Abstract

Abstract

Abstract

Abstract

Abstract

Abstract

A new three-dimensional coordination polymer, [Ho(5-nip)(phen)(NO₃)(DMF)] (5-nip=5-nitroisophthalic acid and phen=1,10-phenanthroline), was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the title complex crystallizes in space group P2/m with a=1.0906(3) nm, b=1.2804 (3) nm, c=1.6987(4) nm, β=91.400(5)°, Z=4, D_c1.931 Mg/m³, F(000)= 1352. Each Ho(III) ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate NO⁻₃ anion, one DMF molecule and one 1,10-phenanthroline molecule. The complex is constructed with one-dimensional ribbons featuring dinuclear units and the one-dimensional ribbons are further assembled into two-dimensional networks by strong π-π stacking interactions with the distance of 0.327 nm, then the networks are arranged into three-dimensional structure according to ABAB fashion. The complex exhibits high stability up to 600 °C. Its enthalpy change of formation of the reaction in liquid-phase in solvent DMF was measured using an RD496-III type microcalorimeter with a value of (−11.016±0.184) kJ·mol⁻¹.

Treatment of hydrate rare-earth (RE=La, Pr, Nd, Sm-Lu) chloride with ammonium pyrrolidinyldithiocarboxylate (apdtc) and 1,10-phenanthroline (phen) gave rise to thirteen complexes with an empirical formula RE[(pdtc)₃(phen)]. The enthalpies of solution of hydrate rare-earth (RE=Sm-Ho, Tm-Lu) chloride, apdtc and phen in ethanol were measured by an RD-496 ?? microcalorimeter at 298.15 K, along with the mixing enthalpy of ethanol solution of APDC and that of phen and the enthalpies of reaction of formation of the title complexes in ethanol. The enthalpies of reaction of formation of the title complexes in solid were available through a rationally thermochemical cycle. Using an RD-496 ?? microcalorimeter, a model was developed for calculating the specific heat capacity and the responding specific heat capacity of the complexes were determined. The thermochemical properties, including the enthalpies of solution of hydrate rare earth chloride in ethanol, the enthalpies of reaction of formation of the title complexes in ethanol, the enthalpies of reaction of formation of the title complexes in solid, the special heat capacities at room temperature, the standard molar enthalpies of combustion and the standard molar enthalpies of formation for this series of complexes versus the atomic numbers of rare earth, presented triplet effect, which is representative of certain covalent bond between RE and the ligands and the result of 4f electron not shielded fully by 5s5p.

The solid potassium L-threonate hydrate, K(C₄H₇O₅)·H₂O, was synthesized by the reaction of L-threonic acid with aqueous potassium hydrogen carbonate and characterized by means of chemical and elemental analyses, IR and TG-DTG. Low-temperature heat capacity of K(C₄H₇O₅)·H₂O has been precisely measured with a small sample precise automated adiabatic calorimeter over the temperature range from 78 to 395 K. An obvious process of the dehydration occurred in the temperature region of 364–382 K. The peak temperature of the dehydration of the compound has been observed to be (380.524±0.093) K by means of the heat capacity measurements. The molar enthalpy, Δ_dH_m, and molar entropy, Δ_dS_m, of the dehydration of K(C₄H₇O₅)·H₂O were calculated to be (19.655±0.012) kJ/mol and (51.618±0.051) J/(K·mol) by the analysis of the heat-capacity curve. The experimental molar heat capacities of the solid from 78 to 362 K and from 382 to 395 K have been respectively fitted to two polynomial equations of heat capacities against the reduced temperatures by least square method. The constant-volume energy of combustion of the compound, Δ_cU_m, has been determined to be (−1749.71±0.91) kJ·mol⁻¹ by an RBC-II precision rotary-bomb combustion calorimeter at 298.15 K. The standard molar enthalpy of formation of the compound, Δ_fH^⊖_m, has been calculated to be (−1292.56±1.06) kJ·mol⁻¹ from the combination of the standard molar enthalpy of combustion of the compound with other auxiliary thermodynamic quantities.

A calculation formula for determining the specific heat capacity of solid compound with an improved RD496-III microcalorimeter was derived. The calorimetric constant and precision determined by the Joule effect were (63.901±0.030) µV/mW and 0.3% at 298.15 K, respectively, and the total disequilibrium heat has been measured by the Peltier effect. The specific heat capacities of two standard substances (benchmark benzoic acid and α-Al₂O₃) were obtained with this microcalorimeter, and the differences between their calculated values and literature values were less than 0.4%. Similarly, the specific heat capacities of thirteen solid complexes, RE(Et₂dtc) ₃(phen) (RE=La, Pr, Nd, SmLu, Et₂dtc: diethyldithiocarbamate ion, phen:1,10-phenanthroline) were gained, and their total deviations were within 1.0%. These values were plotted against the atomic numbers of rare-earth, which presents tripartite effect, suggesting a certain amount of covalent character in the bond of RE³⁺ and ligands, according to Nephelauxetic effect of 4f electrons of rare earth ions.

