CH Mode Mixing Determines the Band Shape of the Carboxylate Symmetric Stretch in Apo-EDTA, Ca 2+ –EDTA, and Mg 2+ –EDTA
CH Mode Mixing Determines the Band Shape of the Carboxylate Symmetric Stretch in Apo-EDTA, Ca 2+ –EDTA, and Mg 2+ –EDTA
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CH 模式混合确定 Apo-EDTA、Ca 2 -EDTA 和 Mg 2 -EDTA 中羧酸盐对称拉伸的带形状
DOI：
10.1021/acs.jpca.1c03061
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发表时间：
2021
期刊：
影响因子：
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通讯作者：
Garrett-Roe, Sean
中科院分区：
文献类型：
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作者：
Mitra, Sunayana;Werling, Keith;Berquist, Eric J.;Lambrecht, Daniel S.;Garrett-Roe, Sean
EDTA与Ca ~（2+）和Mg ~（2+）络合的红外光谱中含有迄今为止未识别的振动带。本研究分配的峰在线性和二维红外光谱的EDTA，有和没有Ca 2+或Mg 2+离子。二维红外光谱和DFT计算表明，在离子的存在和不存在下，羧酸盐的对称伸缩和终端CH弯曲振动混合。我们介绍了一种方法来计算参与系数，量化的贡献，羧酸盐的对称伸缩，CH wag，CH扭曲，和CH？在1400-1550 cm-1的区域。在参与系数的帮助下，我们将1400-1430 cm-1区域归属于羧酸盐对称伸缩，它可以与CH模混合。我们将1000-1380 cm-1区域指定为CH扭曲模，1380-1430 cm-1区域指定为wag模，1420-1650 cm-1区域指定为n-H模。羧酸根-Ca ~（2+）和羧酸根-Mg ~（2+）复合物之间结合几何形状的差异表现为两种复合物中混合模式之间的新对角线和交叉峰。小的Mg 2+离子结合EDTA比Ca 2+离子，这会导致红移的COO对称伸展的矢状羧酸盐。能量分解分析进一步表征了静电和变形能在结合复合物中的重要性。
The infrared spectra of EDTA complexed with Ca2+and Mg2+contain, to date, unidentified vibrational bands. This study assigns the peaks in the linear and two-dimensional infrared spectra of EDTA, with and without either Ca2+or Mg2+ions. Two-dimensional infrared spectroscopy and DFT calculations reveal that, in both the presence and absence of ions, the carboxylate symmetric stretch and the terminal CH bending vibrations mix. We introduce a method to calculate participation coefficients that quantify the contribution of the carboxylate symmetric stretch, CH wag, CH twist, and CH scissor in the 1400–1550 cm–1region. With the help of participation coefficients, we assign the 1400–1430 cm–1region to the carboxylate symmetric stretch, which can mix with CH modes. We assign the 1000–1380 cm–1region to CH twist modes, the 1380–1430 cm–1region to wag modes, and the 1420–1650 cm–1region to scissor modes. The difference in binding geometry between the carboxylate–Ca2+and carboxylate–Mg2+complex manifests as new diagonal and cross-peaks between the mixed modes in the two complexes. The small Mg2+ion binds EDTA tighter than the Ca2+ion, which causes a redshift of the COO symmetric stretches of the sagittal carboxylates. Energy decomposition analysis further characterizes the importance of electrostatics and deformation energy in the bound complexes.