Ion Mobility and Fourier Transform Ion Cyclotron Resonance Collision Cross Section Techniques Yield Long-Range and Hard-Sphere Results, Respectively
Ion Mobility and Fourier Transform Ion Cyclotron Resonance Collision Cross Section Techniques Yield Long-Range and Hard-Sphere Results, Respectively
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离子淌度和傅里叶变换离子回旋共振碰撞截面技术分别产生长程和硬球结果
DOI：
10.1021/jasms.2c00112
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发表时间：
2022
影响因子：
3.2
通讯作者：
Dearden, David V.
中科院分区：
文献类型：
--
作者：
Heravi, Tina;Arslanian, Andrew J.;Johnson, Spencer D.;Dearden, David V.
我们测定了单电荷和双电荷葫芦[n]脲（n= 5-7）、十甲基葫芦[5]脲和环己基葫芦[5]脲与碱金属阳离子（Li+-Cs+）配合物的碰撞截面（CCS）值。这些宿主是相对刚性的。对于给定主体的计算建模结构，使用投影近似（PA）计算的CCS值对于+1和+2络合物几乎相同，具有弱的金属离子依赖性，而对于相同结构的CCS的轨迹方法（TM）计算一致地产生对于+2络合物比对应的+1络合物大7-10%的值，并且几乎没有金属离子依赖性。在实验上，我们通过傅里叶变换离子回旋共振（“CRAFTI”）方法使用横截面积测量了葫芦脲主体的+1和+2络合物对在SF6中的相对CCS值。在质心碰撞能量<1.30 eV时，CRAFTI CCS值对+1和+2复合物中的相对结合能敏感，但在碰撞能量> 1.40 eV时（足以使离子退相干发生在基本上每次碰撞时），这种依赖性不明显。与PA计算一致，这些实验发现+2络合物离子的CCS值在其+1对应物的CCS值的94%和105%之间（随着金属离子尺寸增加）。相反，但与TM CCS计算一致的是，在接近热能的条件下，在可极化性低得多的N2中对相同络合物进行的离子迁移率测量发现，+2络合物的CCS在所有情况下都比相应的+1络合物的CCS大9-12%，几乎没有金属离子依赖性。
We determined collision cross section (CCS) values for singly and doubly charged cucurbit[n]uril (n= 5–7), decamethylcucurbit[5]uril, and cyclohexanocucurbit[5]uril complexes of alkali metal cations (Li+–Cs+). These hosts are relatively rigid. CCS values calculated using the projection approximation (PA) for computationally modeled structures of a given host are nearly identical for +1 and +2 complexes, with weak metal ion dependence, whereas trajectory method (TM) calculations of CCS for the same structures consistently yield values 7–10% larger for the +2 complexes than for the corresponding +1 complexes and little metal ion dependence. Experimentally, we measured relative CCS values in SF6for pairs of +1 and +2 complexes of the cucurbituril hosts using the cross-sectional areas by Fourier transform ion cyclotron resonance (“CRAFTI”) method. At center-of-mass collision energies <∼30 eV, CRAFTI CCS values are sensitive to the relative binding energies in the +1 and +2 complexes, but at collision energies >∼40 eV (sufficient that ion decoherence occurs on essentially every collision) that dependence is not evident. Consistent with the PA calculations, these experiments found that the +2 complex ions have CCS values ranging between 94 and 105% of those of their +1 counterparts (increasing with metal ion size). In contrast, but consistent with the TM CCS calculations, ion mobility measurements of the same complexes at close to thermal energies in much less polarizable N2find the CCS of +2 complexes to be in all cases 9–12% larger than those of the corresponding +1 complexes, with little metal ion dependence.