Supramolecular Chirogenesis in a Sterically Hindered Porphyrin: A Critical Theoretical Analysis.

The determination of molecular stereochemistry and absolute configuration is an important part of modern chemistry, pharmacology, and biology. Electronic circular dichroism (ECD) spectroscopy is a widely used tool for chirality assignment, especially with porphyrin macrocycles employed as reporter chromophores. However, the mechanisms of induced ECD in porphyrin complexes are yet to be comprehensively rationalized. In this work, the ECD spectra of a sterically hindered hexa-cationic porphyrin with two camphorsulfonic acids in dichloromethane and chloroform were experimentally measured and computationally analyzed. The influence of geometric factors such as the position of chiral guest molecules, distortion of the porphyrin macrocycle, and orientation of aromatic and non-aromatic peripheral substituents on the ECD spectra was theoretically studied. Various potential pitfalls, such as a lack of significant conformations and accidental agreement of experimental and simulated spectra, are considered and discussed.