Structural, photophysical and theoretical studies of two dodecachlorinated porphyrins

摘要

Two dodecachlorinated porphyrins, 2,3,7,8,12,13,17,18-octachloro-5,10,15, 20-tetra(4-chlorophenyl)porphyrin free base (TCl_(12)PPH_2) and its nickel compound (TCl_(12)PPNi), have been synthesized. Single-crystal X-ray diffraction analysis shows that porphyrin rings are heavily distorted and exhibit saddled conformations. The Soret and Q bands of two compounds are red-shifted compared to their non-chlorinated counterparts. Theoretical calculations reveal that the optical band gap of TCl _(12)PPH_2 is reduced, whereas that of TCl_(12)PPNi remains almost the same as to its non-chlorinated nickel compound due to the concurrent lowering of HOMO and LUMO energy levels. The frontier molecular orbitals are degenerated due to the decrease of symmetry of the molecules.