Solvation of LiClO4 and NaClO4 in deuterated acetonitrile studied by means of infrared and Raman spectroscopy

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2002-06, Vol.58 (8), p.1747-1756
• Main Authors: Seo, Jun-Sik, Cheong, Byeong-Seo, Cho, Han-Gook
• Format: Article
• Language: English
• Subjects: Acetonitriles - chemistry; Deuterium; Lithium Compounds - chemistry; Molecular Structure; Perchlorates - chemistry; Sodium Compounds - chemistry; Solvents; Spectroscopy, Fourier Transform Infrared; Spectrum Analysis, Raman; Vibration
• ISSN: 1386-1425
• DOI: 10.1016/s1386-1425(01)00636-9

Vibrational characteristics of CD3CN solutions of LiClO4 and NaClO4 have been studied by means of infrared and Raman spectroscopy. Blue shifts of 22 and 11 cm(-1) of the v2 C[triple bond]N stretch are observed resulting from interaction of CD3CN with Li+ and Na+, respectively. The number of primary solvation sites of both Li+ and Na+ in acetonitrile is believed to be four from the comparison of the Raman intensities of the C[triple bond]N stretch for free CD3CN and those coordinated to Li+ and Na+. Evidently formation of contact ion pairs of the cation (Li+ or Na+) and anion (ClO4-) is more probable at a higher concentration of the salt. The characteristics of the v2 C[triple bond]N stretch, v4 C-C stretch, and v8 CCN deformation bands vary substantially upon coordination, while other vibrational bands are relatively immune to the donor-acceptor interaction. DFT calculations have also been performed at the BLYP/6-31 + G(2d,p) level to examine the structures and vibrational characteristics of CD3CN coordinated to Li+ and Na+. The calculated results are in good agreement with the observed vibrational characteristics.