Knowledge Bank

Rotationally resolved fluorescence excitation spectra of mono- and disolvated water and ammonia complexes of 2-pyridone (2PY) have been obtained. The inertial parameters derived by fitting the spectra of several isotopically labeled species have been used to determine the effective structures of the complexes, shown below. [FIGURE] The monosolvated 2PY-water complex has hydrogen bond lengths and angles that are surprisingly rigid. The monosolvated ammonia complex exhibits $NH3$ hindered internal rotation with ground and excited state barriers of $V3=300cm-1$ and $V3=70cm-1$, respectively. The barriers are thought to be due to hydrogen bonding between the H atoms of ammonia and the carbonyl oxygen. No internal rotation exists for either disolvated species of 2PY. However, non-planarity of the bridging hydrogen gives rise to separate conformers in both complexes. The dynamical properties of the complexed structures will be discussed.