Kinga Wzgarda-Raj

This study presents a multiscale physicochemical analysis of defect formation mechanisms in paraffin-based organic systems subjected to different thermal histories. Paraffin materials, structurally analogous to biomimetic lipid matrices used in biomedical applications, were examined using differential scanning calorimetry (DSC) to determine the influence of processing conditions and storage temperature on phase stability and microstructural organization. Samples produced on two technological lines—a low-temperature process (D1) and a high-temperature process (D2)—were analyzed immediately after production and after storage at 15 °C, 25 °C, and 40 °C. DSC measurements revealed modifications in melting and crystallization profiles, together with additional thermal effects that suggest possible phase reorganization and changes in crystallization behavior under selected storage conditions. These effects were particularly visible for samples stored at 15 °C. The results provide an integrated thermal and spectroscopic interpretation of phase behavior in paraffin-based organic materials.

This study defines an operational protonation window for selecting the cytosinium–cytosine [CytH ⁺ …Cyt] synthon in nitrocarboxylate salts.

This study presents a comparative structural and supramolecular analysis of two newly synthesised co-crystals of phenazine with hydroxybenzoic acid derivatives: 4-hydroxybenzoic acid and 3,4,5-trihydroxybenzoic acid.

Mercaptopyridines, heteroaromatic compounds containing thiol groups, are widely studied for their applications in coordination chemistry, supramolecular design and materials science due to their selective binding properties and photoresponsiveness. In this work, we investigated the crystallization of 4-mercaptopyridine with cyanuric acid under strictly controlled conditions. A solution of both components in aqueous ethanol was subjected to UV irradiation and then allowed to crystallize slowly at 4 °C, followed by ambient conditions. Three crystalline products were isolated and were structurally characterized, namely, a cocrystal of cyanuric acid with 1,2-di(pyridin-4-yl)disulfane, C ₁₀ H ₈ N ₂ S ₂ ·C ₃ H ₃ N ₃ O ₃ , ( I ), a cocrystal of cyanuric acid with di(pyridin-4-yl)sulfane, C ₁₀ H ₈ N ₂ S·C ₃ H ₃ N ₃ O ₃ , ( II ), and a new 3:2 cocrystal of cyanuric acid with di(pyridin-4-yl)sulfane, 2C ₁₀ H ₈ N ₂ S·3C ₃ H ₃ N ₃ O ₃ , ( III ). No crystalline material was obtained under dark conditions, and cocrystal ( III ) was observed only after UV irradiation, which also yielded larger and better-quality single crystals than visible light. The results are consistent with oxidative coupling of 4-mercaptopyridine in solution under the applied conditions, giving disulfane and sulfane species that subsequently cocrystallize with cyanuric acid. Two of the cocrystals correspond to previously reported forms [CSD refcodes KIRGIF and KIRGOL; Gogoi et al. (2023). J. Mol. Struct. 1289 , 135806], whereas cocrystal ( III ) is reported here for the first time.

Four new crystal structures of trithiocyanuric acid (TTCA) with diazine derivatives have been determined, revealing key N–H⋯S interactions that stabilize molecular aggregates. TTCA forms two types of chains—linear and zigzag—each with distinct structural characteristics. Geometry and Hirshfeld surface analyses, supported by quantum-theoretical calculations, demonstrate that both chain arrangements are equally feasible, arising from inherent preferences in the crystal's structural organization. The critical role of intermolecular hydrogen bonds, particularly those involving amine groups as proton donors, in stabilizing these cocrystals is highlighted. To analyze the energy parameters, we applied the many-body extension of the supramolecular interaction energy approach for chain complexes in their crystal-state geometry, allowing decomposition of the interaction energy into two- and many-body contributions. The prevalent hydrogen bonding synthon, R² ₂(8), which forms both linear and zigzag chain structures, was found to be crucial in stabilizing the TTCA aggregates.

Carnosine coordination compounds have been the subject of much research. The presented temperature-dependent structural and spectroscopic analyses indicate the robustness and reactivity of the activated coordinatively unsaturated Cu( car ) ₂ dimer.

