title: How does aromaticity rule the thermodynamic stability of hydroporphyrins?
abstract: Several measures of aromaticity including energetic, magnetic, and electron density criteria are employed to show how aromatic stabilization can explain the stability sequence of hydroporphyrins, ranging from porphin to octahydroporphin, and their preferred hydrogenation paths. The methods employed involve topological resonance energies and their circuit energy effects, bond resonance energies, multicenter delocalization indices, ring current maps, magnetic susceptibilities, and nuclear-independent chemical shifts. To compare the information obtained by the different methods, the results have been put in the same scale by using recently proposed approaches. It is found that all of them provide essentially the same information and lead to similar conclusions. Also, hydrogenation energies along different hydrogenation paths connecting porphin with octahydroporphin have been calculated with density functional theory. It is shown by using the methods mentioned above that the relative stability of different hydroporphyrin isomers and the observed inaccessibility of octahydroporphin both synthetically and in nature can be perfectly rationalized in terms of aromaticity.
authors.affiliation: Department of Physical Chemistry, University of Vigo, Lagoas-Marcosende s/n, 36310 Vigo, Spain.
authors.forename: Nicolás
authors.initials: N
authors.lastname: Otero
authors.forename: Stijn
authors.initials: S
authors.lastname: Fias
authors.forename: Slavko
authors.initials: S
authors.lastname: Radenković
authors.forename: Patrick
authors.initials: P
authors.lastname: Bultinck
authors.forename: Ana M
authors.initials: AM
authors.lastname: Graña
authors.forename: Marcos
authors.initials: M
authors.lastname: Mandado
mesh_terms: D006865:Hydrogenation; D008958:Models, Molecular; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D011166:Porphyrins