Enthalpy Changes For Formation Research Articles

Determination of Thermodynamic Properties for the Esterification of Levulinic Acid with 1-Butene

The thermodynamic equilibrium of the liquid phase esterification of levulinic acid (LA) with 1-butene (1B) to obtain sec-butyl levulinate (SBL) was studied. Equilibrium experiments were performed in a batch reactor at 2.5 MPa in the temperature range of 363–393 K using Amberlyst-15 as the catalyst. The thermodynamic equilibrium for the side reactions (i.e., isomerization of 1B to trans-2-butene, isomerization of trans-2-butene to cis-2-butene, and esterification of LA with these isomers) was also studied. The thermodynamic properties of the reaction were determined experimentally and compared to theoretical estimations and reported literature values. The enthalpy and entropy changes of the esterification reaction with 1B at 298.15 K were estimated to be −(32.9 ± 1.6) kJ/mol and −(70 ± 4) J/(mol·K), respectively. As for the SBL thermodynamic properties, it was found that the liquid phase enthalpy change of formation and entropy at 298.15 K were −(737.1 ± 0.3) kJ/mol and (423 ± 3) J/(mol·K), respectively.

RELATIONSHIP OF ACIDITY-BASICITY OF SALTS OF 3d -METALS WITH THEIR ABILITY FOR FORMATION OF AQUA (AMMIN) COMPLEX COMPOUNDS

The general nature of the relationship between the acid-base properties (electronegativity) of 3d-metal salts and their ability to form aqua and ammine complex compounds (hydrates and ammoniates) has been established. The thermal strength of metal-ligand bonds (H 2 O, NH 3 ), defined as the enthalpy of formation of a complex compound per bond depends on many factors: the coordination number of the central metal ion, the nature of the metal, anion, and ligand. An increase in the electronegativity of compounds in the series nitrates – chlorides – sulfates of 3d-metals (Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , as well as its decrease when H 2 O is replaced by NH 3 (with the same coordination number) results in an increase in strength by a decrease in enthalpy per 1 metal-ligand bond of complex compounds. In turn, the change in electronegativity is due to the size-charge parameters (metal ionic radius, counter ion charge) of the cations and anions that make up the compounds. There is a correspondence in the change in the total enthalpy of formation of aqua complex compounds (crystalline hydrates) and their diluted solutions. An explanation of this relationship is proposed, based on the recognition of the important role of the chemical component in the process of dissolution of compounds in water. Similar, albeit in a less pronounced form, processes take place in 3d-metal hydroxides, which have mainly basic properties. When water molecules are replaced by ammonia molecules, the solubility of hydroxides in the series Mn(OH) 2 , Fe(OH) 2 , Co(OH) 2, Ni(OH) 2 , Cu(OH) 2 , Zn(OH) 2 significantly increases, indicating, together with a change in color, the strengthening of complex compounds. Found regularities make it possible to use the electronegativity parameter to predict and control complexation in other groups of compounds (salts, hydroxides, and molecular ligands).

Updated E-NRTL Model for High-Concentration MEA Aqueous Solution by Regressing Thermodynamic Experimental Data at High Temperatures

Chemical absorption using amine solutions is a promising technology for post combustion CO2 Capture (PCC) from flue gas. Monoethanolamine (MEA) aqueous solution has been used in many projects as a benchmark solution and its research results are widely shared with many literatures. Aspen Plus® is a useful computational simulation software to design the PCC system totally including operating conditions. It provides example files of rate-based MEA models using electrolyte NRTL methods. Basically, these models can compute nearly accurate results fitting to experimental data within a limited operating temperature and concentration range. However, there are a non-negligible difference between experimental and calculation results, especially in the vapor-liquid equilibrium (VLE) at high temperatures and high MEA concentrations. This report offers the updated electrolyte NRTL model of 30wt% and higher concentrations MEA solution by regressing specific heat capacity, heat of CO2 absorption and VLE experimental data obtained at high temperatures. Since these thermodynamic properties are mutually dependent and affected by internal model parameters like activity coefficients, standard enthalpy change of formation of principal ions, we tried to fit all properties in the MEA-H2O-CO2 ternary system that is consistent with the MEA-H2O binary system by using a combination method of the provided data regression functionality and external spread-sheet software. The updated model reflected the above modification can more accurately simulate thermodynamic properties of high concentration MEA solutions at high temperatures.

