This study systematically investigates multicomponent crystals of the antidepressant iproniazid (IPN) with six isomeric dihydroxybenzoic acids (DHBAs), revealing how hydroxyl substitution patterns dictate structural outcomes. Seven distinct solid forms-including a salt, cocrystals, and a cocrystal hydrate-were characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis, CLP-Pixel lattice energy calculations, and thermal analysis. The coformers generate remarkable supramolecular diversity, ranging from discrete tetramers ([IPN+23DHBA] (1:1)) and helical chains ([IPN+25DHBA] (1:1)) to ionic networks ([IPN+26DHBA] (1:1)) and a cohesive 3D framework ([IPN+35DHBA] (1:1)). Lattice energy calculations establish a stability ranking with the [IPN+35DHBA] (1:1) cocrystal being the most stable (-300.0 kJ.mol(-1)). A notable paradox emerges for [IPN+23DHBA] (1:1), where the most negative Coulombic term is counteracted by exceptionally large repulsion energy from close-packed H center dot center dot center dot H interactions, resulting in the least negative total lattice energy (-263.8 kJ.mol(-1)). Conformational analysis reveals systematic modulation of IPN geometry in response to coformer isomerism, with the C-N-N-C torsion angle adapting between -86.5 degrees and 98.5 degrees to optimize hydrogen-bonding alignment. The melting points of the multicomponent crystals range from 117.8 degrees C ([IPN+24DHBA] (1:1)) to 166.7 degrees C ([IPN+35DHBA] (1:1)). The results provide fundamental insights into synthon competition and the energetic landscape of multicomponent crystals, highlighting how systematic isomeric variation serves as a precise tool for modulating both structure and stability.

To comprehensively characterize the solution and sublimation thermodynamics of 1:1 multicomponent crystals of the antidepressant drug iproniazid (IPN) with six positional isomers of dihydroxybenzoic acid (DHBA) in acetonitrile, and to establish structure-thermodynamic relationships guiding coformer selection in pharmaceutical development. Temperature-dependent solubilities were measured over 293.15–313.15 K using the shake-flask method. Activity coefficients were derived via the Schrӧder-van Laar equations. Standard formation thermodynamic parameters were calculated from solubility data. Sublimation parameters were indirectly evaluated using a thermodynamic cycle linking dissolution, solvation, and sublimation. Activity coefficients showed positive deviations from ideality for most compounds, while 25DHBA and 35DHBA exhibited negative deviations, indicating favorable solute–solvent interactions. All stable systems formed spontaneously through an enthalpy-driven mechanism. Sublimation enthalpies were highly endothermic (233.2–266.5 kJ·mol−1) and correlated with the calculated total lattice energies, providing a quantitative measure of crystal lattice strength relevant to pharmaceutical processing and storage. Positional isomerism of the DHBA coformer governs the thermodynamic stability of IPN multicomponent crystals through a balance of intra- and intermolecular interactions. The integrated thermodynamic cycle approach offers an experimentally accessible framework for evaluating sublimation parameters, providing practical guidance for coformer selection, solid form screening, and predicting physical stability in pharmaceutical development.

PURPOSE:This study investigated the phenomenon of polymorphism in the pharmaceutical salt riluzole salicylate with the aim to modify the aqueous solubility and dissolution rate of riluzole. METHODS:Preparation routes and transformation pathways were investigated using mechanoactivation, sonication, sublimation and melt crystallization. The thermal-induced phase transformations were interpreted by thermal microscopy and ex situ PXRD analysis. The crystal structure of Form 3 was solved from powder diffraction data. The differences in non-covalent interactions in crystals of Form 1 and Form 3 and their role in structure stabilization were studied by QTAIMC analysis, fingerprint plots, energy frameworks and lattice energy calculations. Cocrystallization thermodynamic functions and relationships between three polymorphs were established based on DSC, solubility and lattice energy data. RESULTS:Two novel polymorphs of riluzole salicylate with higher melting points were discovered and characterized in addition to reported Form 1. The stable Form 3 can be obtained easily by milling or from the slurry, while the metastable Form 2 forms only by melt crystallization or resublimation. Form 3 has stronger hydrogen bonding and more balanced non-covalent interactions than Form 1, making it thermodynamically favored at room temperature, while Form 1 is more stable near absolute zero. CONCLUSION:Polymorphism significantly affects the pharmaceutical properties of riluzole salicylate. Selective preparation of polymorphs enables tuning of solubility and dissolution, linking crystal structure and thermodynamics to drug delivery optimization. Slower release kinetics of Form 1 compared to Form 3 and parent RLZ indicates its potential use as a prolonged form.