The constant-volume combustion energy, Δ_cU (GUDN, s, 298.15 K), enthalpy of solution in acetic ether, Δ H^θ_m and kinetic behavior of the exothermic decomposition reaction of the title compound (GUDN) are determined by a precise rotating bomb calorimeter, a Calvet microcalorimeter and DSC, respectively. Its standard enthalpy of combustion, Δ, H^θ_m: (GUDN, s, 298.15 K), standard enthalpy of formation, Δ, H^θ_m (GUDN, s, 298.15 K) and kinetic parameters of the exothermic main decomposition reaction in a temperature-programmed mode [the apparent activation energy ( E_a ) and pre-exponential factor (A)] are calculated. The values of Δ_cU (GUDN, s, 298.15 K), Δ H^θ_m (GUDN, s, 298.15 K), Δ, H^θ_m (GUDN, s, 298.15 K) and Δ_solH^θ_m of GUDN are (-7068.64×2.37) I-g (-1467.66×0.50) kJ · mol⁻¹, (-319.76×0.58) kJ · mol⁻¹ and (165.737×0.013) kJ·mol⁻¹, respectively. The kinetic model function in integral form and the value of E_a and A of the exothermic main decomposition reaction of GUDN are 220.20 kl · mol⁻¹ and 10^21.18 s⁻¹, respectively. The critical temperature of thermal explosion of GUDN is 217.6 °C.

The enthalpy change of the complexation reactions of the first-row transitional metal chlorides including CrCl₃, MnCl₂, FeCl₂, CoCl₂, NiCl₂ and CuCl₂ with L-α-histidine in water were determined by a microcalorimeter at 298.15-323.15 K. The standard enthalpy of formation of Cr(His) (aq) and M(His) (aq) (M=Mn, Fe, Co, Ni and Cu) were calculated. Based on the thermodynamic and kinetic equations of the reactions, three thermodynamic parameters (the activation enthalpy, the activation entropy, the activation free energy), the rate constants, and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) are obtained. The solid complexes of CrCl₃, MnCl₂, FeCl₂, CoCl₂, NiCl₂ and CuCl₂ with histidine were prepared and identified as Cr(His)₂Cl₃·H₂O. Mn(His)₂Cl₂·4H₂O. Fe(His)₂Cl₂·H₂O, Co(His)₂Cl₂·H₂O, Ni(His)₂Cl₂·H₂O and CU(HiS)₂Cl₂·H₂O by chemical and elemental analyses. The bonding characteristics of these complexes were characterized by R as well. The results showed that, with the atomic number increasing, three thermodynamic parameters, ΔG, ΔH and ΔS of the complexation reaction of these metal chlorides with L-α-histidine in water present an analogy regularity.

The complex of Zn(AcO)₂·2H₂O and threonine was prepared in the mixture solvent of water-acetone, the composition of which was identified as Zn(Thr)(AcO)₂·2H₂O by chemical and elemental analyses. The complex was investigated by XRD, JR, TG-DTG and DSC methods. The result of TG-DTG shows that the thermal decomposition processes of the complex can be divided into three stages, which were dehydration (I), partial decomposition (II) and complete decomposition into ZnO (III). Dehydration enthalpy was 126.89 kj·mol⁻¹, decomposition enthalpy of the stage (II) was 79.50 kJ·mol⁻¹. The study of non-isothermal kinetics shows that the mechanism of the dehydration stage was Maple Power of n=3/2, the apparent activation energy E was 145.32 kJ·mol⁻¹ and the pre-exponential factor A was 1.4125×10¹⁷ s⁻¹, and that of ligand-losting process was nucleation and growth mechanism (Avrami-Erofeev equation n=1/2), its E was 189.33 kJ·mol⁻¹, and A was 3.4674×s⁻¹. The empirical kinetics model equations of the investigated processes were proposed.

