Conformational property of ethoxybenzene as studied by laser-jet spectroscopy and theoretical calculations

Abstract

The conformational property of ethoxybenzene has been investigated by means of the laser-jet spectroscopy and the theoretical calculations. The quantum-mechanical analysis of the two-dimensional potential surfaces for the S 0 and S 1 states that have been obtained from the DFT and TDDFT calculations, respectively, has been carried out. Its result suggested the existence of the second conformer (gauche) in addition to the main conformer (trans) in the both states, and it was predicted that the 0-0 band of the gauche conformer would appear at about 400 cm -1 lower than that of the trans conformer. The S 1 ← S 0 fluorescence excitation spectrum of jet-cooled ethoxybenzene has been measured. The peak that is assignable to the 0-0 band of the second conformer has been observed, whose spectral position (red-shifted from that of the trans conformer for about 229 cm -1 ) is qualitatively consistent with the theoretical prediction.

Vapor-Phase Raman Spectra, Theoretical Calculations, and the Vibrational and Structural Properties of cis- and trans-Stilbene

“…The elements, B 11 , B 12 , and B 22 , in the kinetic energy term cannot be treated as constants, and their dependences on ϕ 1 and ϕ 2 were approximated by the following expansion, B i , j ( ϕ 1 , ϕ 2 ) = prefix∑ m , n = 0 4 B i , j c m , n ⁡ cos false( 2 m ϕ 1 false) ⁡ cos false( 2 n ϕ 2 false) + prefix∑ m , n = 1 4 B i , j s m , n ⁡ sin false( 2 m ϕ 1 false) ⁡ sin false( 2 n ϕ 2 false) goodbreak0em2em⁣ i , j = false( 1 , 1 false) , false( 1 , 2 false) , false( 2 , 2 false) The expansion coefficients, B i,j c m,n and B i,j s m,n , are functions of moments of inertia of the molecule and internal rotors (i.e., the phenyl rings), and they were evaluated by u...…”

“…This combination of the method and basis set, B3LYP/cc-pVTZ, was used in calculating the two-dimensional potential surface of ethoxybenzene with successful reproduction of the experimental result. 31 Natural Bond Orbital (NBO) Calculations. NBO calculations were performed at the MP2 level of theory and the cc-pVTZ basis set using Gaussian 09 linked to the NBO 5.9 program.…”

“…Gaussian 09 was also used for this purpose as was the B3LYP method with a cc-pVTZ basis set. This combination of the method and basis set, B3LYP/cc-pVTZ, was used in calculating the two-dimensional potential surface of ethoxybenzene with successful reproduction of the experimental result …”