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Addition reaction of azoles to acetone-d6: NMR and computational studies 唑类化合物与丙酮-d6的加成反应:核磁共振和计算研究
IF 1.9 4区 化学 Q2 CHEMISTRY, ORGANIC Pub Date : 2024-05-22 DOI: 10.1002/poc.4612
Rosa M. Claramunt, Dionisia Sanz, Ibon Alkorta, José Elguero

The reactivity of imidazole, pyrazole, 1,2,4-triazole, 1,2,3-triazole, and tetrazole with acetone (propan-2-one) has been studied by 1H and 13C NMR using acetone-d6 as solvent at temperatures ranging from 173 to 300 K at 10 K intervals. Simultaneously, the reaction has been theoretically calculated at the B3LYP/6-311++G(d,p) level, and experimental and theoretical results have been compared. The equilibrium constants between azoles and adducts α,α-dimethyl-azole-methanol were analyzed, assuming that the straight part of the plots –R ln Ke vs. 1/T can be used to determine ΔH and ΔS. Calculated and experimental data are related, but the theoretical values are proportionally higher. The tautomerism of triazoles and tetrazole has been considered in order to discuss the reactions.

以丙酮-d6 为溶剂,在 173 至 300 K 的温度范围内,以 10 K 为间隔,通过 1H 和 13C NMR 研究了咪唑、吡唑、1,2,4-三唑、1,2,3-三唑和四唑与丙酮(丙-2-酮)的反应性。同时,在 B3LYP/6-311++G(d,p) 水平上对该反应进行了理论计算,并对实验结果和理论结果进行了比较。分析了偶氮和加合物 α,α-二甲基偶氮唑-甲醇之间的平衡常数,假定 -R ln Ke vs. 1/T 图的直线部分可以用来确定 ΔH 和 ΔS。计算数据和实验数据是相关的,但理论值按比例来说更高。为了讨论这些反应,我们考虑了三唑和四唑的同分异构现象。
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引用次数: 0
Molecular structure and conformational properties of triflamide derivatives in the gas phase—Part II: 6-Iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxaazadisilepane and 2,2,4,4-tetramethyl-6,8-bis (triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane by gas-phase electron diffraction and theoretical calculations 通过气相电子衍射和理论分析三酰胺衍生物在气相中的分子结构和构象特性--第二部分:6-碘-3-(三酰胺基甲基)-4-三烯丙基-1,4,2,7-恶氮杂二ilepane 和 2,2,4,4-四甲基-6,8-双(三烯丙基)-3-氧杂-6,8-二氮杂-2,4-二硅杂双环[3.2.2]壬烷
IF 1.9 4区 化学 Q2 CHEMISTRY, ORGANIC Pub Date : 2024-05-19 DOI: 10.1002/poc.4613
Bagrat A. Shainyan, Alexey V. Eroshin, Sergey A. Shlykov

6-Iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxazadisilepane 1 and the product of its cyclization, 2,2,4,4-tetramethyl-6,8-bis (triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane 2, have been studied by gas-phase electron diffraction and DFT calculations. The conformational equilibrium in the gas phase was shown to include three and two conformers for 1 and 2, respectively, in contrast to only one conformer determined by single crystal X-ray diffraction. The structural analysis of the conformers was performed and the pathways of the conformational transitions were analyzed.

通过气相电子衍射和 DFT 计算研究了 6-碘-3-(三氟甲基)-4-三氟甲基-1,4,2,7-恶氮杂二ilepane 1 及其环化产物 2,2,4,4-四甲基-6,8-双(三氟甲基)-3-氧杂-6,8-二氮杂-2,4-二硅杂双环[3.2.2]壬烷 2。结果表明,1 和 2 在气相中的构象平衡分别包括三个和两个构象,而单晶 X 射线衍射测定的构象只有一个。对这些构象进行了结构分析,并分析了构象转变的路径。
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引用次数: 0
Molecular dynamics simulation study of post-transition state bifurcation: A case study on the ambimodal transition state of dipolar/Diels–Alder cycloaddition 后过渡态分岔的分子动力学模拟研究:双极性/Diels-Alder 环加成的伏过渡态案例研究
IF 1.9 4区 化学 Q2 CHEMISTRY, ORGANIC Pub Date : 2024-05-03 DOI: 10.1002/poc.4611
Tatsuhiro Murakami, Yuya Kikuma, Daiki Hayashi, Shunichi Ibuki, Shoto Nakagawa, Hinami Ueno, Toshiyuki Takayanagi

