Desymmetrized Leaning Pillar[6]arene

Abstract

In this work, a novel version of macrocyclic arenes, namely leaning pillar[6]arenes, was discovered and it can be considered as a tilted version of a pillar[6]arene with two hydroxy/alkoxy functionalities removed. Through a facile two-step synthetic approaches, in conjunction with a diversity of post-modification possibilities, a series of leaning pillar[6]arenes, with good cavity adaptability and enhanced guest-binding capability, was synthesized, and their self-assembly in single-crystal states is presented. DFT calculations demonstrated that the lower rotational barrier of unsubstituted phenylene rings, the uneven electron density centered at the leaning phenyl rings, and the polarization effect along the edge generated by the hydrogen-bond-induced orientation of hydroxy groups greatly affected the host-guest properties, and meanwhile provided an intuitive explanation for the pillar-like and rigid structure of traditional pillar[6]arenes. Significantly, the crystal structure of cyclo-oligomeric quinone was obtained by direct oxidation of leaning pillar[6]arenes.

Visualization and quantitation of electronic communication pathways in a series of redox-active pillar[6]arene-based macrocycles

“…With the single exception of P1Q 17 , all of these compounds were previously unknown. In general terms, our results indicate that the accumulation of adjacent benzoquinone units in the macrocycle is not favored 20 . However, our yields for the isolated oxidized compounds (P1Q through P4Q) were satisfactory, ranging from a robust 73.2% for P1Q to just 18.5% for P4Q-B.…”

Tiara[5]arenes: Synthesis, Solid‐State Conformational Studies, Host–Guest Properties, and Application as Nonporous Adaptive Crystals

“…As olvent-free T[5]-(OMe) 5 structure [22] (space group P1 ,t riclinic) obtained on crystallization by vapor diffusion of CH 3 OH into CHCl 3 solution, features a C 1 conformation (Figure 2a), with the cavity-forming rings alternatingly up and down. With the odd number of aryl rings,this alternation leaves one remaining ring to be rotated nearly 908 8 with respect to the other four rings.W hile this rotation has also been observed for [1 5 ]paracyclophane and for the leaning pillar [6]arene, [23] this rotational distortion is not intrinsic to these C À Hf unctionalized para-bridged macrocycles.…”

Structural Diversification of Pillar[n]arene Macrocycles

“…The leaning PA[6]s were defined as PA[6]s in which the hydroxy or alkoxy substituents are selectively removed from two opposing phenyl rings. The reported synthetic protocol involves two steps: first, the formation of 1,4‐bis(2,5‐diethoxybenzyl)benzene through the reaction between 1,4‐bis(chloromethyl)benzene and 1,4‐diethyoxybenzene in the presence of AlCl 3 , followed by macrocyclization with paraformaldehyde in the presence of BF 3 ⋅O(Et) 2 , yielding the perethoxylated leaning PA[6] (EtLPA[6]) in 36 % yield (Scheme b) . Interestingly, this EtLPA[6] could not only enhance the binding properties of PA[6], but it could also selectively separate 1‐bromoalkane isomers from mixtures of 1/2‐positional isomers through simple solid–vapor adsorption.…”