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Benchmarking Charge-Transfer Excited States in TADF Emitters: ΔDFT Outperforms TD-DFT for Emission Energies. TADF 发射器中电荷转移激发态的基准测试:ΔDFT 在发射能量方面优于 TD-DFT。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-19 DOI: 10.1021/acs.jpca.4c03273
Thomas Froitzheim, Lukas Kunze, Stefan Grimme, John M Herbert, Jan-Michael Mewes

Charge-transfer (CT) excited states are crucial to organic light-emitting diodes (OLEDs), particularly to those based on thermally activated delayed fluorescence (TADF). However, accurately modeling CT states remains challenging, even with modern implementations of (time-dependent) density functional theory [(TD-)DFT], especially in a dielectric environment. To identify shortcomings and improve the methodology, we previously established the STGABS27 benchmark set with highly accurate experimental references for the adiabatic energy gap between the lowest singlet and triplet excited states (ΔEST). Here, we diversify this set to the STGABS27-EMS benchmark by including experimental emission energies (Eem) and use this new set to (re)-evaluate various DFT-based approaches. Surprisingly, these tests demonstrate that a state-specific (un)restricted open-shell Kohn-Sham (U/ROKS) DFT coupled with a polarizable continuum model for perturbative state-specific nonequilibrium solvation (ptSS-PCM) provides exceptional accuracy for predicting Eem over a wide range of density functionals. In contrast, the main workhorse of the field, Tamm-Dancoff-approximated TD-DFT (TDA-DFT) paired with the same ptSS-PCM, is distinctly less accurate and strongly functional-dependent. More importantly, while TDA-DFT requires the choice of two very different density functionals for good performance on either ΔEST or Eem, the time-independent U/ROKS/PCM approaches deliver excellent accuracy for both quantities with a wide variety of functionals.

电荷转移(CT)激发态对于有机发光二极管(OLED),尤其是基于热激活延迟荧光(TADF)的有机发光二极管至关重要。然而,即使采用现代的(随时间变化的)密度泛函理论[(TD-)DFT],尤其是在介电环境中,对 CT 状态进行精确建模仍然具有挑战性。为了找出不足之处并改进方法,我们之前建立了 STGABS27 基准集,其中包含最低单态和三态激发态之间绝热能隙 (ΔEST)的高精度实验参考。在此,我们将实验发射能量(Eem)纳入 STGABS27-EMS 基准集,并利用这一新基准集来(重新)评估各种基于 DFT 的方法。令人惊讶的是,这些测试表明,特定状态(非)受限开壳 Kohn-Sham(U/ROKS)DFT 与用于扰动特定状态非平衡溶解的可极化连续体模型(ptSS-PCM)相结合,可在广泛的密度函数范围内为预测 Eem 提供卓越的准确性。与此相反,该领域的主要工具 Tamm-Dancoff-approximated TD-DFT (TDA-DFT) 与相同的 ptSS-PCM 配对,其准确性明显较低,而且强烈依赖于函数。更重要的是,TDA-DFT 需要选择两种截然不同的密度函数,才能在 ΔEST 或 Eem 上获得良好的性能,而与时间无关的 U/ROKS/PCM 方法则能在使用多种函数的情况下为这两个量提供出色的精度。
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引用次数: 0
Prediction of Redox Potentials for U, Np, Pu, and Am in Aqueous Solution. 水溶液中铀、镎、钚和镅的氧化还原电位预测。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-03 DOI: 10.1021/acs.jpca.4c02902
Felipe R Dutra, Monica Vasiliu, Amber N Gomez, Donna Xia, David A Dixon