The potential energy surfaces for the reactions of 1,3-butadiene with 2-hydroxythioacrolein and 2-aminoacrolein exhibit ambimodal transition states leading to both dipolar (4 + 3) and Diels–Alder (4 + 2) cycloaddition products, thereby demonstrating a post transition state bifurcation feature. We have investigated the bifurcation dynamics of these reactions using three molecular dynamics (MD) methods: quasi-classical trajectory, classical MD, and ring-polymer MD simulations. The trajectory calculations were performed with the semiempirical GFN2-xTB method with the element-specific parameters optimized to reproduce the density-functional theory calculations. The effect of water solvation was examined using an implicit solvation model, revealing significant differences in bifurcation dynamic between gas-phase and solution-phase reactions. Nuclear quantum effects were found to play a crucial role in the proton-transfer process from the (4 + 3) intermediate to the (4 + 3) product in the case of the 2-aminoacrolein reaction.

1,3 丁二烯与 2-hydroxythioacrolein 和 2-aminoacrolein 反应的势能面显示了导致双极(4 + 3)和 Diels-Alder (4 + 2)环加成产物的非模态过渡态,从而显示了过渡态后分岔特征。我们使用三种分子动力学(MD)方法研究了这些反应的分岔动力学:准经典轨迹、经典 MD 和环状聚合物 MD 模拟。轨迹计算采用半经验 GFN2-xTB 方法,并对特定元素参数进行了优化,以重现密度泛函理论计算结果。利用隐式溶解模型研究了水溶的影响,发现气相反应和溶液相反应的分岔动态存在显著差异。研究发现,在 2-氨基丙烯醛反应中,核量子效应在质子从 (4 + 3) 中间体转移到 (4 + 3) 产物的过程中发挥了关键作用。
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引用次数: 0
Mechanism of the desulfurization route of the reduction of SO2 on carbons. Dimerization of Disulfur and Tetrasulfur 碳上还原二氧化硫的脱硫途径的机理。二硫和四硫的二聚反应
IF 1.9 4区 化学 Q3 Chemistry Pub Date : 2024-04-23 DOI: 10.1002/poc.4610
Eduardo Humeres, Marília Isabel Tarnowski Correia, Nito Angelo Debacher, Regina de F. P. M. Moreira

The desulfurization of carbons modified with SO2 was studied as a dispersion in boiling cyclohexane (81°C) using activated carbon (mAC) and graphene oxide (mGO), modified by SO2. The steady-state species in the carbon matrix after the catalytic reduction of SO2 was considered a trisulfane. For mAC, there was a burst of a sulfur species identified as S2 by UV spectrum with a maximum at 217 nm (εM at 217 nm = 2.56 × 103) that showed a second-order decay of absorbance with kS2 = 47.29 M-1·sec-1 (ΔG354= 18.1 kcal·mol-1). The product was postulated to be S4. No other consecutive reaction was observed because of the possible adsorption of S4 in the carbon matrix. The desulfurization of mGO was shown by XPS and the kinetics were a second-order decay up to 16 min (kS2= 18.41 M-1·sec-1;ΔG354= 18.8 kcal·mol-1) followed by a second-order increase of absorbance with kS4 = 3.84 M-1·sec-1 (ΔG354= 19.9), where the product showed a double maximum at 260-285 nm typical of S8. These results are consistent with a mechanism of consecutive thermodynamically favorable dimerizations of S2 and S4 and with the desulfurization mechanism that has been previously postulated.

利用经二氧化硫改性的活性炭(mAC)和氧化石墨烯(mGO),研究了经二氧化硫改性的碳在沸腾的环己烷(81°C)中分散的脱硫过程。在催化还原 SO2 后,碳基质中的稳态物质被认为是三硫烷。就 mAC 而言,在 217 纳米波长(217 纳米波长处的εM = 2.56 × 103)处出现了紫外光谱最大值(= 47.29 M-1-sec-1(= 18.1 千卡-摩尔-1))的硫物种猝灭,其吸光度呈二阶衰减(= 47.29 M-1-sec-1 = 18.1 千卡-摩尔-1)。推测产物为 S4。由于碳基质中可能吸附了 S4,因此没有观察到其他连续反应。XPS 显示了 mGO 的脱硫过程,其动力学是在 16 分钟内出现二阶衰减(18.41 M-1-sec-1;= 18.8 kcal-mol-1),随后吸光度出现二阶上升(= 3.84 M-1-sec-1;= 19.9),产物在 260-285 纳米波长处显示出典型的 S8 双最大值。这些结果与 S2 和 S4 连续发生热力学上有利的二聚化机理以及之前推测的脱硫机理相一致。
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引用次数: 0
A study of the global and local aromaticity of hetero[8]circulenes 杂[8]环烯的整体和局部芳香性研究
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-04-11 DOI: 10.1002/poc.4609
Satewaerdi Helili, Ablikim Kerim

