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Keywords = NCO-compounds

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13 pages, 2963 KiB  
Article
Optimizing the Structure and Performances of Cu-MOF@Ti3C2TX Hybrid Electrodes by Introducing Modulated Ligand
by Sumin Li, Xiaokun Qu, Feng Liu, Pingwei Ye, Bo Yang, Qiang Cheng, Mengkun Yang, Yijing Nie and Maiyong Zhu
Nanomaterials 2025, 15(11), 864; https://doi.org/10.3390/nano15110864 - 4 Jun 2025
Viewed by 511
Abstract
To date, two-dimensional metal–organic frameworks (2D MOFs) have attracted much attention in many fields. Owing to their ultra-high porosity and specific surface area, great structural diversity and functional tunability, as well as feasible precision design at the molecular level, 2D MOFs have won [...] Read more.
To date, two-dimensional metal–organic frameworks (2D MOFs) have attracted much attention in many fields. Owing to their ultra-high porosity and specific surface area, great structural diversity and functional tunability, as well as feasible precision design at the molecular level, 2D MOFs have won rapid development in the field of energy storage. However, as a coordination compound, MOFs possess poor structural stability and are prone to structural collapse in electrochemical reactions, which seriously limits their electrochemical performance. Therefore, there is an urgent need to improve the structural stability of MOF electrode materials. In this study, a 2D MOF@Ti3C2TX hybrid was constructed, in which urea pyrimidinone isocyanate (UPy-NCO) units were introduced via a condensation reaction with the active functional groups on MOFs, thus forming multiple hydrogen bonds among MOF frameworks to strengthen their structural stability. Importantly, 2,6-diaminopyridine was utilized to modulate the structure and properties. Initially, the mono-coordination model of the N atom on a pyridine ring with metal ions could create defects and form further pores. Two −NH2 groups helped to improve the grafting reaction degree of UPy-NCO, leading to an increased ratio of forming quadruple hydrogen bonds (H-bonds), further strengthening the structure of the hybrid. As expected, the Cu-MOF@Ti3C2TX-20%DAP-UPy hybrid exhibited a specific capacitance of 148 F g−1 at 1 A g−1, which is 45% higher than that of Cu-MOF@Ti3C2TX-UPy (102 F g−1). A good capacitance retention of 88% was obtained as the current density increased from 0.2 to 5 A g−1. Moreover, excellent cycling stability (91.1%) was obtained at 1 A g−1 after 5000 cycles. Full article
(This article belongs to the Special Issue Advanced 2D Materials for Emerging Application)
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15 pages, 1596 KiB  
Article
Bacterial Volatile Organic Compounds as Potential Caries and Periodontitis Disease Biomarkers
by Maisa Haiek, Vladislav Dvoyris, Yoav Y. Broza, Hossam Haick, Ervin Weiss and Yael Houri-Haddad
Int. J. Mol. Sci. 2025, 26(8), 3591; https://doi.org/10.3390/ijms26083591 - 10 Apr 2025
Viewed by 750
Abstract
Oral diseases represent a significant global health and economic burden, necessitating the development of effective diagnostic tools. This study investigates the volatile organic compound (VOC) profiles of bacteria associated with dental caries and periodontal disease to explore their potential as diagnostic biomarkers. Four [...] Read more.
