Investigations of the influence of molecular geometry on the spectroscopic and photochemical properties of α-oxo[1.n]paracyclophanes (cyclophanobenzophenones)

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

Research output: Contribution to journalArticle

17 Citations (Scopus)

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 × 108, 0.93 × 108, 0.30 × 108, 0.06 × 108, and 0.04 × 108 M-1 s-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
StatePublished - 1989
Externally publishedYes

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Phosphorescence
Hydrogen
Geometry
Atoms
Model structures
Acetonitrile
Absorption spectra
Rate constants
1,4-cyclohexadiene
acetonitrile

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Investigations of the influence of molecular geometry on the spectroscopic and photochemical properties of α-oxo[1.n]paracyclophanes (cyclophanobenzophenones). / Turro, Nicholas J.; Gould, Ian; Liu, Jennifer; Jenks, William S.; Staab, Heinz; Alt, Reinhold.

In: Journal of the American Chemical Society, Vol. 111, No. 16, 1989, p. 6378-6383.

Research output: Contribution to journalArticle

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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 × 108, 0.93 × 108, 0.30 × 108, 0.06 × 108, and 0.04 × 108 M-1 s-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.",
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AU - Gould, Ian

AU - Liu, Jennifer

AU - Jenks, William S.

AU - Staab, Heinz

AU - Alt, Reinhold

PY - 1989

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N2 - 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 × 108, 0.93 × 108, 0.30 × 108, 0.06 × 108, and 0.04 × 108 M-1 s-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.

AB - 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 × 108, 0.93 × 108, 0.30 × 108, 0.06 × 108, and 0.04 × 108 M-1 s-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.

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