Consistent assignment of the vibrations of symmetric and asymmetric meta-disubstituted benzenes

Abstract

The assignment of vibrational structure in spectra gives valuable insights into geometric and electronic structure changes upon electronic excitation or ionization; particularly when such information is available for families of molecules. We give a description of the phenyl-ringlocalized vibrational modes of the ground (S0) electronic states of sets of meta-disubstituted benzene molecules including both symmetrically-and asymmetrically-substituted cases. As in our earlier work on monosubstituted benzenes [A. M. Gardner and T. G. Wright. J. Chem.Phys. 135 ( 2011) 114305], para-disubstituted benzenes [A

Jet-Cooled Spectroscopy ofortho-Hydroxycyclohexadienyl Radicals

“…The formation of local modes which break the symmetry of the molecule has been observed previously by Kemp et al In their studies on meta-disubstituted benzenes, they observed that, upon increasing the mass of one substituent, the symmetric and asymmetric stretches of the C–X bonds (where X represents the substituent) eventually became local modes, where only one stretching mode was active and the other near stationary, and vice versa …”

“…The formation of local modes which break the symmetry of the molecule has been observed previously by Kemp et al In their studies on meta-disubstituted benzenes, they observed that, upon increasing the mass of one substituent, the symmetric and asymmetric stretches of the C−X bonds (where X represents the substituent) eventually became local modes, where only one stretching mode was active and the other near stationary, and vice versa. 30 Another, smaller, anomaly is mode ν 32 ′ , which contains the character of both the a″ mode ν 32 (60%) and the a′ mode ν 23 ″ (19%). Upon visual inspection, this mode is clearly dominated by the asymmetric out-of-plane ring distortion, along with large amplitudes of CH/CH 2 /OH wag.…”

Electronic, vibrational, and torsional couplings in N-methylpyrrole: Ground, first excited, and cation states

“…This is analogous to a scheme employed for monosubstituted benzenes 34 and extended to the disubstituted benzenes. [35][36][37] For NMP, the Pi labels employed are based on the motions of the vibrations in N-fluoropyrrole-further details and vibrational mode diagrams can be found in Ref. 33.…”