Chemistry and Chemical Biology ETDs

Publication Date

5-12-1961

Abstract

A variety of lanthanide chelates were prepared for preliminary luminescence studies under excitation by ultraviolet light. From these, chelates of benzoylacetone, dibenzoylmethane, tribenzoylmethane, and 8-hydroxyquinoline were selected for more extensive investigation. Energies of the lowest excited singlet and triplet states of the chelates were determined. Average values of 24,500 cm-1 and 20,500 cm-1 respectively were obtained for the dibenzoylmethides and 24,400 cm-1 and 21,450 cm-1 for the benzoylacetonates. Only small variations of a few hundred wavenumbers in the positions of the excited states were found as the chelated ion was varied. This investigation in conjunction with complementary work by others has shown that intramolecular energy transfer from the excited complex molecule to the chelated lanthanide ion, resulting in line emission from the ion, does not occur when the emitting triplet state of the molecule is very far below the resonance level of the ion. It is concluded that the energy transfer process proceeds via the lowest triplet state or some other nearby excited state. Possible mechanisms for the transfer process are discussed. The Förster mechanism and the charge transfer mechanism suggested by Sponer have been discarded in favor of an electron exchange mechanism in which the total spin is conserved. Expressions for determining the probability constants for radiationless processes within complex molecules from quantum yield measurements are derived. Measurements and partial analyses of the vibrational band structure of the fluorescence and phosphorescence emissions from the chelates have been performed. The more intense bands appeared at intervalsof between 1000 to 1300 cm-1. These progressions are probably harmonics of carbon-carbon or carbon-oxygen fundamental modes. Spectral lines originating from the 4f electronic states of lanthanide ions coupled with vibrational modes of the chelate molecules have been photographed. Vibrational progressions of between 40 and 60 cm-1 have been measured. These vibrations are of somewhat higher frequencies than those reported previously for hydrated neodymium salts; however, they are on the right order of magnitude expected for metal-oxygen vibrations. Line emission was exhibited by chelated holmium and thulium ions. Emission from these coordinated ions has not been reported previously. Prominent lines obtained from holmium trisbenzoylacetonate were found at 6588 and 6601 A. Those obtained from thulium trisbenzcylacetonate were located at 4712, 4729, 4743, 4785, 4816, 6496, and 6617 A.

Language

English

Document Type

Dissertation

Degree Name

Chemistry

Level of Degree

Doctoral

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Glenn Arthur Crosby

Second Committee Member

Jesse LeRoy Riebsomer

Third Committee Member

Guido Herman Daub

Fourth Committee Member

Abraham Rosenzweig

Fifth Committee Member

Milton Kahn

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