The redox properties of the actinides in aqueous solution are important for fuel production/reprocessing and understanding the environmental impact of nuclear waste. The redox potentials for U, Np, Pu, and Am in oxidation states from 0 up to VII (as appropriate) in aqueous solutions have been predicted at the density functional theory level with the B3LYP functional, Stuttgart small core pseudopotential basis sets for the actinides, and explicit (30H2O molecules)/implicit treatment of the aqueous solvent using the self-consistent reaction field COSMO and SMD approaches for the implicit solvation. The predictions of the structural parameters of clusters incorporating first and second solvation shells are consistent with the available experimental data. Our results are typically within 0.2 V of the available experimental data using two explicit solvation shells with an implicit solvent model. The use of the PW91 functional substantially improved the prediction of the Pu(VI/V) redox couple. The redox couples for An(VI/IV) and An(V/IV) which involve the addition of protons and removal of the actinyl oxygens led to slightly larger differences from an experiment. The An(IV/0) and An(III/0) couples were reliably predicted with our approach. Predictions of the unknown An(II/I) redox potentials were negative, consistent with expectations, and predictions for unknown An(VII/VI), An(III/II), and An(II/0) redox couples improve prior estimates.

锕系元素在水溶液中的氧化还原特性对于燃料生产/后处理以及了解核废料对环境的影响非常重要。在密度泛函理论水平上,利用 B3LYP 功能、锕系元素的斯图加特小核伪势基集以及水溶剂的显式(30H2O 分子)/隐式处理(使用自洽反应场 COSMO 和隐式溶解的 SMD 方法),预测了氧化态为 0 至 VII(视情况而定)的铀、镎、钚和镅在水溶液中的氧化还原电势。对包含第一和第二溶壳的团簇结构参数的预测与现有实验数据一致。使用两个显式溶壳和一个隐式溶剂模型,我们的结果与现有实验数据的误差通常在 0.2 V 以内。使用 PW91 函数大大提高了对 Pu(VI/V) 氧化还原偶的预测。An(VI/IV)和 An(V/IV) 的氧化还原反应涉及质子的加入和放线氧原子的去除,因此与实验数据的差异略大。我们的方法可靠地预测了 An(IV/0) 和 An(III/0) 对偶。对未知 An(II/I)氧化还原电位的预测为负值,与预期一致,对未知 An(VII/VI)、An(III/II)和 An(II/0) 氧化还原偶的预测改善了先前的估计。
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引用次数: 0
High-Temperature Pyrolysis Study of 2-Methyl-2-butanol behind Reflected Shock Wave: Shock Tube and Computational Study. 反射冲击波后 2-甲基-2-丁醇的高温热解研究:冲击管和计算研究。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-08 DOI: 10.1021/acs.jpca.4c01593
Subhadarsi Nayak, Balla Rajakumar

Pyrolysis of a branched alcohol, 2-methyl-2-butanol (2M2BOH), was carried out behind the reflected shock wave in the temperature range of 1011-1303 K and under pressures varying from 9.3 to 14.6 atm. Qualitative and quantitative analysis of the postshock mixture was performed using gas chromatography-mass spectrometry and gas chromatography with a flame ionization detector, respectively. The rate coefficients for the C-C and C-O bond cleavage reaction pathways were calculated using the variational transition-state theory. The Rice-Ramsperger-Kessel-Marcus/Master equation was employed to calculate the rate coefficients for the H2O-elimination reactions, unimolecular dissociation, and isomerization reaction pathways. The overall decomposition rate coefficient for the 2-methyl 2-butanol (2M2BOH) was estimated to be ktotalexpt(1011-1303K)=(3.29±0.73)×1011×exp[-(47.41±0.53T)]s-1, where activation energy is given in kcal mol-1. The reaction path analysis was performed, which gives information regarding the contribution of individual intermediate species toward the decomposition of 2M2BOH. A set of reactions was proposed and used to simulate the combustion chemistry of 2M2BOH, which consists of 48 reactions and 39 species. The experimentally measured and simulated mole fractions for the reactant and products showed reasonably good agreement. This work additionally investigates the effect of branching on the decomposition kinetics of long-chain alcohols.