Updated e-NRTL model for high-concentration MEA aqueous solution by regressing thermodynamic experimental data at high temperatures

Chemical absorption using amine solutions is a promising technology for post combustion CO2 Capture (PCC) from flue gas. Monoethanolamine (MEA) aqueous solution has been used in many projects as a benchmark solution and the experimental and analytical results are available in the literature for diverse operating conditions. Aspen Plus® is a widely used computational simulation software for design of PCC systems including operating conditions. Two example files of rate-based MEA models using electrolyte non-random two liquid (e-NRTL) methods are included in Aspen Plus. Basically, e-NRTL models can provide relatively accurate results by fitting parameters to experimental data within a limited temperature and concentration range. However, there are a non-negligible difference between experimental and calculation results, especially in regard to the vapor-liquid equilibrium (VLE) at high temperatures and high MEA concentrations. This paper updates the e-NRTL model for the solutions with 30 wt% and higher MEA by data regression of the specific heat capacity, the heat of CO2 absorption, and VLE experimental data obtained at high temperatures. Since these thermodynamic properties are mutually dependent and affected by internal model parameters such as activity coefficients, standard enthalpy change of formation of principal ions, all properties in the MEA-H2O-CO2 ternary system that are consistent with the MEA-H2O binary system were fitted by using a combination of the built-in data regression functionality and external spread-sheet software. The updated model more accurately simulates thermodynamic properties of high concentration MEA solutions at high temperatures.

A simple heuristic approach to estimate the thermochemistry of condensed-phase molecules based on the polarizable continuum model.

A simple model based on a quantum chemical approach with polarizable continuum models (PCMs) to provide reasonable translational and rotational entropies for liquid phase molecules was developed. A translational term was evaluated with free-volume compensation for the Sackur-Tetrode equation. We assumed that the free-volume corresponds to the cavity volume in the PCM. A rotational term was modeled as restricted rotation of a dipole in the electrostatic field. Entropies were assessed for twenty species in the liquid-phase using the proposed model, and the computed values were compared with experimental values. Quantum chemistry calculations were conducted at the ωB97X-D/6-311++G(d,p) level with the conductor-like PCM method. Predicted entropies were in good agreement with the experimental entropies, and the root mean square deviation was 17.2 J mol-1 K-1. The standard enthalpy change of formation was then investigated for eleven specific species. The CBS-QB3//ωB97X-D method provides a reasonable standard enthalpy of formation for gasified species; however, improvement of the accuracy is required for liquid species. Finally, the dependence of the Gibbs energy on temperature was investigated for the eleven specific species. When the ideal gas treatment is used, the Gibbs energy trends for the gaseous and liquid phases are quasi-parallel for all of the species, although the Gibbs energy trends for liquids based on the proposed model intersected the gaseous trend (i.e. the intersection is the boiling point). However, the model significantly under or overestimated the experimental boiling points. The error of the boiling points was predominantly due to the inaccuracy of the enthalpy.

Application of spectral graph theory on the enthalpy change of formation of acyclic saturated ketones

The dependence of the enthalpy change of formation of saturated acyclic ketones on molecular structure (the number of carbon atoms, the position of the carbonyl group, and the branching of the molecules) was investigated. For this purpose, a simple computational model, the parameterization of which is based on spectral graph theory, was developed. It was found that the major part of the enthalpy change of formation is determined by molecular size, whereas the fine structure of the enthalpy change of formation is determined by the branching of the molecule and the position of the carbonyl group. The developed model proved itself very useful for such investigations. The model is simple and practical, and the agreement between the experimental and calculated enthalpy changes of formation is very good, with an average relative error of 0.7%.

