2+, or the trication [CoIII(η5‐C5H4CONHC5H4NH)2]3+, [1H2]3+. The derivatives of the reaction with fumaric acid, namely, [CoIII(η5‐C5H4CONHC5H4N)(η5‐C5H4CONHC5H4NH)]2+·[PF6]–·1/2[fumarate]2–, [1H]2+·PF6–·1/2[fumarate]2–, and [CoIII(η5‐C5H4CONHC5H4NH)2]3+·[PF6]–·[H(fumarate)2]3–·H3O+·H2O, [1H2]3+·[PF6]–·[H(fumarate)2]3–·H3O+·H2O, contain either the dianion [fumarate]2– or the hydrogen‐bridged supramolecular trianion [H(fumarate)2]3–, depending on the amide/acid stoichiometric ratio. In the case of maleic acid, on the other hand, the possibility of intramolecular hydrogen‐bond formation generates exclusively salts of the hydrogen maleate anions, namely, [CoIII(η5‐C5H4CONHC5H4N)(η5‐C5H4CONHC5H4NH)]2+·5/2[PF6]–·3/2[Hmaleate]–, 2[1H]2+·5/2[PF6]–·3/2[Hmaleate]–, 2[CoIII(η5‐C5H4CONHC5H4NH)2]3+·3[PF6]–·3[Hmaleate]–·2H2O, 2[1H2]3+·3[PF6]–·3[Hmaleate]–·2H2O and [CoIII(η5‐C5H4CONHC5H4NH)2]3+·2[PF6]–·[Hmaleate]–·H2O, [1H2]3+·2[PF6]–·[Hmaleate]–·H2O, in which the hydrogen maleate anions act as bridges between the protonated bis‐amido organometallic sandwiches. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Tetraaquabis(hydrogen maleato)cadmium(II)

The title compound, [Cd(C4H3O4)2(H2O)4], crystallizes in the centrosymmetric space group P\overline 1 with the Cd atom occupying an inversion centre and the monodentate hydrogen maleate anions arranged in a trans configuration. A network of intra- and intermolecular O—H⋯O bonds helps to stabilize the crystal packing.

Benzoylmethyltriphenylphosphonium hydrogen maleate: supramolecular layer formation due to C—H...O interactions

The molecule of the title salt, C26H22OP+.C4H3O4−, consists of a benzoyl­methyl­tri­phenyl­phospho­nium cation (HBPPY) and a hydrogen maleate anion. Owing to a strong O—H⋯O intraionic hydrogen bond, each hydrogen maleate ion forms a ring, described by the graph-set notation S11(7). Several C—H⋯O interactions are present between the cations and anions and contribute to the stabilization of the crystal structure.

Diaqua(diethylenetriamine-κ3N)(perchlorato-κO)copper(II) hydrogenmaleate

The title compound, [Cu(ClO4)(dien)(H2O)2](Hmal), where dien is diethyl­enetri­amine (C4H13N3) and Hmal (C4H3O4) is the hydrogenmaleate anion, contains discrete [Cu(dien)(H2O)2]2+ cations and ClO4− and Hmal− anions. The cation has a square-pyramidal geometry for the primary dien and aqua ligands, with the perchlorate weakly coordinated in a sixth position opposite the apex. The cation and anion lie on crystallographic mirror planes. For the cation, the mirror plane bisects the mol­ecule and runs through two O atoms of the water mol­ecules and the central N atom of the dien ligand. The mirror plane bisects the perchlorate through Cl and two O atoms. A mirror plane is perpendicular to the plane of the Hmal anion, bisecting the central C=C double bond and containing the hydroxyl H atom.

4-aminopyridinium hydrogen maleate.

The title compound, C(5)H(7)N(2)(+)...C(4)H(3)O(4)(-), crystallizes in space group P2(1) with one ion pair in the asymmetric unit. The hydrogen maleate anion possesses nearly planar geometry and displays an extremely short intramolecular O--H...O hydrogen bond, with an O...O distance of 2.4198 (19) A. Classical N-H...O hydrogen bonds, together with short C--H...O contacts, generate an extensive hydrogen-bonding network.

Strong symmetrical intramolecular hydrogen bonds in diprotonated piperazinium bis(hydrogenmaleate)

In the title salt, C4H12N22+·2C4H3O4−, the diprotonated piperazine cation links to two hydrogen maleate anions through N—H⋯O hydrogen bonds. An H atom is approximately centered in an extremely short intramolecular hydrogen bond of the O⋯H⋯O type in each of the hydrogen maleate anions.

