Potassium Hydrogen Maleate Research Articles

Growth Aspect, Structural and Optical Properties of Unidirectional Growth of Potassium Hydrogen Maleate Single Crystal by Sankaranarayanan–Ramasamy (SR) Method

Growth Aspect, Structural and Optical Properties of Unidirectional Growth of Potassium Hydrogen Maleate Single Crystal by Sankaranarayanan–Ramasamy (SR) Method

Molecular Optimization for Nuclear Spin State Control via a Single Electron Spin Qubit by Optimal Microwave Pulses: Quantum Control of Molecular Spin Qubits

Quantum state control is one of the most important concepts in advanced quantum technology, emerging quantum cybernetics and related fields. Molecular open shell entities can be a testing ground for implementing quantum control technology enabling us to manipulate molecular spin quantum bits (molecular spin qubits). In well-designed molecular spins consisting of unpaired electron and nuclear spins, the electrons and nuclear spins can be bus and client qubits, respectively. Full control of molecular spin qubits, in which client spins interact via hyperfine coupling, is a key issue for implementing quantum computers (QCs). In solid-state QCs, there are two approaches to the control of nuclear client qubits, namely, direct control of nuclear spins by radio-wave (RF) pulses and indirect control via hyperfine interactions by microwave pulses applied to electron spin qubits. Although the latter is less popular in the literature, the indirectness has advantage of greatly reducing unnecessary interactions between a qubit system and its environment. In this work, we investigate molecular spin optimization to find optimal experimental conditions which can afford to achieve the high fidelity of quantum gates by the indirect control scheme. In the present quantum systems, one electron is directly controlled by pulsed ESR techniques without manipulating individual hyperfine resonance, but the states of two nuclear client spins are indirectly steered via hyperfine interactions. Single crystals of potassium hydrogen maleate (KHM) radical and 13C-labeled malonyl radical are chosen as typical molecular spin qubits which exemplify the importance of the symmetry of hyperfine tensors and their collinear properties. We have found that both the non-collinearity of the principal axes of hyperfine coupling tensors and the non-distinguishability/non-equivalency between nuclear spins are key issues which extremely reduce the gate fidelity.

Syntheses, Crystal Structures and an Overview of Alkali Metal Maleates

The crystal structures of four alkali salts of maleic acid have been determined by single crystal X-ray diffraction: crystals of rubidium hydrogen maleate, RbH(C4H2O4), are very nearly centrosymmetrical, i. e., only one hydrogen atom position in the crystal structure violates the centrosymmetry. Thus, the space group is Pbc21 rather than Pbcm. The compound is isotypic with potassium hydrogen maleate, KH(C4H2O4), which has previously been described in space group Pbcm. It has been reinvestigated to prove that the correct space group is also Pbc21. The isotypic pair of rubidium hydrogen maleate maleic acid, RbH(C4H2O4) H2(C4H2O4), and caesium hydrogen maleate maleic acid, CsH(C4H2O4)H2(C4H2O4), crystallise in the triclinic space group P1̄. The geometry of the maleate units in these compounds corresponds well to data of other metal maleates. The only significant variation, concerning the intra-anionic hydrogen bond, is discussed. Furthermore, an overview of previously reported metal maleate structures is given, with special regard to the symmetry of the intramolecular hydrogen bond.

DFT Study of Proton Dynamics in the Potassium Hydrogen Maleate Crystal: the Infrared Versus the Inelastic Neutron Scattering Spectra

Abstract The structure, harmonic frequencies and infrared (IR) intensities of the fundamental transitions in potassium hydrogen maleate (KHM) crystal have been computed using the BLYP/6-31G** method with periodic boundary conditions. The inelastic neutron scattering (INS) intensities of the fundamental transitions were evaluated and compared with the experimental INS spectra of hydrogenated sample and isotopic analogues of the KHM crystal; the agreement is reasonable good. Spectroscopic manifestations of the proton dynamics in the strong intramolecular H-bond were clarified by comparison of the computed frequencies of the IR and INS-active fundamental transitions. Due to several reasons, the number of the bands and their relative intensity were found to differ between the INS and IR spectra of the KHM crystal. Reduced masses for the asymmetric O…H…O stretching vibrations of the hydrogen maleate ion appear to be larger 1 a.m.u. because of the strong coupling between the bridging proton motion and the various intramolecular vibrations.

