Succinic or glutaric anhydride modified linear unsaturated (epoxy) polyesters

A series of N-alkyl-N-alkyl′-pyrrolidinium-bis(trifluoromethanesulfonyl) imide (TFSI⁻) room temperature ionic liquids (RTILs) has been investigated by means of thermogravimetric analysis (TG), differential scanning calorimetry, FT-IR spectroscopy, and X-ray diffraction analysis. These compounds exhibit a thermal stability up to 548–573 K. The mass loss starting temperature, T _ml, falls in a narrow range of temperatures: 578–594 K. FT-IR spectra, performed before and after 24 h isothermal experiments at 553 and 573 K, have confirmed their great thermal stability. Below the ambient temperature, these compounds exhibit a complex behavior. N-methyl-N-propyl-pyrrolidinium-TFSI is the sole liquid which crystallizes without forming any amorphous phase even after quenching in liquid nitrogen. Its crystalline phase has a melting point, T _m, of 283 ± 1 K. When the amorphous solid is heated, the N-butyl-N-ethyl-pyrrolidinium-TFSI presents a glass transition temperature, T _g, at 186 K followed by a cold crystallization, T _cc, at 225 K, and a final T _m at 262 K. The N-butyl-N-methyl-pyrrolidinium-TFSI exhibits a T _g between 186 and 181 K, its cold crystallization leading to two different solid phases. Solid phase I has a melting point T _I,m = 252 K and phase II, T _II,m = 262 K. When the amorphous phase is obtained at a cooling rate of 10 K/min, its T _cc is 204 K, and a metastable solid phase (III) is obtained which transforms into the phase II at 226 K. However, when the sample is quenched, the amorphous phase transforms into phase II at T _cc = 217 K and phase I at 239 K. P₁₅-TFSI exhibits the most complicated pattern as, on cooling, it leads to both a crystallized phase at 237 K and an amorphous phase at 191 K. On heating, after a T _g at 186 K and a T _cc at 217 K, two solid–solid phase transitions are observed at 239 K and 270 K, the final T _m being 279 K.     

Heat capacities and thermodynamic properties of <Emphasis Type="Italic">N</Emphasis>-(tert-butoxycarbonyl)-<Emphasis Type="SmallCaps">l</Emphasis>-phenylalanine (C<Subscript>14</Subscript>H<Subscript>19</Subscript>NO<Subscript>4</Subscript>)

The heat capacities of N-(tert-butoxycarbonyl)-l-phenylalanine (abbreviated to NTBLP in this article), as an important chemical intermediates used to synthesize proteins and polypeptides, were measured by means of a fully automated adiabatic calorimeter over the temperature range from 78 to 350 K. The measured experimental heat capacities were fitted to a polynomial equation as a function of temperature. The thermodynamic functions, H _T − H _298.15K and S _T − S _298.15K, were calculated based on the heat capacity polynomial equation in the temperature range of (80–350 K) with an interval of 5 K. The thermal stability of the compound was further studied using TG and DSC analyses; a possible mechanism for thermal decomposition of the compound was suggested.     

Solidification of molten zinc chloride

Solidification of molten zinc chloride was studied both experimentally and theoretically. By isothermal thermal analysis the time needed for the melt to crystallize at a given temperature ranging between 453 and 553 K was determined and the data obtained were compared with those of a calculated TTT curve. The extremum coordinates (temperature T _N, time t _N) of the curve, critical cooling rate v _CR, interfacial energy σ, and an additional parameter of kinetics barrier for nucleation ɛ were determined as T _N=508 K, t _N=7.29 s, v _CR=11.38 K s⁻¹, σ=0.11956 J m⁻² and ɛ=0.5712. By non-isothermal method the critical cooling rate of glass formation was determined as 1.25 K s⁻¹.     

