HYDROGEN-BONDING INDUCED PHOSPHORESCENCE IN N-HETEROCYCLES

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1974

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Ohio State University

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Abstract

While most N-heterocycles phosphoresce with moderate yields in a variety of matrices, a few, particularly those with ortho-nitrogens, show a striking solvent effect, A dramatic appearance of phosphorescence from non-emitting, hydrocarbon solutions at $77^{\circ} K$ of cinnoline, 4-methylcinnoline, phthalazine, and 9,10-diazaphenanthrene is seen with the addition of small amounts of strongly hydrogen-bonding alcohols. An investigation of the role of hydrogen-bonding in the luminescence behavior of these molecules, along with appropriate spectral data is presented which suggests chat in hydrocarbon solutions a near degeneracy exists between the lowest $\pi\pi^{*}$ and a higher $n\pi^{*}$ triplet, and that the Low yield of phosphorescence results from a rapid triplet radiationless decay. The pseudo-Jahn-Teller effect is offered as an explanation of this fast decay.

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This work was supported by the AEC.
Author Institution: Department of Chemistry, University of California; Department of Chemistry, Florida State University

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