Isoperibol Solution-reaction Calorimeter Research Articles

Crystal Structures and Solution Chemical Properties of Two Lactate Complexes Mn[(C3H5O3)2(H2O)2]⋅H2O(s) and Cu(C3H5O3)2(s)

Trihydrated manganese lactate Mn[(C3H5O3)2(H2O)2]⋅H2O(s) and anhydrous copper lactate Cu(C3H5O3)2(s) were synthesized. Crystal structures of the two compounds were characterized by X-ray single crystal diffraction technique. The compositions, spatial structures and coordination modes of the two compounds were determined by analysis of their molecular structures and crystal structures. Lattice potential energies of the compounds were calculated by using the crystallographic data. Molar enthalpies of dissolution of these metal complexes in the ultrapure water were measured by an isoperibol solution-reaction calorimeter with an accuracy of ±0.3%. On the basis of Pitzer's electrolyte solution theory, infinite dilution molar enthalpies of dissolution and Pitzer's parameters of the two lactate complexes soluble in water at T = 298.15 K were calculated. The infinite dilution molar enthalpies (ΔsHm∞) of dissolution of the title compounds were combined with lattice potential energies (UPOT) by a designed thermodynamic cycle, and the average molar enthalpy of hydration of the common lactate ion was calculated to be (407.207 ± 0.038) kJ·mol−1. The mechanism of thermal decomposition or dehydration of the trihydrated manganese lactate was explored by TG-DSC technique, and the difference between molar enthalpies (ΔsHm) of dissolution of trihydrated manganese lactate and anhydrous copper lactate at the same concentration was revealed.

Crystal structure and thermodynamic properties of the coordination compound calcium D-gluconate Ca[D-C6H11O7]2(s)

The coordination compound calcium D-gluconate, Ca[D-C6H11O7]2(s), was synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. Single crystal X-ray diffraction technique revealed that the compound was formed by two D-gluconate anions and one calcium (II) cation. And the D-gluconate anion had a curved chain configuration with an intramolecular bond. The compound exhibited an outstanding chelate property of D-gluconate anions to calcium (II) cations, and the calcium (II) cation was eight-coordinated and chelated by four D-gluconate anions. The lattice potential energy and ionic volume of the anion were calculated to be 1434.05 kJ⋅mol−1 and 0.4211 nm3 from crystallographic data. In accordance with famous Hess law, a reasonable thermochemical cycle was designed and the standard molar enthalpy of formation of Ca[D-C6H11O7]2(s) was calculated as ΔsHm[Ca[D-C6H11O7]2, s] = -(3545.19 ± 1.07) kJ⋅mol−1 by use of an isoperibol solution-reaction calorimeter. Furthermore, molar heat capacities of the compound were measured using a Quantum Design Physical Properties Measurement System (PPMS) with specific heat option within the temperature range from (1.9–300) K. The heat capacities of the compound increased with the temperature and no thermal anomaly was found in the whole temperature region. The experimental data was fitted to a function of the absolute temperature T with a series of theoretical and empirical models for the proper temperature ranges. The values of standard thermodynamic function, Cp,mo/J⋅K−1⋅mol−1, Δ0THmo/kJ⋅mol−1, Δ0TSmo/J⋅K−1⋅mol−1, and ΔoTGmo/T/J⋅K−1⋅mol−1 (=Δ0TSmo-Δ0THmo/T) from T = (0–300) K was calculated based on the fitting results. The standard molar heat capacity, entropy and enthalpy of the compound at T = 298.15 K and 0.1 MPa was determined to be Cp,mo= (493.20 ± 2.70) J·K−1 mol−1, Hmo= (75934 ± 805) J·mol−1, Smo= (471.55 ± 2.78) J·K−1 mol−1, and Gmo/T = - (64658 ± 808) J·K−1⋅mol−1, respectively.

