Seymour J M, Gousseva E, Towers Tompkins F K, Parker L G, Alblewi N O, Clarke C J, Hayama S, Palgrave R G, Bennett R A, Matthews R P, Lovelock K R J
Department of Chemistry, University of Reading, Reading, UK.
School of Chemistry, University of Nottingham, Nottingham, UK.
Faraday Discuss. 2024 Oct 25;253(0):251-272. doi: 10.1039/d4fd00029c.
Using a combination of liquid-phase X-ray spectroscopy experiments and small-scale calculations we have gained new insights into the speciation of halozincate anions in ionic liquids (ILs). Both core and valence X-ray photoelectron spectroscopy (XPS) experiments were performed directly on the liquid-phase ILs, supplemented by Zn 1s X-ray absorption near edge structure (XANES) spectroscopy. Density functional theory (DFT) calculations were carried out on both 1- and 2- halozincate anions, in both a generalised solvation model SMD (Solvation Model based on Density) and the gas phase, to give XP spectra and total energy differences; time-dependent DFT was used to calculate XANES spectra. Speciation judgements were made using a combination of the shape and width of the experimental spectra, and visual matches to the calculated spectra. For 2- halozincate anions, excellent matches were found between the experimental and calculated XP spectra, clearly showing that only 2- halozincate anions were present at all zinc halide mole fractions, , studied. At specific values of (0.33, 0.50, 0.60) only one halozincate anion was present; equilibria of different halozincate anions at those values of were not observed. All findings show that chlorozincate anion and bromozincate anion speciation matched at the same . Based on the results, predictions are made of the halozincate anion speciation for all values of up to 0.67. Caution is advised when using differences in calculated total energies obtained from DFT to judge halozincate anion speciation, even when the SMD was employed, as predictions based on total energy differences did not always match the findings from the experimental and calculated spectra. Our findings clearly establish that the combination of high-quality experimental data from multiple spectroscopies and a wide range of calculated structures are essential to have high confidence in halozincate anion speciation identification.
通过结合液相X射线光谱实验和小规模计算，我们对离子液体（ILs）中卤化锌酸根阴离子的形态有了新的认识。核心和价态X射线光电子能谱（XPS）实验均直接在液相离子液体上进行，并辅以Zn 1s X射线吸收近边结构（XANES）光谱。对1-卤化锌酸根阴离子和2-卤化锌酸根阴离子在广义溶剂化模型SMD（基于密度的溶剂化模型）和气相中都进行了密度泛函理论（DFT）计算，以得出XPS光谱和总能差；含时密度泛函理论用于计算XANES光谱。形态判断结合了实验光谱的形状和宽度，并与计算光谱进行直观匹配。对于2-卤化锌酸根阴离子，实验和计算得到的XPS光谱之间有很好的匹配，清楚地表明在所研究的所有卤化锌摩尔分数下仅存在2-卤化锌酸根阴离子。在特定的摩尔分数值（0.33、0.50、0.60）时仅存在一种卤化锌酸根阴离子；未观察到不同卤化锌酸根阴离子在这些摩尔分数值下的平衡。所有发现表明，氯锌酸根阴离子和溴锌酸根阴离子的形态在相同的摩尔分数下相匹配。基于这些结果，对高达0.67的所有摩尔分数值的卤化锌酸根阴离子形态进行了预测。即使采用了SMD，在使用从DFT获得的计算总能差来判断卤化锌酸根阴离子形态时也应谨慎，因为基于总能差的预测并不总是与实验和计算光谱的结果相符。我们的发现清楚地表明，来自多种光谱学的高质量实验数据与广泛的计算结构相结合对于对卤化锌酸根阴离子形态鉴定有高度信心至关重要。