Oral diseases represent a significant global health and economic burden, necessitating the development of effective diagnostic tools. This study investigates the volatile organic compound (VOC) profiles of bacteria associated with dental caries and periodontal disease to explore their potential as diagnostic biomarkers. Four microbial strains—Streptococcus mutans (700610), Streptococcus sanguis (NCO 2863), Porphyromonas gingivalis (ATCC 33277), and Fusobacterium nucleatum (PK1594)—were cultured (N = 24), alongside intraoral samples (N = 60), from individuals with common oral diseases. Headspace VOCs were analyzed using gas chromatography-mass spectrometry (GC-MS), and statistical analyses were conducted by applying non-parametric Wilcoxon and Kruskal–Wallis tests. VOC identification was performed using the NIST14 database. Strain-specific VOC signatures were identified, with P. gingivalis and F. nucleatum exhibiting distinct profiles from each other and from Streptococcus strains. Comparative analysis of disease cohorts revealed statistically significant differences at multiple retention times between caries, gingivitis, and periodontitis. These findings suggest that VOC profiling enables differentiation between bacterial strains and disease phenotypes, supporting their potential application as diagnostic biomarkers for oral diseases. This study establishes a foundational framework for VOC-based diagnostic methodologies in dental pathology. Full article
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18 pages, 2591 KiB  
Article
α-Tocopherol and Trolox as Effective Natural Additives for Polyurethane Foams: A DFT and Experimental Study
by Dalal K. Thbayh, Dóra Mentes, Zsanett R. Boros, Marcin Palusiak, László Farkas, Béla Viskolcz and Béla Fiser
Molecules 2024, 29(24), 6037; https://doi.org/10.3390/molecules29246037 - 21 Dec 2024
Cited by 2 | Viewed by 1045
Abstract
In this work, α-tocopherol and trolox were studied as compounds that have high biological activity. α-Tocopherol is considered a food additive because the refining process of vegetable oils causes the depletion of this vitamin, and thus, its inclusion is required to keep them [...] Read more.
In this work, α-tocopherol and trolox were studied as compounds that have high biological activity. α-Tocopherol is considered a food additive because the refining process of vegetable oils causes the depletion of this vitamin, and thus, its inclusion is required to keep them from oxidizing. Computational tools have determined the antioxidant activity of these additives. The geometries of the studied molecules were optimized using two density functional methods, including M05-2X and M06-2X, in combination with the 6-311++G(2d,2p) basis set. The results indicated that when comparing the antioxidant activity of α-tocopherol and trolox, they were very similar to each other, but α-tocopherol had an antioxidant activity slightly higher, around 1.2 kJ/mol, than trolox. Thus, these additives can be used as polymer additives to protect materials from free-radical-induced stress. To test their applicability in polymeric formulations, flexible polyurethane foams were prepared with varying α-tocopherol ratios and NCO indices (1.0 and 1.1). Increasing the α-tocopherol content reduced the compressive force and altered the mechanical properties, likely due to its presence in the foam structure. This additive not only fine-tuned the mechanical properties but also provided antioxidant effects, enabling multiple enhancements in polymeric products with a single additive. Full article
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10 pages, 1488 KiB  
Communication
Alkoxy Substituted Brominated closo-Dodecaborates with Functionalized Aliphatic Spacers
by Satoshi Yamamoto, Hibiki Nakamura, Yumiko K. Kawamura, Taro Kitazawa, Mutsumi Kimura and Yu Kitazawa
Chemistry 2024, 6(6), 1635-1644; https://doi.org/10.3390/chemistry6060099 - 15 Dec 2024
Viewed by 1235
Abstract
The utilization of dodecaborate boron clusters, [B12X12]2− (X = Cl, Br, or I), as membrane carriers has been demonstrated recently, and their activity is known to be due to their superchaotropic nature. In this work, the mono-alkylation of [...] Read more.
The utilization of dodecaborate boron clusters, [B12X12]2− (X = Cl, Br, or I), as membrane carriers has been demonstrated recently, and their activity is known to be due to their superchaotropic nature. In this work, the mono-alkylation of [B12Br11OH]2− to functionalize it with an aliphatic spacer was developed with a view to expanding the known chemical space of membrane carriers based on [B12Br12]2−. A new and improved facile route for the preparation of [B12Br11OH]2−, which is an important precursor to other [B12Br11OR]2− species, is reported. Various alkoxylated [B12Br11O(CH2)5Z]2− (Z = OH, N(CO)2C6H4, CN and N3) derivatives were prepared via a divergent synthesis based on [B12Br11O(CH2)5Br]2−. One of the newly synthesized compounds was utilized as a membrane carrier, and its impact on cell viability was examined. Full article
(This article belongs to the Section Molecular Organics)
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13 pages, 2719 KiB  
Article
Structure-Based Identification of Novel Histone Deacetylase 4 (HDAC4) Inhibitors
by Rupesh Agarwal, Pawat Pattarawat, Michael R. Duff, Hwa-Chain Robert Wang, Jerome Baudry and Jeremy C. Smith
Pharmaceuticals 2024, 17(7), 867; https://doi.org/10.3390/ph17070867 - 2 Jul 2024
Cited by 1 | Viewed by 2208
Abstract
Histone deacetylases (HDACs) are important cancer drug targets. Existing FDA-approved drugs target the catalytic pocket of HDACs, which is conserved across subfamilies (classes) of HDAC. However, engineering specificity is an important goal. Herein, we use molecular modeling approaches to identify and target potential [...] Read more.
