Vibrational Stark Effect (VSE), the characteristic IR band shift in response to an electric field, is an effective methodology to study changes in the electrostatic environment around a probe. In the event of hydrogen bonding with the environment, experiments require additional NMR studies to sort the electrostatics from other interactions that contribute to observed Stark shifts.  We use QM/MM simulations, involving ab initio methods with the CHARMM additive force field, to calculate the stark shift of a methyl-thiocyanate (MtCN) probe between an aprotic (dimethyl sulfoxide) and protic (water, formamide or trifluoroethanol) solvent. By including the interacting solvent molecule in QM calculations, our methods inherently account for all specific chemical interactions. Our simulations satisfactorily reproduce the experimentally observed nitrile blue shift from aprotic to protic solvents. Hence, QM/MM simulations represent a direct technique to calculate VSE and may be employed to probe heterogeneous environments such as proteins and nucleic acids.

Quantum mechanical/molecular mechanical simulations: An efficient strategy to calculate vibrational Stark shift

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.