Photoisomerization of a Chiral Imine Molecular Switch Followed by Matrix‐Isolation VCD Spectroscopy

Abstract

Characterizing the stereochemistry of transient photoisomerization products remains a big challenge for the design of molecular machines, such as unidirectional molecular motors. Often these states are not stable long enough to be characterized in detail using conventional spectroscopic tools. The structurally simple camphorquinone imine 1 serves to illustrate the advantage of combining the matrix-isolation technique with vibrational circular dichroism (VCD) spectroscopy for the investigation of photoisomerizations of chiral molecules. In particular, it is shown that both (E)- and (Z)-1 can be generated photochemically at cryogenic temperatures in an argon matrix, and more importantly, that the stereochemistry of both switching states can be characterized reliably.

Sulfoxide‐Induced Homochiral Folding of ortho‐Phenylene Ethynylenes (o‐OPEs) by Silver(I) Templating: Structure and Chiroptical Properties

“…These results indicate the different disposition of the p ‐tolyl groups in the ( S , S )‐ 3 :Ag 3 complex compared with that in the other complexes. These experimental results represent one of the very scarce examples of VCD switches reported to date …”

“…These resultsi ndicate the different disposition of the p-tolyl groups in the (S,S)-3:Ag 3 complexc ompared with that in the other complexes.T hese experimental results repre- sent one of the very scarce examples of VCD switches reported to date. [48] Theoretical studies on o-OPE:Ag I complexes To better understanda ll of theseo bservations, we carried out theoretical calculations for the Ag I complexes of o-OPE ligands (S,S)-1-8.F or (S,S)-1,t heoretical calculations revealed that the more favorable situation corresponded to silver coordinated between the alkyne and OMe (Figure 9), in which both ÀOMe groups wereoriented to the Ag + ion, leading to ahighly stabilizing interaction. The systemi ns uch ad isposition adopted an anti conformation.…”

Instrumentation for Vibrational Circular Dichroism Spectroscopy: Method Comparison and Newer Developments

“…Couplets in particular were enhanced due to the increased resolution. This method is having a renaissance, with Vass, Xu, Merten and co-workers using improved instrumentation and reporting studies of propylene oxide, methyl lactate, and small alcohols correlated with spectral simulations to determine structures of isolated molecules or of their complexes in the matrix [ 110 , 111 , 112 ].…”

Computation of Solid-State Vibrational Circular Dichroism in the Periodic Gauge

“…23 We recently published a survey on different computational tools to describe conformational sampling. 24 Typically, VCD is measured in liquid state or in or in isolated conditions such as noble gas matrices, [26][27][28][29][30] which is a largely standardised procedure, but requires sample solubility and may exhibit spurious solvent effects. However, in analogy to IR absorption, VCD can also be measured conveniently in solid state.…”