Thermoanalytical behaviour of carbaryl and its copper(II) and zinc(II) complexes

Non-isothermal techniques, i.e. thermogravimetry (TG) and differential scanning calorimetry (DSC), have been applied to investigate the thermal behaviour of carbaryl (1-naphthyl-N-methylcarbamate = 1-Naph-N-Mecbm) and its complexes, M(1-Naph-N-Mecbm)₄X₂, where M = Cu, X = Cl, NO₃ and CH₃COO and M = Zn, X = Cl. Carbaryl and Zn(1-Naph-N-Mecbm)₄Cl₂ complex exhibit two-stage thermal decomposition while the copper(II) complexes exhibit three and four-stage decomposition in their TG curves. The nature of the metal ion has been found to play highly influential role on the nature of thermal decomposition products as well as energy of activation ‘E*’. The presence of different anions does not seem to alter the thermal decomposition patterns. The complexes display weak to medium intensity exothermic and endothermic DSC curves, while the free ligand exhibits two endothermic peaks. The kinetic and thermodynamic parameters namely, the energy of activation ‘E*’, the frequency factor ‘A’ and the entropy of activation ‘S*’ etc. have been rationalized in relation to the bonding aspect of the carbaryl ligand. The nature and chemical composition of the residues of the decomposition steps have been studied by elemental analysis and FTIR data.     

Molar heat capacity and thermodynamic properties of 1,2-cyclohexane dicarboxylic anhydride [C8H10O3]

The molar heat capacity C _p,m of 1,2-cyclohexane dicarboxylic anhydride was measured in the temperature range from T=80 to 390 K with a small sample automated adiabatic calorimeter. The melting point T _m, the molar enthalpy Δ_fus H _m and the entropy Δ_fus S _m of fusion for the compound were determined to be 303.80 K, 14.71 kJ mol⁻¹ and 48.43 J K⁻¹ mol⁻¹, respectively. The thermodynamic functions [H _T-H _273.15] and [S _T-S _273.15] were derived in the temperature range from T=80 to 385 K with temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning calorimeter (DSC) and thermogravimetry (TG), when the process of the mass-loss was due to the evaporation, instead of its thermal decomposition.     

Uncompensated magnetization in the layered molecular antiferromagnet {N(n-C5H11)4[MnFe(ox)3]}∞

Studies on the magnetic properties of the molecular antiferromagnetic material {N(n-C₅H₁₁)₄[Mn^IIFe^III(ox)₃]}_∞, carried out by various physical techniques (AC/DC magnetic susceptibility, magnetization, heat capacity measurements and Mössbauer spectroscopy) at low temperatures, have been presented. Different experimental observations complement each other and provide a clue for the observation of an uncompensated magnetization below the Néel temperature and short-range correlations persisting high above T_N. It is understood that the honeycomb layered structure of the compound contains non-equivalent magnetic sub-lattices, (Mn^II–ox–Fe^III_A–...) and (Mn^II–ox–Fe^III_B–...), where different responses of the Fe^III_A and Fe^III_B spin sites towards an external magnetic field might be responsible for the observation of the uncompensated magnetization in this compound at T < T_N. The present magnetic system is an S = 5/2 2-D Heisenberg antiferromagnet system with the intralayer exchange parameter J/k_B = −3.29 K. A very weak interlayer exchange interaction was anticipated from the spin wave modeling of the magnetic heat capacity for T < 0.5T_N. The positive sign of the coupling between the layers has been concluded from the Mössbauer spectrum in the applied magnetic field. Frustration in the magnetic interactions gives rise to the uncompensated magnetic moment in this compound at low temperatures.     

Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex

The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF₆)₂ (bztpen=N‐benzyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethylenediamine) displays an S=1/2?S=3/2 spin crossover (SCO) behavior (T_1/2=370 K, ΔH=12.48 kJ mol^?1, ΔS=33 J K^?1 mol^?1) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0?S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120–420 K affording a detailed picture of how the electronic distribution of the t_2g–e_g orbitals modulates the structure of the {FeNO}⁷ bond, providing valuable magneto–structural and spectroscopic correlations and DFT analysis.     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  

Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials.     

