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18 pages, 1822 KiB  
Article
Pyrrolopyrimidines: Design, Synthesis and Antitumor Properties of Novel Tricyclic Pyrrolo [2,3-d]pyrimidine Derivatives
by Buer Song, Zarifa Murtazaeva, Lifei Nie, Rustamkhon Kuryazov, Shukhrat Gaybullaev, Chao Niu, Khurshed Bozorov, Haji Akber Aisa and Jiangyu Zhao
Molecules 2025, 30(14), 2917; https://doi.org/10.3390/molecules30142917 - 10 Jul 2025
Viewed by 916
Abstract
The pyrrolo[2,3-d]pyrimidine (7-deazapurine) scaffold is a unique heterocyclic system included in the composition of most nucleotides. In this study, series of the pyrrolo[2,3-d]pyrimidine-imines and 3-halo-substituted pyrrolo[2,3-d]pyrimidines were designed and prepared in high yields. Condensed pyrimidines [...] Read more.
The pyrrolo[2,3-d]pyrimidine (7-deazapurine) scaffold is a unique heterocyclic system included in the composition of most nucleotides. In this study, series of the pyrrolo[2,3-d]pyrimidine-imines and 3-halo-substituted pyrrolo[2,3-d]pyrimidines were designed and prepared in high yields. Condensed pyrimidines are obtained via carbonyl-amine condensation and carbon-halogen bond formation. Pyrrolo[2,3-d]pyrimidine-imines containing a bromine substituent at position C-4 of the phenyl ring and azepine side-ring exhibited superior antitumor activity on the colon cancer HT-29 cell line; IC50 values were 4.55 and 4.01 µM, respectively. These results revealed an interesting pattern, where condensed pyrimidinones containing an azepine ring demonstrated selective antitumor activity on the colon cancer cell line HT-29. In addition, the molecular docking results suggest that compound 8g provided a thorough understanding of its interactions with the DDR2 active site. This could pave the way for further development and optimization of DDR-targeting drugs, contributing to advancements in cancer therapeutics. This lead compound may serve as design templates for further studies. Full article
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12 pages, 1303 KiB  
Article
Iodine-Substituted Dithiocarbamic Flavanones—A Structure–Activity Relationship Study of Their Antioxidant Properties
by Mihail Lucian Birsa and Laura Gabriela Sarbu
Molecules 2025, 30(11), 2280; https://doi.org/10.3390/molecules30112280 - 22 May 2025
Viewed by 401
Abstract
The antioxidant properties of novel diiodo-substituted 3-dithiocarbamic flavanones were investigated. The three frameworks that proved to be the most active ones in our previous studies were selected. By varying the nature of the substituent at the para position of flavanone ring B, [...] Read more.
The antioxidant properties of novel diiodo-substituted 3-dithiocarbamic flavanones were investigated. The three frameworks that proved to be the most active ones in our previous studies were selected. By varying the nature of the substituent at the para position of flavanone ring B, a structure–activity relationship study on radical scavenging properties was performed. The influence of these substituents (F, Cl, Br and H) was investigated against DPPH and ABTS+•. The results indicate that the presence of the halogen substituents induces better antioxidant properties than ascorbic acid and BHT. The highest radical scavenging activity was found in the case of morpholine carbodithioates. Regarding the ABTS+• assay, all investigated flavanones exhibited better antioxidant properties than BHT. Full article
(This article belongs to the Special Issue Molecular Approaches to Drug Discovery and Development)
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23 pages, 8630 KiB  
Article
Finely-Tuned Bis(imino)pyridylcobalt Complexes Enhance Ethylene Polymerization: The Role of Bulky and Halogen Substituents
by Elizabeth Ogbe, Yanping Ma, Yizhou Wang, Jiahao Gao, Yang Sun and Wen-Hua Sun
Molecules 2025, 30(4), 859; https://doi.org/10.3390/molecules30040859 - 13 Feb 2025
Viewed by 733
Abstract
The bis(imino)pyridylcobalt complexes have been finely tuned through using the aniline derivative bearing a meta-chloro substituent, besides its ortho- and para-di(4-fluorophenyl)methyl and ortho-methyl substituents for the series of 2-[1-(3-chloro-4,6-bis((di(4-fluorophenyl)methyl)-2-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(II) chlorides (2,6-Me2Ph, Co1; 2,6-Et2Ph, Co2 [...] Read more.