Cocrystals of thiourea with pyrazine N -oxide as thiourea–pyrazine N -oxide (2/1), C ₄ H ₄ N ₂ O·2CH ₄ N ₂ S, ( I ), and with phenazine as thiourea–phenazine (6/7), 7C ₁₂ H ₈ N ₂ ·6CH ₄ N ₂ S, ( II ), both crystallize in the monoclinic space group P 2 ₁ / c . In the crystalline state, molecules of both components are linked by N—H...N hydrogen bonds. In addition, there are R ₂ ² (8) hydrogen-bond synthons between thiourea molecules in both crystal structures. Furthermore, bifurcated hydrogen bonds between the –NH groups in the thiourea molecule and the N and O atoms in the N -oxide ring [in ( I )], as well as the N atom in the central phenazine ring [in ( II )], play a significant role in both structures. This emerging motif was thoroughly examined using quantum chemistry methods.

The first in situ preparation and single-crystal structure identification of pure 1-(pyridin-4-yl)-4-thiopyridine (PTP), C₁₀H₈N₂S, a simple and basic derivative of mercaptopyridine, from a crystallization mixture is described. The same PTP was found in two multicomponent crystal forms with 3,5-dinitrobenzoic acid as a classic two-component cocrystal, namely, 1-(pyridin-4-yl)-4-thiopyridine–3,5-dinitrobenzoic acid (1/1), C₇H₄N₂O₆·C₁₀H₈N₂S, and with 2-hydroxy-3,5-dinitrobenzoic acid as a salt formed via proton transfer from the hydroxy group of the acid to the pyridyl N atom of PTP, namely, 4-(4-sulfanylidene-1,4-dihydropyridin-1-yl)pyridin-1-ium 1-carboxy-3,5-dinitrophenolate, C₁₀H₉N₂S⁺·C₇H₃N₂O₇ ⁻. The protonation energy of PTP is 944.64 kJ mol⁻¹, indicating slightly greater N-basicity compared to pyridine, a well characterized and very basic chemical reference. A variety of molecular interactions can be observed in the three new crystal structures of PTP, which are all discussed in detail. Our findings confirm those of previous studies, indicating that PTP and 4-mercaptopyridine may, under suitable conditions, be chemically converted to one another, and that this process can be stimulated by light (UV–Vis).

X-ray diffraction studies reveal that pyrazine-2-thiol undergoes condensation to 2,2′-dithiobispyrazine [systematic name: 2-(pyrazin-2-yldisulfanyl)pyrazine], C₈H₆N₄S₂ (I), under aerial conditions. In the molecule of I, the pyrazine rings are arranged in an almost perpendicular manner, with an absolute value of the C—S—S—C torsion angle of −91.45 (6)°. A search in the Cambridge Structural Database confirmed that such a conformation is typical for disulfide compounds. Three different rotamers of disulfide I were studied using quantum theoretical studies. The rotamer of lowest energy was observed in the crystalline state in the structure stabilized by hydrogen-bond, chalcogen-bond and stacking interactions. Further quantum chemical computations confirm that 2,2′-dithiobispyrazine can react according to the S_N2 mechanism.

In these studies, we designed and investigated cyto- and genotoxic potential of five ruthenium cyclopentadienyl complexes bearing different phosphine and phosphite ligands. All of the complexes were characterized with spectroscopic analysis (NMR, FT-IR, ESI-MS, UV-vis, fluorescence and XRD (for two compounds)). For biological studies, we used three types of cells – normal peripheral blood mononuclear (PBM) cells, leukemic HL-60 cells and doxorubicin-resistance HL-60 cells (HL-60/DR). We compared the results obtained with those obtained for the complex with maleimide ligand CpRu(CO)₂(η¹-N-maleimidato) 1, which we had previously reported. We observed that the complexes CpRu(CO)(PPh₃)(η¹-N-maleimidato) 2a and CpRu(CO)(P(OEt)₃)(η¹-N-maleimidato) 3a were the most cytotoxic for HL-60 cells and non-cytotoxic for normal PBM cells. However, complex 1 was more cytotoxic for HL-60 cells than complexes 2a and 3a (IC₅₀ = 6.39 μM vs. IC₅₀ = 21.48 μM and IC₅₀ = 12.25 μM, respectively). The complex CpRu(CO)(P(OPh)₃)(η¹-N-maleimidato) 3b is the most cytotoxic for HL-60/DR cells (IC₅₀ = 104.35 μM). We found the genotoxic potential of complexes 2a and 3a only in HL-60 cells. These complexes also induced apoptosis in HL-60 cells. Docking studies showed that complexes 2a and CpRu(CO)(P(Fu)₃)(η¹-N-maleimidato) 2b have a small ability to degrade DNA, but they may cause a defect in DNA damage repair mechanisms leading to cell death. This hypothesis is corroborated with the results obtained in the plasmid relaxation assay in which ruthenium complexes bearing phosphine and phosphite ligands induce DNA breaks.