在温度为 1011-1303 K、压力为 9.3-14.6 atm 的条件下,在反射冲击波后面对支链醇 2-甲基-2-丁醇(2M2BOH)进行了热解。分别使用气相色谱-质谱法和气相色谱-火焰离子化检测器对冲击后混合物进行了定性和定量分析。C-C 和 C-O 键裂解反应途径的速率系数是利用变异过渡态理论计算得出的。采用 Rice-Ramsperger-Kessel-Marcus/Master 方程计算了 H2O 消解反应、单分子解离和异构化反应途径的速率系数。据估计,2-甲基-2-丁醇(2M2BOH)的总体分解速率系数为 ktotalexpt(1011-1303K)=(3.29±0.73)×1011×exp[-(47.41±0.53T)]s-1 ,其中活化能的单位为 kcal mol-1。通过反应路径分析,可以了解 2M2BOH 分解过程中各个中间产物的贡献。提出了一组反应并用于模拟 2M2BOH 的燃烧化学反应,其中包括 48 个反应和 39 种物质。实验测量和模拟的反应物和产物的摩尔分数显示出相当好的一致性。这项工作还研究了分支对长链醇分解动力学的影响。
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引用次数: 0
An Exhaustive Quantum-Classical Study of C6F6+ Using the Newly Formulated Parallel TDDVR Method. 使用新制定的并行 TDDVR 方法对 C6F6+ 进行详尽的量子-经典研究。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-09 DOI: 10.1021/acs.jpca.4c02108
Subhankar Sardar

We recently implemented our parallelized quantum-classical dynamical approach, known as the Time-Dependent Discrete Variable Representation (TDDVR) method, which is applied to the spectroscopically important hexafluorobenzene (HFBz) radical cation, where several conical intersections exist in their seven lowest excited electronic states (S11B2u, S21E1g, S31B1u, S41E1u, and S51A2u) considering degeneracy among potential energy surfaces (PESs), to demonstrate their various dynamical aspects. This new parallel version shows almost linear scalability with increasing number of computing processors. To get photoelectron (PE) spectra, Mass-Analyzed Threshold Ionization (MATI) spectra, population dynamics, and many other dynamical observables, the first-principles dynamics is applied at the state-of-the-art level to the corresponding Hamiltonian, where the Jahn-Teller (JT) and pseudo-Jahn-Teller (PJT) type interactions are involved in those coupled seven electronic states. The quantum-classical method is used to thoroughly analyze the effects of these couplings on the nuclear dynamics of the involved electronic states, and the findings are compared with those observables obtained from experiments. Intrinsic dynamical properties are explained using the reduced densities of the wave packet (WP) in a coupled electronic manifold. The PE and MATI spectra of HFBz computed using TDDVR are found to be in good agreement with earlier experimental data and other theoretically simulated spectra.

我们最近实现了并行化的量子经典动力学方法,即时间离散变量表示法(TDDVR),并将其应用于光谱学上重要的六氟苯(HFBz)自由基阳离子,考虑到势能面(PES)之间的退化性,在其七个最低激发电子态(S11B2u、S21E1g、S31B1u、S41E1u 和 S51A2u)中存在多个锥形交叉点,以展示它们的各种动力学方面。随着计算处理器数量的增加,新的并行版本显示出几乎线性的可扩展性。为了获得光电子(PE)光谱、质谱分析阈值电离(MATI)光谱、种群动力学和许多其他动力学观测值,第一原理动力学被应用到相应的哈密顿方程中,其中贾恩-泰勒(JT)和伪贾恩-泰勒(PJT)类型的相互作用涉及到这些耦合的七个电子态。我们采用量子经典方法深入分析了这些耦合对所涉及电子态核动力学的影响,并将分析结果与实验所获得的观测数据进行了比较。利用耦合电子流形中波包(WP)的还原密度解释了内在动力学特性。使用 TDDVR 计算出的 HFBz 的 PE 和 MATI 光谱与早期的实验数据和其他理论模拟光谱非常吻合。
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引用次数: 0
Fundamental Limits in Measuring the Anisotropic Rotational Diffusion of Single Molecules. 测量单分子各向异性旋转扩散的基本限制。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-08 DOI: 10.1021/acs.jpca.4c03160
Weiyan Zhou, Tingting Wu, Matthew D Lew