The bis(imino)pyridylcobalt complexes have been finely tuned through using the aniline derivative bearing a meta-chloro substituent, besides its ortho- and para-di(4-fluorophenyl)methyl and ortho-methyl substituents for the series of 2-[1-(3-chloro-4,6-bis((di(4-fluorophenyl)methyl)-2-methylphenylimino)ethyl]-6-[1-(arylimino)ethyl]pyridylcobalt(II) chlorides (2,6-Me2Ph, Co1; 2,6-Et2Ph, Co2; 2,6-iPr2Ph, Co3; 2,4,6-Me3Ph, Co4; and 2,6-Et2-4-MePh, Co5). The compounds were characterized using elemental analysis, 1H/13C NMR, FT-IR spectroscopy, and the single-crystal X-ray diffraction used in confirming the molecular structures of Co1, Co2, Co4, and Co5. The newly synthesized precatalysts, maintaining steric influences with the addition of an electron-withdrawing meta-chloro group, achieved higher activities along with better thermal stability, and controlled molecular weights of polyethylenes obtained. Upon activation with either MAO or MMAO, all catalysts exhibited remarkable activity for ethylene polymerization, for example, 9.2 × 106 g mol−1 h−1 by Co1 at 70 °C with 30 min and 18.0 × 106 g mol−1 h−1 by Co4 with the first 5 min. Co4 demonstrated exceptionally thermal stability with the peak activity of 8.9 × 106 g mol−1 h−1 at 70 °C and slightly decreased to 7.2 × 106 g mol−1 h−1 at 80 °C, and even maintained an activity of 1.6 × 106 g mol−1 h−1 at 100 °C. More importantly, all resultant polyethylenes were characterized as having vinyl-terminal and high-linear feature along with narrow dispersity; the molecular weights could be adapted in the ranges from 6.4 to 50.0 kg mol−1. In comparison with previous cobalt analogs, the current system performed better thermal stability and polymerization efficiency. Therefore, such robust complex catalysts are potentially considered for the polyethylene industry. Full article
(This article belongs to the Special Issue Organometallic Compounds: Design, Synthesis and Application)
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22 pages, 2915 KiB  
Article
Antistaphylococcal Triazole-Based Molecular Hybrids: Design, Synthesis and Activity
by Kostiantyn Shabelnyk, Alina Fominichenko, Oleksii Antypenko, Olexandr Gaponov, Svitlana Koptieva, Svitlana Shyshkina, Oleksii Voskoboinik, Sergiy Okovytyy, Serhii Kovalenko, Valentyn Oksenych and Oleksandr Kamyshnyi
Pharmaceuticals 2025, 18(1), 83; https://doi.org/10.3390/ph18010083 - 11 Jan 2025
Cited by 2 | Viewed by 1666
Abstract
Background: In the era of resistance, the design and search for new “small” molecules with a narrow spectrum of activity that target a protein or enzyme specific to a certain bacterium with high selectivity and minimal side effects remains an urgent problem of [...] Read more.