The sublimation thermodynamics of the neuroprotective and potential anticancer drug riluzole was studied by the transpiration method, and the obtained data were used in a virtual screening based on cocrystallization Gibbs free energy estimation. The method was successfully validated against 19 reported riluzole crystal forms and correctly predicted the salt formation with dihydroxybenzoic acid isomers. Variation of experimental conditions led to the isolation of the novel polymorphic modification of riluzolium 2,6-dihydroxybenzoate and the new salt cocrystal of riluzole with 2,3-dihydroxybenzoic acid with an unexpected (3:4) stoichiometry. The hydrogen bond topology was found to be identical in polymorphic forms of riluzolium 2,6-dihydroxybenzoate, and the packing difference is caused by the variable mutual orientation of hydrogen-bonded ribbons. The metastable Form 1 was found to undergo an irreversible exothermic phase transition upon heating, indicating a monotropic relationship between the polymorphs. In serial batch crystallization experiments, Form 1 was found to nucleate at a lower supersaturation level with subsequent transformation to Form 2. Thermodynamic functions of salt formation for riluzolium 2,6-dihydroxybenzoate Form 2 from parent compounds have confirmed that the process is enthalpy-driven. At pH > 4.4, the solubility of Form 2 is found to be higher than that of pure riluzole.

To reveal the effect of coordinated organic and inorganic sigma pi-ligands on the magnetocaloric properties of metal ions at room temperature, we have synthesized paramagnetic (5,10,15,20-tetraphenylporphinato)cobalt(II), (chloro)(2,3,7,8,12,13,17,18-octaethylporphinato))manganese(III), their coordination complexes with 1-methyl-2-(pyridin-4 '-yl)-3,4-fullero[60]pyrrolidine (1:3 and 1:2, respectively), and (ethoxy)(oxo)(5,10,15,20-tetraphe-nylporphinato)molybdenum(V) and have fully characterized their chemical structure by UV-vis, IR, 1H NMR, MALDI TOF spectral methods. Using the direct microcalorimetric method and DSC we have obtained, respec-tively, magnetocaloric effect, heat, change of enthalpy/entropy during the magnetization over the temperature range of 285 - 338 K in magnetic fields from zero to 1 T and the specific heat capacities in the temperature range from 270 to 400 K in zero fields for paramagnets synthesized. Involving the results of DFT calculations, we have shown that the electron structure of a central metal atom is the determining factor in the positive magnetocaloric effect in the complexes studied. The decrease in the MCE value is observed in the case of the intramolecular antiferromagnetic interactions in external magnetic fields (manganese(III) complexes) and additional axial bonding of the bulk fullerene-containing base.