Many biophysical techniques, such as single-molecule fluorescence correlation spectroscopy, Förster resonance energy transfer, and fluorescence anisotropy, measure the translation and rotation of biomolecules to quantify molecular processes at the nanoscale. These methods often simplify data analysis by assuming isotropic rotational diffusion, e.g., that molecules wobble within a circular cone. This simplification ignores the anisotropy present in many biological contexts that may cause molecules to exhibit different degrees of diffusion in different directions. Here, we loosen this assumption and establish a theoretical framework for describing and measuring anisotropic rotational diffusion using fluorescence imaging. We show that anisotropic wobble is directly quantified by the eigenvalues of a 3-by-3 positive-semidefinite Hermitian matrix M consisting of the second-order moments of a molecule's transition dipole μ. This formalism enables us to model the influence of unavoidable shot noise using a Hermitian perturbation matrix E; the eigenvalues of E directly bound errors in measurements of wobble via Weyl's inequality. Quantifying various perturbations E reveals that anisotropic wobble measurements are generally more sensitive to errors compared to quantifying isotropic wobble. Moreover, severe shot noise can induce negative eigenvalues in estimates of M, thereby causing the anisotropic wobble measurement to fail. Our analysis, using Fisher information, shows that techniques with worse orientation measurement sensitivity experience stronger perturbations E and require larger signal to background ratios to measure anisotropic rotational diffusion accurately. Our work provides deep insights for improving the state of the art in imaging the orientations and anisotropic rotational diffusion of single molecules.

许多生物物理技术,如单分子荧光相关光谱法、佛斯特共振能量转移法和荧光各向异性法,都是通过测量生物分子的平移和旋转来量化纳米尺度的分子过程。这些方法通常通过假设各向同性的旋转扩散来简化数据分析,例如,分子在圆锥体内摆动。这种简化忽略了许多生物环境中存在的各向异性,这种各向异性可能导致分子在不同方向上表现出不同程度的扩散。在这里,我们放宽了这一假设,并建立了一个理论框架,利用荧光成像来描述和测量各向异性的旋转扩散。我们的研究表明,各向异性摆动可直接通过由分子过渡偶极子 μ 的二阶矩组成的 3 乘 3 正半边赫米特矩阵 M 的特征值来量化。这种形式主义使我们能够利用赫米特扰动矩阵 E 来模拟不可避免的射击噪声的影响;E 的特征值通过韦尔不等式直接约束了摇摆测量的误差。通过量化各种扰动矩阵 E 可以发现,与量化各向同性摆动相比,各向异性摆动测量通常对误差更为敏感。此外,严重的射击噪声会导致 M 的估计值出现负特征值,从而导致各向异性摆动测量失败。我们利用费雪信息进行的分析表明,方位测量灵敏度较差的技术会遇到更强的扰动 E,需要更大的信噪比才能准确测量各向异性旋转扩散。我们的工作为改善单分子定向和各向异性旋转扩散成像技术的现状提供了深刻的见解。
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引用次数: 0
A Tale of Two Tails: Rotational Spectroscopy of N-Ethyl Maleimide and N-Ethyl Succinimide. 两个尾巴的故事:N-Ethyl Maleimide 和 N-Ethyl Succinimide 的旋转光谱。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-09 DOI: 10.1021/acs.jpca.4c02330
Lughnasa York, Caroline Sorrells, Chisom A Dim, Kyle N Crabtree, A O Hernandez-Castillo

