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19 pages, 5252 KiB

Open AccessArticle

Impact of Molecular and Crystal Structure on the Melting Points in Halo-Substituted Phenyl-Quinazolinones

by Ivica Đilović, Nenad Judaš, Mario Komar, Maja Molnar, Marta Počkaj and Tomislav Balić

Crystals 2025, 15(1), 39; https://doi.org/10.3390/cryst15010039 - 30 Dec 2024

Viewed by 718

Abstract

Three halo-substituted phenyl-quinazolinone derivatives were prepared and structurally characterized [1 = 3-(4-chlorophenyl)-6-iodo-2-methylquinazolin-4(3H)-one, 2 = 6-iodo-3-(4-methoxyphenyl)-2-methylquinazolin-4(3H)-one, and 3 = 7-chloro-2-methyl-3-[4-(trifluoromethoxy)phenyl]quinazolin-4(3H)-one)] in order to explore the relationship between structure and melting point in this group of compounds. Depending [...] Read more.

Three halo-substituted phenyl-quinazolinone derivatives were prepared and structurally characterized [1 = 3-(4-chlorophenyl)-6-iodo-2-methylquinazolin-4(3H)-one, 2 = 6-iodo-3-(4-methoxyphenyl)-2-methylquinazolin-4(3H)-one, and 3 = 7-chloro-2-methyl-3-[4-(trifluoromethoxy)phenyl]quinazolin-4(3H)-one)] in order to explore the relationship between structure and melting point in this group of compounds. Depending on the compound, molecules are interconnected by weak π∙∙∙π interactions, have I···Cl or Cl···Cl halogen bonding, or primarily form C–H∙∙∙N, C–H∙∙∙O, and π∙∙∙π interactions (no halogen bonding). The presence of the OCF₃ group leads to interactions between fluorine atoms that are shorter than the sum of the van der Waals radius for fluorine, suggesting that these interactions contribute to the overall lattice energy. The sequence of melting points cannot be fully explained by intermolecular interactions present in the solid state (enthalpy factor). To address this, a concept related to entropy called the functional group rotation influence, which relates to a decrease in fusion entropy caused by the rotational freedom of polyatomic groups, was introduced. Analysis of previously synthesized 3-phenylquinazolinones showed that the compounds with the highest melting point are the quinazoline-substituted and phenyl-nitro-substituted ones. Among halo-phenyl-substituted compounds, the melting point follows the sequence ortho < meta < para. Regarding the halogen atom type, the order of melting points is Cl ≈ Br > F > I for enantiopure and Br > I ≈ Cl > F for racemic compounds. Also, the melting point order correlates to halogen bond energy (I > Br > Cl > F) only when the geometry and energy of these interactions are favorable. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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13 pages, 1058 KiB

Open AccessArticle

Designing Continuous Crystallization Protocols for Curcumin Using PAT Obtained Batch Kinetics

by Mayank Vashishtha, Mahmoud Ranjbar, Gavin Walker and K. Vasanth Kumar

Crystals 2024, 14(12), 1069; https://doi.org/10.3390/cryst14121069 - 12 Dec 2024

Viewed by 774

Abstract

Developing theory-informed standard operating procedures (SOPs) for the continuous crystallisation of pharmaceuticals still remains a bottleneck. For the continuous manufacturing of pharmaceuticals, the current methods rely on the laborious trial-and-error approach to identify process conditions such as the dilution rate (flow per unit [...] Read more.

Developing theory-informed standard operating procedures (SOPs) for the continuous crystallisation of pharmaceuticals still remains a bottleneck. For the continuous manufacturing of pharmaceuticals, the current methods rely on the laborious trial-and-error approach to identify process conditions such as the dilution rate (flow per unit volume of reactor) and initial supersaturation, where the productivity will be at maximum at steady-state conditions. This approach, while proven and considered to be useful, lacks or ignores the information obtained from batch kinetics. Herein for the first time, we propose a theoretical method to develop batch kinetics-informed theoretical procedures for the continuous manufacturing of a model compound curcumin in isopropanol. The theoretical approach uses batch kinetic constants to theoretically identify the optimum dilution rate and the corresponding mass of the model compound curcumin when crystallised, as well as its productivity at steady-state conditions as a function of initial supersaturation. The theory-informed procedures will serve as a valuable guideline to develop operating procedures for the continuous production of the target compound and thus eliminate the trial-and-error approach used to develop the protocols for the continuous manufacturing of pharmaceuticals. We also showed that our methods allow for the estimation of the dilution rate that corresponds to washout conditions (i.e., where all the crystals in the crystalliser will be washed out due to the high flow rate of the input stream) during the continuous manufacturing of crystals. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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20 pages, 4114 KiB

Open AccessArticle

Investigation of AI Algorithms for Photometric Online Analysis in a Draft Tube Baffle Crystallizer

by Laura Marsollek, Julius Lamprecht and Norbert Kockmann

Crystals 2024, 14(12), 1045; https://doi.org/10.3390/cryst14121045 - 30 Nov 2024

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Abstract

The rapid advancement of AI algorithms presents new opportunities for sensing technologies based on image recognition, such as real-time crystallization monitoring. This work investigates the use of computer vision to detect and size crystals in a lab scale draft tube baffle crystallizer (DTBC). [...] Read more.