A neutron scattering study of strong-symmetric hydrogen bonds in potassium and cesium hydrogen bistrifluoroacetates: Determination of the crystal structures and of the single-well potentials for protons

The crystal structures of potassium and cesium bistrifluoroacetates, KH(CF(3)COO)(2) and CsH(CF(3)COO)(2), respectively, were determined at room and cryogenic temperatures with the single crystal neutron diffraction technique. The crystals belong to the monoclinic space groups, I2a and A2a, respectively, and there is no evidence of any structural phase transition. In both crystals, trifluoroacetate entities in centrosymmetric dimers are linked by very short hydrogen bonds lying across a center of inversion. The thermal parameters provide no evidence of any double minimum potential for hydrogen bond protons. Single-minimum potentials were determined via best fitting to the inelastic neutron scattering spectral profiles of the stretching vibrations. They comprise a narrow well for the ground state and a very broad quasiharmonic well for excited states. The spread out of the wave functions of these states shows that protons are no longer confined between the oxygens. Presumably, they are attracted by the lone pairs of oxygen atoms. These potentials emphasize the covalent nature of the OO bond and the ionic character of the hydrogen bond proton.

Anharmonic interactions and infrared bandshape of the hydrogen bond vibration of potassium hydrogen (deuterium) maleate crystals

The spectral profiles of the hydrogen bond vibrations in the potassium hydrogen maleate (KHM) crystal and its deuterated analogue (KDM) were studied theoretically taking into account the Fermi resonance (FR) effect and strong coupling between the hydrogen bond vibration and lattice phonons. In addition, ab initio calculations of the frequencies and intensities of the H(D)-maleate ion for both C 2v and C s symmetry were made. It was found that C s symmetry has to be used and that practically all intense bands have a contribution from the OH vibration. It was shown that, taking into account all the factors: ab initio results, FR and anharmonicity of vibrations, the experimental spectra for both KHM and KDM crystals can be explained adequately. Anharmonic constants were obtained as a result of fitting theoretical spectra to the experimental ones.

Synthesis of Maleated Ionomers via Ring‐Opening Reaction of Epoxidized (Styrene‐Butadiene‐Styrene) Triblock Copolymer with Potassium Hydrogen Maleate and Study of their Properties

A novel method for synthesizing maleated ionomer of (styrene‐butadiene‐styrene) triblock copolymer (SBS) from epoxidized SBS was developed. The epoxidized SBS was prepared via epoxidation of SBS with performic acid formed in situ by 30% H2O2 and formic acid in cyclohexane in the presence of polyethylene glycol 600 as a phase transfer catalyst. The maleated ionomer was obtained by a ring‐opening reaction of the epoxidized SBS solution with an aqueous solution of potassium hydrogen maleate. The optimum conditions for the ring‐opening reaction and some properties of the ionomers were studied. It is necessary to use phase transfer catalyst, ring‐opening catalyst and a pH regulator (dipotassium maleate) for obtaining the epoxy group conversion over 90%. The product was characterized by FTIR spectrophotometry and transmission electron microcroscopy (TEM) to be an ionomer with domains of maleate ionic groups. With increasing ionic groups, the water absorbency and the dilute solution viscosity of the ionomer increase, whereas the oil absorbency decreases. The tensile strength and ultimate elongation of ionomers increase with ionic group content and are higher than those of the original SBS without using any ionic plasticizer, which is usually used with the sulfonated ionomer. The ionomers with 1.2–1.7 mmol ionic groups/g exhibit optimum mechanical properties and behave as thermoplastic elastomers. The ionomer can be used as a compatibilizer for the blends of SBS with oil resistant chlorohydrin rubber (CHR). Addition of 3 wt% ionomer to the blend can increase the tensile strength and ultimate elongation of the blend optimally. The compatibility of the blends enhanced by adding the ionomer was shown by scanning electron microscopy (SEM). The blend of equal weight of SBS and CHR compatibilized by the ionomer behaves as a toluene resistant thermoplastic elastomer.

Synthesis and characterization of maleated ionomers via ring‐opening reaction of epoxidized styrene‐butadiene rubber with potassium hydrogen maleate and study of their behavior as compatibilizer

AbstractA novel method for synthesizing maleate ionomer of (styrene‐co‐butadiene) rubber (SBR) from epoxidized SBR was developed. The epoxidized SBR was prepared via epoxidation of SBR with performic acid formed in situ by H2O2 and formic acid in cyclohexane. The maleated ionomer was obtained by ring‐opening reaction of the epoxidized SBR solution with an aqueous solution of potassium hydrogen maleate. The optimum conditions were studied. It was found that it is necessary to use phase transfer catalyst and ring‐opening catalyst for enhancing the epoxy group conversion. To obtain 100% conversion addition of dipotassium maleate is important. The product was characterized by FTIR spectrophotometry and transmission electron microcroscopy (TEM). The results showed that the product was really an ionomer with domains of maleate ionic groups. Some properties of the ionomer, such as water absorbency, oil absorbency and dilute solution behavior were studied. With increasing ionic groups, the water absorbency of the ionomer increases, whereas the oil absorbency decreases. The dilute solution viscosity of the ionomer increases abruptly with increasing ionic group content. The ionomer can be used as a compatibilizer for the blends of SBS and chlorosulfonated polyethylene (CSPE). Addition of a small amount of the ionomer to the blend can enhance the mechanical properties of the blends. 3 wt % ionomer based on the blend can increase the tensile strength and ultimate elongation of the blend nearly twice. The compatibility of the blends enhanced by adding the ionomer was shown by scanning electron microscopy. The blend of equal parts of SBS and CSPE compatibilized by the ionomer behaves as an oil resistant thermoplastic elastomer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 792–798, 2006

