Excited state dipole moments of anisole in gas phase and solution

Abstract

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.

Additional data for evaluation of the excited state dipole moments of anisole

“…The density ρ of the solution of anisole in ethyl acetate was measured at different mass fractions w in a temperature range of 263 K and 343 K with an increment of 2 K using a density meter (Anton Paar DMA4500M). The cavity volume is determined from the slope of the graph of ρ -1 vs. the mole fraction w at each temperature [1] . A plot of the inverse density of the solution of anisole in ethyl acetate versus the weight fraction of anisole along with the linear fit of the data is shown in Fig.…”

“…Absorption spectra of anisole, dissolved in ethyl acetate have been recorded in a temperature range of − 10 °C and + 70 °C with 5 °C increment using a Varian Cary 50 Scan UV spectrometer [1] . A custom built coolable and heatable cell holder has been constructed using a pair of Peltier elements from Uwe Electronics GmbH.…”

“…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] .…”

Determination of excited state dipole moments in solution via thermochromic methods

“…11 and 12 and (8) , (9) , (10) , (11) are summarized in Tab. 1 along with calculated dipole moment changes from ab initio calculations and the gas phase value (for anisole) from rotationally resolved electronic Stark spectroscopy [19] .…”

“…We have chosen two different systems to describe the method in detail. Anisole [19 , 20] and 2-((4-methoxyphenyl)ethynyl)-3-(1-methyl-1H-indol-3-yl)quinoxaline (Q1) [21] , both in ethyl acetate solution have been chosen as examples for medium size dipole moment and dipole moment change (anisole) and large dipole moment and dipole moment change upon excitation for Q1.…”