Synthesize,crystal structure,heat capacities and thermodynamic properties of a potential enantioselective catalyst

A new potential enantioselective catalyst derived from ferrocene, 1-{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}-benzimidazole (DPFEB), was prepared and its absolute structure was characterized by means of single crystal X-ray diffraction. The molar heat capacity of DPFEB was measured by means of temperature modulated differential scanning calorimetry over the temperature range of 200–530 K, and the thermodynamic functions of [H _T  − H _298.15] and [S _T  − S _298.15] were calculated. Further more, thermogravimetry experiment revealed that DPFEB exhibited a three step thermal decomposition process with the final residual of 28.7%.     

Calorimetric study of molecular superconductor κ-(BEDT-TTF)<Subscript>2</Subscript>Ag(CN)<Subscript>2</Subscript>H<Subscript>2</Subscript>O which contains water in the anion layers

Thermodynamic investigation of an organic superconductor κ-(BEDT-TTF)₂Ag(CN)₂H₂O in which the BEDT-TTF dimers are arranged in the κ-type structure in the donor layers is performed by the relaxation calorimetric technique at low temperatures and under magnetic fields. A thermal anomaly related to the superconductive phase transition was observed at 5 K. The existence of residual γ^* in the superconductive state is about 18% of the normal state γ value, which is larger than those of κ-(BEDT-TTF)₂Cu(NCS)₂, and κ-(BEDT-TTF)₂Cu[N(CN)₂]Br salt. The lattice heat capacity reflected on the β-term in the low-temperature heat capacity was found to be affected by the cooling rate. The disorder produced in the network structure constructed by hydrogen bond in the insulating layer is considered to give low-energy phonon excitations reflected in the heat capacity.     

Synthesis, structure, and properties of a binuclear Fe(III) complex with N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine

Mannich reaction of 2-Amino propanol, 2-tert-butyl-4-methylphenol, and formaldehyde in the ratio of 1:2:2 provides a new compound, N-(1-propanol)-N,N-bis(3-tert-butyl-5-methyl-2-hydroxybenxyl)amine (H₃L), which has been characterized by X-ray crystallography and elemental analysis. In the presence of Et₃N, the reaction of H₃L and FeCl₃·6H₂O gives a dinuclear Fe(III) complex [Fe₂L₂] 1, which has been characterized by X-ray crystallography, magnetic measurement, and cyclic voltammetry. The value of μ_eff at room temperature (5.97 μ_B) is much less than the expected spin-only value (8.37 μ_B) of two high spin (hs) Fe³⁺ (S = 5/2) ions [μ = g[∑ZS(S + 1)]^1/2], indicating there are strong coupling interactions between Fe³⁺ ions. The magnetic behavior of 1 denotes the occurrence of intramolecular antiferromagnetic interactions (J = −13.35 cm⁻¹ ). CV of 1 reveals two reversible waves at 0.433 and 1.227 V versus AgCl/Ag, which can be ascribed to the successive redox coupling of Fe^IIFe^II/Fe^IIIFe^II and Fe^IIIFe^II/Fe^IIIFe^III, respectively.     

A low-temperature heat capacity study of natural lithium micas

Low-temperature heat capacity of natural zinnwaldite was measured at temperatures from 6 to 303 K in a vacuum adiabatic calorimeter. An anomalous behavior of heat capacity function C _p(T) has been revealed at very low temperatures, where this function does not tend to zero. Thermodynamic functions of zinnwaldite have been calculated from the experimental data. At 298.15 K, heat capacity C _p(T) = 339.8 J K⁻¹mol⁻¹, calorimetric entropy S ^o(Т) – S ^o(6.08) = 329.1 J K⁻¹ mol⁻¹, and enthalpy Н ^o(Т) − Н ^o(6.08) = 54,000 J mol⁻¹. Heat capacity and thermodynamic functions at 298.15 K for zinnwaldite having theoretical composition were estimated using additive method of calculation.     