Histone deacetylases (HDACs) are important cancer drug targets. Existing FDA-approved drugs target the catalytic pocket of HDACs, which is conserved across subfamilies (classes) of HDAC. However, engineering specificity is an important goal. Herein, we use molecular modeling approaches to identify and target potential novel pockets specific to Class IIA HDAC-HDAC4 at the interface between HDAC4 and the transcriptional corepressor component protein NCoR. These pockets were screened using an ensemble docking approach combined with consensus scoring to identify compounds with a different binding mechanism than the currently known HDAC modulators. Binding was compared in experimental assays between HDAC4 and HDAC3, which belong to a different family of HDACs. HDAC4 was significantly inhibited by compound 88402 but not HDAC3. Two other compounds (67436 and 134199) had IC50 values in the low micromolar range for both HDACs, which is comparable to the known inhibitor of HDAC4, SAHA (Vorinostat). However, both of these compounds were significantly weaker inhibitors of HDAC3 than SAHA and thus more selective, albeit to a limited extent. Five compounds exhibited activity on human breast carcinoma and/or urothelial carcinoma cell lines. The present result suggests potential mechanistic and chemical approaches for developing selective HDAC4 modulators. Full article
(This article belongs to the Special Issue Small Molecule Drug Discovery: Driven by In-Silico Techniques)
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17 pages, 5205 KiB  
Article
Controlling the Synthesis of Polyurea Microcapsules and the Encapsulation of Active Diisocyanate Compounds
by Efterpi Avdeliodi, Anastasia Tsioli, Georgios Bokias and Joannis K. Kallitsis
Polymers 2024, 16(2), 270; https://doi.org/10.3390/polym16020270 - 18 Jan 2024
Cited by 5 | Viewed by 2793
Abstract
The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active [...] Read more.
The encapsulation of active components is currently used as common methodology for the insertion of additional functions like self-healing properties on a polymeric matrix. Among the different approaches, polyurea microcapsules are used in different applications. The design of polyurea microcapsules (MCs) containing active diisocyanate compounds, namely isophorone diisocyanate (IPDI) or hexamethylene diisocyanate (HDI), is explored in the present work. The polyurea shell of MCs is formed through the interfacial polymerization of oil-in-water emulsions between the highly active methylene diphenyl diisocyanate (MDI) and diethylenetriamine (DETA), while the cores of MCs contain, apart from IPDI or HDI, a liquid Novolac resin. The hydroxyl functionalities of the resin were either unprotected (Novolac resin), partially protected (Benzyl Novolac resin) or fully protected (Acetyl Novolac resin). It has been found that the formation of MCs is controlled by the MDI/DETA ratio, while the shape and size of MCs depends on the homogenization rate applied for emulsification. The encapsulated active compound, as determined through the titration of isocyanate (NCO) groups, was found to decrease with the hydroxyl functionality content of the Novolac resin used, indicating a reaction between NCO and the hydroxyl groups. Through the thorough investigation of the organic phase, the rapid reaction (within a few minutes) of MDI with the unprotected Novolac resin was revealed, while a gradual decrease in the NCO groups (within two months) has been observed through the evolution of the Attenuated Total Reflectance—Fourier-Transform Infrared (ATR-FTIR) spectroscopy and titration, due to the reaction of these groups with the hydroxyl functionalities of unprotected and partially protected Novolac resin. Over longer times (above two months), the reaction of the remaining NCO groups with humidity was evidenced, especially when the fully protected Acetyl Novolac resin was used. HDI was found to be more susceptible to reactions, as compared with IPDI. Full article
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22 pages, 8780 KiB  
Article
Effective Halogen-Free Flame-Retardant Additives for Crosslinked Rigid Polyisocyanurate Foams: Comparison of Chemical Structures
by Johannes U. Lenz, Doris Pospiech, Hartmut Komber, Andreas Korwitz, Oliver Kobsch, Maxime Paven, Rolf W. Albach, Martin Günther and Bernhard Schartel
Materials 2023, 16(1), 172; https://doi.org/10.3390/ma16010172 - 24 Dec 2022
Cited by 4 | Viewed by 3278
Abstract
The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported [...] Read more.
