Perethylated pillar[n]arenes versus pillar[n]arenes: theoretical perspectives.

In this article we obtain the electronic structure, H NMR, and the vibrational spectra of perethylated pillar[n]arene (EtPn) (n = 5-8, 10) macrocycles using the ωB97x-based density functional theory. A single cavitand structure endowed with the robust pillar-like architecture was derived for the EtPn (n = 5-7) hosts while for the EtP8 receptor, two conformers one possessing the single cavitand and other double cavitand structure having four hydroquinone monomeric units in each cavity were obtained as the local minima. A double cavitand conformer of the EtP8 was found to be ~ 50 kJ mol lower in energy than the single cavitand one which was attributed to the increased hydrogen bonding cooperativity and attractive H-H interactions.

Regioselectivity in nonsymmetric methyl pentyl Pillar[5]arene bound to non-symmetric axles.

The present work illustrates regioselective binding of nonsymmetric axle BuX (X = F, Cl, Br, CN) and 5-bromovaleronitrile (BVN) to the non-symmetric methyl pentyl pillar[5]arene (MPP5). Theoretical calculations reveal that the guest encapsulation within MPP5 is spontaneous and the conformer showing X weakly bound to pentyl rim of MPP5 is favoured over its other conformer wherein it interacts with methyl rim of the host. The noncovalent interactions namely C-H---π, C-H---X and H-H prevail over C-H⋯O hydrogen bonding in the complexes of MPP5.

Probing Binding of Ethylated Pillar[5]arene with Pentene and Chlorobutane Positional Isomers.

Host guest binding from alkyl-modified pillararene macrocycles has been of significant interest in a variety of applications in the domains of supramolecular chemistry. In this work, we analyze the selectivity in binding of the ethylated pillar[5]arene (EtP5) macrocycle with 1-pentene, and 2-pentene, and the 1- and 2-chlorobutane isomer guests employing the ωB97x-based density functional theory. EtP5 reveals stronger binding with 1-pentene the accompanying change of energy upon the complexation being 85.