Background: In the era of resistance, the design and search for new “small” molecules with a narrow spectrum of activity that target a protein or enzyme specific to a certain bacterium with high selectivity and minimal side effects remains an urgent problem of medicinal chemistry. In this regard, we developed and successfully implemented a strategy for the search for new hybrid molecules, namely, the not broadly known [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines. They can act as “building blocks” and allow for the introduction of certain structural motifs into the desired final products in order to enhance the antistaphylococcal effect. Methods: The “one-pot” synthesis of the latter is based on the conversion of substituted 4-hydrazinoquinazolines or substituted 2-aminobenzonitriles and carboxylic acid derivatives to the target products. The possible molecular mechanism of the synthesized compounds (DNA gyrase inhibitors) was investigated and discussed using molecular docking, and their further study for antistaphylococcal activity was substantiated. Results: A significant part of the obtained compounds showed high antibacterial activity against Staphylococcus aureus (MIC: 10.1–62.4 µM) and 5-bromo-2-(3-(furan-3-yl)-1H-1,2,4-triazol-5-yl)aniline and 5-fluoro-2-(3-(thiophen-3-yl)-1H-1,2,4-triazol-5-yl)aniline, with MICs of 5.2 and 6.1 µM, respectively, approaching the strength of the effect of the reference drug, “Ciprofloxacin” (MIC: 4.7 µM). The conducted SAR and ADME analyses confirm the prospects of the further structural modification of these compounds. The obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antimicrobial activity and deserve further structural modification and detailed study as effective antistaphylococcal agents. The SAR analysis revealed that the presence of a cycloalkyl or electron-rich heterocyclic fragment in the third position of the triazole ring was essential for the antibacterial activity of the obtained compounds. At the same time, the introduction of a methyl group into the aniline moiety led to an enhancement of activity. The introduction of halogen into the aniline fragment has an ambiguous effect on the level of antistaphylococcal activity and depends on the nature of the substituent in the third position. Conclusions: Obtained [2-(3-R-1H-[1,2,4]-triazol-5-yl)phenyl]amines reveal significant antistaphylococcal activity and deserve for further detailed study as effective antibacterial agents. Full article
(This article belongs to the Section Biopharmaceuticals)
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19 pages, 5556 KiB  
Article
Exploring the Impact of Structural Modifications of Phenothiazine-Based Novel Compounds for Organic Solar Cells: DFT Investigations
by Walid Taouali, Amel Azazi, Rym Hassani, Entesar H. EL-Araby and Kamel Alimi
Polymers 2025, 17(1), 115; https://doi.org/10.3390/polym17010115 - 5 Jan 2025
Cited by 9 | Viewed by 1768
Abstract
This paper explores a novel group of D-π-A configurations that has been specifically created for organic solar cell applications. In these material compounds, the phenothiazine, the furan, and two derivatives of the thienyl-fused IC group act as the donor, the π-conjugated spacer, and [...] Read more.
This paper explores a novel group of D-π-A configurations that has been specifically created for organic solar cell applications. In these material compounds, the phenothiazine, the furan, and two derivatives of the thienyl-fused IC group act as the donor, the π-conjugated spacer, and the end-group acceptors, respectively. We assess the impact of substituents by introducing bromine atoms at two potential substitution sites on each end-group acceptor (EG1 and EG2). With the donor and π-bridge held constant, we have employed density functional theory and time-dependent DFT simulations to explore the photophysical and optoelectronic properties of tailored compounds (M1–M6). We have demonstrated how structural modifications influence the optoelectronic properties of materials for organic solar cells. Moreover, all proposed compounds exhibit a greater Voc exceeding 1.5 V, a suitable HOMO-LUMO energy gap (2.14–2.30 eV), and higher dipole moments (9.23–10.90 D). Various decisive key factors that are crucial for exploring the properties of tailored compounds—frontier molecular orbitals, transition density matrix, electrostatic potential, open-circuit voltage, maximum absorption, reduced density gradient, and charge transfer length (Dindex)—were also explored. Our analysis delivers profound insights into the design principles of optimizing the performance of organic solar cell applications based on halogenated material compounds. Full article
(This article belongs to the Special Issue Polymeric Materials in Energy Conversion and Storage, 2nd Edition)
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14 pages, 4225 KiB  
Article
Hybrid Materials Based on Carbon Nanotubes and Tetra- and Octa-Halogen-Substituted Zinc Phthalocyanines: Sensor Response Toward Ammonia from the Quantum-Chemical Point of View
by Pavel Krasnov, Victoria Ivanova, Darya Klyamer, Dmitry Bonegardt, Aleksandr Fedorov and Tamara Basova
Sensors 2025, 25(1), 149; https://doi.org/10.3390/s25010149 - 30 Dec 2024
Viewed by 864
Abstract
This paper presents the results of quantum-chemical modeling performed by the Density Functional-Based Tight Binding (DFTB) method to investigate the change in the band structure of hybrid materials based on carbon nanotubes and unsubstituted, tetra-, or octa-halogen-substituted zinc phthalocyanines upon the adsorption of [...] Read more.