The topological resonance energy (TRE) method was used to investigate the aromaticity of hetero[8]circulenes in both their neutral and doubly charged ion states. The compounds varying stabilities in different charged states were explained in terms of the topological charge stabilization rule. The TRE-based aromaticity indices were compared with those obtained by the gauge-including magnetically induced currents (GIMIC) method. However, the lack of correlation between the TRE and GIMIC aromaticity indices, as well as the contradictory trends observed, suggest that further investigation is necessary to fully understand the aromaticity of hetero[8]circulenes. We employed the circuit resonance energy (CRE) method to assess local aromaticity. Our CRE results indicate that individual benzene or heterocyclic five-membered units within the molecule maintain their strong aromatic character and serve as the primary source of global aromaticity, both in their neutral and doubly charged ion states. Although our CRE results provide valuable insights, it is important to note that there are cases where the magnitude of local aromaticity predicted by the nucleus-independent chemical shift (NICS[0] and NICS[1]) indices does not align with our CRE results.

拓扑共振能(TRE)方法用于研究杂[8]环烯在中性和双电荷离子状态下的芳香性。根据拓扑电荷稳定规则解释了化合物在不同带电状态下的不同稳定性。将基于 TRE 的芳香指数与通过量规包括磁感应电流 (GIMIC) 方法获得的芳香指数进行了比较。然而,TRE 芳香指数与 GIMIC 芳香指数之间缺乏相关性,而且观察到的趋势相互矛盾,这表明有必要进行进一步研究,以全面了解杂[8]环烯的芳香性。我们采用了电路共振能量 (CRE) 方法来评估局部芳香性。我们的 CRE 结果表明,分子中的单个苯或杂环五元单元在中性和双电荷离子状态下都能保持其强烈的芳香特性,并成为全局芳香性的主要来源。尽管我们的 CRE 结果提供了有价值的见解,但必须注意的是,在有些情况下,核无关化学位移(NICS[0] 和 NICS[1])指数预测的局部芳香性大小与我们的 CRE 结果并不一致。
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引用次数: 0
The measurement of one-electron redox potentials of free radicals 测量自由基的单电子氧化还原电位
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-04-05 DOI: 10.1002/poc.4608
Igor V. Khudyakov

The paper is devoted to the measurements of one-electron redox potentials of transient free radicals Eo. These values can be measured in the reversible redox reactions of radicals under investigation with a reference pair, which Eo is known. Several Eo of transient radicals are presented. The convenient and important objects for Eo measurement are quinone/semiquinone radical-anions. A general problem of measurement of thermodynamic properties of short-lived transients is discussed.

本文致力于测量瞬时自由基 Eo 的单电子氧化还原电位。这些值可在自由基的可逆氧化还原反应中通过已知 Eo 的参比对进行测量。本文介绍了几种瞬态自由基的 Eo。方便测量 Eo 的重要对象是醌/半醌自由基阴离子。讨论了测量短寿命瞬态热力学性质的一般问题。
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引用次数: 0
Computational studies on exothermic carbon–carbon bond cleavages 碳-碳键裂解放热计算研究
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-03-26 DOI: 10.1002/poc.4606
Athanassios Nicolaides, Hideo Tomioka

Structural aspects of single CC bond dissociation energies are examined and it is shown that in certain cases a negative bond dissociation energy (BDE) implies a very weak bond and an unstable species prone to bond breaking resulting in dissociation or structural rearrangement. It is proposed that, in such cases, a better quantitative indicator for the strength of the bond is the activation energy required for its fission. o-Phenelylene bis(nitrene) 1 is computed to have the most negative CC BDE for an observable species. Under cryogenic conditions, activation energy for the dissociation of this bond has been measured as only 2.8 kcal/mol, making it the weakest that we know of. An explanation based on the formation of two new bonds as responsible for this extremely weak bond is given.