Mesogenic and magnetic behavior in cobalt(II) and iron(II) compounds with long alkyl chains

Abstract  Metal complexes with long alkyl chains [Co(C16-terpy)₃](BF₄)₂ (1), [Fe(C16-terpy)₂](BF₄)₂ (2), [Co(C16-terpy)₂](BPh₄)₂ (3), [Co(C14-terpy)₂](BF₄)₂ (4), and [Fe(C12C10C5-terpy)₂](BF₄)₂ (5) were synthesized and their physical properties characterized, where C16-terpy, C14-terpy, and C12C10C5-terpy are 4′-hexadecyloxy-2,2′:6′,2′′-terpyridine, 4′-tetradecyloxy-2,2′:6′,2′′-terpyridine, and 4′-5′′′-decyl-1′′′-heptadecyloxy-2,2′:6′,2″-terpyridine, respectively. Complexes 1, 2, and 5 exhibited liquid–crystal properties in the temperature ranges of 371–528 K and 466–556 K, and 88–523 K, respectively. Variable-temperature magnetic susceptibility measurements revealed that the Co(II) complexes 1 and 4 exhibited unique spin transitions (T _1/2↓ = 217 K and T _1/2↑ = 260 K for 1 and T _1/2↓ = 250 K and T _1/2↑ = 307 K for 4), so-called ‘reverse spin transition,’ induced by structural phase transitions. Complex 3 exhibited gradual spin-crossover behavior (T _1/2 = 160 K.), and complex 5 exhibited spin transitions (T _1/2↑ = 288 K and T _1/2↓ = 284 K) at the liquid crystal transition temperature. Compounds with multifunction, i.e., magnetic and liquid–crystal properties, are important in the development of molecular materials. Graphical Abstract  

Volumetric and Ultrasonic Investigation of Glycylglycine in Aqueous FeCl<Subscript>3</Subscript> Solutions

Viscosity, ultrasonic velocity and density measurements have been carried out for glycylglycine in aqueous FeCl₃ solution as a function of molality at T=288.15 K, 298.15 K and 308.15 K. The experimental data have been used to derive properties such as isentropic compressibility (κ _S ), change in isentropic compressibility (Δκ _S ), relative change in isentropic compressibility (Δκ _S /κ ₀), apparent molar compressibility, volume and their limiting apparent molar quantities along with the constants S _K , S _V and viscosity B-coefficient. The obtained thermodynamic properties have been discussed in terms of molecular interactions.     

Molar heat capacities and standard molar enthalpy of formation of 2-amino-5-methylpyridine

The heat capacities (C _p,m) of 2-amino-5-methylpyridine (AMP) were measured by a precision automated adiabatic calorimeter over the temperature range from 80 to 398 K. A solid-liquid phase transition was found in the range from 336 to 351 K with the peak heat capacity at 350.426 K. The melting temperature (T _m), the molar enthalpy (Δ_fus H _m⁰), and the molar entropy (Δ_fus S _m⁰) of fusion were determined to be 350.431±0.018 K, 18.108 kJ mol⁻¹ and 51.676 J K⁻¹ mol⁻¹, respectively. The mole fraction purity of the sample used was determined to be 0.99734 through the Van’t Hoff equation. The thermodynamic functions (H _T-H _298.15 and S _T-S _298.15) were calculated. The molar energy of combustion and the standard molar enthalpy of combustion were determined, ΔU _c(C₆H₈N₂,cr)= −3500.15±1.51 kJ mol⁻¹ and Δ_c H _m⁰ (C₆H₈N₂,cr)= −3502.64±1.51 kJ mol⁻¹, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation of the crystalline compound was derived, Δ_r H _m⁰ (C₆H₈N₂,cr)= −1.74±0.57 kJ mol⁻¹.     