Effect of the ionic strength and temperature on the arsenic(V) -Fe3+ and -Al3+ interactions in aqueous solution

Interactions between arsenic(V) and Fe3+ and Al3+ in aqueous solution were studied by potentiometry and, for Fe3+ system, by UV spectrophotometry too. Potentiometric measurements have evidenced the formation of FeAsO40, AlAsO40 and Al(AsO4)OH− species with formation constant values log β = 17.77, 12.68 and 8.29, respectively, at I = 0.1 mol L−1 and T = 298.15 K. In order to applied speciation study to different kind of natural waters, the effect of the ionic strength on the thermodynamic parameters was analysed in the 0.1 ≤ I ≤ 0.7 mol L−1 range and modeled by a Debye-Hückel type equation. In addition, the formation enthalpy changes of the species were determined by direct calorimetric titrations, in order to define the effect of temperature on the strength of interactions. Examples of distribution of species were reported in different experimental conditions. Finally, the ability of arsenate “to sequester” Fe3+ and Al3+ cations was evaluated by pL0.5 empiric parameter, that represents the ligand concentration required to sequester 50% of the metal cation present in traces.

Thermodynamic Analysis of the Experimental Equilibria for the Liquid-Phase Etherification of Isobutene with C1 to C4 Linear Primary Alcohols

The chemical equilibrium of the liquid-phase syntheses of 2-methoxy-2-methylpropane (MTBE), 2-ethoxy-2-methylpropane (ETBE), 2-methyl-2-propoxypropane (PTBE), and 1-tert-butoxybutane (BTBE) by reaction of isobutene with methanol, ethanol, 1-propanol, and 1-butanol, respectively, has been studied. Four different ion exchange resins as the catalysts, and two different reactor systems, namely, a batch reactor and a setup of tubular reactors, were used. Temperature and pressure were in the range 313–383 K and 1.5–2.0 MPa, respectively. MTBE and ETBE synthesis reactions experiments were carried out mainly to validate the reliability of the reaction systems. Experiments in PTBE and BTBE etherifications allowed estimating thermodynamic properties for those reactions and involved species, namely, molar standard enthalpy and entropy changes of reaction and molar enthalpy change of formation of the four ethers. A comparison of estimated reaction thermodynamic values among the homologous series of linear alcohols, and with results quoted in the literature, when available, has been made.

Thermodynamic Data for the Modeling of Lanthanoid(III) Sequestration by Reduced Glutathione in Aqueous Solution

This contribution reports the results of an investigation on the speciation of various lanthanoid(III) cations (Ln3+), namely, La3+, Nd3+, Sm3+, Eu3+, Gd3+, Dy3+, and Yb3+, in the presence of reduced glutathione (or simply glutathione, GSH), in NaCl(aq) at I = 0.15 mol·dm–3 and T = 298.15 K. GSH forms in all cases the same four species, namely, Ln(GSH)H3, Ln(GSH)H2, Ln(GSH)H, and Ln(GSH)OH, whose stability depends on the type of lanthanoid, although it is also possible to consider an average stability for a generic lanthanoid, at least for the protonated species. Measurements at different temperatures and ionic strengths for the La3+/GSH and Gd3+/GSH systems have also been performed, to evaluate their effect on the speciation of both GSH and the Ln3+ cations. The dependence of the determined stability constants on I and T has been modeled by an extended Debye–Huckel type and by the van’t Hoff equations. In this last case, the formation enthalpy changes of La3+/GSH species have also been determined. The st...

Gas-phase solvation of protonated amino acids by methanol.

The enthalpy and entropy changes for the formation of the 1:1 complexes of methanol with various gaseous protonated amino acids have been measured using pulsed-ionization high-pressure mass spectrometry. The enthalpy changes for formation of the clusters Gly(MeOH)H(+), Ala(MeOH)H(+), Val(MeOH)H(+), Leu(MeOH)H(+), Ile(MeOH)H(+), and Pro(MeOH)H(+) have been determined to be -92.0, -83.3, -82.4, -79.5, -78.7, and -73.6 kJ mol(-1), respectively. These values agree very well with the energetic values computed at the MP2(full)/6-311++G(2d,2p)//B3LYP/6-311+G(d,p) level of theory for the lowest energy adducts in each system. Both experimental observations and computational determinations of the potential energy surface for the glycine system suggest that a mixture of low-lying isomers may be present for each of the cluster systems examined. The primary structural motif for these clusters is the coordination of the methanol molecule to the ammonium group of the protonated amino acid via a strong ionic hydrogen bond. For the amino acids studied here, computational results reveal that one methanol molecule does not sufficiently stabilize any zwitterionic structure such that no appreciable extent of proton transfer from the amino acid to methanol was observed.