Synthesis, Crystal Structure and Magnetic Properties of Diaqua(1,10-Phenanthroline-N,N')-Hydrogenmaleatocopper(Ii) Hydrogenmaleate Monohydrate

Reaction of freshly-prepared CuCO3, phenanthroline monohydrate and maleic acid in CH3OH/H2O(1 : 1 v/v) at pH=2.13 yielded diaqua(1,10-phenanthroline-N,N')hydrogenmaleatocopper(II) hydrogenmaleate monohydrate, [Cu(phen)(H2O)2(C4H3O4)](C4H3O4)(H2O), which consists of [Cu(phen)(H2O)2(C4H3O4)]+ complex cations, hydrogenmaleate anions and lattice H2O molecules. Within the complex cations, the Cu atoms are each square-pyramidally coordinated by two N atoms of one chelating phen ligand and three O atoms of two H2O molecules and one hydrogenmaleato ligand with one H2O molecule at the apical position (d(Cu-N) = 2.001, 2.009 Å, equatorial d(Cu-O) = 1.966 Å and axial d(Cu-O) = 2.235 Å). Through hydrogen bonding, the complex cations, hydrogenmaleate anions and lattice H2O molecules are assembled into 1D chains, which are held together by weak Cu···O interactions (3.139 Å) to form corrugated 2D layers. Significant π-π stacking interactions between neighboring phen ligands leads to supramolecular assembly of the 2D layers. Over the temperature range 5-300 K, the complex obeys the Currie-Weiss law with an effective magnetic moment of 1.78 BM at room temperature.

The crystal structure of an anomalous and tautomeric salt: 2:1 complex of (E)-2(1H)-6-methyl-pyridiniminium hydrogen maleate with maleic acid

An anomalous salt in the 2:3 ratio of the original partners of 2-amino-3-methylpyridine and maleic acid, named tautomerically and structurally as the 2:1 complex of (E)-2(1H)-6-methyl-pyridiniminium hydrogen maleate with maleic acid, has been prepared and characterized by X-ray crystallography. The salt crystallizes in the monoclinic space group C2/c with a=15.891(2)Å,b=5.4040(10)Å,c=30.761(4)Å,β=94.810(10)°, V=2632.3(7)Å3,Z=4. The maleic acid partner adopts two forms of configuration, the hydrogen maleate anion and the original maleic acid. The hydrogen maleate anion is tied by O–H⋯O short intramolecular hydrogen bonds with a non-centered hydrogen atom, and bridged by maleic acid with hydrogen bond of OH⋯O to form whole crystal. The hydrogen maleate anion is linked to the individual pyridinium cation by intermolecular hydrogen bond of N(sp2)–H⋯O and N(sp3)–H⋯O. The heterocycle is fully protonated, which arouses amino–imino tautomerization. The geometrical arrangement in the crystal structure is characterized by the formation of laminar dimers of centrosymmetric pyridiniminium hydrogen maleate that is arranged in a manner of layer upon layer.

A theoretical study of the effect of a tetraalkylammonium counterion on the hydrogen bond strength in Z-hydrogen maleate.

High-level ab initio calculations (B3LYP/6-31+G and QCISD(T)/6-311+G**) were carried out to resolve the disagreement between recent experimental and computational estimates of the relative strength of the intramolecular hydrogen bond in Z-hydrogen maleate anion with respect to the normal hydrogen bond in maleic acid. The computational estimates for the strength of the intramolecular hydrogen bond in the gas-phase maleate anion are in a range of 14-28 kcal/mol depending on the choice of the reference structure. Computational data suggest that the electrostatic influence of a counterion such as a tetraalkylammonium cation can considerably weaken the hydrogen bonding interaction (by 1.5-2 times) in the complexed hydrogen maleate anion relative to that in the naked anion. The estimated internal H-bonding energies for a series of Z-maleate/R4N+ salts (R = CH3, C2H5, CH3CH2CH2CH2) range from 8 to 13 kcal/mol. The calculated energy differences between the E- and Z-hydrogen maleates complexed to Me4N+, Et4N+, and Bu4N+ cation are 4.9 (B3LYP/6-31+G(d,p)) and 5.7 and 5.8 kcal/mol (B3LYP/6-31G(d)). It is also demonstrated that the sodium cation exerts a similar electrostatic influence on the hydrogen bond strength in bifluoride anion (FHF-). The present study shows that while low-barrier short hydrogen bonds can exist in the gas phase (the barrier for the hydrogen transfer in maleate anion is only 0.2 kcal/mol at the QCISD(T)/6-311+G//QCISD/6-31+G level), whether they can also be strong in condensed media or not depends on how their interactions with their immediate environment affect their strength.