The rapid advancement of AI algorithms presents new opportunities for sensing technologies based on image recognition, such as real-time crystallization monitoring. This work investigates the use of computer vision to detect and size crystals in a lab scale draft tube baffle crystallizer (DTBC). A specially developed analytical bypass was implemented on the DTBC to enable a low-influence analysis without invasive intrusion into the process. By utilizing AI models such as YouOnlyLookOnce version 8 (YOLOv8), YOLOv8 Segmentation (YOLO8seg), and the convolutional network for biomedical image segmentation U-Net, this study assesses their effectiveness in determining crystal size distributions from photometric images. While U-Net was deemed unsuitable due to computational demands and accuracy issues, YOLOv8 and YOLO8seg performed better in terms of efficiency and precision. YOLO8seg, specifically, achieved the highest accuracy, with a mean average precision (mAP) of 82.3%, and excelling in detecting larger crystals, but underperforming with crystals smaller than 90 µm. Despite this limitation, YOLO8seg was able to compete with the manual methods and was superior to the state-of-the-art algorithm mask region convolutional neural network (Mask R-CNN) in terms of accuracy. The study suggests that specific training and adaptation of the imaging conditions could further improve the crystal detection performance. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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16 pages, 6122 KiB

Open AccessArticle

The Melt–Crystal Interface in the Production of Monocrystalline Sapphire via Heat Exchanger Method—Numerical Simulation Aspects

by Werner Eßl, Georg Reiss, Raluca Andreea Trasca, Masoud Sistaninia, Peter Raninger and Sina Lohrasbi

Crystals 2024, 14(12), 1036; https://doi.org/10.3390/cryst14121036 - 28 Nov 2024

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Abstract

In this work, selected numerical simulation aspects are analyzed in terms of their effect on predictions of the m-c interface. The fixed-grid enthalpy porosity phase change model, which is highly attractive in the field of modeling sapphire crystallization processes, is examined for its [...] Read more.

In this work, selected numerical simulation aspects are analyzed in terms of their effect on predictions of the m-c interface. The fixed-grid enthalpy porosity phase change model, which is highly attractive in the field of modeling sapphire crystallization processes, is examined for its sensitivity to the mushy zone parameter as well as the grid resolution. A further focus is set to the simulation of thermal transport including internal radiation in the crystal and the melt via the finite volume method. Depending on the purpose of the investigation, different requirements on the angular resolutions are relevant. While most of the m-c interface as well as the temperature distribution remain practically unchanged at reasonable resolutions, a high sensitivity of the m-c interface in the near-wall region is demonstrated. This sensitivity is also observed in terms of radiative transport and, hence, the total heat transfer. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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15 pages, 7659 KiB

Open AccessArticle

Mn(III)–Salen Complexes with Metallophilic Interactions

by Tomáš Šilha, Radovan Herchel and Ivan Nemec

Crystals 2023, 13(8), 1217; https://doi.org/10.3390/cryst13081217 - 6 Aug 2023

Cited by 1 | Viewed by 1758

Abstract

We synthesized a series of five novel Mn–salen-based compounds (1a–1c, 2a, 2b) through the reaction between precursor chloride complexes and potassium silver/gold dicyanide. The prepared compounds were structurally and magnetically characterized. Our findings revealed that all the [...] Read more.

We synthesized a series of five novel Mn–salen-based compounds (1a–1c, 2a, 2b) through the reaction between precursor chloride complexes and potassium silver/gold dicyanide. The prepared compounds were structurally and magnetically characterized. Our findings revealed that all the Mn(III) central atoms exhibited an axially elongated coordination polyhedron, leading to the observation of axial magnetic anisotropy as indicated by the negative axial magnetic parameter D, which was determined through fitting the experimental magnetic data and supported by theoretical CASSCF/NEVPT2 calculations. Furthermore, we observed magnetic-exchange interactions only in compounds with a special supramolecular topology involving O–H···O hydrogen-bonded dimers. In these cases, the weak magnetic exchange (J/cm⁻¹ = −0.58(2) in 1b and −0.73(7) in 2b) was mediated by the O–H···O hydrogen bonds. These findings were further supported by BS–DFT calculations, which predicted weak antiferromagnetic exchanges in these complexes and ruled out exchange interactions mediated by diamagnetic cyanido metallo–complex bridges. Additionally, we investigated the observed Ag···π (1b) and Au···Au (2b) interactions using QT–AIM calculations, confirming their non-covalent nature. We compared these results with previously reported Mn–salen-based compounds with metallophilic interactions arising from the presence of the [Ag/Au(CN)₂]⁻ bridging units. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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17 pages, 6024 KiB

Open AccessArticle

Temperature Induced Monoclinic to Orthorhombic Phase Transition in Protonated ZSM-5 Zeolites with Different Si/Al Ratios: An In-Situ Synchrotron X-ray Powder Diffraction Study

by Nicola Precisvalle, Maura Mancinelli, Matteo Ardit, Giada Beltrami, Lara Gigli, Alfredo Aloise, Enrico Catizzone, Massimo Migliori, Girolamo Giordano, Vincenzo Guidi and Annalisa Martucci

Crystals 2023, 13(6), 979; https://doi.org/10.3390/cryst13060979 - 20 Jun 2023

Cited by 1 | Viewed by 2157

Abstract

ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic P2₁/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic [...] Read more.