Broadband microwave spectra of N-ethyl maleimide (NEM) and N-ethyl succinimide (NES) have been recorded using chirped pulse Fourier transform microwave spectroscopy in the Ka-band (26.5-40 GHz). The spectra for both molecules were fit to a Watson A-reduced Hamiltonian in the Ir representation to obtain best fit experimental rotational constants (NEM: A0 = 2143.1988(29), B0 = 1868.7333(22), C0 = 1082.98458(36); NES: A0 = 2061.47756(14), B0 = 1791.73517(12), C0 = 1050.31263(11)), centrifugal distortion constants, and nuclear quadrupole coupling constants. While the heavy atoms of the five-membered ring of both molecules are planar, the ethyl chain has its terminal methyl group perpendicular to the ring. Along the relaxed potential energy curve for the ethyl dihedral angle (θ1 = C(6)-C(5)-N-C(4)), the ethyl group experiences significant steric strain when it is in the plane of the ring, associated with the interaction of the ethyl group with the two carbonyl oxygens. This leads to calculated barriers of θ1 = 1469 cm-1 and θ1 = 1680 cm-1 in N-ethyl maleimide and N-ethyl succinimide, respectively.

使用 Ka 波段(26.5-40 GHz)啁啾脉冲傅立叶变换微波光谱仪记录了 N-乙基马来酰亚胺(NEM)和 N-乙基琥珀酰亚胺(NES)的宽带微波光谱。对这两种分子的光谱进行了欧式表示的沃森 A 还原哈密顿拟合,以获得最佳拟合实验旋转常数(NEM:A0 = 2143.1988(29),B0 = 1868.7333(22),C0 = 1082.98458(36);NES:A0 = 2061.47756(14),B0 = 1791.73517(12),C0 = 1050.31263(11))、离心变形常数和核四极耦合常数。虽然这两个分子的五元环的重原子都是平面的,但乙基链的末端甲基与环垂直。沿着乙基二面角(θ1 = C(6)-C(5)-N-C(4))的松弛势能曲线,当乙基位于环的平面上时,它经历了显著的立体应变,这与乙基与两个羰基氧原子的相互作用有关。这导致 N-乙基马来酰亚胺和 N-乙基琥珀酰亚胺的计算势垒分别为 θ1 = 1469 cm-1 和 θ1 = 1680 cm-1。
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引用次数: 0
Chiral Inversion of Au40(SR)24 Nanocluster Driven by Rotation of Gold Tetrahedra in the Kekulé-like Core. 凯库勒类核中的金四面体旋转驱动 Au40(SR)24 纳米簇的手性反转。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-09 DOI: 10.1021/acs.jpca.4c01421
Hengzhi Liu, Ying Yang, Zhongyun Ma, Yong Pei

Studying the chiral characteristics and chiral inversion mechanisms of gold nanoclusters is important to promote their applications in the field of chiral catalysis and chiral recognition. Herein, we investigated the chiral inversion process of the Au40(SR)24 nanocluster and its derivatives using density functional theory calculations. The results showed that the chiral inversion process can be achieved by rotation of tetrahedra units in the gold core without breaking the Au-S bond. This work found that Au40 nanoclusters protected by different ligands have different chiral inversion mechanisms, and the difference is mainly attributable to the steric effects of the ligands. Moreover, the chiral inversion of the derivative clusters (Au34, Au28, and Au22) of the Au40 nanocluster can also be accomplished by the rotation of the Au4 tetrahedra units in the gold core. The energy barrier in the chiral inversion process of gold nanoclusters increases with the decrease of Au4 tetrahedra units in the gold core. This work identifies a chiral inversion mechanism with lower reaction energy barriers and provided a theoretical basis for the study of gold nanocluster chirality.

研究金纳米团簇的手性特征和手性反转机制对促进其在手性催化和手性识别领域的应用具有重要意义。在此,我们利用密度泛函理论计算研究了 Au40(SR)24 纳米簇及其衍生物的手性反转过程。结果表明,手性反转过程可以通过金核中四面体单元的旋转来实现,而不会破坏 Au-S 键。该研究发现,受不同配体保护的 Au40 纳米团簇具有不同的手性反转机制,其差异主要归因于配体的立体效应。此外,Au40 纳米簇的衍生物簇(Au34、Au28 和 Au22)的手性反转也可以通过金核中 Au4 四面体单元的旋转来实现。金纳米团簇手性反转过程的能垒随金核中 Au4 四面体单元的减少而增加。这项研究发现了一种反应能垒较低的手性反转机制,为研究金纳米簇的手性提供了理论基础。
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引用次数: 0
Water Dimer under Electric Fields: An Ab Initio Investigation up to Quantum Accuracy. 电场下的水二聚体:量子精度的 Ab Initio 研究。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-08 DOI: 10.1021/acs.jpca.4c01553
Marco Francesco Torre, Alessandro Amadeo, Giuseppe Cassone, Matteo Tommasini, Klaudia Mráziková, Franz Saija

