Denis P. Pishchur

The thermodynamic properties of Fe(II) complexes with 1,2,4-triazoles

The temperature dependences of the heat capacities at 106–330 K of the monoligand Fe(NH2trz)3I2 (I) and mixed-ligand Fe(Htrz)0.3(NH2trz)2.7SiF6 · H2O (II) complexes (Htrz is 1,2,4-triazole, and NH2trz is 4-amino-1,2,4-triazole) were studied by adiabatic vacuum calorimetry. The 1A1 ⇔ 5T2 spin transition was observed in these compounds. The thermodynamic parameters of phase transitions in I and II were determined.

Phase transitions in a metal–organic coordination polymer: [Zn2(C8H4O4)2(C6H12N2)] with guest molecules. Thermal effects and molecular mobility

ABSTRACT Thermal effects of a series of [Zn2(C8H4O4)2(C6H12N2)] porous compound with the guest molecules located in the pores were studied using differential scanning calorimetry combined with solid-state 1H nuclear magnetic resonance spectroscopy. The intercalation of the molecules was shown to produce various thermal anomalies and phase transitions, which were characterized and analyzed.

Luminescent coordination polymers based on Ca2+ and octahedral cluster anions [{M6Cli8}Cla6]2− (M = Mo, W): synthesis and thermal stability studies

Luminescent coordination polymers (CPs) based on inexpensive stable precursors are attractive materials for applications. Here we report the synthesis and evaluation of the stability and photophysical characteristics of the first examples of phosphorescent CPs based on octahedral molybdenum and tungsten cluster anions. In particular, 1D CP trans-[{Ca(OPPh3)4}{{M6Cli8}Cla6}]∞ (M = Mo, W) can be obtained either directly at increased temperature or via intermediate phases [cis-Ca(OPPh3)4(H2O)2][{M6Cli8}Cla6]·2CH3CN that are stable at room-temperature, but convert to the titled CPs at temperatures above 100 °C.

Thermal effects in guest-host systems: [Zn2(bdc)(S-lac)(dmf)]•PhEtOH: A DSC and NMR study

Differential scanning calorimetry and nuclear magnetic resonance were used to investigate thermal effects in the guest-host systems where homochiral metal-organic sorbent [Zn2 (bdc)(S-lac)(dmf)] is considered as a host while 1-phenylethanol enantiomers and their racemic mixture serve as guest molecules. A maximum energy gain from the guest-host interaction was observed in the system with the racemic mixture. The effect of host-guest recognition was revealed for the case of the host and guest having a similar type of chirality in the presence of antipode guest molecules.

Thermodynamic properties of complex compounds of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane

The temperature dependence of the heat capacity of a complex compound of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane is studied by adiabatic calorimetry in the range of 100–300 K. A specific heat anomaly is found and localized in the temperature range corresponding to the sharp spin transition 1A1 ↔ 5T2 with hysteresis on the temperature dependence of the magnetic susceptibility. The effects of cooperative interaction are revealed on the basis of thermodynamic and magnetochemical data, using two widely used models of spin transition.

High thermal stability of the Ru-ON (MS1) linkage isomer of ruthenium nitrosyl complex [RuNO(Py)4F](ClO4)2 with trans NO-Ru-F coordinate.

The reaction of [RuNO(Py)4OH](PF6)2 with hydrofluoric acid results in the formation of the [RuNO(Py)4F]2+ cation with good yield. The perchlorate salt [RuNO(Py)4F](ClO4)2 was separated and characterized by elemental analysis, IR spectroscopy, and single crystal and powder X-ray diffraction. Though the crystal structure of the salt contained two crystallographically independent [RuNO(Py)4F]2+ cations, the bond distances differed by no more than 0.005 A, and only one ν(NO) vibration band (1907 cm−1 at room temperature) was observed in the IR spectra of the salt. Blue light irradiation (445 nm) at 80 K resulted in the formation of the MS1 linkage isomer with Ru–ON coordination which could be converted to the MS2 linkage isomer (Ru–η2NO coordination) upon IR (980 nm) irradiation. The achieved conversion is equal to 20–23% for the MS1 isomer and 17% for the MS2 isomer. The thermal decay of both metastable isomers was investigated by IR spectroscopy and DSC. The decay temperature for the MS2 isomer was 185 K. For the MS1 isomer, the decay temperature of [RuNO(Py)4F](ClO4)2 (289–291 K) was the highest of all known ruthenium nitrosyl complexes.

Controlled self-assembly of π-stacked/H-bonded 1D crystal structures from polyfluorinated arylamines and 18-crown-6 (2:1). Associates vs co-formers fluorescence properties

Supramolecular 1D assemblies supported by N–H⋯Ocr and π-stacking interactions were designed and synthesized using polyfluorinated arylamines, differing in the nature of the aromatic ring (benzene, naphthalene, pyridine) and para-substituents (H, F, CN, CF3), and 18-crown-6 ether. Co-crystal structures and intermolecular interactions were studied in detail using X-ray analysis and compared with those in individual arylamine crystals. In the co-crystals, all relatively weak H-bonds N–H⋯X (X = F, Nhet, Ncyano) are replaced by the stronger bond N–H⋯Ocrown and π-stacking in pairs of the arylamine molecules is realized. Depending on the arylamine structure, a parallel displaced, rotated, or slipped stack geometry occurs. Using DSC, phase transitions in the co-crystals were determined and the thermal characteristics were found to be reproduced in the melting-crystallization cycles, which indicates the regeneration of the crystal structure. For a number of compounds, there are significant changes in the fluorescence characteristics, in terms of both intensity and wavelength, due to the formation of associates with 18-crown-6: aggregation-induced emission in the pentafluoroaniline associate, a large shift of λem in the 4-cyanotetrafluoroaniline associate, and aggregation-caused quenching in the 4-aminotetrafluoropyridine associate. Crystal structure analysis reveals that π-stacking interactions between arylamines play a key role in the modulation of the solid-state fluorescence properties. The revealed effect of fluorescence build-up/quenching shows these types of supramolecular associates to be promising solid-state chemosensors.

Materials with high proton conductivity above 200 °C based on a nanoporous metal–organic framework and non-aqueous ionic media

Correction for ‘Materials with high proton conductivity above 200 °C based on a nanoporous metal–organic framework and non-aqueous ionic media’ by Valentina G. Ponomareva et al., RSC Adv., 2017, 7, 403–407.

Some basic correlations in the thermal (kinetic) stability of inclusion compounds on the basis of microporous metal–organic frameworks

Metal–organic frameworks (MOFs) have promising practical applications in gas storage, separation and purification, and catalysis. The standard process for MOF production begins with the synthesis of the inclusion compound. The molecules of the organic solvent used are caught in the channels and caves of the MOF structure. These primary inclusion guest molecules are excluded further by the evacuation or by the heating. We investigate a series of inclusion compounds and study the correlation between their thermal (kinetic) stability and the framework and guest molecule properties. Thermogravimetric curves are used for the kinetic studies. Kinetic parameters of decomposition are estimated within the approaches of non-isothermal kinetics (“model-free” kinetics and nonlinear regression methods). We discuss guest molecular kinetic diameters, guest molecule sizes, shape and polarity, the guest phase state (fluid or solid) within the framework pores, the flexibility of the framework structures, the enthalpy and entropy contributions to the kinetic stability and the inclusion compound properties with very similar frameworks (channel walls with similar chemical constitutions), but with different channels length.