Ligand recruitment and spin transitions in the solid-state photochemistry of Fe (III)TPPCl

Aaron S. Rury, Lauren E. Goodrich, Mary Grace Ignacio Galinato, Nicolai Lehnert, Roseanne J. Sension

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6 Scopus citations

Abstract

We report evidence for the formation of long-lived photoproducts following excitation of iron(III) tetraphenylporphyrin chloride (Fe (III)TPPCl) in a 1:1 glass of toluene and CH 2Cl 2 at 77 K. The formation of these photoproducts is dependent on solvent environment and temperature, appearing only in the presence of toluene. No long-lived product is observed in neat CH 2Cl 2 solvent. A 2-photon absorption model is proposed to account for the power-dependent photoproduct populations. The products are formed in a mixture of spin states of the central iron(III) metal atom. Metastable six-coordinate high-spin and low-spin complexes and a five-coordinate high-spin complex of iron(III) tetraphenylporphyrin are assigned using structure-sensitive vibrations in the resonance Raman spectrum. These species appear in conjunction with resonantly enhanced toluene solvent vibrations, indicating that the Fe (III) compound formed following photoexcitation recruits a toluene ligand from the surrounding environment. Low-temperature transient absorption (TA) measurements are used to explain the dependence of product formation on excitation frequency in this photochemical model. The six-coordinate photoproduct is initially formed in the high-spin Fe (III) state, but population relaxes into both high-spin and low-spin state at 77 K. This is the first demonstration of coupling between the optical and magnetic properties of an iron-centered porphyrin molecule.

Original languageEnglish (US)
Pages (from-to)8321-8333
Number of pages13
JournalJournal of Physical Chemistry A
Volume116
Issue number32
DOIs
StatePublished - Aug 16 2012

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry

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