The title ternary complex Nd[(C₅H₈NS₂)₃(C₁₂H₈N₂)] has been synthesized in absolute ethanol by the reaction of NdCl₃·3.74H₂O with ammonium pyrrolidmyldifhiocaboxylate (APDC) and 1,10-phenanthroline (phen·H₂O) at air atmosphere without any cautions against moisture. The bonding characteristics of the complex were characterized by IR, showing that Nd³⁺ is bonded with sulfur atom in the APDC and coordinated with nitrogen atom in the phen. TG-DTG investigation indicates that the title complex was decomposed into Nd₂S₃ and deposited carbon in one step where Nd₂S₃ predominated in the final products. The enthalpy change of formation of the reaction on the title complex in liquid-phase has been determined by a microcalorimeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy) and kinetics parameters (the rate constant, the apparent activation energy, the pre-exponential constant and the reaction order) of the title reaction have been calculated. The enthalpy change of the soLid-phase reaction has been obtained by a thermochemistry cycle.

The solubility property of Zn (NO₃)₂-Try-H₂O system at 25 °C in whole concentration range has been investigated by the semimicro phase equilibrium method. The corresponding phase diagrams and refractive index diagrams were constructed. Under the guidance of the phase equilibrium results, the incongruently soluble compounds of Zn (Try) (NO₃)₂ · 2H₂O (F) and Zn-(Try)₂(NO₃)₂·H₂O (G), which have not been reported previously, were synthesized and characterized by IR, XRD, TG-DTG, as well as chemical and elemental analyses. The constant-volume combustion energies of the compounds, δcE, determined by a precision rotating bomb calorimeter at 298.15 K, were (-13518.98±4.99) Jg⁻¹ and (− 17690.85 ± 4.88) J. g⁻¹, respectively. The standard enthalpies of combustion for these compounds, δc47, were calculated to be (− 5802.36 ± 2.14) kJ·mol⁻¹ and (− 10891.59 ± 3.01) kJ·mol⁻¹ when the standard enthalpies of formation, δ_tH⊖ were (− 1161.18 ± 2.61) kJ·mol⁻¹ and (− 1829.71 ± 4.20) kJ·mol⁻¹. The enthalpies of solution in condition of simulating human gastric juice (37 °C, pH = 1, the solution of hydrochloric acid), which were also measured by a microcalorimeter, were (14.55 ± 0.04) kJ·mol⁻¹and (10.58±0.06) kJ·mol⁻¹, respectively.

The complex of praseodymium chloride lower hydrate with diethylammonium diethyldithiocarbamate (D-DDC) has been synthesized conveniently in absolute alcohol and dry N₂ atmosphere. The title complex was identified as Et₂NH₂ [Pr-(S₂CNEt₂)₄] by chemical and elemental analyses, the bonding characteristics of which were characterized by IR spectrum. The enthalpy of solution for praseodymium chloride hydrate and D-DDC in absolute alcohol at 298.15 K, and the enthalpy changes of liquid-phase reaction of formation for Et₂NH₂ [Pr-(S₂CNEt₂)₄] at different temperatures were determined by microcalorimetry. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of liquid phase reaction of formation were obtained. The enthalpy change of the solid-phase title reaction at 298.15 K was calculated by a thermochemical cycle.

The crystal growth process of Zn(Len)SO₄·0.5H₂O from water and acetone was investigated using a Calvet microcalorimeter. The heat and the rate of heat production during the crystal growth process at 293.15 K, 295.15 K, 298.15 K and 300.15 K were measured. On the basis of experimental and calculated results, the rate constant and the kinetic parameters (the activation energies, the pre-exponential) during the crystal growth process were obtained. The results show that the crystal growth process accorded with the Burton-Cabrera-Frank dislocation theory.

The solubility property of the Z_nCl₂-Leu-H₂O (Leu= L-α-leucine) system at 298.15 K in the whole concentration range was investigated by the semimicro-phase equilibrium method. The corresponding solubility diagram and refractive index diagram were constructed. The results indicated that there was one complex formed in this system, namely, Zn(Leu)Cl2. The complex is congruently soluble in water. Based on phase equilibrium data, the complex was prepared. Its composition and properties were characterized by chemical analysis, elemental analysis, IR spectra, and TG-DTG. The thermochemical properties of coordination reaction of zinc chloride with L-α-leucine were investigated by a microcalorimeter. The enthalpies of solution of L-α-leucine in water and its zinc complex at infinite dilution and the enthalpy change of solid-liquid reaction were determined at 298.15 K. The enthalpy change of solid phase reaction and the standard enthalpy of formation of zinc complex were calculated. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the activation energy, the pre-exponential constant and the reaction order) of the reaction, and the standard enthalpy of formation of Zn(Leu)²⁺ (aq) were obtained. The results showed that the title reaction took place easily at studied temperature.