This paper presents the results of quantum-chemical modeling performed by the Density Functional-Based Tight Binding (DFTB) method to investigate the change in the band structure of hybrid materials based on carbon nanotubes and unsubstituted, tetra-, or octa-halogen-substituted zinc phthalocyanines upon the adsorption of ammonia molecules. The study showed that the electrical conductivity of these materials and its changes in the case of interaction with ammonia molecules depend on the position of the impurity band formed by the orbitals of macrocycle atoms relative to the forbidden energy gap of the hybrids. The sensor response of the hybrids containing halogenated phthalocyanines was lower by one or two orders of magnitude, depending on the number of substituents, compared to the hybrid with unsubstituted zinc phthalocyanine. This result was obtained by calculations performed using the nonequilibrium Green’s functions (NEGF) method, which demonstrated a change in the electrical conductivity of the hybrids upon the adsorption of ammonia molecules. The analysis showed that in order to improve the sensor characteristics of CNT-based hybrid materials, preference should be given to those phthalocyanines in which substituents contribute to an increase in HOMO energy relative to the unsubstituted macrocycles. Full article
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11 pages, 1087 KiB  
Article
Novel Dithiocarbamic Flavanones with Antioxidant Properties—A Structure–Activity Relationship Study
by Mihail Lucian Birsa and Laura Gabriela Sarbu
Int. J. Mol. Sci. 2024, 25(24), 13698; https://doi.org/10.3390/ijms252413698 - 21 Dec 2024
Cited by 1 | Viewed by 808
Abstract
The antioxidant properties of some 3-dithiocarbamic flavanones were investigated. Based on a previous study, we selected three frameworks that proved to be the most active ones. By varying the nature of the substituent at the para-position of flavanone ring B, a structure–activity [...] Read more.
The antioxidant properties of some 3-dithiocarbamic flavanones were investigated. Based on a previous study, we selected three frameworks that proved to be the most active ones. By varying the nature of the substituent at the para-position of flavanone ring B, a structure–activity relationship study on radical scavenging activities was performed. The influence of these substituents (H, F, Cl, Br and I) was evaluated in relation to DPPH, ABTS and FRAP. The results indicated that the presence of the halogen substituent induced better antioxidant properties than ascorbic acid and BHT. The radical scavenging activities were found to decrease in the following order: F > Cl > Br > I > H. This is correlated with the decrease in electronegativity and withdrawing inductive effect of these substituents, which make the C(2)-H bond of the benzopyran ring prone to hydrogen radical transfer. Full article
(This article belongs to the Special Issue Natural Bioactive Compounds for Human Health, 2nd Edition)
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19 pages, 3441 KiB  
Article
The Relationship Between Spin Crossover (SCO) Behaviors, Cation and Ligand Motions, and Intermolecular Interactions in a Series of Anionic SCO Fe(III) Complexes with Halogen-Substituted Azobisphenolate Ligands
by Mai Hirota, Suguru Murata, Takahiro Sakurai, Hitoshi Ohta and Kazuyuki Takahashi
Molecules 2024, 29(22), 5473; https://doi.org/10.3390/molecules29225473 - 20 Nov 2024
Viewed by 1424
Abstract
To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic FeIII complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence [...] Read more.
To investigate the halogen substitution effect on the anionic spin crossover (SCO) complexes, azobisphenolate ligands with 5,5′-dihalogen substituents from fluorine to iodine were synthesized, and their anionic FeIII complexes 1F, 1Cl, 1Br, and 1I were isolated. The temperature dependence of magnetic susceptibility and crystal structure revealed that 1F, 1Cl, and 1Br are all isostructural and exhibit SCO with the rotational motion of the cation and ligands, whereas 1I shows incomplete SCO. Note that 1Cl and 1Br showed irreversible and reversible cooperative SCO transitions, respectively. Short intermolecular contacts between the FeIII complex anions were found despite Coulomb repulsions for all the complexes. The topological analysis of the electron density distributions revealed the existence of X···X halogen bonds, C–H···X, C–H···N, and C–H···O hydrogen bonds, and C–H···π interactions are evident. The dimensionality of intermolecular interactions is suggested to be responsible for the cooperative SCO transitions in 1Cl and 1Br, whereas the disorder due to the freezing of ligand rotations in 1Cl is revealed to inhibit the SCO cooperativity. Full article
(This article belongs to the Special Issue Exclusive Feature Papers in Inorganic Chemistry, 2nd Edition)
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24 pages, 7832 KiB  
Review
3,4-Dihalo-5-hydroxy-2(5H)-furanones: Highly Reactive Small Molecules
by Katarzyna Żurawska, Anna Byczek-Wyrostek, Anna Kasprzycka and Krzysztof Walczak
Molecules 2024, 29(21), 5149; https://doi.org/10.3390/molecules29215149 - 31 Oct 2024
Cited by 3 | Viewed by 2412
Abstract
3,4-Dichloro-5-hydroxy-2(5H)-furanone and its dibromo analog are highly reactive molecules. Both are members of the 2(5H)-furanone family, which are important as pharmacophores present in drugs and natural products. Compounds possessing the 2(5H)-furanone skeleton isolated from plants and marine [...] Read more.
