Designed Molecular Switches: Controlling the Conformation of Benzamido-diphenylacetylenes

Abstract

With the goal of creating a molecular switch, the hydrogen-bonded diphenylacetylene structure has been modified such that an equilibrium now exists between two intramolecular H-bonded states. Through X-ray crystallography and (1)H NMR analysis it is shown that this equilibrium can be biased in a predictable manner by modulating the relative acidity of the amide NH's.

Redox-Dependent Conformational Switching of Diphenylacetylenes

“…(1). Methyl 4-((2-amino-6-benzamidophenyl) ethynyl)benzoate (4) and methyl 2-ethynylbenzoate (6) were prepared according to a literature procedure [31].…”

“…Analogously it should be possible to design a conformational switch in which a H-bond network reconfigures due to a redox-dependent modulation of a H-bond donor. Previous work has shown that the conformational equilibrium in H-bonded DPA's can be controlled by increasing the H-bond donation strength of one NH relative to the other [31,32]. This H-bond strength is readily adjusted through the conjugation of electron-donating or -withdrawing groups to the amide NH.…”

“…In order to test this hypothesis we synthesized diphenylacetylene 3 via an amide bond formation between aniline 1 [31] and ferrocenoyl chloride 2 (Scheme 1). Scheme 1.…”

“…para-Substituted benzoic ester 5, which is incapable of intramolecular H-bonding, was synthesized via amide coupling of aniline 4 [31] with ferrocenoyl chloride (Scheme 2). The second control molecule, 12, was prepared from 3-nitroaniline via an adaptation of a literature route: [31] iodination of 3-nitroaniline, [48] followed by amidation, nitro-group reduction, Sonogashira coupling and coupling with ferrocenoyl chloride, afforded the desired bis(amide). The first of these, 5, estimates the chemical shift of the FcA NH in the absence of H-bonding by positioning the H-bond acceptor para to the alkyne linkage (0% control).…”

Impact of mono- and disubstitution on the colorimetric dynamic covalent switching chalcone/flavanone scaffold

“…Approaches include photoswitchable [14][15][16][17][18][19][20][21][22][23] (e.g. azobenzenes, diarylethenes, and spiropyrans) and chemoswitchable molecules [5][6][7][8]13,24,25 (e.g. diphenylacetylene-and hydrazonebased switches), each offering distinct advantages and disadvantages.…”