To obtain the fundamental knowledge in the field of magnetocaloric behavior of new molecular materials at room temperature, we have synthesized(5,10,15,20-tetraphenylporphinato)terbium(III), (5,10,15,20-tetra(4-tert-butylphenyl)porphinato)terbium(III), and (phthalocyaninato)terbium(III) chlorides and have fully characterized their chemical structure using spectral methods (UV-vis, IR, 1 H NMR, MALDI TOF). The specific heat capacities of paramagnets synthesized were measured at the temperatures from 223 to 393 & Kcy; in zero fields using a DSC method. Magnetocaloric effect, heat, and change of enthalpy/entropy during the magnetization were observed over the temperature range of 278 - 328 K in magnetic fields from zero to 1 T by the direct microcalorimetric method. Using the analysis of the temperature dependences of the magnetocaloric parameters in the lanthanide row, we have established that the control of the magnetic exchange between the spin carrier and the paramagnetic ligand is determined both by the fine tuning of the outer shell of the lanthanide ion and by the substitution in the macrocycle. It was shown at a quantitative level that the terbium ion in the tetrapyrrole complexes carries out the magnetic exchange, being in 4f75d1 configuration.

In the present work, for the first time, a crystal engineeringapproach was systematically applied to produce novel crystalline formsof the tricyclic antidepressant amitriptyline (AMT) with modifiedaqueous dissolution kinetics. Six novel multicomponent crystals, includingthree salts with dicarboxylic acid counterions, two salt cocrystals,and a salt hydrate, were obtained and structurally characterized bysingle-crystal X-ray diffraction analysis. The structural analysisrevealed that all of the investigated crystals contain two-dimensional(2D) bilayers of AMT cations separated by organic counterions; however,the packing arrangements of AMT cations within the bilayers were foundto differ significantly. The structure-directing role of 2D bilayersof AMT was discussed based on insights from periodic density functionaltheory (DFT) computations. The dissolution performance of the obtainedsolid forms was studied in the FaSSGF buffer solution under sink conditionsand compared to that of the commercial form AMT-HCl. The effect ofthe salt formation on the AMT release profile was assessed using fivedifferent dissolution models. The potential of the AMT maleate andAMT oxalate salts as a basis for the design of controlled-releaseforms was discussed. Forthe first time, a crystal engineering method was employedto comprehensively examine the solid-state landscape of amitriptylinewith the goal of altering the drug's aqueous dissolution kinetics.Six new multicomponent crystals were obtained and structurally characterized.The newly obtained solid forms have lower equilibrium solubility anda slower dissolution rate compared to the commercial form. AMT-Mle(1:1) and AMT-Ox (1:1) salts provide the sustained release of AMTfrom the tablet into the FaSSGF media without the need for additionalexcipients.

In this work, the synthesis of a magnetite/graphene composite and a magnetic fluid based on it is carried out. The physical–chemical and magnetic–thermal properties of the obtained samples are studied. It is established that in the magnetite/graphene composite magnetite nanoparticles are adsorbed on the graphene surface in the form of aggregates. It is found that the specific surface area and pore volume of the magnetite/graphene composite are higher than the values for magnetite. Analysis of the rheological curves of the magnetic fluid characterizes its structure as homogeneous and indicates a uniform distribution of the dispersed phase in the dispersion medium. It is established that the magnetic fluid with the composite is thermally stable up to 210°С. The values of the specific heat capacity of the synthesized sample are slightly higher than the heat capacity of the liquid without graphene additives. It is noted that the addition of an insignificant part of graphene to the magnetic phase of the magnetic fluid leads to a twofold increase in the value of the magnetocaloric effect (MCE) and changes the shape of the temperature dependence of the MCE in the studied temperature range.

Two macromolecular complexes derived from poly(propylene imine) with Co(II) and Ni(II) ions have been synthesized by direct complexation between metal salts and the second generation dendrimers. Based on experimental data one can assume the formation of a binuclear complex in the case of Co2+ while the Ni2+ complex is characterized by the filling of all possible coordination sites. Magnetocaloric behaviour of symmetric Co(II) and Ni(II) complexes was found. It has been established that when the synthesized samples are exposed to a magnetic field, the sign of the specific amount of heat (QMCE) changes. Analyzing the obtained data on the magnetocaloric effect of the complexes, it was shown that the MCE values are changed from the negative value DT (Co(II)) =-0.016 K, DT (Ni(II)) =-0.005 K to positive DT (Co (II)) = 0.011 K, DT (Ni(II)) = 0.002 K (at T = 337 K and 1 T). The presence of a maximum in the temperature dependences of the heat capacity indicates a second-order phase transition. It was found for the studied complexes that they exhibit enantiotropic mesomorphism with the formation of columnar phases.& COPY; 2022 Elsevier B.V. All rights reserved.