Equilibrium of the simultaneous etherification of isobutene and isoamylenes with ethanol in liquid-phase

The simultaneous etherification of isobutene and isoamylenes with ethanol has been studied using macroreticular acid ion-exchange resins as catalyst. Most of the experiments were carried out over Amberlyst-35. In addition, Amberlyst-15 and Purolite CT-275 were also tested. Chemical equilibrium of four chemical reactions was studied: ethyl tert-butyl ether formation, tert-amyl ethyl ether formation from isoamylenes (2-methyl-1-butene and 2-methyl-2-butene) and isomerization reaction between both isoamylenes. Equilibrium data were obtained in a batchwise stirred tank reactor operated at 2.0MPa and within the temperature range from 323 to 353K. Experimental molar standard enthalpy and entropy changes of reaction were determined for each reaction. From these data, the molar enthalpy change of formation of ethyl tert-butyl ether and tert-amyl ethyl ether were estimated. Besides, the chemical equilibrium between both diisobutene dimers, 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, was evaluated. A good agreement between thermodynamic results for the simultaneous etherification carried out in this work and those obtained for the isolated ethyl tert-butyl ether and tert-amyl ethyl ether systems was obtained.

Catalytic oxidation of ammonium ion in water with ozone over metal oxide catalysts

Oxidative decomposition of NH4+ (10mmolL−1) with O3 in water was studied at 333K over a variety of metal oxide catalysts without pH control of the solution. Although MgO and NiO had the highest catalytic activities, large amounts of undesired NO3− formed due to low selectivity to gaseous products as well as high activity. Co3O4, which was slightly less active than MgO and NiO, was the best catalyst in terms of activity, selectivity to gaseous products, and dissolution degree among the metal oxide catalysts studied. Over Co3O4, NH4+ was selectively oxidized to N2 with 88% selectivity in water, and the dissolution degree of Co3O4 was less than 1%. Fe2O3, SnO2, Mn3O4, CuO, MgO, and Al2O3 were less selective to gaseous products or much less active for the reaction. The selectivities to gaseous products were strongly related to the standard enthalpy changes of formation per mol of oxygen atom (ΔH°f) of the metal oxides. The metal oxide catalysts with low ΔH°f, like Co3O4, showed high selectivity to gaseous products probably due to the low surface density of the active oxygen formed from O3 on the catalysts. Chloride ions (Cl−) present in the reaction solution significantly accelerated the reaction rate for NH4+ decomposition with O3 in the presence of Co3O4. This was due to the involvement of Cl− in the catalytic cycle. For instance, ClO−, which may form by the reaction of Cl− with O3 over Co3O4, could further oxidize NH4+.

Stabilizing Effect of Mg on the Energetics of the Li(Ni,Co,Al)O2 Cathode Material for Lithium Ion Batteries

Mg-doped LiNi0.80Co0.15Al0.05O2 cathode material shows less degradation than the undoped material during charge/discharge cycles, resulting in significantly improved cell performance. The improved performance may arise from thermodynamic stabilization and/or from kinetic factors, both of which may act to hinder decomposition. To investigate the possible thermodynamic contribution, the change in enthalpy of formation from oxides with Mg doping was investigated using high temperature oxide melt solution calorimetry. The measured enthalpy data plus the estimated configurational entropies indicate that the Mg-doped sample is 3.3 ± 0.9 kJ/mol more stable in free energy than the undoped material. This stabilization is suggested to be mainly due to short range ordering of Ni cations around Mg2+, providing stronger bonding in the structure. This modest thermodynamic stabilization leading to greater short range order may inhibit the formation of a NiO - like phase during cell operation.

Characteristics of phase transition and separation in a In–Ge–Sb–Te system

In-doped GeSbTe films were deposited by ion beam sputtering deposition (IBSD) using Ge2Sb2Te5 (GST) and In3Sb1Te2 (IST) as targets. The phase change characteristics of the resulting films were then investigated by electrical measurements, including static testing, in situ 4-point Rs measurements, X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The threshold voltage of the films increased, with increasing levels of IST. This phenomenon is consistent with the increased crystallization temperature in X-ray data and in situ 4-point Rs data. In addition, in In28Ge12Sb26Te34, multiple Vth values with a stepwise change are observed. The minimum time for the crystallization of InGeSbTe films was shorter than that for GST. X-ray data and Raman data for the crystalline structure show that phase separation to In2Te3 occurred in all of the InGeSbTe samples after annealing at 350°C. Moreover, in the case of InGeSbTe films with high concentrations of In (28at.%), Sb phase separation was also observed. The observed phases indicate that the origin of the phase separation of InGeSbTe films is from the enthalpy change of formation and differences in Ge–Te, In–Te, Sb–Te, In–Sb and In–In bond energies.

