Reversible Soft Mechanochemical Control of Biaryl Conformations through Crosslinking in a 3D Macromolecular Network

Abstract

Tuning the dihedral angle (DA) of axially chiral compounds can impact biological activity,c atalyst efficiency, molecular motor performance,orchiroptical properties.Herein, we report gradual, controlled, and reversible changes in molecular conformation of ac ovalentlyl inked binaphthyl moiety within a3 Dp olymeric network by application of amacroscopic stretching force.Wemanaged direct observation of DA changes by measuring the circular dichroism signal of an optically pure BINOL-crosslinked elastomer network. Stretching the elastomer resulted in aw idening of the DA between naphthyl rings when the BINOL was doubly grafted to the elastomer network;noeffect was observed when asingle naphthyl ring of the BINOL was grafted to the elastomer network. We have determined that ca. 170 %e xtension of the elastomers led to the transfer of am echanical force to the BINOL moiety of 2.5 kcal mol À1 À1 (ca. 175 pN) in magnitude and results in the opening of the DA of BINOL up to 1308 8.

Front Cover: Exploiting Hydrogen Bonding to Direct Supramolecular Polymerization at the Air/Water Interface (ChemNanoMat 1/2023)

“…The compression to the quasi-collapse region of the monolayer required to obtain the observed SPs might indicate a thermodynamic barrier that can be surmounted by applying a mechanical stimulus to the film formed by 2. [33] The formation of H-bonds was confirmed by ex-situ FTIR spectra (Figure 3). Thirty-two monolayers of 2 were transferred onto a…”

Exploiting Hydrogen Bonding to Direct Supramolecular Polymerization at the Air/Water Interface

“…The compression to the quasi-collapse region of the monolayer required to obtain the observed SPs might indicate a thermodynamic barrier that can be surmounted by applying a mechanical stimulus to the film formed by 2. [33] The formation of H-bonds was confirmed by ex-situ FTIR spectra (Figure 3). Thirty-two monolayers of 2 were transferred onto a CaF 2 solid substrate at 30 mN • m À 1 to obtain adequate signal-to-noise ratio.…”

“…The ordered structures at microscopic level were observed exclusively in the first cycle and might contain solid‐like nuclei that persisted as the observed bright dots during the second and third cycles. The compression to the quasi‐collapse region of the monolayer required to obtain the observed SPs might indicate a thermodynamic barrier that can be surmounted by applying a mechanical stimulus to the film formed by 2 [33] …”

Reversible mechanical control of molecular conformation

“…1 , ref. 2 ). This allowed optical measurements to be taken at specific angles, thereby decoupling the confounding contributions arising from the polymer network from the circular dichroism signal arising from the chiral BINOL molecules.…”

“… Stretching and relaxation of a PDMS elastomer causes reversible control over the dihedral angle of crosslinked BINOL molecules. Use of a custom sample holder allows the dihedral angle to be monitored quantitatively without confounding optical contributions from the surrounding elastomer 2 . Copyright Wiley-VCH GmbH.…”