The impact of phosphorus-containing flame retardants (FR) on rigid polyisocyanurate (PIR) foams is studied by systematic variation of the chemical structure of the FR, including non-NCO-reactive and NCO-reactive dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO)- and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing compounds, among them a number of compounds not reported so far. These PIR foams are compared with PIR foams without FR and with standard FRs with respect to foam properties, thermal decomposition, and fire behavior. Although BPPO and DOPO differ by just one oxygen atom, the impact on the FR properties is very significant: when the FR is a filler or a dangling (dead) end in the PIR polymer network, DOPO is more effective than BPPO. When the FR is a subunit of a diol and it is fully incorporated in the PIR network, BPPO delivers superior results. Full article
(This article belongs to the Special Issue Flame Retardants for Polymeric Materials (Second Volume))
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13 pages, 2457 KiB  
Article
An Ab Initio Investigation on Relevant Oligomerization Reactions of Toluene Diisocyanate (TDI)
by Ravikumar Thangaraj, Béla Fiser, Xuanbing Qiu, Chuanliang Li, Béla Viskolcz and Milán Szőri
Polymers 2022, 14(19), 4183; https://doi.org/10.3390/polym14194183 - 5 Oct 2022
Cited by 7 | Viewed by 3229
Abstract
2,4- and 2,6-isomers of toluene diisocyanates (2,4-TDI and 2,6-TDI) are important raw materials in the polyurethane industry. These reactive compounds associate even under ambient conditions to form oligomers, changing the physicochemical properties of the raw material. Kinetically and thermodynamically relevant dimerization reactions were [...] Read more.
2,4- and 2,6-isomers of toluene diisocyanates (2,4-TDI and 2,6-TDI) are important raw materials in the polyurethane industry. These reactive compounds associate even under ambient conditions to form oligomers, changing the physicochemical properties of the raw material. Kinetically and thermodynamically relevant dimerization reactions were selected based on G3MP2B3 calculations from all possible dimers of phenyl isocyanate using these isocyanates as proxies. As it turned out, only the formation of the diazetidine-2,4-dione ring (11-dimer, uretdione) resulted in a species having an exothermic enthalpy of formation (−30.4 kJ/mol at 298.15 K). The oxazetidin-2-one ring product (1-2-dimer) had a slightly endothermic standard enthalpy of formation (37.2 kJ/mol at 298.15 K). The mechanism of the relevant cyclodimerization reactions was investigated further for 2,4-TDI and 2,6-TDI species using G3MP2B3 and SMD solvent model for diazetidine as well as oxazetidin-2-one ring formation. The formation of the uretdione ring structures, from the 2,4-TDI dimer with both NCO groups in the meta position for each phenyl ring and one methyl group in the para and one in the meta position, had the lowest-lying transition state (Δ#E0 = 94.4 kJ/mol) in the gas phase. The one- and two-step mechanisms of the TDI cyclotrimerization were also studied based on the quasi-G3MP2B3 (qG3MP2B3) computational protocol. The one-step mechanism had an activation barrier as high as 149.0 kJ/mol, while the relative energies in the two-step mechanism were significantly lower for both transition states in the gas phase (94.7 and 60.5 kJ/mol) and in ODCB (87.0 and 54.0 kJ/mol). Full article
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6 pages, 1948 KiB  
Communication
X-ray Structures of 3-Acetyloxazolidin-2-one, 3-Acetyloxazolin-2-one and Oxazolin-2(3H)-one
by R. Alan Aitken, Joe S. Logan and Alexandra M. Z. Slawin
Molbank 2022, 2022(3), M1445; https://doi.org/10.3390/M1445 - 14 Sep 2022
Viewed by 1816
Abstract
The X-ray structures of three simple heterocyclic compounds have been obtained for the first time. Structures of both 3-acetyloxazolidin-2-one 1 and its unsaturated analogue 3-acetyloxazolin-2-one 3 show a planar imide nitrogen with the exocyclic C=O oriented anti to the ring N–C(=O) bond and [...] Read more.
