HYDROGEN BONDING IN GROUND AND EXCITED STATES OF PYRAZINE

Author Institution: Department of Chemistry, Tufts University; Department of Chemistry, Williams CollegeIn the complex of pyrazine-hexafluoroisopropanol, the $0_{0}^{0}$ of the lowest $n\pi^{\ast}$ transition is as sharp as that of the parent and is blue-shifted $408 cm^{-1}$, with lifetime shorter than 3 ns. This blue shift roughly gives the hydrogen bond energy in the $S_{1}(nx^{\ast})$ of $2740 cm^{-1}$. Our interpretation to the short lifetime is that due to the large stabilization of the hydrogen bond, the $S_{1}$ is below $T_{2}(xx^{\ast})$. which breaks down the coupling between them, resulting in the quenching of the slow component of fluorescenc