Crystal structure and thermochemical properties of cesium d-gluconate Cs[D-C6H11O7](s)

A novel coordination compound cesium d-gluconate, Cs[D-C6H11O7], have been synthesized and characterized by chemical analysis, elemental analysis, and X-ray diffraction technique. Single-crystal X-ray analysis reveals that the crystal of the compound is monoclinic with space group P21 and Z = 2. The d-gluconate anion in the compound of Cs[D-C6H11O7](s) has a bent-chain conformation, and exhibits an obvious chelate property of d-gluconate anions to cesium(І) cations. The lattice potential energy and ionic volume of the common anion are obtained from crystallographic data. The standard molar enthalpy of formation of the compound Cs[D-C6H11O7](s) is determined to be - (1789.21 ± 0.52) kJ mol−1 by use of an isoperibol solution-reaction calorimeter. The heat capacities of Cs[D-C6H11O7](s) were measured using a Quantum Design Physical Property Measurement System (PPMS) over the temperature range from (1.9–300) K, and the experimental values were fitted as a function of temperature using a series of theoretical and empirical models in the appropriate temperature ranges, from which the corresponding thermodynamic functions were calculated. The molar heat capacity, entropy and enthalpy of Cs[D-C6H11O7](s) at T = 298.15 K and P = 0.1 MP were determined to be Cp,m0=(204.93+2.05)J⋅K−1⋅mol−1, Sm0=(228.21+2.28)J⋅K−1⋅mol−1 and Hm0=(33.928+0.339)kJ⋅mol−1, respectively.

Thermochemical Properties of the Dissolution of Rubidium d-Gluconate Rb[d-C6H11O7]2(s) in Aqueous Solutions

A novel coordination compound rubidium d-gluconate Rb[d-C6H11O7](s) has been synthesized and characterized by chemical analysis, elemental analysis, and X-ray diffraction. Single-crystal X-ray analysis reveals that the crystal is monoclinic with space group P21 and Z = 2. Also, the d-gluconate anion in Rb[d-C6H11O7](s) has a bent-chain conformation, in which the carbon atoms of the anion form two approximate planes. The compound exhibits an obvious chelation of the d-gluconate anions to the rubidum(I) cation and the cation is seven-coordinated to all seven oxygen atoms. The lattice potential energy and ionic volume of the anion d-\( {\text{C}}_{ 6} {\text{H}}_{ 1 1} {\text{O}}_{7}^{ - } \) were obtained to be UPOT = 484.23 kJ·mol−1 and V− = 0.2004 nm3 from crystallographic data. Molar enthalpies of dissolution of Rb[d-C6H11O7](s) in double-distilled water at various molalities were measured by use of an isoperibol solution–reaction calorimeter at T = 298.15 K. According to Pitzer’s electrolyte solution model, the molar enthalpy of dissolution of the title compound at infinite dilution was determined to be \( \Delta_{\text{s}} H_{\text{m}}^{\infty } = (29.76 \pm 0.72){\text{ kJ}}{\cdot}{\text{mol}}^{ - 1} \). The values of the apparent relative molar enthalpies (\( ^{\phi } L_{{}} \)) of the title compound and relative partial molar enthalpies (\( \bar{L}_{2} \) and \( \bar{L}_{1} \)) of the solute and the solvent at different concentrations were derived from the experimental enthalpies of dissolution of the compound. Furthermore, the molar enthalpy of hydration of the anion d-\( {\text{C}}_{ 6} {\text{H}}_{ 1 1} {\text{O}}_{7}^{ - } \) was calculated to be ΔH− = − (166.4 ± 2.7) kJ·mol−1 by use of a thermochemical cycle.

Solubility and molar enthalpy of solution of sucralose in H2O and D2O

The solubility of sucralose, a chlorinated derivate of sucrose was measured for the first time in D2O over a range of temperatures. The results are important to verify the effect of substitution of OH by Cl in the structure of sucrose and the consequent interaction with the heavy water molecules. Our findings indicated that in the temperature range measured, the solubility of sucralose in D2O is 23.3% lower than in H2O. Based on such measurements, the dissolution Gibbs free energy, enthalpy and entropy were then determined. The values of solubility and the mentioned thermodynamic parameters were compared to the ones for sucralose in H2O. Beside the determination of dissolution enthalpy by using the van't Hoff Equation, this thermodynamic property was also measured for the two solvents in an isoperibol solution-reaction calorimeter.

