N-H...pi interactions in pyrroles: systematic trends from the vibrational spectroscopy of clusters
Ingo Dauster1, Corey A Rice, Philipp Zielke
1Institut für Physikalische Chemie, Universität Göttingen, Göttingen, Germany.
Abstract:
Pyrrole and some of its methylated derivatives are aggregated in a controlled way in pulsed supersonic jet expansions. The cluster N-H stretching dynamics is studied using FTIR and Raman spectroscopy. Dimers, trimers and tetramers can be differentiated. Systematic trends in the dimer N-H...pi interaction as a function of methyl substitution are identified and explored for predictions. Overtone jet absorption spectroscopy is used to extract anharmonicities for the N-H bond in different environments. The N-H anharmonicity constant increases by 10% upon dimerization. Bulk matrix shifts can be emulated by the formation of Ar-decorated clusters. The experimental results are expected to serve as benchmarks for an accurate ab initio characterization of the N-H...pi hydrogen bond.
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