Lu Tao, Chen Junhua, Zhang Jiaqi, Gou Qian, Xia Zhining, Feng Gang
School of Chemistry and Chemical Engineering, Chongqing University, Daxuecheng South Rd. 55, 401331, Chongqing, China.
Collaborative Innovation Center for Brain Science, Chongqing University, No. 174 Shazhengjie, Shapingba, 400044, Chongqing, China).
Chemphyschem. 2018 Oct 19;19(20):2655-2661. doi: 10.1002/cphc.201800636. Epub 2018 Aug 22.
To probe the multiple configurations of a weakly bound intermolecular complex, the difluoromethane and 1,1,1,2-tetrafluoroethane dimer was investigated by using pulsed jet Fourier transform microwave spectroscopy coupled with quantum chemical calculations. Three isomers were detected in the supersonic jet. Spectroscopic assignments, ab initio calculations and quantum theory of atoms in molecules (QTAIM) analyses prove that all the observed isomers are stabilized through a net of three weak C-H⋅⋅⋅F-C interactions. The interaction energies are estimated to be within 12-13 kJ mol , dominated by electrostatic and dispersion according to Symmetry-Adapted Perturbation Theory (SAPT) analysis. The spectroscopic measurements were also extended to three and two C isotopologues in natural abundance for the isomers II and III, respectively, which lead to precisely structural determinations of these two isomers. The comparison of the relative intensity of these isomers measured in the carrier gases of argon and helium evidenced that isomer II is the global minimum, while the intensities measured in helium suggested that the population of the three isomers in the jet to be N /N /N ≈1/11/4.
为了探究弱束缚分子间复合物的多种构型，采用脉冲喷射傅里叶变换微波光谱结合量子化学计算对二氟甲烷与1,1,1,2 - 四氟乙烷二聚体进行了研究。在超声速喷射中检测到了三种异构体。光谱归属、从头算计算以及分子中的原子量子理论（QTAIM）分析表明，所有观察到的异构体都是通过三个弱C - H⋅⋅⋅F - C相互作用网络而稳定存在的。根据对称适配微扰理论（SAPT）分析，相互作用能估计在12 - 13 kJ mol 范围内，主要由静电和色散作用主导。光谱测量还分别扩展到了异构体II和III的天然丰度下的三种和两种碳同位素变体，这使得能够精确确定这两种异构体的结构。在氩气和氦气载气中测量这些异构体的相对强度的比较表明，异构体II是全局最小值，而在氦气中测量的强度表明喷射中三种异构体的丰度比为N /N /N ≈1/11/4。
