The excited state dipole moment of anisole has been determined in the gas phase from electronic Stark spectroscopy and in solution using thermochromic shifts in ethyl acetate. Electronic excitation increases the anisole dipole moment in the gas phase from 1.26 D in the ground state to 2.19 D in the electronically excited singlet state, leaving the orientation of the dipole moment practically unchanged. These values are compared to solution phase dipole moments. From variation of the fluorescence emission and absorption maxima with temperature, an excited state dipole moment of 2.7 D was determined. Several solvent polarity functions have been used in combination with experimentally determined cavity volumes at the respective temperatures. Both gas phase and condensed phase experimental dipole moments are compared to the results of ab initio calculations at the CC2 level of theory, using the cc-pVTZ basis set for the isolated molecule and using the COnductor-like Screening MOdel (COSMO), implemented in Turbomole, for the solvated anisole molecule.
We present the temperature dependent density, fluorescence emission and absorption spectroscopic data, that are needed for an evaluation of the excited state dipole moment of anisole in ethyl acetate via the methods of thermochromic shifts. Furthermore, the rotationally resolved electronic Stark spectrum of anisole in the molecular beam is presented. Finally, the Cartesian coordinates of the CC2/cc-pVTZ optimized structures of anisole are given in bohr units. For details about the evaluation of the dipole moments from the given data, see the connected research article: Lindic et al. (2018) [1].
The method basically combines the existing ideas of excited state dipole moment determination via thermochromic fluorescence spectroscopy with the determination of the solvent cavity volume via concentration dependent density measurements of the solution densities at different weight fractions. Additionally, the determination of the cavity volume in dependence of the solvent temperature is included here, which provides a better accuracy of the excited state dipole moment determination. With this step two major sources of errors are eliminated: the use of the very imprecise Onsager radius and the assumption, that the cavity size is temperature independent.
Thermochromic absorption and fluorescence spectroscopy.
Cavity volume determination by density measurements.
Temperature dependent cavity volume determination.
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