The X-ray structures of three simple heterocyclic compounds have been obtained for the first time. Structures of both 3-acetyloxazolidin-2-one 1 and its unsaturated analogue 3-acetyloxazolin-2-one 3 show a planar imide nitrogen with the exocyclic C=O oriented anti to the ring N–C(=O) bond and negligible intermolecular interactions, a pattern consistent with previously reported analogues. In contrast the parent NH heterocycle, oxazolin-2(3H)-one 4, exists as hydrogen bonded dimers of two closely similar independent molecules but an unusual type of disorder involving exchange of the ring O and NH positions results in a very high R factor. Full article
(This article belongs to the Section Structure Determination)
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16 pages, 2656 KiB  
Article
Bispidine Platform as a Tool for Studying Amide Configuration Stability
by Dmitry P. Krut’ko, Alexey V. Medved’ko, Konstantin A. Lyssenko, Andrei V. Churakov, Alexander I. Dalinger, Mikhail A. Kalinin, Alexey O. Gudovannyy, Konstantin Y. Ponomarev, Eugeny V. Suslov and Sergey Z. Vatsadze
Molecules 2022, 27(2), 430; https://doi.org/10.3390/molecules27020430 - 10 Jan 2022
Cited by 11 | Viewed by 3013
Abstract
In this work, the solution conformations of seventeen 3,7-diacyl bispidines were studied by means of NMR spectroscopy including VT NMR experiments. The acyl groups included alkyl, alkenyl, aryl, hetaryl, and ferrocene moieties. The presence of syn/anti-isomers and their ratios were estimated, and some [...] Read more.
In this work, the solution conformations of seventeen 3,7-diacyl bispidines were studied by means of NMR spectroscopy including VT NMR experiments. The acyl groups included alkyl, alkenyl, aryl, hetaryl, and ferrocene moieties. The presence of syn/anti-isomers and their ratios were estimated, and some reasons explaining experimental facts were formulated. In particular, all aliphatic and heterocyclic units in the acylic R(CO) fragments led to an increased content of the syn-form in DMSO-d6 solutions. In contrast, only the anti-form was detected in DMSO-d6 and CDCl3 in the case when R = Ph, ferrocenyl, (R)-myrtenyl. In the case of a chiral compound derived from the natural terpene myrtene, a new dynamic process was found in addition to the expected inversion around the amide N-C(O) bond. Here, rotation around the CO-C=C bond in the acylic R fragment was detected, and its energy was estimated. For this compound, ΔG for amide N-C(O) inversion was found to be equal to 15.0 ± 0.2 kcal/mol, and for the rotation around the N(CO)–C2′ bond, it was equal to 15.6 ± 0.3 kcal/mol. NMR analysis of the chiral bispidine-based bis-amide was conducted for the first time. Two X-ray structures are reported. For the first time, the unique syn-form was found in the crystal of an acyclic bispidine-based bis-amide. Quantum chemical calculations revealed the unexpected mechanism for amide bond inversion. It was found that the reaction does not proceed as direct N-C(O) bond inversion in the double-chair (CC) conformation but rather requires the conformational transformation into the chair–boat (CB) form first. The amide bond inversion in the latter requires less energy than in the CC form. Full article
(This article belongs to the Special Issue Dynamic Stereochemistry of Bioactive Compounds)
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11 pages, 16191 KiB  
Article
Computational Study of Catalytic Urethane Formation
by Hadeer Q. Waleed, Marcell Csécsi, Rachid Hadjadj, Ravikumar Thangaraj, Dániel Pecsmány, Michael Owen, Milán Szőri, Zsolt Fejes, Béla Viskolcz and Béla Fiser
Polymers 2022, 14(1), 8; https://doi.org/10.3390/polym14010008 - 21 Dec 2021
Cited by 12 | Viewed by 4943
Abstract
Polyurethanes (PUs) are widely used in different applications, and thus various synthetic procedures including one or more catalysts are applied to prepare them. For PU foams, the most important catalysts are nitrogen-containing compounds. Therefore, in this work, the catalytic effect of eight different [...] Read more.