3,4-Dichloro-5-hydroxy-2(5H)-furanone and its dibromo analog are highly reactive molecules. Both are members of the 2(5H)-furanone family, which are important as pharmacophores present in drugs and natural products. Compounds possessing the 2(5H)-furanone skeleton isolated from plants and marine organisms exhibit bioactivity against various microorganisms and viruses and can also be used in other medical treatments. The structures of these 3,4-dihalo-2(5H)-furanones cause their high reactivity due to the presence of a carbonyl group on the C2 carbon conjugated with a double bond and a hydroxyl group on the C5 carbon. Two labile halogen atoms on carbons 3 and 4 offer additional possibilities for the introduction of other substituents. These structural features make 3,4-dihalo-5-hydroxy-2(5H)-furanones versatile reactants in chemical synthesis. In this review, we present methods of 3,4-dihalo-5-hydroxy-2(5H)-furanone synthesis, their applications as substrates in various chemical transformations, and examples of their biologically active derivatives. Full article
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8 pages, 757 KiB  
Communication
A Structure–Activity Relationship Study on the Antioxidant Properties of Dithiocarbamic Flavanones
by Mihail Lucian Birsa and Laura Gabriela Sarbu
Antioxidants 2024, 13(8), 963; https://doi.org/10.3390/antiox13080963 - 8 Aug 2024
Cited by 3 | Viewed by 1328
Abstract
The antioxidant properties of 3-dithiocarbamic flavanones have been investigated. The influence of the halogen substituents on ring A of the flavanones and the nature of the secondary amine from the dithiocarbamic moiety have been accounted. The results indicated that the presence of a [...] Read more.
The antioxidant properties of 3-dithiocarbamic flavanones have been investigated. The influence of the halogen substituents on ring A of the flavanones and the nature of the secondary amine from the dithiocarbamic moiety have been accounted. The results indicated that the presence of a halogen substituent at the C-8 position of the benzopyran ring induce better antioxidant properties against DPPH and ABTS than butylated hydroxytoluene (BHT) and ascorbic acid. The presence of a halogen substituent at the mentioned position appears to induce a higher stability for a free radical intermediate at the C-3 position of the benzopyran ring. A free radical enolate is most likely to be involved in the antioxidant activity of this dithiocarbamic flavanone. It is a stable intermediate that supports the influence of dithiocarbamic moiety on the antioxidant properties of the reported flavanones. Full article
(This article belongs to the Section Natural and Synthetic Antioxidants)
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24 pages, 6624 KiB  
Review
Bond Formation at C8 in the Nucleoside and Nucleotide Purine Scaffold: An Informative Selection
by Kjell Undheim
Molecules 2024, 29(8), 1815; https://doi.org/10.3390/molecules29081815 - 17 Apr 2024
Viewed by 2154
Abstract
This paper presents methods for the introduction and exchange of substituents in a nucleobase and its nucleosides and nucleotides with emphasis on the C8-position in the purine skeleton. The nucleobase is open for electrophilic and nucleophilic chemistry. The nucleophilic chemistry consists mainly of [...] Read more.