Theoretical Study of the Low-Barrier Hydrogen Bond in the Hydrogen Maleate Anion in the Gas Phase. Comparison with Normal Hydrogen Bonds

Relative strengths of normal and low-barrier hydrogen bonds (LBHBs) in the gas phase were analyzed by means of quantum-mechanical and thermodynamic calculations on the mesaconic/citraconic and several maleic/fumaric cis/trans isomerization equilibria. All geometries were fully optimized with correlation effects included via second-order Møller−Plesset perturbation theory. The cis isomer of the maleic monoanion (also known as hydrogen maleate) is greatly stabilized in the gas phase owing to the formation of an intramolecular low-barrier hydrogen bond more than 20 kcal/mol stronger, in free energy terms, than the corresponding normal intramolecular hydrogen bond in maleic diacid. The very short internuclear distance (2.41 Å) obtained at the MP2 level between the hydrogen donor and the hydrogen acceptor in hydrogen maleate, as well as the high value of the NMR chemical shift for the participating proton, are two other characteristics experimentally attributed to the formation of an LBHB. The transition state structure for proton exchange in the maleic monoanion is symmetrical. In this structure, the interactions of the central hydrogen atom with the acceptor and the donor atoms are classified as covalent by Bader's theory of molecular structure. In any case, our calculations indicate that the zero-point energy for maleate monoanion is above the energy barrier for proton transfer. This fact allows free motion of the hydrogen atom lying on the ground vibrational state in accordance with the single symmetrical minimum experimentally predicted in nonpolar solvents.

Structure and polarized infrared and Raman spectra of the solid complex of betaine and maleic acid (1:1)

Crystals of betaine maleic acid (BHM) of the formula [(CH 3) 3N +CH 2COOH]·[HCOOCH=CHCOO −] are monoclinic, space group P 1 n , with a = 6.138(3), b = 10.831(4), c = 17.244(5) A ̊ , β = 92.85(4)° and Z = 4. The betaine cation is linked to the maleic monoanion by a strong intermolecular O…O hydrogen bond of length 2.527(3) Å forming a “structure unit”. The hydrogen maleate anion forms a ring structure containing a short, very asymmetric intramolecular hydrogen bond: O…O = 2.429(3), OH = 1.04(4), H…O = 1.39(4) Å. The polarized infrared and Raman spectra of the BHM single crystal have been measured at room temperature. The hydrogen bond modes and the internal vibrations of the maleate anion and betaine cation are discussed in relation to the crystal structure. A broad absorption was observed due to the antisymmetric stretching mode of both short hydrogen bonds, but it could not distinguish features pertaining to the intramolecular and intermolecular hydrogen bonds, respectively.

Structure and polarized infrared and Raman spectra of the solid complex of betaine and maleic acid (1:1)

Crystals of betaine maleic acid (BHM) of the formula [(CH 3) 3N +CH 2COOH]·[HCOOCHCHCOO −] are monoclinic, space group P 1 n , with a = 6.138(3), b = 10.831(4), c = 17.244(5) A ̊ , β = 92.85(4)° and Z = 4. The betaine cation is linked to the maleic monoanion by a strong intermolecular O ⋯ O hydrogen bond of length 2.527(3) Å forming a “structure unit”. The hydrogen maleate anion forms a ring structure containing a short, very asymmetric intramolecular hydrogen bond: O ⋯ O = 2.429(3), OH = 1.04(4), H ⋯ O = 1.39(4) A ̊ . The polarized infrared and Raman spectra of the BHM single crystal have been measured at room temperature. The hydrogen bond modes and the internal vibrations of the maleate anion and betaine cation are discussed in relation to the crystal structure. A broad absorption was observed due to the antisymmetric stretching mode of both short hydrogen bonds, but it could not distinguish features pertaining to the intramolecular and intermolecular hydrogen bonds, respectively.