Polyurethanes (PUs) are widely used in different applications, and thus various synthetic procedures including one or more catalysts are applied to prepare them. For PU foams, the most important catalysts are nitrogen-containing compounds. Therefore, in this work, the catalytic effect of eight different nitrogen-containing catalysts on urethane formation will be examined. The reactions of phenyl isocyanate (PhNCO) and methanol without and in the presence of catalysts have been studied and discussed using the G3MP2BHandHLYP composite method. The solvent effects have also been considered by applying the SMD implicit solvent model. A general urethane formation mechanism has been proposed without and in the presence of the studied catalysts. The proton affinities (PA) were also examined. The barrier height of the reaction significantly decreased (∆E0 > 100 kJ/mol) in the presence of the studied catalysts, which proves the important effect they have on urethane formation. The achieved results can be applied in catalyst design and development in the near future. Full article
(This article belongs to the Special Issue Functional Polyurethanes II)
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9 pages, 3075 KiB  
Article
Acid-Catalyzed Esterification of Betaines: Theoretical Exploration of the Impact of the Carbon Chain Length on the Reaction Mechanism
by Richail Dubien Moulandou-Koumba, Frédéric Guégan, Jean-Maurille Ouamba, Samuel N’Sikabaka and Gilles Frapper
Physchem 2021, 1(3), 288-296; https://doi.org/10.3390/physchem1030022 - 7 Dec 2021
Viewed by 3612
Abstract
Betaine derivatives, especially esters, are compounds of interest for the development of a more sustainable fine chemistry, as they are widely available from biomass and currently produced as side-products from various industries (among which, sugar production). In this publication, we studied the impact [...] Read more.
Betaine derivatives, especially esters, are compounds of interest for the development of a more sustainable fine chemistry, as they are widely available from biomass and currently produced as side-products from various industries (among which, sugar production). In this publication, we studied the impact of carbon chain length on three considered reaction mechanisms for the esterification of (CH3)3N(CH2)nCO2 betaine (n = 1, 2, 3) with glycerol under acid catalysis. DFT calculations show that the mechanism proposed by Bachmann–Frapper et al. may also be active here, but it can interestingly be seen as an avatar of the former proposition by Watson. Conversely, Ingold’s proposition is in this case too energetically prevented. Overall, lower activation barriers and higher reaction exergonicity are reported, suggesting esterification of longer carbon-chain based betaines is more readily achieved. Full article
(This article belongs to the Special Issue Physical Chemistry Perspectives for the New Decade)
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14 pages, 2209 KiB  
Article
Identification and Evaluation of Hazardous Pyrolysates in Bio-Based Rigid Polyurethane-Polyisocyanurate Foam Smoke
by Sanita Reinerte, Vilhelmine Jurkjane, Ugis Cabulis and Arturs Viksna
Polymers 2021, 13(19), 3205; https://doi.org/10.3390/polym13193205 - 22 Sep 2021
Cited by 11 | Viewed by 2512
Abstract
In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on [...] Read more.
In this study, rigid polyurethane (PU) and polyisocyanurate (PIR) foam samples made from renewable material (tall oil fatty acid) based polyols were analyzed by pyrolysis gas chromatography mass spectrometry (Py-GC/MS) to obtain information about the full relative smoke content, with a focus on substance identification by their functional groups and hazardousness. The relative content of gaseous products produced during the thermal degradation was evaluated between the two samples, differenced by their assigned isocyanate (NCO) index value—150 and 300. The main thermal degradation components of the rigid PU-PIR foam were found to originate from the decomposition of isocyanate, primarily forming 4,4′-methylenedianiline, 3,3′-diaminodiphenylmethane, N-methylaniline, aniline, 4-benzylaniline and phenyl isocyanate. Hazard analysis revealed that the most common hazards were the hazards related to health: H315 (36%), H319 (28%), H335 (25%), and H302 (23%). The chemical compound with the highest relative content value—4,4′-methylenedianiline (45.3% for PU and 52.4% for PIR)—was identified to be a suspected carcinogen and mutagen. The focus of the study was identifying and evaluating the relative quantities of the produced gaseous products, examine their hazardousness, and provide information on the released thermal degradation products to form a renewable-source based rigid PU and PIR foam. Full article
(This article belongs to the Special Issue Polyurethane Foams: Current Advances and Future Perspectives)
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11 pages, 3868 KiB  
Article
A Hidden Coordination-Bond Torsional Deformation as a Sign of Possible Spin Transition in Nickel(II)-Bis(nitroxide) Compounds
by Yukiya Kyoden and Takayuki Ishida
Molecules 2020, 25(17), 3790; https://doi.org/10.3390/molecules25173790 - 20 Aug 2020
Cited by 5 | Viewed by 2509
Abstract
Complex formation of nickel(II) tetrafluoroborate and tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) in the presence of sodium cyanate gave a discrete molecule [Ni(phpyNO)2(X)2] (X = NCO). The Ni-O-N-Csp2 torsion angles were reduced on heating; 33.5(5)° and 36.2(4)° at [...] Read more.
