Center for Molecular Spectroscopy and Dynamics

Summary:

A vibrational probe based on isonitrile (NC)-derivatized alanine 1 (Ac-Ala(NC)-NHMe) was synthesized and its structure and vibrational dynamics of its NC stretch mode were examined utilizing FTIR and femtosecond IR pump−probe spectroscopy. It has been found that the probe is characterized by very high sensivity to the hydrogen bonding environment and in comparison to nitrile (CN) the NC stretch mode possesses larger dipole strength when attached to the aliphatic group. Its vibrational lifetime is several times longer than that of azido (N3) stretch mode in azido-derivatized IR probes and it was determined to be 5.52 ps and 5.53 ps in D2O and DMF, respectively. Furthermore, to understand the phenomenon of the vibrational solvatochromism of the new IR probe quantum chemistry calculations of methyl isocyanide in water clusters were carried out and the distributed site model for vibrational solvatochromism was applied.

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