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The conformational space of tryptamine has been thoroughly investigated using rotationally resolved laser-induced fluorescence spectroscopy. Six conformers could be identified on the basis of the inertial parameters of several deuterated isotopomers. Upon attaching a single water molecule, the conformational space collapses into a single conformer. For the hydrogen-bonded water cluster, this conformer is identified unambiguously as tryptamine A. In the complex, the water molecule acts as proton donor with respect to the amino group. An additional interaction with one of the aromatic C-H bonds selectively stabilizes the observed conformer more than all other conformers. Ab initio calculations confirm much larger energy differences between the conformers of the water complex than between those of the monomers.

The rotationally resolved UV spectra of the electronic origins of five isotopomers of the phenol dimer have been measured. The complex spectra are analyzed using a fitting strategy based on a genetic algorithm. The intermolecular geometry parameters have been determined from the inertial parameters for both electronic states and compared to the results of ab initio calculations. In the electronic ground state, a larger hydrogen-bond length than in the ab initio calculations is found together with a smaller tilt angle of the aromatic rings, which shows a more pronounced dispersion interaction. In the electronically excited state, the hydrogen-bond length decreases, as has been found for other hydrogen-bonded clusters of phenol, and the two aromatic rings are tilted less toward each other.

Meerts (2004) Determination of the structure of 7-azaindole in the electronic ground and excited state using high-resolution ultraviolet spectroscopy and an automated assignment based on a genetic algorithm,The rotationally resolved electronic spectra of four different isotopomers of 7-azaindole (IH-pyrrolo(2,3-b)pyridine) have been measured in order to obtain the geometric structure in the electronic ground and excited state. The electronic origins of the rotationally resolved UV spectra overlap strongly and an assigned fit to single rovibronic lines is hardly possible. We performed an automatized fit based on the genetic algorithm to assign all four spectral components simultaneously and extract the molecular constants. The resulting inertial parameters were used to determine the structure of 7-azaindole in the ground and electronically excited state. It was found that the pyridine moiety expands on electronic excitation, while the pyrrole ring showed only mino_r eometricshanges. From the hybrid-type F spectra of three isotopomers, the direction of the A ~' ( m * ) -x ' A ' transition dipole moment for the transition was found to be -21". Evaluation of the individual line shapes yielded an excited state lifetime of 2.55 ns for 7-azaindole.

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