Heat capacities and thermodynamic properties of (<Emphasis Type="Italic">S</Emphasis>)-<Emphasis Type="Italic">tert</Emphasis>-butyl 1-phenylethylcarbamate

An N-tert-butyloxycarbonylated organic synthesis intermediate, (S)-tert-butyl 1-phenylethylcarbamate, was prepared and investigated by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The molar heat capacities of (S)-tert-butyl 1-phenylethylcarbamate were precisely determined by means of adiabatic calorimetry over the temperature range of 80-380 K. There was a solid–liquid phase transition exhibited during the heating process with the melting point of 359.53 K. The molar enthalpy and entropy of this transition were determined to be 29.73 kJ mol⁻¹ and 82.68 J K⁻¹ mol⁻¹ based on the experimental C _p–T curve, respectively. The thermodynamic functions, [H_T⁰ - H_298.15⁰ H_{T}^{0} - H_{298.15}^{0} ] and [S_T⁰ - S_298.15⁰ S_{T}^{0} - S_{298.15}^{0} ], were calculated from the heat capacity data in the temperature range of 80–380 K with an interval of 5 K. TG experiment showed that the pyrolysis of the compound was started at the temperature of 385 K and terminated at 510 K within one step.     

Pressure response of the bimetallic chain compound MnNi(NO2)4(en)2; en = ethylenediamine

The compound MnNi(NO₂)₄(en)₂, en = ethylendiamine, is a rare example of a ferromagnetically coupled bimetallic chain (J_∥ chain ∼ 2–3 K). Further, for this material, a finite inter-chain coupling triggers an antiferromagnetic (AFM) transition below T_N = 2.3 K. Here, we present a susceptibility study of MnNi(NO₂)₄(en)₂ under pressure. From our data, we derive the pressure response of the antiferromagnetic transition temperature T_N. Even up to highest pressure of 8.2 kbar we find a very modest increase of T_N by only ∼0.1 K. Independently, from a pressure study of the lattice parameters of MnNi(NO₂)₄(en)₂, we calculate the bulk module of the material to ∼8.8 GPa. Combining the data T_N(p) with the bulk module yields an anomalously low Grüneisen parameter Γ_mag of only 0.5(5). We discuss possible scenarios accounting for such a low Grüneisen parameter.     

One Dimensional Face-to-Face Stacking of Anderson–Evans [Cr(OH)6Mo6O18]3− Polyoxometalate Anion: Synthesis, Structure, and Physical Properties of (BEDT-TTF)4[Cr(OH)6Mo6O18]⋅2H2O

The synthesis, structural and magnetic characterizations of a new charge transfer salt (BEDT-TTF)₄[Cr(OH)₆Mo₆O₁₈]2H₂O based on the planar paramagnetic Anderson–Evans polyoxometalate are reported. Structural parameters: T=293 K, triclinic (P ), a=5.9545(2) Å, b=16.3767(6) Å, c=21.8643(6) Å, =110.829(2)°, =91.262(2)°, =98.129(1)°, Z=1, R=0.0540. The crystal structure is characterized by a face-to-face stacking of the anions giving rise to a one-dimensional inorganic chain which develops along the a direction. The organic layers contain two crystallographically independent BEDT-TTF dimers that form alternating stacks along the b direction. This organic chain is perpendicular to the inorganic chains. The charges on BEDT-TTF dimers are deduced to +1.2(1) and +1.7(1) on the basis of the intramolecular bond lengths. The EPR spectrum at 2.5 K is characterized by the superposition of BEDT-TTF⁺ and [Cr^III(OH)₆Mo₆O₁₈]^3– signals. The static susceptibility can be fitted by the Curie–Weiss law down to 1.9 K and the magnetic moment at 300 K is estimated to 4.21 _B , suggesting the uncorrelated spin system with BEDT-TTF⁺ (S=1/2) and Cr^III (S=3/2) ions. This interpretion is consistent with the charge disproportionation on BEDT-TTF dimers along the stack, which is supported by the refined molecular structure and is closely related to the insulating behavior (<10^–9Scm^–1 at RT).     

Thermal decomposition and antimicrobial activity of zinc(II) 2-bromobenzoates with organic ligands

New zinc(II) 2-bromobenzoate complex compounds with general formula Zn(2-BrC₆H₄COO)₂·nL·xH₂O (where L = urea, nicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, isonicotinamide, phenazone n = 0–2, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition organic ligand, carbon dioxide and bis(2-bromophenyl)ketone were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 1073 K was zinc oxide. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternate and M. gypseum). It was found that the selected bacteria were more sensitive to the studied zinc(II) complex compounds than the yeast and the filamentous fungi.