The inorganic speciation of tin(II) in aqueous solution

This paper reports new voltammetric measurements on the interactions between tin(II) and the most important natural inorganic ligands, OH−, Cl−, F−, CO32-, SO42- and PO43-. For a better understanding of tin(II) speciation, an analysis is also given of prior data on the same systems from the literature. The formation constants were determined at t=25°C in different ionic media and at different ionic strengths, specifically the following: Sn(OH)q (0.1⩽I/molL−1⩽1.0 in NaNO3), SnClr and Sn(OH)Cl (0.1⩽I/molL−1⩽2.3 in Na(NO3, Cl)), Sn(SO4)r (0.1⩽I/molL−1⩽1.6 in Na(NO3, SO4)), SnHqCO3 and SnHqPO4 (0.15⩽I/molL−1⩽1.0 in NaNO3), where the subscripts r and q represent the stoichiometric coefficients. Concerning the SnFr species, reliable literature values were considered (0.15⩽I/molL−1⩽1.0 in NaClO4). Fifteen voltammetric measurements were performed in synthetic seawater; the total seawater binding ability was evaluated by a model in which synthetic seawater is expressed as a single salt, BA. The formation of species between tin(II) and the anion of the marine salt (A) was also proposed, and the corresponding stability constants at different salinities (5⩽S⩽50) were reported. In addition, studies on the solubility of Sn(OH)2(s) were carried out using voltammetry and light scattering measurements. The “extra-stability” of the mixed species with respect to the parent species was evaluated, in particular for Sn(OH)Cl and the corresponding species involving the anion of the marine salt (A). The dependence of the formation constants on ionic strength was analysed using extended Debye-Hückel and Specific ion Interaction Theory (SIT) type equations. Tin(II) speciation was also evaluated in different natural fluid conditions, where, in all cases, carbonate complexation was predominant, hampering the formation of hydrolytic species throughout the investigated pH range. Moreover, some formation enthalpy changes were calculated for the Sn(OH)+, Sn(OH)2(aq), Sn(OH)2(s), Sn(OH)3-, Sn2(OH)22+, Sn3(OH)42+, Sn(OH)Cl, SnCl+, SnCl2 and SnCl3- species on the basis of the available literature stability constant values at different temperatures and using the empirical relationships reported in the literature. The ΔH values at t=25°C were positive in all cases except for the Sn(OH)2(s) and Sn(OH)3- species, indicating an increase in the stability constant values with increasing temperature.This work represents an advance in the knowledge, understanding and modelling of the inorganic speciation of tin(II) in natural fluids, particularly for solutions containing chloride, fluoride, sulphate, carbonate and phosphate anions.

Thermodynamics of binary and ternary interactions in the tin(II)/phytate system in aqueous solutions, in the presence of Cl− or F−