It is well-established that strong electric fields (EFs) can align water dipoles, partially order the H-bond network of liquid water, and induce water splitting and proton transfers. To illuminate the fundamental behavior of water under external EFs, we present the first benchmark, to the best of our knowledge, of DFT calculations of the water dimer exposed to intense EFs against coupled cluster calculations. The analyses of the vibrational Stark effect and electron density provide a consistent picture of the intermolecular charge transfer effects driven along the H-bond by the increasing applied field at all theory levels. However, our findings prove that at extreme field regimes (∼1-2 V/Å) DFT calculations significantly exaggerate by ∼10-30% the field-induced strengthening of the H-bond, both within the GGA, hybrid GGA, and hybrid meta-GGA approximations. Notably, a linear correlation emerges between the vibrational Stark effect on OH stretching and H-bond strengthening: a 1 kcal mol-1 increase corresponds to an 80 cm-1 red-shift in OH stretching frequency.

强电场(EFs)能使水偶极子排列整齐、使液态水的氢键网络部分有序、诱导水分裂和质子转移,这一点已得到公认。为了阐明水在外部强电场作用下的基本行为,据我们所知,我们首次将暴露在强电场下的水二聚体的 DFT 计算与耦合簇计算进行了对比。通过对振动斯塔克效应和电子密度的分析,我们发现在所有理论水平上,分子间电荷转移效应都是一致的,即外加场的增加会沿着 H 键驱动分子间电荷转移效应。然而,我们的研究结果证明,在极端场条件下(1-2 V/Å),无论是在 GGA、混合 GGA 还是混合元 GGA 近似中,DFT 计算都明显夸大了场诱导的 H 键强化,夸大幅度达 10-30%。值得注意的是,振动斯塔克效应对羟基伸展的影响与 H 键的增强之间存在线性相关:1 kcal mol-1 的增加对应于羟基伸展频率 80 cm-1 的红移。
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引用次数: 0
Efficiency and Mechanism of Catalytic Siloxane Exchange in Vitrimer Polymers: Modeling and Density Functional Theory Investigations. Vitrimer 聚合物中催化硅氧烷交换的效率和机理:建模与密度泛函理论研究。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-03 DOI: 10.1021/acs.jpca.4c01394
Md Sherajul Islam, Gary Kedziora, Jonghoon Lee, Alex Stafford, Vikas Varshney, Dhriti Nepal, Luke A Baldwin, Ajit K Roy

Of late, siloxane-containing vitrimers have gained significant interest due to their fast dynamic characteristics over a reasonable temperature range (180-220 °C), making them well-suited for diverse applications. The exchange reaction pathway in the siloxane vitrimers is accountable for the covalent adaptive network, with the reaction's effectiveness being regulated by either organic or organometallic catalysts. However, directly studying the exchange reaction pathway in the bulk phase using experimental approaches is challenging because of the intricate and interconnected structure of these vitrimers. Here, we perform comprehensive density functional theory (DFT) and experimental investigations to discover the detailed catalytic efficacy of siloxane exchange and provide direction for the reaction process using a 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyst. The calculated transition barrier energy and catalytic efficiency of hexamethyldisiloxane and dihydroxy-dimethylsilane exchange derived from the nudged elastic band with transition-state calculations strongly agree with the experimental findings. In addition, Fukui indices, along with partial charges, are employed to evaluate the nucleophilic and electrophilic behaviors of silanol and siloxane molecules. Our analysis revealed that by utilizing the Fukui indices of both the acid and the base, we can make an approximate estimation of the respective kinetics of the SN2 process in the siloxane exchange reaction mechanism. These findings establish a foundation for comprehending a crucial aspect of the exchange mechanism in siloxane vitrimer systems and could aid in the development of novel catalysts.

