Abstract
Linear π-conjugated porphyrin oligomers are of significant current interest due to their potential applications as molecular wires. In this study we investigate electronic communication in linear butadiyne-linked copper porphyrin oligomers by electron paramagnetic resonance (EPR) spectroscopy via measurement of the exchange interaction, J, between the copper(ii) centers. The contributions of dipolar and exchange interactions to the frozen solution continuous wave (cw) EPR spectra of the compounds with two or more copper porphyrin units were explicitly accounted for in numerical simulations using a spin Hamiltonian approach. It is demonstrated that a complete numerical simulation of the powder spectrum of a large spin system with a Hamiltonian dimension of 26244 and beyond can be made feasible by simulating the spectra in the time domain. The exchange coupling in the Cu2 dimer (Cu⋯Cu distance 1.35 nm) is of the order of tens of MHz (Ĥ = -2JS1·S2) and is strongly modulated by low-energy molecular motions such as twisting of the molecule.
| Original language | English |
|---|---|
| Pages (from-to) | 16057-16061 |
| Number of pages | 5 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 19 |
| Issue number | 24 |
| Early online date | 9 Jun 2017 |
| DOIs | |
| Publication status | E-pub ahead of print - 9 Jun 2017 |
Funding
We thank the EPSRC (EPL011972/1) and the ERC (grant 320969) for financial support. The authors would like to acknowledge the use of the University of Oxford Advanced Research Computing (ARC) facility in carrying out this work (http://dx.doi.org/10.5281/ zenodo.22558). The authors also acknowledge the use of the IRIDIS High Performance Computing Facility, and associated support services at the University of Southampton, in the completion of this work. We thank the EPSRC UK National Mass Spectrometry Facility at Swansea University for MALDI spectra.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry