Conformational analysis of selected [2.2]heterophanes: A comparison of stereochemical switching via computational chemistry

Massimo D Bezoari,Carly Bourgeois

doi:10.7710/2168-0620.0271

Abstract

Conformational switching of selected [2.2]heterophanes was investigated by computational chemistry. Analyses were carried out by various methods, including Conformational Search in HyperChem, and forced conformational transformations with Energy Profile in Spartan. Stable anti and syn conformers arising from flipping of aromatic rings within the molecules were observed. The activation energies of the ring flipping process, as well as dipole moments and directions, were obtained by molecular mechanics. The present work shows that simple computational techniques can be employed to screen certain compounds as potential candidates for molecular machinery. Thus, heterophanes demonstrated reversible shifts between two or more configurations which are energetically stable and have different electronic properties, constituting a basic requirement for possible applications as molecular switches.

Highlights

IntroductionSince the early 20th century, phane compounds have gained attention for their synthetic challenge, unusual properties (such as aromatic rings that deviate from planarity due to strain), ring current effects, and other transannular interactions that could give rise to charge transfer, and organic conductors (Cram, 1983)
Since the early 20th century, phane compounds have gained attention for their synthetic challenge, unusual properties, ring current effects, and other transannular interactions that could give rise to charge transfer, and organic conductors (Cram, 1983)
Two molecular mechanics methods in HyperChem were screened to determine which computational approach would be best suited for the analyses of heterocyclic aromatic compounds by comparison to previous reports of computational and instrumentally based experiments (Tai, Lii, and Allinger, 1989; National Institute of Standards and Technology, 2018; Katrizky, Ramsden, Joule, and Zhdankin, 2010)

Summary

Introduction

Since the early 20th century, phane compounds have gained attention for their synthetic challenge, unusual properties (such as aromatic rings that deviate from planarity due to strain), ring current effects, and other transannular interactions that could give rise to charge transfer, and organic conductors (Cram, 1983). The term “cyclophane” implies that benzene constitutes at least one of the aromatic rings. Fivemembered aromatic rings (e.g. furan, pyrrole, and thiophene) are termed -excessive due to delocalization of lone pairs of the heteroatoms into the overlapping p-orbital system of the rings, activating them relative to benzene. The number of bridges and the number of atoms in the bridge backbones are indicated in square brackets; the locations of substitution of the aromatic rings are given in rounded parentheses. [2.2](2,5)furanophane (Figure 1) is a excessive heterophane containing two furan rings, with two bridges, each containing two main-chain carbon atoms, the bridges being bonded at C-2 and C-5 of the furan rings (Smith, 1964). The Systematic naming method (Commission on Nomenclature of Organic Chemistry, 1998) is not used in the present work

Methods

Results

Conclusion