研究了单 CC 键离解能的结构方面,结果表明,在某些情况下,负键离解能(BDE)意味着键非常弱,是一种不稳定的物质,容易断键导致离解或结构重排。根据计算,邻苯乙烯双(腈)1 在可观察到的物种中具有最负的 CC BDE。在低温条件下,该键解离的活化能仅为 2.8 kcal/mol,是我们所知的最弱的键。我们给出的解释是,这种极弱的键是由两个新键的形成造成的。
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引用次数: 0
Theoretical investigation of substituted end groups in thiophene-phenyl-thiophene (TPT) derivatives for high efficiency organic solar cells 用于高效有机太阳能电池的噻吩-苯基-噻吩 (TPT) 衍生物中取代端基的理论研究
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-03-14 DOI: 10.1002/poc.4607
Sonia Sadiq, Rasheed Ahmad Khera, Ahmed M. Tawfeek, Mahmoud A. A. Ibrahim, Faheem Abbas, Sajjad Ali, Ahmed Mahal, Duan Meitao, Muhammad Waqas

The field of organic solar cells has witnessed notable advancements in the past few years, mostly due to the development of novel materials for the active layer. The current investigations reveal the potential of nine previously unexplored molecules (TP1–TP9) designed by end group modification of TPT4F molecule. These molecules were investigated at MPW1PW91/6-31G (d, p) with DFT and TD-DFT approach to study the various photovoltaic and geometrical parameters. The results obtained through computations indicated improvement in the investigated parameters. The terminal group modification shifted the absorption maximum towards longer wavelength in the UV-visible region. Highly conjugated modified acceptors reduced the band gap. The lower excitation energies increased the rate of charge transfer. The designed molecules showed improved excited state lifetime in comparison to the reference. The open circuit voltage was determined using the PTB7 polymer, which exhibited a noticeable improvement, especially in TP1 (1.70 eV), TP3 (1.75 eV), TP4 (1.68 eV), TP6 (1.85 eV), and TP7 (1.75 eV) when compared with reference (1.59 eV). Moreover, charge transfer investigations of designed molecules with PTB7 complex were performed by analyzing the concentration of charge transfer over molecular orbitals, that is, HOMO to LUMO. All of the preceding investigations targeted to achieve high-efficiency organic cells reveal that the altered molecules can be considered effective candidates to tackle future energy problems.

过去几年,有机太阳能电池领域取得了显著进展,这主要归功于活性层新型材料的开发。目前的研究揭示了通过对 TPT4F 分子进行端基修饰而设计的九种以前未曾探索过的分子(TP1-TP9)的潜力。研究人员在 MPW1PW91/6-31G (d, p) 条件下,采用 DFT 和 TD-DFT 方法对这些分子进行了研究,以探讨各种光电和几何参数。计算得出的结果表明,所研究的参数得到了改善。端基修饰使吸收最大值向紫外-可见光区的长波长移动。高共轭修饰的受体降低了带隙。较低的激发能量提高了电荷转移速率。与参照物相比,设计的分子显示出更长的激发态寿命。使用 PTB7 聚合物测定的开路电压与参考值(1.59 eV)相比有明显改善,特别是在 TP1(1.70 eV)、TP3(1.75 eV)、TP4(1.68 eV)、TP6(1.85 eV)和 TP7(1.75 eV)。此外,还通过分析分子轨道(即 HOMO 到 LUMO)上的电荷转移浓度,对设计的分子与 PTB7 复合物进行了电荷转移研究。前面所有以实现高效有机电池为目标的研究都表明,改变后的分子可被视为解决未来能源问题的有效候选分子。
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引用次数: 0
The curious case of the colored crystals of N-substituted 2-oxo-1,2-dihydropyridinyl-3-yl amines and amides: Self-association in the solid state N-取代的 2-氧代-1,2-二氢吡啶-3-基胺和酰胺的有色晶体奇案:固态中的自结合
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-02-28 DOI: 10.1002/poc.4603
Wendy A. Loughlin, Ian D. Jenkins, Peter C. Healy, N. David Karis, Gregory K. Pierens

During a previous investigation of pyridone derivatives as inhibitors of glycogen phosphorylase, we observed that some N-substituted 2-oxo-1,2-dihydropyridinyl-3-yl amines and amides exhibited different colors, ranging from red to green to blue to teal. Remarkably, one compound (compound 8) could be crystallized in both a red form and a green form. To try to understand these observations, we have carried out further spectroscopic studies in the solid state and in solution employing UV-visible spectroscopy, NMR spectroscopy, and X-ray crystallography, along with molecular mechanics and DFT calculations on selected compounds. Evidence was obtained in the solid state for the self-association of pyridones into dimeric complexes or near-planar dimers induced by intermolecular hydrogen bonding and possible π-stacking, whereas monomeric structures for two compounds were proposed in chloroform, in agreement with the DFT calculated chemical shifts. In this study, it was determined that the colors observed could not be attributed to hydrogen bonding or possible π-bond stacking in the novel relatively unconjugated pyridone derivatives. A possible explanation for the colors is suggested: a contaminant formed by aerial oxidation of trace amounts of the 3-aminopyridone starting material. This result contrasts with existing literature reports of UV and fluorescence spectra, which indicated distinct coloration for conjugated 2-pyridone compounds. The spectroscopic results, including X-ray structural data for five pyridones, contribute to a deeper understanding of structural interactions in pyridone derivatives.

