## LSU Historical Dissertations and Theses

1990

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Chemistry

Robert V. Nauman

#### Abstract

This work includes: (1) a search for charge transfer interaction involving hexamethyldipyrromethene (HL) as a donor; (2) a spectroscopic study of hexamethyldipyrromethene anion (L$\sp-$), and, (3) an investigation of the spectroscopic characteristic of the copper chelate CuL$\sb2$. There are presented reactions in which HL may react with some electron acceptors. It is reported that TCNE interacts with HL to form a 1:1 complex that has an equilibrium constant of (2.5 0.9) $\times$ 10$\sp{15}$. Spectroscopic results indicate that haloacetones also interact with HL. Hexamethyldipyrromethene is a molecule that consists of two methyl substituted pyrrole rings joined by means of a vinyl bridge. Its anion has been obtained by means of different reagents in various solvents and has been studied by using several instrumental techniques. Spectroscopic features such as visible absorption band maxima and $\sp1$H NMR chemical shifts depend on the counter ion (an alkali metal ion, Y$\sp{+}$). A study of the novel Y$\sp{+}$L$\sp{-}$ species allows a characterization of the L$\sp{-}$ moiety free from interligand peturbation or other orbitals that are present in the transition metal complexes (ML$\sb2$). In this study; characterization of the Y$\sp{+}\rm L\sp{-}$ species by means of visible absorption, FT-IR, luminescence, and high resolution NMR techniques is presented. It is concluded that the Y$\sp{+}$L$\sp{-}$ species constitute bridged complexes. In particular, a $\sp7$Li NMR downfield chemical shift of 1.66 ppm showed that the cation in Li $\sp{+}$L$\sp{-}$ is indeed coordinated to the nitrogens. An equilibrium between two Y$\sp{+}$L$\sp{-}$ species has been clearly demonstrated by means of NMR and visible absorption spectra. A spectroscopic study of the CuL$\sb2$ complex is also included. This species may display a unique visible absorption band or two bands; the absorption depends on the method of synthesis. Qualitative experiments which seem to indicate that both spectra arise from a single molecule in two different geometries are presented.

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