This paper presents methods for the introduction and exchange of substituents in a nucleobase and its nucleosides and nucleotides with emphasis on the C8-position in the purine skeleton. The nucleobase is open for electrophilic and nucleophilic chemistry. The nucleophilic chemistry consists mainly of displacement reactions when the C8-substituent is a good leaving group such as a halogen atom. The heteroatom in amines, sulfides, or oxides is a good nucleophile. Halides are good reaction partners. Metal-promoted cross-coupling reactions are important for carbylations. Direct oxidative metalation reactions using sterically hindered metal amides offer chemo- and regio-selectivity besides functional tolerance and simplicity. The carbon site is highly nucleophilic after metalation and adds electrophiles resulting in chemical bond formation. Conditions for metal-assisted reactions are described for nucleobases and their glycosides. Full article
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16 pages, 5920 KiB  
Article
Halogen Bond-Assisted Supramolecular Dimerization of Pyridinium-Fused 1,2,4-Selenadiazoles via Four-Center Se2N2 Chalcogen Bonding
by Evgeny A. Dukhnovsky, Alexander S. Novikov, Alexey S. Kubasov, Alexander V. Borisov, Nkumbu Donovan Sikaona, Anatoly A. Kirichuk, Victor N. Khrustalev, Andreii S. Kritchenkov and Alexander G. Tskhovrebov
Int. J. Mol. Sci. 2024, 25(7), 3972; https://doi.org/10.3390/ijms25073972 - 3 Apr 2024
Cited by 9 | Viewed by 2120
Abstract
The synthesis and structural characterization of α-haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles with various counterions is reported herein, demonstrating a strategy for directed supramolecular dimerization in the solid state. The compounds were obtained through a recently discovered 1,3-dipolar cycloaddition reaction between nitriles and bifunctional 2-pyridylselenyl reagents, [...] Read more.
The synthesis and structural characterization of α-haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles with various counterions is reported herein, demonstrating a strategy for directed supramolecular dimerization in the solid state. The compounds were obtained through a recently discovered 1,3-dipolar cycloaddition reaction between nitriles and bifunctional 2-pyridylselenyl reagents, and their structures were confirmed by the X-ray crystallography. α-Haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles exclusively formed supramolecular dimers via four-center Se···N chalcogen bonding, supported by additional halogen bonding involving α-haloalkyl substituents. The introduction of halogens at the α-position of the substituent R in the selenadiazole core proved effective in promoting supramolecular dimerization, which was unaffected by variation of counterions. Additionally, the impact of cocrystallization with a classical halogen bond donor C6F3I3 on the supramolecular assembly was investigated. Non-covalent interactions were studied using density functional theory calculations and topological analysis of the electron density distribution, which indicated that all ChB, XB and HB interactions are purely non-covalent and attractive in nature. This study underscores the potential of halogen and chalcogen bonding in directing the self-assembly of functional supramolecular materials employing 1,2,4-selenadiazoles derived from recently discovered cycloaddition between nitriles and bifunctional 2-pyridylselenyl reagents. Full article
(This article belongs to the Section Biochemistry)
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23 pages, 7478 KiB  
Article
Predicting Organometallic Intermediates in the Surface-Assisted Ullmann Coupling of Chrysene Isomers
by Jakub Lisiecki and Paweł Szabelski
Molecules 2024, 29(7), 1553; https://doi.org/10.3390/molecules29071553 - 30 Mar 2024
Cited by 1 | Viewed by 1327
Abstract
On-surface polymerization of functional organic molecules has been recently recognized as a promising route to persistent low-dimensional structures with tailorable properties. In this contribution, using the coarse-grained Monte Carlo simulation method, we study the initial stage of the Ullmann coupling of doubly halogenated [...] Read more.
On-surface polymerization of functional organic molecules has been recently recognized as a promising route to persistent low-dimensional structures with tailorable properties. In this contribution, using the coarse-grained Monte Carlo simulation method, we study the initial stage of the Ullmann coupling of doubly halogenated chrysene isomers adsorbed on a catalytically active (111) crystalline surface. To that end, we focus on the formation of labile metal-organic precursor structures preceding the covalent bonding of chrysene monomers. Four monomeric chrysene units with differently distributed halogen substituents were probed in the simulations, and the resulting precursor structures were compared and quantified. Moreover, the effect of (pro)chirality of chrysene tectons on the structure formation was elucidated by running separate simulations in enantiopure and racemic systems. The calculations showed that suitable manipulation of the halogen substitution pattern allows for the creation of diverse precursor architectures, ranging from straight and winded chains to cyclic oligomers with enantiopure, racemic, and nonracemic composition. The obtained findings can be helpful in developing synthetic strategies for covalent polymers with predefined architecture and functionality. Full article
(This article belongs to the Special Issue Exclusive Feature Papers in Physical Chemistry, 2nd Edition)
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16 pages, 4424 KiB  
Article
Synthesis and Structure of Unsymmetrical Anthracenyl-Isoxazole Antitumor Agents Via the Diastereoselective Bromination of 3-(9′-Anthryl)-Isoxazole Esters
by Michael J. Campbell, Daniel A. Decato, Chun Li, Matthew J. Weaver and Nicholas R. Natale
Crystals 2024, 14(3), 256; https://doi.org/10.3390/cryst14030256 - 5 Mar 2024
Cited by 1 | Viewed by 1952
Abstract
In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report [...] Read more.