Comment on: ‘A symmetric hydrogen bond revisited: potassium hydrogen maleate by variable temperature, variable pressure neutron diffraction and plane-wave DFT methods’ [Chem. Phys. Lett. 381 (2003) 102

In their recent Letter Wilson, Thomas and Morrison [Chem. Phys. Lett. 381 (2003) 102] questioned the hydrogen bonding potential function in potassium hydrogen maleate that was proposed by Fillaux, Leygue, Tomkinson, Cousson and Paulus [Chem. Phys. 244 (1999) 387]. Wilson et al.’s argument is not supported by any new experimental data of significance. Moreover, the plane-wave DFT potential they calculate for the hydrogen bond was determined in a range of little significance to the experimental data. Fillaux et al.’s potential still represents the fullest description of the totality of experimental observations.

Reply to comment on: ‘A symmetric hydrogen bond revisited: potassium hydrogen maleate by variable temperature, variable pressure neutron diffraction and plane-wave DFT methods’ [Chem. Phys. Lett. 381 (2003) 102

Issues raised by Fillaux et al. [Chem. Phys. Lett., this issue] regarding the Letter by Wilson et al. [Chem. Phys. Lett. 381 (2003) 102] are considered, and the aims of the modelling undertaken by Wilson et al. on the potassium hydrogen maleate system reiterated, in particular the fact that the equilibrium PES is discussed in Wilson et al. (2003).

A symmetric hydrogen bond revisited: potassium hydrogen maleate by variable temperature, variable pressure neutron diffraction and plane-wave DFT methods

The symmetric hydrogen bond in potassium hydrogen maleate has been re-investigated by diffraction and computational methods. Single crystal neutron diffraction under varying temperature (30–295 K) and pressure (ambient-4 kbar) confirmed the crystallographically-constrained symmetric disposition of the hydrogen atom in the short, strong hydrogen bond for each of eight sets of (p,T) conditions. Plane-wave DFT calculations show the hydrogen atom still to occupy this symmetric position even when crystallographic symmetry is removed, in stark contrast to the results from isolated molecule ab initio calculations. These results demonstrate that the symmetric (or close to symmetric) nature of this hydrogen bond is intrinsic.

Hydrogen bonding and quantum dynamics in the solid state

Hydrogen bonding is of great importance to many fields in physics, chemistry and biology. However, a comprehensive view of this interaction is still far from being achieved. Recent developments of experimental techniques such as neutron diffraction, inelastic neutron scattering (INS), quasi-elastic neutron scattering (QENS) and nuclear magnetic resonance (NMR) T1 measurements provide new information on the structure and dynamics of hydrogen bonds. The INS technique is unique to observing proton dynamics in the quantum regime. In the most favourable cases, potential functions for the proton motions are determined accurately and can be compared with those derived from other techniques or calculated with quantum chemistry methods. Two classical examples are presented to illustrate recent developments. First, tautomerism in centrosymmetric dimers is a prototypical example for proton transfer. The potential functions determined with vibrational spectroscopy or derived from QENS or NMR T1 measurements are quite different. This is tentatively related to the characteristic time scale for each technique. Second, the strong symmetric hydrogen bond in the potassium hydrogen maleate is a model for the intermediate state in the proton transfer chemical reaction. The potential function for the proton determined with INS is quite different from the single minimum potential normally anticipated. The new concept of hydrogen bonding-antibonding vibrational state is emphasized. In all cases, advanced techniques yield a rather complex view of hydrogen bonds dominated by quantum effects that cannot be yet rationalized with the available theoretical tools of quantum chemistry.

