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Enhanced Rotation by Ground State Destabilization in Amphidynamic Crystals of a Dipolar 2,3-Difluorophenylene Rotator as Established by Solid State 2H NMR and Dielectric Spectroscopy
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-06-23 , DOI: 10.1021/acs.jpcc.0c05314 Ieva Liepuoniute 1 , Chau Minh Huynh 1, 2 , Salvador Perez-Estrada 1, 3 , Yangyang Wang 4 , Saeed Khan 1 , K. N. Houk 1 , Miguel A. Garcia-Garibay 1
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2020-06-23 , DOI: 10.1021/acs.jpcc.0c05314 Ieva Liepuoniute 1 , Chau Minh Huynh 1, 2 , Salvador Perez-Estrada 1, 3 , Yangyang Wang 4 , Saeed Khan 1 , K. N. Houk 1 , Miguel A. Garcia-Garibay 1
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We report the synthesis and rotational dynamics of the pillared metal–organic framework Zn2(F2BDC)2(DABCO) where F2BDC = 2,3-difluorobenzene-1,4-dicarboxylate acts as a rotating dipolar linker and DABCO = 1,4-diazabicyclo[2.2.2]octane acts as a spacer (F2MOF 1). The pillared structure of F2MOF 1 was confirmed by X-ray diffraction and CP-MAS 13C NMR analyses. Using variable temperature solid state 2H NMR and broadband dielectric spectroscopy, we characterized the rotational dynamics of the dipolar F2BDC linker in the solid state. Variable temperature (VT) quadrupolar echo 2H NMR measurements revealed a rotational activation energy of Ea = 6.8 ± 0.1 kcal/mol, which agreed well with temperature- and frequency-dependent dielectric measurements, indicating a barrier of Ea = 7.1 ± 0.5 kcal/mol. Structural data from single crystal X-ray diffraction and quantum mechanical calculations (DFT) suggest that the rotational potential is determined by steric interactions between the dipolar rotator and the stator linkers such that fluorine atoms in the F2BDC linker reduce the activation energy by destabilization of the coplanar BDC ground state.
中文翻译：
固态2 H NMR和介电谱法建立的偶极2,3-二氟亚苯基转子的两性晶体中基态失稳增强旋转
我们报告了有柱金属-有机骨架Zn 2（F 2 BDC）2（DABCO）的合成和旋转动力学，其中F 2 BDC = 2,3-二氟苯-1,4-二羧酸盐起旋转偶极接头作用，DABCO = 1,4-二氮杂双环[2.2.2]辛烷用作间隔基（F 2 MOF 1）。通过X射线衍射和CP-MAS 13 C NMR分析确认了F 2 MOF 1的柱状结构。使用可变温度固态2 H NMR和宽带介电谱，我们表征了偶极F 2的旋转动力学BDC链接器处于固态。可变温度（VT）四极回波2 H NMR测量显示，旋转活化能E a = 6.8±0.1 kcal / mol，与温度和频率相关的介电测量值吻合得很好，表明E a = 7.1±0.5的势垒大卡/摩尔 来自单晶X射线衍射和量子力学计算（DFT）的结构数据表明，旋转电势由偶极旋转子与定子连接子之间的空间相互作用决定，这样F 2 BDC连接子中的氟原子会因不稳定而降低活化能共面BDC基态
更新日期：2020-07-16
中文翻译：
固态2 H NMR和介电谱法建立的偶极2,3-二氟亚苯基转子的两性晶体中基态失稳增强旋转
我们报告了有柱金属-有机骨架Zn 2（F 2 BDC）2（DABCO）的合成和旋转动力学，其中F 2 BDC = 2,3-二氟苯-1,4-二羧酸盐起旋转偶极接头作用，DABCO = 1,4-二氮杂双环[2.2.2]辛烷用作间隔基（F 2 MOF 1）。通过X射线衍射和CP-MAS 13 C NMR分析确认了F 2 MOF 1的柱状结构。使用可变温度固态2 H NMR和宽带介电谱，我们表征了偶极F 2的旋转动力学BDC链接器处于固态。可变温度（VT）四极回波2 H NMR测量显示，旋转活化能E a = 6.8±0.1 kcal / mol，与温度和频率相关的介电测量值吻合得很好，表明E a = 7.1±0.5的势垒大卡/摩尔 来自单晶X射线衍射和量子力学计算（DFT）的结构数据表明，旋转电势由偶极旋转子与定子连接子之间的空间相互作用决定，这样F 2 BDC连接子中的氟原子会因不稳定而降低活化能共面BDC基态
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