In pursuit of unsymmetrical precursors for the novel series of anthracenyl-isoxazole amide (AIM) antitumor agents, a series of substituted anthracenes were subjected to bromination and re-aromatization in our study, during which we solved four single crystal X-ray diffractometry (Sc-xrd) structures which we report herein. The C-9 nitrile oxide, after its reaction with bromine, was isolated, but when subjected to re-aromatization, it returned to the starting 10-bromo nitrile oxide 1, which did provide an accurate crystal structure, with R = 0.018. The 10-halogenated 3-(9’-anthryl)-isoxazole esters were subjected to bromination and re-aromatization. Surprisingly, the yields obtained in the presence of the isoxazole were reasonably good (62–68% isolated yields), and the major diastereomers allowed for the characterization using Sc-xrd. The penta bromo product 2 showed a trans, trans, cis relationship for the four bromines on the A-ring of the anthracene, and we observed that for the unit cell, the atropisomers displayed a 1:1 ratio at the chiral axis between the isoxazole and anthrancene rings. Similarly, the 10-chloro 3 indicated a ratio of 1:1 at the chiral axis in the crystal structure. A base-induced re-aromatization afforded 3,10-dihalogenated analogues selectively in very good yields (X = Cl, 89%; X = Br 92%), of which the dibromo 4 was characterized using Sc-xrd. The improved yields of the unique diastereomeric bromination products suggested the consideration of a novel electrophilic aromatic substitution mechanism driven by the stereo-electronic environment, imposed by the isoxazole ester substituent. The promise of the application of this chemistry in the future development of AIM antitumor agents is suggested. Full article
(This article belongs to the Special Issue Feature Papers in Biomolecular Crystals in 2022-2023)
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13 pages, 5301 KiB  
Article
Fragmentation Pathway of Organophosphorus Flame Retardants by Liquid Chromatography–Orbitrap-Based High-Resolution Mass Spectrometry
by Kangcong Li, Yan Gao, Xiuqin Li, Yan Zhang, Benfeng Zhu and Qinghe Zhang
Molecules 2024, 29(3), 680; https://doi.org/10.3390/molecules29030680 - 1 Feb 2024
Cited by 3 | Viewed by 2213
Abstract
Organophosphorus flame retardants (OPFRs) have been widely used in polymeric materials owing to their flame retardant and plasticizing effects. Investigating the fragmentation pathway of OPFRs is of great necessity for further discovering and identifying novel pollutants using orbitrap-based high-resolution mass spectrometry (HRMS). A [...] Read more.
Organophosphorus flame retardants (OPFRs) have been widely used in polymeric materials owing to their flame retardant and plasticizing effects. Investigating the fragmentation pathway of OPFRs is of great necessity for further discovering and identifying novel pollutants using orbitrap-based high-resolution mass spectrometry (HRMS). A total of 25 OPFRs, including alkyl, halogenated, and aromatic types, were analyzed in this study. The fragmentation pathways of the OPFRs were investigated using orbitrap-based HRMS with high-energy collision dissociation (HCD) in positive mode. The major fragmentation pathways for the three types of OPFRs are greatly affected by the substituents. In detail, the alkyl and halogenated OPFRs underwent three McLafferty hydrogen rearrangements, wherein the substituents were gradually cleaved to form the structurally stable [H4PO4]+ (m/z = 98.9845) ions. In contrast, the aromatic OPFRs would cleave not only the C-O bond but also the P-O bond, depending on the substituents, to form fragment ions such as [C6H7O]+ (m/z = 95.0495) or [C7H7]+ (m/z = 91.0530), among others. Using HRMS improved the accuracy of fragment ion identification, and the pathway became more evident. These fragmentation laws can provide identification information in pollutant screening work and theoretical references for the structural characterization of compounds with diverse substituent structures. Full article
(This article belongs to the Special Issue Mass Spectrometry for Biomedical and Food Analysis)
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