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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. [ABSTRACT FROM AUTHOR]

The binding effects of Mn2+ and Ca2+ ions on the vibrational properties of adenine-thymine (AT) base pairs have been investigated using density functional theory. The metallic atoms were coordinated to N3 and N7 atoms of adenine, respectively. We analyze the geometric properties of different metal-AT base pairs structures, as well as the vibrational bands that can be used to detect the presence of metallic ions. In particular we have found that strong vibrational amplitudes of metallic atoms are expected for the vibrational bands in the range between 400-500 cm-1. Also, we point out the effects of cations binding over a series of selected modes, corresponding to experimental data, providing values for the resulting shifts for each of these vibrational bands. [ABSTRACT FROM AUTHOR]