X-ray, FTIR,1H and13C NMR, PM3 and AM1 studies of (N—H⋯N)+and (O—H⋯O)–hydrogen bonds in a complex of 1,8-diaminonaphthalene with maleic acid: proton cavity and basicity of proton sponges

The crystal structure of the title complex has been determined by X-ray analysis. All H atoms were located and refined isotropically; R= 0.041 for 1595 observed reflections. The intramolecular hydrogen bonds are asymmetrical and are characterized by the following distances and angles: 2.670 (3)Å and 146 (3)°Å for the (NHN)+ bridge in the protonated 1,8-diaminonaphthalene cation (DAN+H) and 2.423 (2)Å and 177 (3)°Å for the (OHO)– bridge in the hydrogen maleate anion (HM–). The N+H3 group is engaged in two intermolecular bonds with the anion [N+(H)⋯O distances 2.794 (2) and 2.856 (3)Å]. The interactions of the NH2 group with the anion are weaker [N(H)⋯O distances 3.078 (3) and 3.225 (3)Å]. Most of the bond distances and angles in DAN+H·HM– are very similar to those in the complex of 1,8-bis (dimethylamino)naphthalene with maleic acid, DMAN+H·HM–. The deformations of the naphthalene skeleton in DAN+H·HM– and DMAN+H·HM– are also comparable. In DMAN+H, the proton is located in a cavity formed by four methyl groups, therefore, its exchange is slow on the NMR timescale. In DAN+H the proton is not inside a cavity and the exchange becomes rapid. Although spherical repulsions are not negligible, the cavity is of prime importance for the large basicity of DMAN. The PM3 method reproduces correctly the cation structure and its interactions with the anion but the O⋯O distance in the anion is too long. The AM1 method failed to reproduce the structure of the complex correctly.

Solid-state structures and conformational studies of four 1,2,3,4-tetrahydroacridine Alzheimer's disease therapeutics

The solid-state structures of four 1,2,3,4-tetrahydroacridines [tacrine hydrochloride monohydrate (1), 7-methoxytacrine hydrochloride monohydrate (2), velnacrine hydrogenmaleate (3) and suronacrine hydrogenmaleate (4)] were determined from single-crystal X-ray diffraction analysis. (1): monoclinic,P21/n, a=8.778(1),b=8.521(1),c=17.603(2)A, β=101.34(1)°. (2): monoclinic,C2/c, a=12.326(7),b=18.050(9),c=13.822(8)A, β=113.70(4)°. (3): triclinic,\(P\bar 1\),a=7.349(2),b=9.417(3),c=12.557(4)A, α=109.62(2), β=98.12(2), γ=101.18(2)°. (4): monoclinic,P21/n, a=8.513(6),b=18.74(1),c=13.401(6)A, β=91.21(5)°. FinalR factors for compounds(1)–(4) are 0.047, 0.057, 0.057, 0.11, respectively. The overall arrangement of the common aminotetrahydroacridine skeleton looks similar in all derivatives. However, whereas enantiomerization of the unsubstituted cyclohexenyl rings occurs in (1) and (2), onlyquasi-axially hydroxyl substituted diastereomers are found for (3) and (4). This is presumably due to the different propensities for hydrogen bonding of axially vs. equatorially disposed hydroxyl groups with the hydrogenmaleate anions. Empirical and semiempirical calculations were performed to examine the conformational behavior of the four compounds, bothin vacuo and in solution.

X-ray, Fourier-transform infrared,1H and13C nuclear magnetic resonance, and PM3 studies of (N—H⋯N)+and (O—H⋯O)–intramolecular hydrogen bonds in a complex of 1,8-bis(dimethylamino)naphthalene with maleic acid

The crystal structure of the title compound has been determined by X-ray analysis. The intramolecular hydrogen bond lengths are 2.606(3)A for the (NHN)+ bridge in protonated 1,8-bis(dimethylamino)naphthalene cation (DMAN+H) and 2.401(4)A for the (OHO)– bridge in the hydrogen maleate anion (HM–). The H-bonds are asymmetrical and not strictly linear: NHN, 157(3)° and OHO, 170(5)°. The geometries of the N—H⋯N and O—H⋯C bridges of the investigated cation and anion are dominated by the spherical repulsions of their constituent atoms.The overlapping bands in the absorbance IR spectra of potassium hydrogen (deuteron) maleate are separated in the second-derivative spectra. The strong mixing of the in-plane modes with skeletal modes in the hydrogen maleate ion causes a larger separation (Δν≈ 115 cm–1) of the ν(CO) bands in comparison with those in other type A acid salts containing intermolecular hydrogen bonds (Δν≈ 20–35 cm–1). The observed lack of solvent effect on the IR absorption suggests that the hydrogen bonds in tetrabutylammonium hydrogen maleate and 1,8-bis(dimethylamino)naphthalene hydrogen maleate are not extremely polarizable. 1H and 13C NMR chemical shifts of the investigated compound were measured and identified in two-dimensional (2D) experiments. The 1H NMR spectra show two narrow signals at ca. 19.5 and 18.7 ppm due to the OHO and NHN protons, respectively. The structural parameters of the cation and anion were also determined by quantum-mechanical calculations with the semiempirical MNDO-PM3 method.

