Chiroptical Symmetry Analysis of Trianglimines: A Case Study

Abstract

It is well established that chiroptical responses, based on the unique reaction to circularly polarized light by chiral non-racemic systems, are sensitive to the stereochemistry of the featuring systems. This behavior has promoted the use of chiroptical spectroscopies as a mandatory tool in the structure determination of molecules for decades. Recently, the higher sensitivity of chiroptical techniques compared to the conventional UV/Vis absorption and fluorescence spectroscopies or electrochemistry has awakened much interest in the development of chiroptical everyday applications. While chiroptical responses could be predicted by ab initio calculations, large systems calculated at a high level of theory may have an important computational cost; therefore, more intuitive methods are desired to design systems with tailored chiroptical responses. In this regard, the exciton chirality method has been often used in conformationally stable systems incorporating at least two independent chromophores. Taking this method into consideration, in our previous work, we described the chiroptical symmetry analysis (CSA) based on symmetry selection rules. To explore the scope of the CSA, herein we perform the chiroptical symmetry analysis of diverse trianglimines and draw general conclusions to assist on the design of chiroptical systems with high symmetry.

Distinct Helical Molecular Orbitals through Conformational Lock**

“…Couplings between the three S1 monomeric excitations were computed as a Coulombic interaction of their transition densities by Gaussian 16 and ECD spectra were computed with EXAT code [39–42] . The obtained results are in very good agreement with those predicted by TD‐DFT, strongly supporting the hypothesis that the strong ECD is due to exciton couplings of local excitations on the butadiyne moieties following the selection rules imposed by symmetry (Figure S26, for more details, see the Supporting Information) [43, 44] . Hence, we conclude that the DPBD moieties in these SBF macrocycles interact through an exciton coupling mechanism, at least for low excited states.…”

“…[39][40][41][42] The obtained resultsa re in very good agreement with those predicted by TD-DFT,s trongly supporting the hypothesis that the strong ECD is due to exciton couplings of local excitationsont he butadiyne moieties following the selection rules imposed by symmetry ( Figure S26, for more details, see the Supporting Information). [43,44] Hence, we conclude that the DPBD moieties in these SBF macrocycles interactt hrough an exciton coupling mechanism, at least for low excited states. Fractions Aa nd Bfrom the enantiomeric resolution are shown in black and red, respectively.…”

Chiroptical Sensing: A Conceptual Introduction

“…iv) with the geometric parametes, predict the electronic and magnetic dipole moment of each transition, and consequantly the rotary strength. As a case study, the chiroptical symmetry analysis of trianglimines has been recently performed [78]. responses, ii) using group theory, obtain the symmetry-based irreduible representations to determine the allowed transitions, iii) considering the relative orientation between the chromophores, and using the Davydov´s equation, determine the energy differene between the different transitions.…”

“…iv) with the geometric parametes, predict the electronic and magnetic dipole moment of each transition, and consequantly the rotary strength. As a case study, the chiroptical symmetry analysis of trianglimines has been recently performed [78].…”

Chiroptical Sensing

“…[62] The chiroptical symmetry analysis of trianglimines has been recently performed as a case study. [63]…”