Theoretical CD spectrum calculations of the crown‐ether aralkyl‐ammonium salt complex

Abstract

Rotatory strengths of the alpha-(1-naphtyl)-ethylammonium perchlorate (NEA)-phenazino-18-crown-6 ether molecular complex is determined theoretically by the coupled oscillator model and using ab initio random phase approximation (RPA) to describe local excitations on the chromophores. The computational results are compared to the experimental circular dichroism (CD) spectrum published previously. The good qualitative agreement between calculated and measured optical rotatory strengths allows one to assign the CD bands of the complex in a unique manner.

X-ray and Optical Circular Dichroism as Local and Global Ultrafast Chiral Probes of [12]Helicene Racemization

“…53 Figure 2b also shows that only HS is a global chiral structure, while TS has a vanishingly small OCD, as expected from its C s symmetry. For the HS conformation, the anisotropy factor has a maximum value of ∼5.1%, in good agreement with previous calculations for [10]helicene. 49 To illustrate the capacity of the XCD as a local chirality probe, Figure 3 shows the XCD signals calculated by substituting a H atom with a F atom at different positions along the TS and HS structures.…”

“…The circular dichroism signal (CD) is defined as the difference between the absorption of left-and right-handed circularly polarized light and is widely used for the infrared to near-ultraviolet (UV) detection of molecular chirality. 9,10 CD is then denoted optical circular dichroism (OCD). While chirality commonly relies on a chiral center, global chiral geometries such as axial, planar, propeller-type, and helical are known as well.…”

X-ray circular dichroism signals: a unique probe of local molecular chirality

“… 1 Optical activity and circular dichroism (CD) are well established spectroscopic techniques to detect molecular chirality in the infrared (IR) to the near-ultraviolet (UV) regimes. 2 , 3 These signals vanish for ensembles of randomly oriented achiral molecules and carry valuable information about absolute molecular conformations. A considerable effort has been made recently to enhance these signals, 4 which are intrinsically weak compared to linear absorption signals since they depend on higher order terms in the multipolar expansion of the field–molecule interaction.…”

Non-local real-space analysis of chiral optical signals

“…In the electric and magnetic dipole approximation, the CD signal, eqn (1), is given by the rotatory strength. 17 Being the product of a vector and a pseudo-vector, it must vanish under coordinate inversion for a non-chiral molecule that is invariant under coordinate inversion.…”