Si掺杂调控15‑冠‑5配位Li^(+)机理的理论研究

Theoretical Studies on Mechanism of 15-Crown-5 Coordinating with Li^(+)Regulated by Si Doping

基于密度泛函理论研究了以—SiMe_(2)—SiMe_(2)—单元或—CH_(2)—SiMe_(2)—单元取代—CH_(2)—CH_(2)—的方式调控15-冠-5配位Li^(+)性能的机理。结果表明掺杂Si能够增大冠醚的尺寸,并且通过不同的掺杂方式可以有效增强/减弱冠醚配位Li^(+)的能力。分子中的原子(AIM)理论的电子密度拓扑分析和对称匹配微扰理论(SAPT)能量分解分析表明,冠醚与Li^(+)的相互作用本质为伴随少量轨道极化和电子转移的离子-偶极相互作用。由于Si的电子比C更容易被O和Li^(+)极化,因此Si掺杂能够增强冠醚-Li^(+)之间的静电相互作用和诱导相互作用,但自然布居分析表明,若掺杂之后冠醚环内存在Si—O—Si单元,整体上将使O难以充分极化Si的电子,同时导致带正电的Si与Li^(+)距离更近,因此不利于冠醚配位Li^(+)。

This study mainly focused on the effect of substituting—CH_(2)—CH_(2)—with—SiMe_(2)—SiMe_(2)—or—CH_(2)—SiMe_(2)—on the coordination ability of 15-crown-5 with Li^(+)based on density functional theory calculations.The results show that Si doping can not only lead to increased size of crown ethers,but can also effectively regulate the coordination ability of crown ethers with Li^(+)by tuning the doping level and position.Atoms in molecules(AIM)analysis of electron density and symmetry-adapted perturbation theory(SAPT)energy decomposition analysis indi-cate that the interactions between the intrinsic/Si-doped crown ethers and Li^(+)are essentially ion-dipole interactions,accompanied by slight orbital polarization and electron transfer.Since the electrons of Si are polarized more easily by O and Li^(+)than those of carbon atoms,Si doping can thus enhance the electrostatic and induction interactions be-tween crown ethers and Li^(+).However,natural population analysis demonstrates that if the Si doping introduces Si—O—Si structures into the crown ethers,it could prevent O from fully polarizing the electrons of Si,and results in a closer distance between positively charged Si and Li^(+),thereby impeding the coordination of crown ethers with Li^(+).