Elucidating the mechanism behind the infrared spectral features and dynamics observed in the carbonyl stretch region of organic carbonates interacting with lithium ions

Ultrafast infrared spectroscopy has become a very important tool for studying the structure and ultrafast dynamics in solution. In particular, it been recently applied to investigate molecular interactions motions of lithium salts organic carbonates. However, there discrepancy interpretation spectral features derived from these spectroscopies. Hence, mechanism behind appearing carbonyl stretching region was further investigated using linear nonlinear spectroscopic tools co-solvent dilution strategy. Lithium perchlorate binary mixture dimethyl carbonate (DMC) tetrahydrofuran used as part strategy identify changes with number carbonates first solvation shell since both solvents have similar interaction energetics ion. Experiments showed that more than one is always participating ion structures, even at low concentration DMC. Moreover, temperature-dependent study revealed exchange solvent molecules coordinating not thermally accessible room temperature. Furthermore, time-resolved IR experiments confirmed presence vibrationally coupled stretches among coordinated DMC demonstrated this process significantly altered by limiting shell. Overall, presented experimental findings strongly support vibrational energy transfer off-diagonal on 2DIR spectra solutions salt