Alkyne-Bridged Multi[Copper(II) Porphyrin] Structures: Nuances of Orbital Symmetry in Long-Range, Through-Bond Mediated, Isotropic Spin Exchange Interactions.

Journal Article

Spin and conformational dynamics in symmetric alkyne-bridged multi[copper(II) porphyrin] structures have been studied in toluene solution at variable temperature using steady-state electron paramagnetic resonance (EPR) spectroscopy. Comparison of the dimer EPR spectra to those of Cu porphyrin monomers shows evidence of an isotropic exchange interaction (Javg) in these biradicaloid structures, manifested by a significant line broadening in the dimer spectra. The extent line broadening depends on molecular structure and temperature, suggesting Javg is modulated by conformational dynamics that impact the torsional angle distribution between the porphyrin-porphyrin least-squares planes. Computational simulation of the experimental EPR spectra, using a developed algorithm for J modulation in flexible organic biradicals, supports this hypothesis. Comparison of ethyne and butadiyne alkyne bridges reveals remarkable sensitivity to orbital interactions between the spacer and the metal, reflected in measurements of Javg as a function of temperature. The results suggest orbital symmetry relationships may be more important than recognized in design of optimized molecular spintronic devices.

Full Text

Duke Authors

Cited Authors

  • Wang, R; Brugh, AM; Rawson, J; Therien, MJ; Forbes, MDE

Published Date

  • July 2017

Published In

Volume / Issue

  • 139 / 29

Start / End Page

  • 9759 - 9762

PubMed ID

  • 28578583

Electronic International Standard Serial Number (EISSN)

  • 1520-5126

International Standard Serial Number (ISSN)

  • 0002-7863

Digital Object Identifier (DOI)

  • 10.1021/jacs.7b03252

Language

  • eng