Complex formation of nickel(II) tetrafluoroborate and tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) in the presence of sodium cyanate gave a discrete molecule [Ni(phpyNO)2(X)2] (X = NCO). The Ni-O-N-Csp2 torsion angles were reduced on heating; 33.5(5)° and 36.2(4)° at 100 K vs. 25.7(10)° and 32.3(11)° at 400 K. The magnetic behavior was almost diamagnetic below ca. 100 K, and the χmT value reached 1.04 cm3 K mol−1 at 400 K. An analysis using the van’t Hoff equation indicates a possible spin transition at T1/2 >> 400 K. Density functional theory calculation shows that the singlet-quintet energy gap decreases as the structural change from 100 to 400 K. The geometry optimization results suggest that the diamagnetic state has the Ni-O-N-Csp2 torsion angles of 32.7° while the Stotal = 2 state has those of 11.9°. The latter could not be experimentally observed even at 400 K. After overviewing the results on the known X = Br, Cl, and NCS derivatives, the magnetic behavior is described in a common phase diagram. The Br and Cl compounds undergo the energy level crossing of the high-/low-spin states, but the NCS and NCO compounds do not in a conventional experimental temperature range. The spin transition mechanism in this series involves the exchange coupling switch between ferro- and antiferromagnetic interactions, corresponding to the high- and low-spin phases, respectively. Full article
(This article belongs to the Special Issue Spin Crossover (SCO) Research 2020)
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15 pages, 2200 KiB  
Article
Low-Melting Manganese(II)-Based Ionic Liquids: Syntheses, Structures, Properties and Influence of Trace Impurities
by Tim Peppel, Monika Geppert-Rybczyńska, Christin Neise, Udo Kragl and Martin Köckerling
Materials 2019, 12(22), 3764; https://doi.org/10.3390/ma12223764 - 15 Nov 2019
Cited by 8 | Viewed by 3425
Abstract
The synthesis of more than 10 new magnetic ionic liquids with [MnX4]2− anions, X = Cl, NCS, NCO, is presented. Detailed structural information through single-crystal X-ray diffraction is given for (DMDIm)[Mn(NCS)4], (BnEt3N)2[Mn(NCS)4 [...] Read more.
The synthesis of more than 10 new magnetic ionic liquids with [MnX4]2− anions, X = Cl, NCS, NCO, is presented. Detailed structural information through single-crystal X-ray diffraction is given for (DMDIm)[Mn(NCS)4], (BnEt3N)2[Mn(NCS)4], and {(Ph3P)2N}2[Mn(NCO4)]·0.6H2O, respectively. All compounds consist of discrete anions and cations with tetrahedrally coordinated Mn(II) atoms. They show paramagnetic behavior as expected for spin-only systems. Melting points are found for several systems below 100 °C classifying them as ionic liquids. Thermal properties are investigated using differential scanning calorimetry (DSC) measurements. The physicochemical properties of density, dynamic viscosity, electrolytic conductivity, and surface tension were measured temperature-dependent of selected samples. These properties are discussed in comparison to similar Co containing systems. An increasing amount of bromide impurity is found to affect the surface tension only up to 3.3%. Full article
(This article belongs to the Special Issue Ionic Liquids: A Greener Approach in Catalysis)
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