title: Combined MCD/DFT/TDDFT Study of the Electronic Structure of Axially Pyridine Coordinated Metallocorroles.
abstract: A series of metallocorroles were investigated by UV-vis and magnetic circular dichroism spectroscopies. The diamagnetic distorted square-pyramidal main-group corrole Ga(tpfc)py (2), the diamagnetic distorted octahedral transition-metal adduct Co(tpfc)(py)2 (3), and paramagnetic distorted octahedral transition-metal complex Fe(tpfc)(py)2 (4) [H3tpfc = tris(perfluorophenyl)corrole] were studied to investigate similarities and differences in the electronic structure and spectroscopy of the closed- and open-shell metallocorroles. Similar to the free-base H3tpfc (1), inspection of the MCD Faraday B-terms for all of the macrocycles presented in this report revealed that a ΔHOMO < ΔLUMO [ΔHOMO is the energy difference between two highest energy corrole-centered π-orbitals and ΔLUMO is the energy difference between two lowest energy corrole-centered π*-orbitals originating from ML ± 4 and ML ± 5 pairs of perimeter] condition is present for each complex, which results in an unusual sign-reversed sequence for π-π* transitions in their MCD spectra. In addition, the MCD spectra of the cobalt and the iron complexes were also complicated by a number of charge-transfer states in the visible region. Iron complex 4 also exhibits a low-energy absorption in the NIR region (1023 nm). DFT and TDDFT calculations were used to elaborate the electronic structures and provide band assignments in UV-vis and MCD spectra of the metallocorroles. DFT and TDDFT calculations predict that the orientation of the axial pyridine ligand(s) has a very minor influence on the calculated electronic structures and absorption spectra in the target systems.
authors.forename: Hannah M
authors.initials: HM
authors.lastname: Rhoda
authors.affiliation: †Department of Chemistry, University of Akron, 190 E. Buchtel Common, Akron, Ohio 44325-3601, United States.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Crandall
authors.affiliation: §Department of Chemistry, Colgate University, Hamilton, New York 13346, United States.
authors.forename: G Richard
authors.initials: GR
authors.lastname: Geier
authors.affiliation: †Department of Chemistry, University of Akron, 190 E. Buchtel Common, Akron, Ohio 44325-3601, United States.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ziegler
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin