title: Controllable and reversible inversion of the electronic structure in nickel N-confused porphyrin: a case when MCD matters.
abstract: Nickel N-confused tetraphenylporphyrin, 1, and nickel 2-N-methyl-N-confused tetraphenylporphyrin, 1-Me, exhibit unusual sign-reversed (positive-to-negative intensities in ascending energy) MCD spectra in the Q-type band region, suggesting a rare ΔHOMO < ΔLUMO relationship between π and π* MOs in the porphyrin core. Simple and reversible deprotonation of the external NH proton in 1 dramatically changes the electronic structure of the porphyrin core into the ΔHOMO > ΔLUMO combination characteristic for the meso-(tetraaryl)porphyrins. DFT, time-dependent DFT, and semiempirical ZINDO/S calculations on 1, 1-Me, and 1(-) confirm the experimental finding and successfully explain the MCD pattern in the target compounds.
authors.affiliation: Department of Chemistry, University of Akron, Akron, Ohio 44325-3601, USA.
authors.forename: Saovalak
authors.initials: S
authors.lastname: Sripothongnak
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Ziegler
authors.forename: Michael R
authors.initials: MR
authors.lastname: Dahlby
authors.forename: Victor N
authors.initials: VN
authors.lastname: Nemykin