Density functional studies on N-fused porphyrin. Electronic, magnetic and metal binding properties

Density functional calculations have been performed to understand the electronic and magnetic properties along with the metal complexation ability of N-fused porphyrin (NFP), and doubly-N-fused porphyrin (N2FP). DFT computations predict that the planar N2FP is a second order saddle point. The minimum energy structure, 5, is nonplanar and 8.0 kcal mol−1 lower in energy than the planar structure. Despite the nonplanarity, N2FP has only 3.0 kcal mol−1 additional strain energy compared to NFP. NFP can form stable metal complexes with Cu(I) metal ion. The most stable structure for Cu(I)NFP prefers dome conformation. Nucleus independent chemical shift (NICS) calculations reveal that NFP has much reduced global ring current (NICS −8.5). However, effective interaction between the two tri-pentacyclic rings in N2FP enhances the global ring current (NICS −17.5).