Ab initio SCF and møller-plesset calculations on the hydrogen bond in hydrogen maleate

Energies of the hydrogen maleate anion were calculated for the proton located centrally ( C 2v symmetry) and off centre of the hydrogen bond (C 5 symmetry) using the STO-3G, 4-31G, 6-311G, 6-31++G and 6-31G ∗∗ basis sets with the Møller-Plesset (second order) (MP2) correlation correction on the 4-31G and 6-311G optimized geometries. The adiabatic proton potential barrier at the Hartree-Fock level is highest with the 6-311G calculation (2.12 kcal mol −1), but MP2 correction reduces it to 0.1 kcal mol −1. Non-adiabatic barriers are substantially higher. The solvation effect, calculated with a model reported previously, raises the barrier slightly. Geometrical parameters are discussed with respect to the possible strain imposed by the hydrogen bond.

Charge-transfer Character in the Intramolecular Hydrogen Bond: Electronic Structures and Spectra of Hydrogen Maleate Anion and Related Molecules

Abstract Ultraviolet absorption spectra were measured with aqueous solutions of maleic acid (H2M) at various pH values and in concentrated sulfuric acid solutions. With the aid of the theoretical calculations of electronic structures by the modified CNDO-CI method, relatively strong bands observed at 193.5 nm for H2M, at 210.0 nm for the hydrogen maleate anion (HM−), and at 202.8 and ≈230 nm for the dinegative ion (M2−) are assigned to the π–π* transition bands. Special attention was paid to the charge-transfer (CT) character (pertinent to the strong intramolecular hydrogen bond) in the excited states of HM−. Configuration analysis of the wave functions revealed us that the first π–π* band of HM− covered by the much stronger 210 nm band is rich in the CT character pertinent to the hydrogen bond.

Solvent extraction of anions with metal chelate cations—XVIII : Spectrophotometric determination of maleic acid in the presence of fumaric acid by solvent extraction with tris(1,10-phenanthroline)iron(ii) chelate cations

A new colorimetric method is proposed for the determination of maleic acid. Among aliphatic dicarboxylic acids tested, maleic acid was found to be selectively extracted into nitrobenzene as the red ion-association complex (λ max 516 nm) formed between the hydrogen maleate anion and the tris(1,10-phenanthroline)iron(II) cation. At least a 32-fold molar excess of tris(1,10-phenanthroline)iron(II) relative to maleic acid is needed and the optimal pH range is 3–5. A linear relationship is obtained over the concentration range 10 −5–10 −4 M maleic acid. The relative standard deviation was 1.0 %. The colour intensity of the extract remains constant at room temperature for at least 24 hr. A large amount of fumaric acid, the trans-isomer of maleic add, is not extracted under the same conditions. This makes it possible to determine maleic acid in the presence of fumaric acid.

Structure and stability of carboxylate complexes. Part VIII. Crystal and molecular structures of copper(II) hydrogen maleate tetrahydrate and copper(II) maleate hydrate

The crystal and molecular structures of copper(II) hydrogen maleate tetrahydrate and copper(II) maleate hydrate have been determined by three-dimensional X-ray methods. In copper(II) hydrogen maleate (monoclinic, a= 3·594, b= 18·79, c= 9·69 A, γ= 93·25°, space group l2/m, diffractometer data, R= 0·039) the copper atoms are co-ordinated only by water molecules to form [Cu(H2O)4]n2n+ chain cations which are hydrogen bonded to the planar hydrogen maleate anions. In the hydrogen maleate anion the intra-molecular hydrogen bond is 2·409 A. The copper co-ordination octahedron is distorted, Cu–OH2(bridging) 1·959 and 2·682 A, and Cu–OH2(non-bridging) 1·933 A. In copper maleate tetrahydrate (monoclinic, twinned, a= 8·78, b= 7·88, c= 5·35, γ= 125·1°, P21, photographic data, R= 0·096) the copper atom is in a five-co-ordinate square-pyramidal environment. The ligands are a water molecule, Cu–OH2, 2·26 A, a chelating maleate group forming a seven-membered chelate ring, and two oxygen atoms of two other maleate groups. In the basal plane the average copper–oxygen bond length is 1·99 A. Each maleate group is bound to three copper atoms to form a polymeric sheet. The sheets are joined by hydrogen bonding.