Crystal structure and chemical thermodynamic properties of potassium d-gluconate K(d-C6H11O7)(s)

An important coordination compound potassium d-gluconate K[d-C6H11O7](s) has been synthesized by liquid phase method. The chemical component and crystal structure of the important compound are characterized by chemical analysis, elemental analysis, and X-ray crystallography. Single-crystal X-ray analysis reveals that the compound exhibits the chelate property of d-gluconate anions to K+ cations, a six-membered chelate ring is formed by the coordination of K+ with O2 of carboxylate and O4 of hydroxyl in a d-gluconate, and one cation is coordinated to six d-gluconate anions. The lattice potential energy and ionic volume of the anion [d-C6H11O7]− are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed according to the practical synthesis reaction of the compound and the standard molar enthalpy of formation of the compound is calculated to be −(1754.17 ± 0.19) kJ mol−1 as an important physical quantity in chemical thermodynamics by an isoperibol solution–reaction calorimeter. Molar enthalpies of dissolution of the compound at various molalities are measured at T = 298.15 K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be \(\Delta_{\text{s}} H_{\text{m}}^{\infty }\) = (27.92 ± 0.21) kJ mol−1. In terms of the above value, the standard molar enthalpy of formation of the anion [d-C6H11O7]− in the aqueous solution is determined to be = −(1473.87 ± 0.28) kJ mol−1. The values of relative apparent molar enthalpies (Φ L) and relative partial molar enthalpies of the solvent (\(\bar{L}_{1}\)) and the compound (\(\bar{L}_{2}\)) at different concentrations m/(mol kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.

Thermochemical Properties of Dissolution of Nicotinic Acid C6H5NO2(s) in Aqueous Solution

Nicotinic acid (also known as niacin) was recrystallized from anhydrous ethanol. X-ray crystallography was applied to characterize its crystal structure. The crystal belongs to the monoclinic system, space group P2(1)/c. The crystal cell parameters are a = 0.71401(4) nm, b = 1.16195(7) nm, c = 0.71974(6) nm, α = 90°, β = 113.514(3)°, γ = 90° and Z = 4. Molar enthalpies of dissolution of the compound, at different molalities m/(mol·kg−1) were measured with an isoperibol solution–reaction calorimeter at T = 298.15 K. The molar enthalpy of solution at infinite dilution was calculated, according to Pitzer’s electrolyte solution model and found to be \( \Delta_{\text{sol}} H_{m}^{\infty } = ( 2 7. 3 \pm 0. 2) \) kJ·mol−1 and Pitzer’s parameters (\( \beta_{{\text{MX}}}^{{\text{(0)}L}} \), \( \beta_{{\text{MX}}}^{{\text{(1)}L}} \) and \( C_{{\text{MX}}}^{\phi L} \)) were obtained. The values of apparent relative molar enthalpies (\( {}^{\phi }L \)) and relative partial molar enthalpies (\( \overline{{L_{2} }} \) and \( \overline{{L_{1} }} \)) of the solute and the solvent at different molalities were derived from the experimental enthalpy of dissolution values of the compound. Also, the standard molar enthalpy of formation of the anion \( {\text{C}}_{ 6} {\text{H}}_{ 4} \text{NO}_{2}^{-} \) in aqueous solution was calculated to be \( {\Delta_{\text{f}}^{} H}_{\text{m}}^{\text{o}} ({\text{C}}_{ 6} {\text{H}}_{ 4} {\text{NO}}_{2}^{-} \text{,aq}) = - \left( {603.2 \pm 1.2} \right)\;{\text{kJ}}{\cdot}{\text{mol}}^{-1} \).

