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Issue 42, 2010
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Double-resonance spectroscopy of the jet-cooled free base and Cu(ii) complex of protoporphyrin IX

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Abstract

The excited-state dynamics of porphyrins, and related compounds, impact on their applications as photosensitizers for tumor-targeting drugs and solar cells. Many researchers have examined the influence of non-planar distortions in the ground-state geometry on the properties of photoexcited states. We have identified the added importance of conformational changes in the excited state, relative to the initial geometry, on the resulting decay pathways. The ground-state structure and photodynamics of free-base and Cu(II) complexes of protoporphyrin IX, laser desorbed into a cold supersonic expansion, have been investigated using infrared ion-dip spectroscopy combined with density-functional theory calculations. The vibrational bands associated with the N–H stretching mode of the free base are broader in the first electronically excited state, accessed via the Q band of protoporphyrin IX, than the corresponding bands in the ground-electronic state. This is attributed to rapid intersystem crossing in the excited state promoted by extension of the N–H bonds. Our calculations show that the stretching modes are highly anharmonic, which suggests the likelihood that other conformational changes are also taking place in the excited state.

Graphical abstract: Double-resonance spectroscopy of the jet-cooled free base and Cu(ii) complex of protoporphyrin IX

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Article information


Submitted
14 Jun 2010
Accepted
19 Aug 2010
First published
20 Sep 2010

Phys. Chem. Chem. Phys., 2010,12, 14076-14081
Article type
Paper

Double-resonance spectroscopy of the jet-cooled free base and Cu(II) complex of protoporphyrin IX

J. M. Beames, A. J. Hudson, T. D. Vaden and J. P. Simons, Phys. Chem. Chem. Phys., 2010, 12, 14076
DOI: 10.1039/C0CP00874E

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