Investigations of the Influence of Molecular Geometry on the Spectroscopic and Photochemical Properties of α-Oxo[1.n]paracyclophanes (Cyclophanobenzophenones)

Nicholas J. Turro, Ian R. Gould, Jennifer Liu, William S. Jenks, Heinz Staab, Reinhold Alt

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

The spectroscopic and photochemical properties of a family of α-oxo[1.n]Paracyclophanes (8-12) for n = 8–12, respectively) have been investigated. Compared to a model structure possessing a nominal T1(nπ*) state (4,4'-dimethylbenzophenone, DM-BZ), photochemical and photophysical evidence is presented that the nπ* character of T1 decreases as the cyclophane ring size decreases. For example, the rate constants for hydrogen atom abstraction from 1,4-cyclohexadiene in acetonitrile are 1.6 X 108, 0.93 X 108, 0.30 X 108, 0.06 X 108, and 0.04 X 108M-1s-1 for triplet 12–8, respectively, a result consistent with decreasing nπ* character and decreasing reactivity toward hydrogen atom abstraction with decreasing value of n. The spectroscopic properties (vibrational structure of the phosphorescence spectrum, phosphorescence lifetime, phosphorescence excitation spectra, triplet-triplet absorption spectra) also vary in a manner consistent with decreasing nπ* character as the cyclophane ring size decreases.

Original languageEnglish (US)
Pages (from-to)6378-6383
Number of pages6
JournalJournal of the American Chemical Society
Volume111
Issue number16
DOIs
StatePublished - Aug 1989
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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