Solvent dependent triplet state delocalization in a co-facial porphyrin heterodimer

Susanna Ciuti, Jacopo Toninato, Antonio Barbon, Niloofar Zarrabi, Prashanth K. Poddutoori, Art van der Est, Marilena Di Valentin

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The excited triplet state of a cofacial aluminum(iii) porphyrin-phosphorus(v) porphyrin heterodimer is investigated using transient EPR spectroscopy and quantum chemical calculations. In the dimer, the two porphyrins are bound covalently to each other via a μ-oxo bond between the Al and P centres, which results in strong electronic interaction between the porphyrin rings. The spin polarized transient EPR spectrum of the dimer is narrower than the spectra of the constituent monomers and the magnitude of the zero-field splitting parameter D is solvent dependent, decreasing as the polarity of the solvent increases. The quantum chemical calculations show that the spin density of the triplet state is delocalized over both porphyrins, while magnetophotoselection measurements reveal that, in contrast to the value of D, the relative orientation of the ZFS axes and the excitation transition dipole moments are not solvent dependent. Together the results indicate that triplet state wavefunction is delocalized over both porphyrins and has a modest degree of charge-transfer character that increases with increasing solvent polarity. The sign of the spin polarization pattern of the dimer triplet state is opposite to that of the monomers. The positive sign of D predicted for the monomers and dimer by the quantum chemical calculations implies that the different signs of the spin polarization patterns is a result of a difference in the spin selectivity of the intersystem crossing.

Original languageEnglish (US)
Pages (from-to)30051-30061
Number of pages11
JournalPhysical Chemistry Chemical Physics
Volume24
Issue number48
DOIs
StatePublished - Nov 21 2022

Bibliographical note

Funding Information:
This work was supported by Grant-in-Aid (GIA No. 380228 to PPK) from the University of Minnesota Duluth and by an NSERC Discovery Grant (2015-04021) to AvdE. This work was made possible by the facilities of the Shared Hierarchical Academic Research Computing Network (SHARCNET: http://www.sharcnet.ca) and Compute/Calcul Canada. Financial support to MDV and AB (Biomolecular DSSCs Project from Interdepartmental Center Giorgio Levi Cases for Energy Economics and Technology) is gratefully acknowledged.

Funding Information:
This work was supported by Grant-in-Aid (GIA No. 380228 to PPK) from the University of Minnesota Duluth and by an NSERC Discovery Grant (2015-04021) to AvdE. This work was made possible by the facilities of the Shared Hierarchical Academic Research Computing Network (SHARCNET: http://www.sharcnet.ca ) and Compute/Calcul Canada. Financial support to MDV and AB (Biomolecular DSSCs Project from Interdepartmental Center Giorgio Levi Cases for Energy Economics and Technology) is gratefully acknowledged.

Publisher Copyright:
© 2022 The Royal Society of Chemistry.

Fingerprint

Dive into the research topics of 'Solvent dependent triplet state delocalization in a co-facial porphyrin heterodimer'. Together they form a unique fingerprint.

Cite this