EPR of Photoexcited Triplet-State Acceptor Porphyrins.

Journal Article (Journal Article)

The photoexcited triplet states of porphyrin architectures are of significant interest in a wide range of fields including molecular wires, nonlinear optics, and molecular spintronics. Electron paramagnetic resonance (EPR) is a key spectroscopic tool in the characterization of these transient paramagnetic states singularly well suited to quantify spin delocalization. Previous work proposed a means of extracting the absolute signs of the zero-field splitting (ZFS) parameters, D and E , and triplet sublevel populations by transient continuous wave, hyperfine measurements, and magnetophotoselection. Here, we present challenges of this methodology for a series of meso -perfluoroalkyl-substituted zinc porphyrin monomers with orthorhombic symmetries, where interpretation of experimental data must proceed with caution and the validity of the assumptions used in the analysis must be scrutinized. The EPR data are discussed alongside quantum chemical calculations, employing both DFT and CASSCF methodologies. Despite some success of the latter in quantifying the magnitude of the ZFS interaction, the results clearly provide motivation to develop improved methods for ZFS calculations of highly delocalized organic triplet states.

Full Text

Duke Authors

Cited Authors

  • Redman, AJ; Moise, G; Richert, S; Viere, EJ; Myers, WK; Therien, MJ; Timmel, CR

Published Date

  • June 2021

Published In

Volume / Issue

  • 125 / 21

Start / End Page

  • 11782 - 11790

PubMed ID

  • 34276860

Pubmed Central ID

  • PMC8279703

Electronic International Standard Serial Number (EISSN)

  • 1932-7455

International Standard Serial Number (ISSN)

  • 1932-7447

Digital Object Identifier (DOI)

  • 10.1021/acs.jpcc.1c03278

Language

  • eng