ZSM-5 zeolite is the synthetic counterpart to mutinaite. After thermal activation of the as-synthesized form, the symmetry of the ZSM-5 zeolite is lowered to the monoclinic P2₁/n. ZSM-5 then undergoes a polymorphic displacive phase transition from the monoclinic P2₁/n to the orthorhombic Pnma, Pn2₁a or P2₁2₁2₁ space groups, which occurs upon heating. This phase transition can be influenced by factors such as the type and amount of sorbate molecules present in the zeolite channels. ZSM-5 has many applications, including as a catalyst or sorbent in various industries, where high thermal stability is required. In this study, four ZSM-5 zeolites with different Si/Al ratios were investigated by synchrotron X-ray powder diffraction at both room temperature and high temperature conditions to determine the effects of chemical composition on the structural response of the zeolite lattice. The results showed that the ZSM-5 zeolites retained their crystallinity and structural features throughout the thermal treatment, indicating that they could be used as effective acid catalysts. Distortions in the zeolite framework can occur after TPA+ decomposition and thermal activation, affecting thermal regeneration and efficiency. The charge balance in ZSM-5 is achieved by the formation of Brønsted acid sites, and variations in bonding geometries are influenced by the initial Si/Al ratio. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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11 pages, 27553 KiB

Open AccessArticle

The Crystal Structure of Calcium Sebacate by X-ray Powder Diffraction Data

by Mattia Lopresti, Marco Milanesio and Luca Palin

Crystals 2023, 13(2), 261; https://doi.org/10.3390/cryst13020261 - 2 Feb 2023

Cited by 1 | Viewed by 2635 | Correction

Abstract

Sodium sebacate salts have several industrial applications as additives, lubricants, and a metal self-healing promoter in general industry, and some derivatives also have wide applications in cosmetics and pharmaceutical fields. Calcium sebacate formation and precipitation can be detrimental for the systems where sodium [...] Read more.

Sodium sebacate salts have several industrial applications as additives, lubricants, and a metal self-healing promoter in general industry, and some derivatives also have wide applications in cosmetics and pharmaceutical fields. Calcium sebacate formation and precipitation can be detrimental for the systems where sodium sebacate is used. It is thus important to investigate their crystallization features. Sodium and calcium sebacate were prepared, purified, and crystallized with different approaches to carry out a full X-ray diffraction powder diffraction structural analysis since suitable single crystals cannot be obtained. The calcium sebacate crystal structure was solved by simulated annealing. Calcium ions form layers connected by straight “all trans” sebacate molecules, a conformation that is also suggested by Fourier-transform infrared spectroscopy FTIR data. Water molecules are caged within calcium layers. The crystal structure is characterized by the calcium layers bent by

10.65

^{°}

with respect to the plane where sebacate chains lie, different from other dicarboxilic salts, such as cesium suberate, where the layers are perpendicular to the cation planes. The sodium sebacate crystal structure resulted in being impossible to be solved, despite several crystallization attempts and the different data collection approaches. FTIR spectroscopy indicates marked differences between the structures of calcium and sodium sebacate, suggesting a different type of metal coordination by carboxyls. Calcium sebacate shows a bis-bidentate chelating and bridging configuration (

(κ^{2}) - (κ^{1} - κ^{1}) - μ_{3} - C a r b

), while for sodium sebacate, FTIR spectroscopy indicates an ionic interaction between sodium and the carboxyls. A thermogravimetric analysis TGA was carried out to assess the hydration states of the two salts. Calcium sebacate shows, as expected, a total weight loss of ca. 7%, corresponding to the single water molecule located in the crystal structure, while sodium sebacate shows no weight loss before total combustion, indicating that its structure is not hydrated. Scanning electron microscopy SEM images show different morphologies for calcium and sodium salts, probably a consequence of the different interactions at the molecular lever suggested by FTIR and TGA. The used approach can be extended to fatty acid salt in general, a still under-explored field because of the difficulty of growing suitable single crystals. Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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1 pages, 163 KiB

Open AccessCorrection

Correction: Lopresti, M. et al. The Crystal Structure of Calcium Sebacate by X-ray Powder Diffraction Data. Crystals 2023, 13, 261

by Mattia Lopresti, Marco Milanesio and Luca Palin

Crystals 2024, 14(3), 277; https://doi.org/10.3390/cryst14030277 - 15 Mar 2024

Viewed by 966

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Young Crystallographers Across Europe)

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