LAUSR

Abstract DFT investigations on M-BCP8 (M = Zn, Ni) bridled chiral porphyrins were performed. The conformational flexibility depending on the metal ion, the environment, or the electronic redox state was analysed in the framework of Kohn–Sham formalism, within a Generalized Gradient functional, namely GGA-PBE, corroborated with triple-zeta Slater basis sets. Correlations between the metal ion size and the deformation of the porphyrinic core highlight a more pronounced deformation for Ni 2+ -BCP8 than for Zn 2+ -BCP8, suggesting that the short distances in Ni-N porphyrins are responsible for the ruffling of the porphyrinic core, whereas the Zn 2+ ion being larger, fits better in the cavity and does not impose any strong deformation. Description of the most stable atropoisomer was proved in agreement with experimental NMR and X-ray measurements. The free base and the Zn 2+ complex exhibit a preferential αααα conformation in solution, while for Ni 2+ analogue, the atropisomer was 100% αβαβ . In the case of ZnBCP-8 the main atropoisomer is changing in comparison with the crystal data, obtaining in dichloromethane and nitrobenzene a more stable Zn open conformation but in equilibrium with the closed conformation. Stabilization due to solvation was investigated, explaining the difference of behaviour observed for ZnBCP-8. The effect of supramolecular aggregation observed experimentally was theoretically investigated in terms of dimer formation. We also calculated the BSSE errors and even the thermodynamic entropy and ZPE parameters that can eventually influence the αβαβ/αααα equilibriums.