近来,含硅氧烷的玻璃rimers 因其在合理温度范围(180-220 °C)内的快速动态特性而备受关注,这使它们非常适合各种应用。硅氧烷玻璃体中的交换反应途径是共价自适应网络的主要成分,反应的有效性受有机或有机金属催化剂的调节。然而,由于硅氧烷玻璃体的结构错综复杂、相互关联,利用实验方法直接研究体相中的交换反应途径具有挑战性。在此,我们利用 1,5,7-三氮杂双环[4.4.0]癸-5-烯(TBD)催化剂进行了全面的密度泛函理论(DFT)和实验研究,以发现硅氧烷交换的详细催化功效并为反应过程提供方向。通过裸弹带和过渡态计算得出的六甲基二硅氧烷和二羟基二甲基硅烷交换的过渡势垒能和催化效率与实验结果非常吻合。此外,我们还利用福井指数和部分电荷来评估硅醇和硅氧烷分子的亲核和亲电行为。我们的分析表明,通过利用酸和碱的福井指数,我们可以大致估算出硅氧烷交换反应机理中 SN2 过程各自的动力学。这些发现为理解硅氧烷三聚体体系中交换机制的一个重要方面奠定了基础,有助于新型催化剂的开发。
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引用次数: 0
Energetic and Electronic Properties of UO0/± and UF0/±. UO0/± 和 UF0/± 的能量和电子特性。
IF 2.7 2区 化学 Q3 CHEMISTRY, PHYSICAL Pub Date : 2024-07-18 Epub Date: 2024-07-02 DOI: 10.1021/acs.jpca.4c02845
João G F Romeu, Ashley R E Hunt, Gabriel F de Melo, Kirk A Peterson, David A Dixon

High-level electronic structure calculations were conducted to examine the bonding and spectroscopic properties of the UO0/± and UF0/± diatomic molecules. The low-lying Ω states were described by using multireference SO-CASPT2 calculations. The adiabatic electronic affinity (AEA), adiabatic ionization energy (IE), and bond dissociation energy (BDE) were calculated at the Feller-Peterson-Dixon (FPD) level. The ground state of UO is predicted to be 5I4, and that of UF is 4I9/2. The calculated AEAs of UO and UF are 1.123 and 0.453 eV, respectively, and the corresponding IEs are 5.976 and 6.278 eV. The BDE of UO (749.5 kJ/mol) is predicted to be considerably higher than that of UF (627.2 kJ/mol), and both are higher than those predicted for UB, UC, and UN. NBO calculations show strong ionic character for the ground states of UO and UF and bond orders that range from 2 to 3 and from 1 to 2, respectively. Comparisons of the calculated properties to those of the series comprising UB, UC, and UN diatomic molecules are given.

为了研究 UO0/± 和 UF0/± 二原子分子的成键和光谱特性,我们进行了高水平电子结构计算。低洼Ω态是通过多参考 SO-CASPT2 计算描述的。在费勒-彼得森-迪克森(FPD)水平上计算了绝热电子亲和力(AEA)、绝热电离能(IE)和键解离能(BDE)。预测 UO 的基态为 5I4,UF 的基态为 4I9/2。计算得出的 UO 和 UF 的 AEA 分别为 1.123 和 0.453 eV,相应的 IE 分别为 5.976 和 6.278 eV。根据预测,UO 的 BDE(749.5 kJ/mol)大大高于 UF 的 BDE(627.2 kJ/mol),两者都高于 UB、UC 和 UN 的 BDE。NBO 计算显示,UO 和 UF 的基态具有很强的离子特性,键序分别为 2 至 3 和 1 至 2。计算结果的性质与 UB、UC 和 UN 双原子分子系列的性质进行了比较。
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The Journal of Physical Chemistry A
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