title: Magnetic Circular Dichroism Spectroscopy of meso-Tetraphenylporphyrin-Derived Hydroporphyrins and Pyrrole-Modified Porphyrins.
abstract: A large set of free-base and transition-metal 5,10,15,20-tetraphenyl-substituted chlorins, bacteriochlorins, and isobacteriochlorins and their pyrrole-modified analogues were investigated by combined UV-visible spectroscopy, magnetic circular dichroism (MCD), density functional theory (DFT), and time-dependent DFT (TDDFT) approaches and their spectral characteristics were compared to those of the parent compounds, free-base tetraphenylporphyrin 1H2 and chlorin 2H2. It was shown that the nature of the pyrroline substituents in the chlorin derivatives dictates their specific UV-vis and MCD spectroscopic signatures. In all hydroporphyrin-like cases, MCD spectroscopy suggests that the ΔHOMO is smaller than the ΔLUMO for the macrocycle-centered frontier molecular orbitals. DFT and TDDFT calculations were able to explain the large broadening of the UV-vis and MCD spectra of the chlorin diones and their derivatives compared to the other hydroporphyrins and hydroporphyrin analogues. This study contributes to the further understanding of the electronic effects of replacing a pyrrole in porphyrins by pyrrolines or other five-membered heterocycles (oxazoles and imidazoles).
authors.affiliation: Department of Chemistry & Biochemistry, University of Minnesota Duluth , Duluth, Minnesota 55812, United States.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Rhoda
authors.affiliation: Department of Chemistry, University of Connecticut , Unit 3060, Storrs, Connecticut 06269-3060, United States.
authors.forename: Joshua
authors.initials: J
authors.lastname: Akhigbe
authors.affiliation: Department of Chemistry, University of Connecticut , Unit 3060, Storrs, Connecticut 06269-3060, United States.
authors.forename: Junichi
authors.initials: J
authors.lastname: Ogikubo
authors.affiliation: Department of Chemistry & Biochemistry, University of Minnesota Duluth , Duluth, Minnesota 55812, United States.
authors.forename: Jared R
authors.initials: JR
authors.lastname: Sabin
authors.affiliation: Department of Chemistry, University of Akron , Akron Ohio 44325-3601, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ziegler
authors.affiliation: Department of Chemistry, University of Connecticut , Unit 3060, Storrs, Connecticut 06269-3060, United States.
authors.forename: Christian
authors.initials: C
authors.lastname: Brückner
authors.affiliation: Department of Chemistry & Biochemistry, University of Minnesota Duluth , Duluth, Minnesota 55812, United States.
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin
mesh_terms: D002942:Circular Dichroism; D060328:Magnetic Phenomena; D011166:Porphyrins / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D011166:Porphyrins; D011758:Pyrroles