A Joint Venture of Ab Initio Molecular Dynamics, Coupled Cluster Electronic Structure Methods, and Liquid-State Theory to Compute Accurate Isotropic Hyperfine Constants of Nitroxide Probes in Water,Journal of Chemical Theory and Computation

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A Joint Venture of Ab Initio Molecular Dynamics, Coupled Cluster Electronic Structure Methods, and Liquid-State Theory to Compute Accurate Isotropic Hyperfine Constants of Nitroxide Probes in Water
Journal of Chemical Theory and Computation ( IF 5.7 ) Pub Date : 2021-09-13 , DOI: 10.1021/acs.jctc.1c00582
Bikramjit Sharma ₁ , Van Anh Tran ₂ , Tim Pongratz ₃ , Laura Galazzo ₄ , Irina Zhurko ₅ , Enrica Bordignon ₄ , Stefan M Kast ₃ , Frank Neese ₂ , Dominik Marx ₁

Affiliation

The isotropic hyperfine coupling constant (HFCC, A^iso) of a pH-sensitive spin probe in a solution, HMI (2,2,3,4,5,5-hexamethylimidazolidin-1-oxyl, C₉H₁₉N₂O) in water, is computed using an ensemble of state-of-the-art computational techniques and is gauged against X-band continuous wave electron paramagnetic resonance (EPR) measurement spectra at room temperature. Fundamentally, the investigation aims to delineate the cutting edge of current first-principles-based calculations of EPR parameters in aqueous solutions based on using rigorous statistical mechanics combined with correlated electronic structure techniques. In particular, the impact of solvation is described by exploiting fully atomistic, RISM integral equation, and implicit solvation approaches as offered by ab initio molecular dynamics (AIMD) of the periodic bulk solution (using the spin-polarized revPBE0-D3 hybrid functional), embedded cluster reference interaction site model integral equation theory (EC-RISM), and polarizable continuum embedding (using CPCM) of microsolvated complexes, respectively. HFCCs are obtained from efficient coupled cluster calculations (using open-shell DLPNO-CCSD theory) as well as from hybrid density functional theory (using revPBE0-D3). Re-solvation of “vertically desolvated” spin probe configuration snapshots by EC-RISM embedding is shown to provide significantly improved results compared to CPCM since only the former captures the inherent structural heterogeneity of the solvent close to the spin probe. The average values of the A^iso parameter obtained based on configurational statistics using explicit water within AIMD and from EC-RISM solvation are found to be satisfactorily close. Using either such explicit or RISM solvation in conjunction with DLPNO-CCSD calculations of the HFCCs provides an average A^iso parameter for HMI in aqueous solution at 300 K and 1 bar that is in good agreement with the experimentally determined one. The developed computational strategy is general in the sense that it can be readily applied to other spin probes of similar molecular complexity, to aqueous solutions beyond ambient conditions, as well as to other solvents in the longer run.

中文翻译：

从头算分子动力学、耦合簇电子结构方法和液态理论的联合体，用于计算水中氮氧化物探针的精确各向同性超精细常数

溶液中 pH 敏感自旋探针的各向同性超精细耦合常数 (HFCC, A ^iso )，HMI (2,2,3,4,5,5-六甲基咪唑烷-1-氧基，C ₉ H ₁₉ N ₂ O)使用最先进的计算技术整体进行计算，并根据室温下的 X 波段连续波电子顺磁共振 (EPR) 测量光谱进行测量。从根本上说，该研究的目的是在使用严格的统计力学与相关电子结构技术相结合的基础上，描绘当前基于第一原理的水溶液中 EPR 参数计算的前沿。特别是，通过利用周期性体解的从头分子动力学 (AIMD) 提供的完全原子、RISM 积分方程和隐式溶剂化方法（使用自旋极化 revPBE0-D3 混合泛函）来描述溶剂化的影响，分别是嵌入簇参考相互作用位点模型积分方程理论（EC-RISM）和微溶剂化复合物的可极化连续介质嵌入（使用CPCM）。 HFCC 是通过高效耦合簇计算（使用开壳 DLPNO-CCSD 理论）以及混合密度泛函理论（使用 revPBE0-D3）获得的。与 CPCM 相比，通过 EC-RISM 嵌入对“垂直去溶剂化”自旋探针配置快照进行重新溶剂化可提供显着改善的结果，因为只有前者捕获了靠近自旋探针的溶剂的固有结构异质性。根据使用 AIMD 内的显式水和 EC-RISM 溶剂化的构型统计数据获得的A ^iso参数的平均值非常接近。使用这种显式溶剂化或 RISM 溶剂化与 HFCC 的 DLPNO-CCSD 计算相结合，提供了 300 K 和 1 bar 下水溶液中 HMI 的平均A ^iso参数，该参数与实验确定的参数非常一致。所开发的计算策略是通用的，因为它可以很容易地应用于具有相似分子复杂性的其他自旋探针，超出环境条件的水溶液，以及从长远来看其他溶剂。

更新日期：2021-10-12

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