Theoretical study on the structure and stability of ring inverted porphyrin isomers

B3LYP/6-31+G** and B3LYP/6-31G calculations were done on 28 isomers of ring inverted porphyrin isomers. A systematic approach is adopted by computing the effect of relative stabilities and structural reorganization upon sequential ring-inversion. While the initial and all subsequent inversions lead to severe increase in the strain, the increase find to be non-linear and in most cases, the inverted structures encounter ring fusions. Both fused and non-fused structures of the singly, doubly, triply and fully inverted isomers were located as minima on the potential energy surface. Consistently, the non-fused isomers are lower in energy compared to their fused counterparts, which indicates that even in the inverted structures the extended conjugation bring in stabilization