Crystal structure and thermodynamic properties of sodium d-gluconate Na[d-C6H11O7](s)

The sodium d-gluconate Na[d-C6H11O7](s) has been synthesized and characterized by elemental analysis and X-ray crystallography. X-ray single-crystal analysis reveals that the compound exhibits an obvious chelate property of d-gluconate anions to sodium cation, and the latter is coordinated to six d-gluconate anions. The lattice potential energy of the compound and ionic volume of the d-gluconate anion are obtained from crystallographic data. In accordance with law of Hess, a reasonable thermochemical cycle is designed and the standard molar enthalpy of formation of the compound Na[d-C6H11O7](s) is determined to be −(1472.68 ± 0.48) kJ mol−1 by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of Na[d-C6H11O7](s) at various molalities are measured at T = 298.15 K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is determined to be (23.783 ± 0.128) kJ mol−1.

Crystal structure and thermochemical properties of potassium pyruvate C3H3O3K(s)

One important compound potassium pyruvate C3H3O3K(s) is synthesized and characterized by chemical analysis, elemental analysis, and X-ray crystallography. X-ray single-crystal structural analysis reveals that the compound is formed by one CH3COCOO− anion and one metal cation K+. An obvious feature of the crystal structure of the compound is the formation of the five-membered chelate ring, and it is good for the stability of the compound in structure. The lattice potential energy of the compound and ionic volume of the anion CH3COCOO− are obtained from crystallographic data. The lattice potential energy is determined to be: UPOT[C3H3O3K(s)] = 567.7 kJ mol−1. The V− (the volume of the anion CH3COCOO−) is estimated to be 0.088 nm3. Molar enthalpies of dissolution of the compound at various molalities in the double-distilled water are measured by use of an isoperibol solution-reaction calorimeter at 298.15 K. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of C3H3O3K(s) at infinite dilution is derived to be 22.9 kJ mol−1. The values of relative apparent molar enthalpies (ΦL), relative partial molar enthalpies (\( \bar{L}_{2} \)) of the compound, and relative partial molar enthalpies (\( \bar{L}_{1} \)) of the solvent (water) at different concentrations m/(mol kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound. Finally, the molar enthalpy of hydration of the anion CH3COCOO−(g) is calculated to be −227.8 kJ mol−1 by the design of the thermochemical cycle.

Crystal Structure and Thermochemical properties of Rubidium Pyruvate CH3COCOORb

One important compound rubidium pyruvate C3H3O3Rb(s) was synthesized and characterized by chemical analysis, elemental analysis and X–ray crystallography. X–ray single crystal structural analysis revealed that the compound is composed of one anion CH3COCOO− and one cation Rb+. An obvious feature of the crystal structure of the compound is the formation of a five-membered chelate ring, which is good for the stability of the compound. The lattice potential energy and ionic volume of the common anion were obtained from crystallographic data. The lattice potential energy $$ U_\text{POT}^{{}} $$ [C3H3O3Rb(s)] is 570.0 kJ·mol−1 and the volume of the anion CH3COCOO− is 0.1139 nm3. Molar enthalpies of dissolution of the compound at various molalities in the doubly distilled water were determined by use of an isoperibol solution-reaction calorimeter at 298.15 K. According to Pitzer’s model, the molar enthalpy of dissolution of C3H3O3Rb(s) at infinite dilution was derived to be 50.0 kJ·mol−1. Finally, the molar enthalpy of hydration of CH3COCOO−(g) was calculated to be −232.0 kJ·mol−1 from a thermochemical cycle.

Crystal structure and thermochemistry of anhydrous potassium 2-pyrazine carboxylate (C5H3KN2O2)

Potassium 2-pyrazine carboxylate C5H3KN2O2 [abbreviated as K(PCA)(s)] was synthesized, and the synthesis was carried out in the mixed solvent of ethanol and water. Its crystal structure was characterized by X-ray crystallography. And its low-temperature heat capacities were measured by use of a precise automatic adiabatic calorimeter with a small sample in the temperature region of 78–400 K. A polynomial equation of experimental molar heat capacities as a function of the temperature has been obtained. The smoothed molar heat capacities and thermodynamic functions of the compound were calculated based on the fitted polynomial equation. A reasonable thermochemical cycle was designed on the basis of the synthesis reaction of the substance, and the standard molar enthalpies of dissolution for the reactants and products of the reaction in the selected solvent were measured by an isoperibol solution-reaction calorimeter, respectively. The enthalpy change of the reaction was calculated as—(65.396 ± 0.388) kJ mol−1. Finally, the standard molar enthalpy of formation of the title complex was calculated as—(532.106 ± 1.196) kJ mol−1 by using the Hess thermochemical cycle. Furthermore, the reliability of the designed thermochemical cycle was verified by UV–Vis spectra of the solutions obtained from the dissolution of reactants and products.

