First-Principles Discrete Model of the Vibrational Solvatochromism based on Effective Fragment Potentials
MQM2016
Short abstract:
Over the last two decades, the vibrational solvatochromism of small infrared (IR) probes
has been of great interest for the chemistry community because it can be used to extract
the critical (spatial and dynamical) information about the local molecular environments in
bulk solutions and in biopolymers.[1,2] The combination of a vibrational solvatochromism
model with appropriate ultrafast vibrational spectroscopy tool opens a window to look for
processes within 0.1-100 ps time resolution.[2] However, in order to successfully use the
IR probes for that purpose, it is crucial to understand the underlying physics of the
vibrational frequency shift and transition dipole moment changes upon solvation process.
The vibrational solvatochromism models that were used so far were limited to the
Coulombic interactions treated semi-empirically.[2,3] Here, we show the ab initio model
which is capable of reproducing experimental vibrational frequency shifts of localized
vibrational chromophores.[4] Our theory is fully derived from the gas-phase properties of
solute and solvent molecules and does not involve any empirical parameterization. In
particular, our results show that exchange-repulsion induced blue shifts are strong,
especially in the case of H-bonding. In addition, dispersion effects contribute to strong red
shifts. The neglect of these effects leads to breakdown of the vibrational Stark model in
protic environments.
References:
[1] J. Ma et al., Annu. Rev.
Phys. Chem., 2015, 66, 357-377
[2] H, Kim and M. Cho, Chem. Rev., 2013, 113,
5817-5847
[3] S. D. Fried and S. G. Boxer, Acc. Chem. Res., 2015, 48,
998-1006
[4] B. Błasiak and M. Cho, J. Chem. Phys., 2015, 143, 164111