Aromatic pathways in carbathiaporphyrins.

Magnetically induced current densities and current pathways have been calculated for carbaporphyrins and carbathiaporphyrins using the gauge including magnetically induced current (GIMIC) method. The aromatic character and current pathways are obtained from the calculated current density susceptibilities. The current-density calculations show that five of the studied carbaporphyrinoids are aromatic, two are antiaromatic, and one is nonaromatic. The analysis of the current pathways of the investigated molecules reveals some general trends for the current flow in carbaporphyrinoids. Insertion of a CH2 group into the all-carbon ring generally cuts or restricts the current flow, leading to a stronger current of the alternative pathway of the ring. No obvious trends regarding the current strengths and pathways of the thiophene and cyclopentadienyl rings were obtained. The present study shows that it is indeed difficult to predict the electron delocalization pathways of general carbaporphyrinoids. Thus, a careful analysis of the current density is necessary for determining their electron delocalization pathways.