在之前研究吡啶酮衍生物作为糖原磷酸化酶抑制剂的过程中,我们观察到一些 N-取代的 2-氧代-1,2-二氢吡啶-3-基胺和酰胺呈现出不同的颜色,从红色到绿色到蓝色再到茶色。值得注意的是,有一种化合物(化合物 8)既能以红色形式结晶,也能以绿色形式结晶。为了理解这些观察结果,我们利用紫外可见光谱、核磁共振光谱和 X 射线晶体学,对固态和溶液进行了进一步的光谱研究,并对选定的化合物进行了分子力学和 DFT 计算。在固态下,有证据表明吡啶酮在分子间氢键和可能的 π 堆积作用的诱导下自结合成二聚体复合物或近平面二聚体,而在氯仿中,有两种化合物的单体结构与 DFT 计算的化学位移一致。本研究确定,在新型相对非共轭吡啶酮衍生物中观察到的颜色不能归因于氢键或可能的 π 键堆叠。对这些颜色的可能解释是:微量的 3-氨基吡啶酮起始材料在空气中氧化形成的污染物。这一结果与现有文献报道的紫外光谱和荧光光谱形成鲜明对比,后者显示共轭 2-吡啶酮化合物具有明显的颜色。光谱结果,包括五种吡啶酮的 X 射线结构数据,有助于加深对吡啶酮衍生物结构相互作用的理解。
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引用次数: 0
Theoretical study on the kinetics and reaction mechanism involved in the reduction of quinone by 1-benzyl-1,4-dihydronicotinamide 关于 1-苄基-1,4-二氢烟酰胺还原醌的动力学和反应机理的理论研究
IF 1.8 4区 化学 Q3 Chemistry Pub Date : 2024-02-22 DOI: 10.1002/poc.4605
Manuel E. Medina, Hugo A. Jiménez-Vazquez, Luis G. Zepeda-Vallejo, Ángel Trigos

Although it is well known that coenzyme NAD(P)H is involved in anabolic and catabolic reactions in the living organism, there is still significant controversy over the reaction mechanism involved in this biochemical transformation. Thus, 1-benzyl-1,4-dihydronicotinamide was used as a NAD(P)H model in the reduction reaction of 1,4-benzoquinone (Q), 2,3,5,6-tetrachloro-1,4-benzoquinone, and 2,3-dicyano-1,4-benzoquinone in acetonitrile medium. The kinetic calculations support that formal hydride transfer is the main mechanism promoting Q reduction, while the two-step process dominates 2,3-dicyano-1,4-benzoquinone reduction. Interestingly, only the single-electron transfer mechanism takes place when 2,3,5,6-tetrachloro-1,4-benzoquinone is used, affording the corresponding semiquinone derivative as the main product. This mechanistic behavior is related to the presence or absence of electron-withdrawing groups in the quinones used. Furthermore, the kinetic study results showed that calculated reaction rate constants are in close agreement with experimental results. The results support that formal hydride transfer on the reduction reaction of Q by 1-benzyl-1,4-dihydronicotinamide in acetonitrile proceeds through a hydrogen coupled electron transfer mechanism. This theoretical analysis provides valuable knowledge that can be extrapolated to study the reduction of quinones performed by NADH and NADPH in physiological media.

尽管众所周知,辅酶 NAD(P)H 参与了生物体内的合成代谢和分解代谢反应,但对于这种生化转化所涉及的反应机制仍存在很大争议。因此,在 1,4-苯醌(Q)、2,3,5,6-四氯-1,4-苯醌和 2,3-二氰基-1,4-苯醌在乙腈介质中的还原反应中,使用了 1-苄基-1,4-二氢烟酰胺作为 NAD(P)H 模型。动力学计算支持形式氢化物转移是促进 Q 还原的主要机制,而两步过程则主导 2,3-二氰基-1,4-苯醌的还原。有趣的是,在使用 2,3,5,6-四氯-1,4-苯醌时,只有单电子转移机制发生,并产生相应的半醌衍生物作为主要产物。这种机理行为与所使用的醌类化合物中是否存在抽电子基团有关。此外,动力学研究结果表明,计算出的反应速率常数与实验结果非常接近。结果证明,1-苄基-1,4-二氢烟酰胺在乙腈中对 Q 的还原反应是通过氢耦合电子转移机制进行的。这一理论分析提供了宝贵的知识,可用于研究生理介质中 NADH 和 NADPH 对醌类化合物的还原反应。
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引用次数: 0
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Journal of Physical Organic Chemistry
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