ESP–ALIE Analysis as a Theoretical Tool for Identifying the Coordination Atoms of Possible Multisite Extractants: Validation and Prediction

In the sense of green chemistry and green engineering, it is of great significance to obtain a simple and practicable quantum chemistry approach for extractant prescreening toward platinum group metals (PGMs). In this work, we assessed the performances of five functionals (B3LYP, CAM-B3LYP, M06, M06-2X, and ωB97X-D) and two solvation models (the SMD and SMD-GIL models) for identifying the coordination atoms of possible multisite extractants by ESP–ALIE analysis (i.e., a combination of electrostatic potential analysis and average local ionization energy analysis). First, for the test sets consisting of two neutral extractants and two ionic liquid extractants in ionic liquid solvents for Pd­(II) extraction, the reliability of ESP–ALIE analysis for complexation site identification was validated by the crystal evidences. Subsequently, to provide data for the predictive ability of ESP–ALIE analysis, variable influence factors (e.g., extractant concentration, HCl concentration, and Cl– concentration) and mechanism on the Pt­(IV) extraction with a neutral extractant in ionic liquid diluents were explored. The extracted complex Pt­(BMImT)2Cl4, whose single-crystal data were first reported herein, validated the theoretical forecast from the ESP–ALIE point of view. Overall, ESP–ALIE analysis is a promising quantum chemistry tool for identifying the coordination atoms of possible multisite extractants toward PGMs.从绿色化学与绿色工程的视角而言，开发一种简便可行的量子化学方法用于铂族金属（Platinum Group Metals, PGMs）萃取剂的预筛选，具有重要的研究价值。本研究针对潜在多位点萃取剂的配位原子识别任务，评估了5种泛函（B3LYP、CAM-B3LYP、M06、M06-2X及ωB97X-D）与2种溶剂化模型（SMD及SMD-GIL模型）在ESP–ALIE分析（即静电势分析与平均局部电离能分析的结合方法）中的应用表现。首先，针对由用于钯(II)（Palladium(II)）萃取的2种中性萃取剂与2种离子液体萃取剂（于离子液体溶剂中）组成的测试集，本研究通过晶体学证据验证了ESP–ALIE分析用于配位位点识别的可靠性。随后，为了验证ESP–ALIE分析的预测能力，本研究探究了以中性萃取剂在离子液体稀释剂中萃取铂(IV)（Platinum(IV)）过程的可变影响因素（如萃取剂浓度、HCl浓度与Cl⁻浓度）及萃取机理，并为该分析方法的预测能力提供了数据支撑。本次研究首次报道了萃取配合物Pt(BMImT)₂Cl₄的单晶数据，该配合物从ESP–ALIE分析的视角验证了此前的理论预测。综上，ESP–ALIE分析是一种极具应用前景的量子化学工具，可用于识别铂族金属萃取体系中潜在多位点萃取剂的配位原子。