Rajapaksha Harindu, Benthin Grant C, Kravchuk Dmytro V, Lightfoot Haley, Mason Sara E, Forbes Tori Z
Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States.
Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, United States.
Inorg Chem. 2023 Oct 23;62(42):17265-17275. doi: 10.1021/acs.inorgchem.3c02502. Epub 2023 Oct 10.
Noncovalent interactions (NCIs) can influence the stability and chemical properties of pentavalent and hexavalent actinyl (AnO) compounds. In this work, the impact of NCIs (actinyl-hydrogen and actinyl-cation interactions) on the enthalpy of formation (Δ) and vibrational features was evaluated using Np(VI) tetrachloro compounds as the model system. We calculated the Δ values of these solid-state compounds through density functional theory+ thermodynamics (DFT+ T) and validated the results against experimental Δ values obtained through isothermal acid calorimetry. Three structural descriptors were evaluated to develop predictors for Δ, finding a strong link between Δ and hydrogen bond energy () for neptunyl-hydrogen interactions and total electrostatic attraction energy () for neptunyl-cation interactions. Finally, we used Raman spectroscopy together with bond order analysis to probe Np=O bond perturbation due to NCIs. Our results showed a strong correlation between the degree of NCIs by axial oxygen and red-shifting of Np=O symmetrical stretch (ν) wavenumbers and quantitatively demonstrated that NCIs can weaken the Np=O bond. These properties were then compared to those of related U(VI) and Np(V) phases to evaluate the effects of subtle differences in the NCIs and overall properties. In general, the outcomes of our study demonstrated the role of NCIs in stabilizing actinyl solid materials, which consequently governs their thermochemical behaviors and vibrational signatures.
非共价相互作用（NCIs）会影响五价和六价锕酰（AnO）化合物的稳定性和化学性质。在本研究中，以Np(VI)四氯化合物为模型体系，评估了非共价相互作用（锕酰-氢和锕酰-阳离子相互作用）对生成焓（Δ）和振动特征的影响。我们通过密度泛函理论+热力学（DFT+T）计算了这些固态化合物的Δ值，并根据等温酸量热法获得的实验Δ值对结果进行了验证。评估了三个结构描述符以开发Δ的预测因子，发现对于锕酰-氢相互作用，Δ与氢键能（）之间存在强关联，对于锕酰-阳离子相互作用，Δ与总静电吸引能（）之间存在强关联。最后，我们结合拉曼光谱和键序分析来探究由于非共价相互作用引起的Np=O键扰动。我们的结果表明，轴向氧引起的非共价相互作用程度与Np=O对称拉伸（ν）波数的红移之间存在强相关性，并定量证明了非共价相互作用会削弱Np=O键。然后将这些性质与相关的U(VI)和Np(V)相的性质进行比较，以评估非共价相互作用和整体性质细微差异的影响。总体而言，我们的研究结果证明了非共价相互作用在稳定锕酰固体材料中的作用，从而决定了它们的热化学行为和振动特征。
