Aggregation induced spectral splitting and Fermi resonance of Ethylene Carbonate in binary mixture.

ABSTRACT

The vibration band of the ring stretching (ν14), the fundamental ring breathing (ν17) and the Fermi resonance band of carbonyl stretching mixing with the overtone of the ring breathing (ν5 + 2ν17) have been investigated in solid ethylene carbonate (EC) and EC/CH3CN and EC/CHCl3 binary mixture. Dimer structure with aggregation-induced spectral splitting model (AIS) was applied to calculate the vibration spectra using the B3LYP-D3/6-311+G (d,p) procedure. The noncoincidence effect (NCE) and concentration induced frequency shifts of the ν14 and ν5 could be well explained by AIS model based on the dimer structure. Four bands were observed with two in the isotropic and two in the anisotropic Raman spectra and their NCE value decreased with the decrease of EC volume fraction in the binary mixture, and finally disappeared. NCE value and the Fermi resonance constants of EC at different concentrations were calculated from the experimental data.