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 (ν_{5 +} 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.

Keywords: Aggregation-induced spectral splitting; DFT calculations; Dimer; Fermi resonance; Intermolecular interaction.