In this study, the existing set of carbamazepine (CBZ) cocrystals was extended through the successful combination of the drug with the positional isomers of acetamidobenzoic acid. The structural and energetic features of the CBZ cocrystals with 3- and 4-acetamidobenzoic acids were elucidated via single-crystal X-ray diffraction followed by QTAIMC analysis. The ability of three fundamentally different virtual screening methods to predict the correct cocrystallization outcome for CBZ was assessed based on the new experimental results obtained in this study and data available in the literature. It was found that the hydrogen bond propensity model performed the worst in distinguishing positive and negative results of CBZ cocrystallization experiments with 87 coformers, attaining an accuracy value lower than random guessing. The method that utilizes molecular electrostatic potential maps and the machine learning approach named CCGNet exhibited comparable results in terms of prediction metrics, albeit the latter resulted in superior specificity and overall accuracy while requiring no time-consuming DFT computations. In addition, formation thermodynamic parameters for the newly obtained CBZ cocrystals with 3- and 4-acetamidobenzoic acids were evaluated using temperature dependences of the cocrystallization Gibbs energy. The cocrystallization reactions between CBZ and the selected coformers were found to be enthalpy-driven, with entropy terms being statistically different from zero. The observed difference in dissolution behavior of the cocrystals in aqueous media was thought to be caused by variations in their thermodynamic stability.

Polymorphism is a common phenomenon among single- and multicomponent molecular crystals that has a significant impact on the contemporary drug development process. A new polymorphic form of the drug carbamazepine (CBZ) cocrystal with methylparaben (MePRB) in a 1:1 molar ratio as well as the drug's channel-like cocrystal containing highly disordered coformer molecules have been obtained and characterized in this work using various analytical methods, including thermal analysis, Raman spectroscopy, and single-crystal and high-resolution synchrotron powder X-ray diffraction. Structural analysis of the solid forms revealed a close resemblance between novel form II and previously reported form I of the [CBZ + MePRB] (1:1) cocrystal in terms of hydrogen bond networks and overall packing arrangements. The channel-like cocrystal was found to belong to a distinct family of isostructural CBZ cocrystals with coformers of similar size and shape. Form I and form II of the 1:1 cocrystal appeared to be related by a monotropic relationship, with form II being proven to be the thermodynamically more stable phase. The dissolution performance of both polymorphs in aqueous media was significantly enhanced when compared with parent CBZ. However, considering the superior thermodynamic stability and consistent dissolution profile, the discovered form II of the [CBZ + MePRB] (1:1) cocrystal seems a more promising and reliable solid form for further pharmaceutical development.

In this work, magnetite crude oil-based magnetic fluids have been synthesized and studied. Their physicochemical parameters (density, viscosity, magnetic phase particle size) have been determined. IR spectroscopy and thermogravimetric analysis have been performed. The magnetocaloric properties (magnetocaloric effect and heat capacity) of magnetic fluids have been determined by the microcalorimetric method in the temperature range of 278-350 K in the magnetic field changing its value from 0 to 1.0 T. The maximum value of the magnetocaloric effect of a magnetic fluid with a magnetic phase volume concentration of 0.08 is 0.0035 K at 310 K and at the magnetic induction to 1.0 T. The obtained samples of magnetic fluids have low production costs because crude oil is used as the carrier fluid and can be recommended for various applications of the petroleum and gas industry, for example, for well killing.

