Machine-Learning-Assisted Synthesis of Polar Racemates
Machine-Learning-Assisted Synthesis of Polar Racemates
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DOI：
10.1021/jacs.0c01239
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发表时间：
2020-04-22
影响因子：
15
通讯作者：
Poeppelmeier, Kenneth R.
中科院分区：
文献类型：
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作者：
Nisbet, Matthew L.;Pendleton, Ian M.;Poeppelmeier, Kenneth R.
外消旋体作为非线性光学和压电材料最近受到关注。在这里，应用机器学习辅助合成空间方法来合成 Delta,Lambda-[Cu(bpy)(2)(H2O)](2)[MF6](2)中心点 3H(2)O（M = Ti、Zr、Hf；bpy = 2,2'-联吡啶）家族（空间群：Pna21）中缺失的 M = Ti、Zr 成员。在每个（CuO，MO2）/bpy/HF（aq）（M = Ti，Zr，Hf）体系中，极性非中心对称外消旋体（M-NCS）与基于交替Cu（bpy）（H2O）（2）（2+）和MF62-基本结构单元（空间群：Ti-CS（Pnma），Zr-CS（P1）， Hf-CS (P2/n))。机器学习模型根据反应参数进行训练，以公正地了解每个成分空间的潜在统计趋势。人类可解释的决策树表明，对于含有 Zr 或 Hf 的反应，相选择主要由 bpy:CuO 摩尔比驱动，并预测 Ti-NCS 化合物的形成需要减少 HF 的量以提高 pH 值，我们通过实验验证了这一点。预测留一金属排除 (LOO) 模型进一步证实 Ti 系统中的行为与 Zr 和 Hf 系统中的行为不同。通过氟 K 边 X 射线吸收光谱探讨了这种区别的化学起源。 F1s X 射线吸收光谱中的前边缘特征揭示了 Ti(3d-t(2g)) 和 F(2p) 态之间强配体与金属 p 键合，这将 TiF62- 阴离子与 ZrF62- 和 HfF62- 阴离子区分开来。
Racemates have recently received attention as nonlinear optical and piezoelectric materials. Here, a machine-learningassisted composition space approach was applied to synthesize the missing M = Ti, Zr members of the Delta,Lambda-[Cu(bpy)(2)(H2O)](2)[MF6](2)center dot 3H(2)O (M = Ti, Zr, Hf; bpy = 2,2'-bipyridine) family (space group: Pna21). In each (CuO, MO2)/bpy/HF(aq) (M = Ti, Zr, Hf) system, the polar noncentrosymmetric racemate (M-NCS) forms in competition with a centrosymmetric one-dimensional chain compound (M-CS) based on alternating Cu(bpy)(H2O)(2)(2+) and MF62- basic building units (space groups: Ti-CS (Pnma), Zr-CS (P1), Hf-CS (P2/n)). Machine learning models were trained on reaction parameters to gain unbiased insight into the underlying statistical trends in each composition space. A human-interpretable decision tree shows that phase selection is driven primarily by the bpy:CuO molar ratio for reactions containing Zr or Hf, and predicts that formation of the Ti-NCS compound requires that the amount of HF present be decreased to raise the pH, which we verified experimentally. Predictive leave-one-metal-out (LOO) models further confirm that behavior in the Ti system is distinct from that of the Zr and Hf systems. The chemical origin of this distinction was probed via fluorine K-edge X-ray absorption spectroscopy. Pre-edge features in the F1s X-ray absorption spectra reveal the strong ligand-to-metal p bonding between Ti(3d-t(2g)) and F(2p) states that distinguishes the TiF62- anion from the ZrF62- and HfF62- anions.