Low-temperature heat capacities and standard molar enthalpy of formation of 2-pyrazinecarboxylate cupric(II) complex Cu(pyza)2(H2O)2

2-Pyrazinecarboxylate cupric(II) complex Cu(pyza)2(H2O)2(s) was synthesized by the method of liquid phase synthesis. The composition and structure of the compound were characterized by chemical and elemental analyses and X-ray crystallography. Low-temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 400 K. A polynomial equation of the heat capacities as a function of the temperature was fitted by the least-square method. The smoothed heat capacities and the thermodynamic functions of the compound relative to 298.15 K were calculated and tabulated at an interval of 5 K. In accordance with Hess’ law, a thermochemical cycle was designed, the enthalpy change in the reaction of 2-pyrazinecarboxylic acid with cupric acetate monohydrate was determined by the use of an isoperibol solution-reaction calorimeter, and the standard molar enthalpy of formation of the complex was calculated to be −(1191.282 ± 2.457) kJ mol−1 by the use of the dissolution enthalpies and other auxiliary thermodynamic quantities.

Study on thermodynamic property for ionic liquid [C4mim][Lact](1-butyl-3-methylimidazolium lactic acid)

Lactic acid ionic liquid [C4mim][Lact] (1-butyl-3-methylimidazolium lactic acid) was synthesized by the neutralization method. Using the solution–reaction isoperibol calorimeter, the molar enthalpies of solution, ΔsolHm, with different molalities were determined in the temperature range from (288.15 to 308.15 ± 0.01) K with an interval of 5 K. In terms of Archer’s method, the standard molar enthalpy of solution for [C4mim][Lact], \( \Delta _{\text{sol}} H_{\text{m}}^{\theta } \), was obtained, and then, the values of apparent relative molar enthalpy, ΦL, and the Pitzer’s parameters \( \beta_{\text{MX}}^{(0)\text{L}} \) and \( \beta_{\text{MX}}^{(1)\text{L}} \) were determined for [C4mim][Lact]. The plot of \( \Delta _{\text{sol}} H_{\text{m}}^{\theta } \) versus (T—298.15) K is a good straight line, and its slope is the standard molar heat capacity of solution, \( \Delta C_{\text{p,m}}^{\theta } = 240\,{\text{J}}\,{\text{K}}^{ - 1} \). According to Glasser’s theory of lattice energy, the hydration enthalpy of cation and anion, (ΔH+ + ΔH−) = −471 kJ mol−1, in infinite dilution and the hydration enthalpy of anion, ΔH−([Lact]−) = −257 kJ mol−1, were obtained at 298.15 K. The heat capacity of aqueous [C4mim][Lact], Cp(sol), and the apparent molar heat capacity, ΦCp, of various specific molalities were also obtained.

Crystal structure and thermochemical properties of 2-pyrazine carboxylate lithium monohydrate [Li(pyza)(H2O)] n (s)(pyza=2-pyrazine carboxylate)

A 2-pyrazine carboxylate lithium monohydrate [Li(pyza)(H2O)] n was synthesized in a mixed solution of redistilled water and anhydrous ethanol. X-Ray crystallography was applied to characterizing its crystal structure. Low temperature molar heat capacities were measured in a temperature range of from 78 K to 400 K with a precision automatic adiabatic calorimeter. Two polynomial equations of experimental molar heat capacity as a function of temperature were obtained by the least-squares method. The smoothed molar heat capacities and thermodynamic functions of the compound were calculated based on the fitted polynomial equations. In accordance with Hess’s law, a reasonable thermochemical cycle was designed based on the preparation reaction of the target compound. The standard molar enthalpies of dissolution for the reactants and products of the designed thermochemical reaction were measured by an isoperibol solution-reaction calorimeter, and the enthalpy change of the reaction was obtained, i.e., Δr H m θ =-(30.084±0.329) kJ/mol. The standard molar enthalpy of the formation of the target compound was determined as $\Delta _f H_{m\{ [Li(pyza)(H_2 O)]_n (s)\} }^\theta = - (260.844 \pm 1.178)$ kJ/mol based on the enthalpy change of the reaction and standard molar enthalpies of the formation of other reactants and products. In addition, UV-Vis spectroscopy and the data of the refractive indexes were used to confirm whether the designed Hess thermochemical cycle was reasonable and reliable.