An extensive study of the tin(II)/phytate (Phy) system was carried out in NaNO3(aq), at different ionic strengths (0.10⩽I/mol·L−1⩽1.00) and temperatures (278.15⩽T/K⩽328.15), by potentiometric and voltammetric techniques. The stability and formation enthalpy changes of six SnHqPhy species were determined. To better characterise this system, some potentiometric titrations were also carried out in mixed ionic media (NaNO3(aq)+NaCl(aq) and NaNO3(aq)+NaF(aq)) at total ionic strength I=1.00mol·L−1. The formation of some ternary mixed SnHqPhyCl and SnHqPhyF species (charges omitted for simplicity) was found. The formation enthalpies of the complex species were calculated, at I=0.40mol·L−1 in NaNO3(aq), by the dependence of stability constants on temperature obtained by potentiometric titrations, in the range 278.15⩽T/K⩽328.15. The complex formation process is endothermic, and the main contribution to tin(II) complexation by phytate is entropic in nature. For example, for the SnPhy species we have, at T=298.15K and I=0.40mol·L−1 in NaNO3(aq): ΔH=57.7±2.8kJmol·L−1, ΔG=−99.9±1.7kJmol·L−1, and TΔS=158±3kJmol·L−1. The ionic strength dependence of the formation constants of the simple tin(II)/phytate species, was modelled by the Debye–Hückel and the SIT approaches. The sequestering ability of phytate towards tin(II) was evaluated by calculating the pL0.5 values (i.e., the total ligand concentration necessary to bind 50% of cation present in trace) at different ionic strengths, ionic media, and pH. The sequestering ability increases with increasing the pH, whilst it decreases with increasing the ionic strength (the same behaviour shown by the stability constants). Moreover, taking into account the different sequestering ability of phytate towards tin(II) in the different ionic media, the trend: pL0.5=5.70 (in NaNO3(aq)+NaF(aq))>pL0.5=5.16 (in NaNO3(aq)+NaCl(aq))>pL0.5=4.86 (in NaNO3(aq)) was observed at pH 8.1 and I=1.00mol·L−1. This is due to the presence of a second ligand (Cl− or F−) that stabilizes the complex species with the formation of ternary complex species. Some empirical relationships were also found.

Formation abilities and electronic properties of Mg-TM-H (TM = Sc, Ti, V, Y, Zr, Nb) crystal

Theoretical studies of structures, cohesive energies,reaction enthalpies and densities of states (DOSs) of Mg7TMH16 (TM=Sc, Ti, V, Y, Zr, Nb) compounds are performed using the first-principles method based on the density functional theory in the generalized gradient approximation. The cohesive energies are calculated to analyze the stability, and the formation abilities of Mg7TiH16 and Mg7NbH16 are stronger than others. The obtained formation enthalpy for hydride Mg7TMH16 is used to investigate the possible pathways of formation reaction. The calculated formation enthalpy changes show that the decomposition temperature of Mg7TMH16 is lower than that of MgH2. The electronic DOSs reveal that all the hydrides studied here exhibit metallic characteristics.

Preparation, Crystal Structure and Enthalpy Change of Formation of the Reaction in Liquid Phase of a New Three‐Dimensional Mixed‐Ligand Holmium(III) Coordination Polymer Based on Strong π‐π Stacking Interactions

AbstractA 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, Dc1.931 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.

Synthesis, crystal structure and thermal decomposition of a novel praseodymium supermolecular complex

A novel complex, [Pr(5-nip)(phen)(NO3)(DMF)] (5-nip: 5-nitroisophthalic acid; phen: 1,10-phenanthroline, DMF: N,N-dimethylformamide), was prepared and characterized by single crystal X-ray diffraction, elemental analysis, IR spectrum and DTG-DSC techniques. The results show that the crystal is monoclinic, space group P2(1)/n with a=11.0876(6) A, b=12.8739(7) A, c=16.9994(8) A; β=91.193(4)°, Z=4, Dc=1.822 Mg m–3, F(000)=1320. Each Pr(III) ion is nine-coordinated by one chelating bidentate and two monodentate bridging carboxylate groups, one chelating bidentate nitryl group, 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. The complex has high stability up to 500°C. The enthalpy change of formation of the compound in DMF was measured using an RD496-III type microcalorimeter with the value of –9.214±0.173 kJ mol–1.

Syntheses, characterization and the liquid-phase formation enthalpy changes of two new one-dimensional ribbon-like lanthanide supermolecular polymers

Two novel one-dimensional ribbon-like mixed-ligand supermolecular polymers, [Ln(5-nip)(phen)(NO 3) (DMF)] n (Ln = Pr ( 1) and Ho ( 2)), assembled into two-dimensional networks by strong π–π stacking interactions, have been synthesized by reactions of lanthanide (III) salts with 5-nitroisophatha acid (5-H 2nip) and 1,10-phenanthroline (phen) in DMF solvent. They possessed high thermal stabilities and their liquid-phase formation enthalpy changes were determined in DMF solvent at 25.15 °C using an RD496-III type microcalorimeter, which were Δ r H m θ ( 1 ) = − 9.21 kJ mol − 1 , and Δ r H m θ ( 2 ) = − 11.02 kJ mol − 1 , respectively.