Results are presented from a physicochemical study of magnetite magnetic fluid of synthesized with addition of graphene. It is shown that adding graphene during the synthesis of the dispersed phase affects the specific surface of the magnetic phase, the thermal stability, the viscosity, and the heat capacity of the magnetic fluid.

The dendritic iron (III) complex of the third generation (3-K2.10-(FeCl3)(9)) has been synthesised by complex formation between metal salt and organic ligand and studied. The structural characterisation and mesomorphic properties of the synthesised dendritic complex were investigated by FT-IR spectroscopy, X-ray diffraction measurements, polarising optical microscopy, and differential scanning calorimetry. It was shown that the given complex forms a columnar (Col(h)) mesophase with the transition to glass state upon cooling. The specific heat capacity of the complex was determined for the first time. The temperature dependencies of the specific heat capacity of the ligand and Fe(III) complex with the third-generation dendrimer show maxima that indicate a 'crystal - mesophase' transition. In order to determine the magnetocaloric effect, magnetisation experiments at fields from 0 to 1.0 T were performed from 263 to 358 K. The temperature dependence of the magnetocaloric effect is extreme. In the temperature range 340 - 350 K there is a sharp maximum indicating a magnetic phase transition. A correlation was found between the 'crystal - mesophase' transition and magnetic phase transition of the Fe(III) complex. The experimentally discovered fact of the existence of the liquid crystalline phase and the spin crossover in the same temperature region suggests the use of this compound in high-tech industries.

Porphyrin complexes of 3d-metals with an open electronic shell are ranked as molecular materials with both electronic functionality and paramagnetic behavior due to exhibiting a positive magnetocaloric effect (MCE) at the temperature close to the room. We have determined MCE, heat, and an enthalpy/entropy change during magnetization of chloride ligated pentacoordinated iron(III) 5,10,15,20-tetraphenylporphin, (Cl)FeTPP and dimethylformamide ligated sixcoordinated iron(III) mesoporphyrin IX, [(DMF)2FeMP]+Cl- at 278?338 K in magnetic fields from 0 to 1.0 T by the direct microcalorimetric method. The specific heat capacity in solid (Cl) FeTPP/[(DMF)2FeMP]+Cl- was directly determined depending on the temperature in zero magnetic fields using DSC. To improve understanding of the correlation between magnetic properties of the iron(III) complexes and its spin state, we have compared the magnetic behavior of paramagnets studied with those for manganese(III) porphyrins. Both the iron(III) spin state and the exchange (ferromagnetic or antiferromagnetic depending on functional substitution in a complex) between a paramagnetic ligand and the central ion are reflected in the magnetocaloric behavior of iron(III) porphyrins studied.

The magnetic fluids based on magnetite nanoparticles were synthesized using mixed surfactants (oleic acid/alkenyl succinic anhydride) dispersed in different carrier media (polyethylsiloxane and dialkyldiphenyl). The physicochemical properties of magnetic fluids (density, viscosity, saturation magnetization, magnetic phase concentration, magnetic core size) were determined. Magnetic fluids are stable in a wide temperature range. All the samples of the magnetic fluids exhibit typical superparamagnetic behavior. The magnetocaloric effect and the specific heat capacity of the magnetic fluids were first direct determined at 288–350 K in a magnetic field of 0–1.0 T. The field dependences of the magnetocaloric effect have a classic linear form. The temperature dependences of the magnetocaloric effect of magnetic fluids in magnetic fields have an extreme character. Thermodynamic parameters of magnetic fluids (magnetization namely enthalpy/entropy change) were determined. The specific heat capacity of magnetic fluid samples in a zero magnetic field was obtained at different temperatures (at 278–350 K) on a differential scanning calorimeter and on the original microcalorimeter. The temperature dependences of the heat capacity of magnetic fluids in magnetic fields have an extreme character. It was established that the difference in heat capacity values obtained in and without the magnetic field is within the experimental error. The extreme character of the heat capacity is reflected in the magnetocaloric effect temperature dependences.