Molar heat capacities and solution thermochemistry of n-undecylammonium bromide monohydrate C11H28BrNO(s)

Crystal structure of n-undecylammonium bromide monohydrate was determined by X-ray crystallography. Molar enthalpies of dissolution of the compound at different concentrations (m/mol kg−1) were measured by an isoperibol solution reaction calorimeter at T = 298.15 K. According to the Pitzer electrolyte solution theory, molar enthalpy of dissolution of the compound at infinite dilution was determined as $$ \Delta _{\text{s}} H_{\text{m}}^{\infty } ({\text{C}}_{11} {\text{H}}_{28} {\text{BrNO}}) $$ = 32.40 kJ mol−1 and Pitzer’s parameters ( $$ \beta_{\text {MX}}^{(0)\text {L}} $$ and $$ \beta_{\text {MX}}^{(1)\text {L}} $$ ) were obtained. The values of apparent relative molar enthalpies ( $$ {}^{\varPhi}L $$ ) of the title compound and relative partial molar enthalpies ( $$ \overline{{L_{2} }} $$ and $$ \overline{{L_{1} }} $$ ) of the solute and the solvent at different concentrations were derived from experimental values of enthalpies of dissolution of the compound. Low-temperature heat capacities of the compound were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 390 K. Two solid–solid phase transitions were observed for the title compound. The temperatures, molar enthalpies and entropies of the phase transitions were determined as T trs,1 = (314.42 ± 0.229) K, T trs,2 = (338.66 ± 0.228) K, Δtrs H m,1 = (15.542 ± 0.059) kJ mol−1, Δtrs H m,2 = (6.431 ± 0.209) kJ mol−1, Δtrs S m,1 = (49.803 ± 0.079) J K−1 mol−1 and Δtrs S m,2 = (17.658 ± 0.072) J K−1 mol−1, respectively, based on the analysis of heat capacity curve. Two polynomial equations of heat capacities as a function of temperature were fitted by least squares method. Based on the two polynomial equations, smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 5-K intervals.

Study on Thermodynamic Properties of Ionic Liquid 1-Ethyl-3-methylimidazolium Alanine

用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸([C2mim][Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01)K-(308.15±0.01)K温度范围内每隔5K,测定不同质量摩尔浓度离子液体在水中的溶解焓(△sol Hm).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(△solHmθ),并计算了其相对表观摩尔溶解焓(ΦL).在298.15 K下,根据Glasser经验方法得到了格子能UPOT=566 kJ· mol-1,并计算了其阴阳离子水化焓值(△H++ △H-)=-620 kJ·mol-1及阴离子水化焓△H-([Ala]-)=-387 kJ· mol-1此外,估算了[C2mim][Ala]水溶液的热容(Cp(sol))和表观摩尔热容(ΦCp).

Thermodynamic study on complex of neodymium with glycine

Neodymium complex with glycine, Nd(Gly)2Cl3·3H2O, was synthesized and characterized by IR spectra. The thermal stability of the complex was tested through TG and DTG and a possible mechanism of thermal decomposition was proposed. The heat capacities of the complex were measured by using an automated adiabatic calorimeter over the temperature range from T=(80 to 380)K, the thermodynamic functions, [HT−H298.15] and [ST−S298.15], were calculated based on the heat capacity measurements. Two (solid+solid) phase transitions in the ranges of T=(170 to 247)K were observed with the peak temperatures of 184.896K and 231.217, respectively. The standard molar enthalpy of formation of [Nd(Gly)2Cl3·3H2O] was determined to be (−3081.3±1.1)kJ·mol−1 in terms of an isoperibol solution-reaction calorimeter.