Structure and dynamics of the symmetric hydrogen bond in potassium hydrogen maleate: a neutron scattering study

The crystal structure of potassium hydrogen maleate KH(OOC–CHCH–COO) has been studied at 300, 14 and 5 K using three-dimensional single-crystal neutron diffraction data. There is no evidence for any phase transition. The crystal structure is orthorhombic, P bcm (D 2h ll), with four entities in the unit cell ( Z=4), in accord with previous X-ray diffraction work. The ion is nearly planar and deviation from C 2v symmetry is negligible. The short internal hydrogen bond parallel to the c axis, R O⋯O=2.427(1) Å at 5 K, is symmetrical with the proton located at the center. Inelastic neutron scattering (INS) spectra, from 16 to 4000 cm −1, of the fully hydrogenated sample and partially deuterated analogues, KH(OOC–CDCD–COO) and KD(OOC–CHCH–COO), have been recorded for powdered samples and aligned single crystals at 20 K. Complex spectral profiles are observed for the stretching mode of the hydrogen bond, ν a OHO, and for the totally symmetric out-of-plane deformation of the maleate ion. An isotopic mixture of KH(OOC–CDCD–COO), 20%, and KD(OOC–CDCD–COO), 80%, reveals that intermolecular coupling is negligible. Frequencies and intensities are amenable to symmetrical potential functions with a central minimum between secondary minima at higher energy. The INS and infrared band profiles suggest that the planar conformation with C 2v symmetry of the maleate ring is unstable in excited vibrational states. The quantum nature of the hydrogen bond is emphasised with the concept of `hydrogen bonding/anti-bonding' states.

Strong anharmonic effects and generation of anomalously broad bands of high frequency vibrations of molecular type crystals

A theoretical approach was developed to explain the abnormally broad shape bands of ν(XH) stretching vibrations. It was shown that taking into account anharmonic effects such as strong interaction ν(XH) stretching vibrations with the lattice phonons and the Fermi resonance and added to them the Davydov splitting effect in the crystal with a complex structure of the unit cell allows us to describe the principal features of the shape band of high frequency crystal vibrations. We apply the obtained theoretical results for reconstruction of IR spectra of potassium hydrogen maleate (KHM) and adipic acid crystals.

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.

Polarized infrared spectra of potassium hydrogen maleate and potassium deuterium maleate single crystals

The polarized infrared spectra of single crystals for potassium hydrogen maleate (KHM) and its deuterated analogue (KDM) have been measured at room and low (approximately 15 K) temperature. The hydrogen bond and internal vibrations of the maleate ion are discussed. The antisymmetric stretching vibration, ν aOHO, of the strong hydrogen bond gives rise to an intense, broad absorption with its centre of gravity at approximately 820(±50)cm −1, divided into three broad bands at 990, 700 and 545 cm −1 by wide ‘transmission windows’ (at 795 and 605 cm −1). These transmission windows result from the strong anharmonic interaction of ν aOHO with some of the internal modes of the maleate anion. Deuteration results in a surprisingly small change in the ν aOHO absorption. The γOHO vibration obeys C s site symmetry selection rules; thus the hydrogen-bond potential in the KHM crystal is symmetrical with a single minimum. The possibility of coupling between the νCO and νCO vibrations is considered.

A calorimetric study of the short hydrogen-bond system Heat capacities of potassium hydrogen maleate and potassium hydrogen fumarate

The heat capacities of potassium hydrogen maleate and potassium hydrogen fumarate have been measured from 13 to 300 K with an adiabatic calorimeter. No thermal anomalies were observed in either compound. Harmonic-oscillator heat-capacity functions were fitted to the experimental results. Equally good fits were obtained for the two compounds. The differences in the optimized parameters involved in the heat-capacity function have been discussed. The standard thermodynamic functions have been calculated up to 300 K.

Far i.r. spectra of potassium hydrogen maleate

Polarized far i.r. spectra of potassium hydrogen maleate monocrystals recorded at 295 and 10 K are reported and tentative assignments of bands are given.

Vibrational spectra of potassium hydrogen 3,4 furandicarboxylate and intramolecular H-bond

I.r. and Raman spectra of potassium hydrogen 3,4 furandicarboxylate are presented. An assignment of the band is proposed and the details of the hydrogen bond bonds are discussed by analogy with potassium hydrogen maleate. Anharmonic coupling between ν as, OHO and ν s OHO is found in the combination band at about 1000 cm −1.

Molecular vibrational spectroscopy with neutrons, recent results from the spallation neutron source

The Spallation Neutron Source (SNS) is a new source for neutron research. Incident neutrons, with energies up to ca 20,000 cm −1, can be used to excite internal molecular vibrations. A new generation of spectrometers has been produced. These instruments have very high resolution, by the normal standards of neutron spectroscopy. Results will be presented which show this improved resolution. The intensities of the bands observed in neutron spectroscopy contain information on the vibrational displacement of the scattering atom. Results on potassium hydrogen maleate are presented.