Mirzaei Saber, Espinoza Castro Victor M, Hernández Sánchez Raúl
Department of Chemistry, University of Pittsburgh 219 Parkman Ave. Pittsburgh Pennsylvania 15260 USA
Chem Sci. 2022 Jan 26;13(7):2026-2032. doi: 10.1039/d1sc07041j. eCollection 2022 Feb 16.
Macrocyclic arenes laid the foundations of supramolecular chemistry and their study established the fundamentals of noncovalent interactions. Advancing their frontier, here we designed rigidified resorcin[4]arenes that serve as hosts for large nonspherical anions. In one synthetic step, we vary the host's anion affinity properties by more than seven orders of magnitude. This is possible by engineering electropositive aromatic C-H bond donors in an idealized square planar geometry embedded within the host's inner cavity. The hydrogen atom's electropositivity is tuned by introducing fluorine atoms as electron withdrawing groups. These novel macrocycles, termed fluorocages, are engineered to sequester large anions. Indeed, experimental data shows an increase in the anion association constant ( ) as the number of F atoms increase. The observed trend is rationalized by DFT calculations of Hirshfeld Charges (HCs). Most importantly, fluorocages in solution showed weak-to-medium binding affinity for large anions like [PF] (10< <10 M), and high affinity for [MeSO] ( >10).
大环芳烃奠定了超分子化学的基础，对它们的研究确立了非共价相互作用的基本原理。为了拓展其前沿领域，我们设计了刚性化的间苯二酚[4]芳烃，用作大型非球形阴离子的主体。在一个合成步骤中，我们将主体的阴离子亲和性能改变了七个多数量级。这是通过在主体内腔中嵌入的理想方形平面几何结构中设计正电性芳族C-H键供体来实现的。通过引入作为吸电子基团的氟原子来调节氢原子的正电性。这些新型大环化合物，称为氟笼，被设计用于螯合大型阴离子。实际上，实验数据表明，随着F原子数量的增加，阴离子缔合常数（ ）增大。通过Hirshfeld电荷（HCs）的DFT计算使观察到的趋势合理化。最重要的是，溶液中的氟笼对[PF]等大型阴离子表现出弱至中等的结合亲和力（10< <10 M），而对[MeSO]表现出高亲和力（ >10）。
