Electronic and spectroscopic properties of porphyrinoid macrocycles are, to a large extent, determined by the number of π-electrons participating in the conjugation network. Full control of the number of π-electrons implies full control of the aromatic or antiaromatic character of the molecule. To achieve this, knowledge about the electron delocalization pathways within a molecule is essential. Experimentally, these pathways are not easily accessible. Therefore theoretical studies are necessary to complement experiments that aim at systematically synthesizing porphyrinoids with distinct properties.

A computational approach to achieve this is the gauge including magnetically induced current density method (GIMIC). GIMIC is a independent program that is used for the calculation of magnetically induced current densities using London orbitals.[1, 2] Numerical integration of the current flow around molecular rings and along selected chemical bonds can be used for determining current pathways and the degree of aromaticity of various molecules according to the magnetic criterion.[3,4] In my talk I am going to present the GIMIC method and briefly discuss the idea behind it. I will illustrate what type of information is accessible through current density studies. Some very recent results on carbaporphyrinoids will be highlighted showing the potential and the challenges of the method.[5,6]

References:
[1] J. Jusélius, D. Sundholm and J. Gauss, J. Chem. Phys., 121, 3952-3963 (2004).
[2] H. Fliegl, S. Taubert, O. Lehtonen and D. Sundholm, Phys. Chem. Chem. Phys., 13, 20500- 20518 (2011).
[3] R. Valiev, H. Fliegl and D. Sundholm, Phys. Chem. Chem. Phys., 16, 11010-11016 (2014).
[4] H. Fliegl, F. Pichierri and D. Sundholm, J. Phys. Chem. A, 119, 2344-2350 (2015).
[5] R. Valiev, H. Fliegl and D. Sundholm, J. Phys. Chem. A, 119, 1201-1207 (2015).
[6] R. Valiev, H. Fliegl and D. Sundholm, Phys. Chem. Chem. Phys., 17, 14215-14222 (2015).