Ground and Excited State Electronic Properties of Halogenated Tetraarylporphyrins. Tuning the Building Blocks for Porphyrin-based Photonic Devices

Sung Ik Yang, Jyoti Seth, Jon Paul Strachan, Steve Gentemann, Dongho Kim, Dewey Holten, Jonathan S. Lindsey, David F. Bocian

Research output: Contribution to journalArticle

132 Citations (Scopus)

Abstract

The rational design of molecular photonic devices relies on the ability to select components with predictable electronic structure, excited state lifetimes and redox chemistry. Electronic communication in multiporphyrin arrays depends critically on the relative energies and electron density distributions of the frontier molecular orbitals, especially the energetically close highest occupied molecular orbitals (a2u and a1u). To explore how these ground and excited state properties can be modulated, we have synthesized and characterized 40 free base (Fb), magnesium and zinc tetraarylporphyrins. The porphyrins bear meso-substituents with the following substitution patterns: (1) four identical substituents (phenyl, o-chlorophenyl, p-chlorophenyl, o,o′-difluorophenyl, pentafluorophenyl, mesityl); (2) one, two, three or four o,o′-dichlorophenyl substituents; (3) one p-ethynylphenyl group and three mesityl or pentafluorophenyl groups; (4) one p-ethynyl-o,o′-dichlorophenyl or p-ethynyl-o,o′-dimethylphenyl and three phenyl groups. For each neutral complex the ground state electronic properties were investigated using electrochemical methods and optical absorption spectroscopy. Similarly the absorption, emission, and relaxation properties of the lowest singlet excited state were probed by time-resolved absorption and fluorescence methods. Each oxidized complex was investigated by static absorption and liquid and frozen solution EPR spectroscopy. The collective results of these investigations have provided insights into the direct (orbital overlap) and indirect (inductive/conjugative) mechanisms by which halogenated phenyl rings influence the static and dynamic electronic properties of neutral and oxidized porphyrinic chromophores. Three key findings are as follows. (1) The effective electron-withdrawing strength of halogenated phenyl rings required to reverse the ordering of the a2u and a1u HOMOs in Mg versus Zn tetraarylporphyrins has been elucidated. (2) Appropriate halogenation can significantly increase the excited state lifetime of a Zn porphyrin relative to the unsubstituted complex. (3) Halogenation can be used to modulate redox potentials in a manner that complements the enhancement of other electronic properties. The insights gained from study of this library of porphyrins provide a foundation for tuning the electronic properties of monomeric porphyrins as building blocks for multichromophoric assemblies in optoelectronics and other applications.

Original languageEnglish
Pages (from-to)117-147
Number of pages31
JournalJournal of Porphyrins and Phthalocyanines
Volume3
Issue number2
DOIs
Publication statusPublished - 1999 Jan 1

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Photonic devices
Porphyrins
Excited states
Electronic properties
Ground state
Tuning
Halogenation
Molecular orbitals
Electronic density of states
Chromophores
Absorption spectroscopy
Optoelectronic devices
Light absorption
Magnesium
Electronic structure
Paramagnetic resonance
Zinc
Substitution reactions
Fluorescence
Spectroscopy

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Yang, Sung Ik ; Seth, Jyoti ; Strachan, Jon Paul ; Gentemann, Steve ; Kim, Dongho ; Holten, Dewey ; Lindsey, Jonathan S. ; Bocian, David F. / Ground and Excited State Electronic Properties of Halogenated Tetraarylporphyrins. Tuning the Building Blocks for Porphyrin-based Photonic Devices. In: Journal of Porphyrins and Phthalocyanines. 1999 ; Vol. 3, No. 2. pp. 117-147.
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Ground and Excited State Electronic Properties of Halogenated Tetraarylporphyrins. Tuning the Building Blocks for Porphyrin-based Photonic Devices. / Yang, Sung Ik; Seth, Jyoti; Strachan, Jon Paul; Gentemann, Steve; Kim, Dongho; Holten, Dewey; Lindsey, Jonathan S.; Bocian, David F.

In: Journal of Porphyrins and Phthalocyanines, Vol. 3, No. 2, 01.01.1999, p. 117-147.

Research output: Contribution to journalArticle

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AU - Yang, Sung Ik

AU - Seth, Jyoti

AU - Strachan, Jon Paul

AU - Gentemann, Steve

AU - Kim, Dongho

AU - Holten, Dewey

AU - Lindsey, Jonathan S.

AU - Bocian, David F.

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