The standard molar enthalpy of formation of a new copper(II) Schiff-base complex and its interaction with bovine serum albumin

A new copper(II) Schiff-base complex [Cu(HL)·NO3·MeOH] was prepared by using equivalent molar of Valen Schiff-base ligand [H2LN,N′-ethylene-bis(3-methoxysalicylideneimine)] and Cu(NO3)2·3H2O. The structure of the complex was confirmed by single-crystal X-ray diffraction. Based on an ideal and feasible thermochemical cycle, the standard molar enthalpy of formation of the complex was estimated to be: ΔfHmθ [Cu(HL)·NO3·MeOH(s), 298.15K]=–(945.40±2.44)kJmol−1 by an advanced solution-reaction isoperibol calorimeter. In particular, the interaction between the complex and bovine serum albumin (BSA) was investigated using the fluorescence quenching method. Fluorescence quenching data showed that the quenching mechanism of BSA treated by the complex was static quenching, which was highly accord with the non-radioactive energy transfer theory. And some relevant parameters such as binding sites, binding distance and intermolecular forces between the complex and BSA were also obtained by analyzing the fluorescence spectral data.

Preparation, structure, and thermochemical properties of a copper(II) Schiff-base complex

A copper(II) Schiff-base complex [CuL·2MeOH·H2O] was prepared by reaction of the ligand [H2L = N, N′-o-phenylene-bis(3-methoxysalicylideneimine)] and Cu(OAc)2·H2O in methanol at 328.15 K. X-ray diffraction analysis revealed that the title complex was crystallized in the triclinic crystal system with space group P–1, in which copper(II) ion was located in the N2O2 ligand binding sites. According to two designed thermochemical cycles, the dissolution enthalpies of relevant substances of two reactions in the calorimetric solvents were determined by a solution-reaction isoperibol calorimeter, respectively. Combined with some other auxiliary thermodynamic data, the standard molar enthalpies of formation of the ligand and the complex were calculated to be: $$ \Delta_{\text{f}} H_{\text{m}}^{\theta } $$ [H2L(s), 298.15 K] = −(384.2 ± 9.10) kJ mol−1 and $$ \Delta_{\text{f}} H_{\text{m}}^{\theta } $$ [CuL·2MeOH·H2O (s), 298.15 K] = −(1072.6 ± 9.2) kJ mol−1.

Crystal structure and thermochemical properties of a novel coordination compound sodium pyruvate C3H3O3Na(s)

A novel coordination compound sodium pyruvate C3H3O3Na(s) is synthesised by a liquid phase reaction. The compound has an obvious bioactivity and can be used as the biological carbon source and the chemical identification of primary and secondary alcohols. It can be also used to determinate transaminase. Elemental analysis and X-ray crystallography are used to characterise the composition and crystal structure of the compound. Single crystal X-ray analysis reveals that the compound is formed by one CH3COCOO− anion and one Na+ cation. An obvious feature of the crystal structure is the formation of the five-membered chelate ring by the coordination of O1 of carboxylate and O3 of keto form with Na+ cation, and it is good for the stability of the compound in structure. The lattice potential energy and ionic volume of the anion are obtained from crystallographic data. In accordance with Hess’ law, a reasonable thermochemical cycle is designed according to the practical synthesis reaction of the compound and the standard molar enthalpy of formation of the compound is calculated as an important physical quantity in chemical thermodynamics by use of an isoperibol solution-reaction calorimeter. Molar enthalpies of dissolution of the compound at various molalities are measured at T=298.15K in the double-distilled water. According to Pitzer’s electrolyte solution theory, molar enthalpy of dissolution of the title compound at infinite dilution is calculated to be ΔsHm∞=(19.81±0.69)kJ·mol−1. The values of relative apparent molar enthalpies (ΦL) and relative partial molar enthalpies of the solvent (L¯1) and the compound (L¯2) at different concentrations m/(mol·kg−1) are derived from the experimental values of the enthalpies of dissolution of the compound.