Red-shifted and improper blue-shifted hydrogen bonds in dimethyl ether (DME)n (n=1–4) and hydrated (DME)n (n=1–4) clusters. A theoretical study

✍ Scribed by S. Vijayakumar; P. Kolandaivel

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 301 KB
• Volume: 734
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2004.08.015

✦ Synopsis

In the present study, dimethyl ether (DME), dimethyl ether dimer (DME) 2 , trimer (DME) 3 , tetramer (DME) 4 and hydration of these clusters have been investigated using the ab initio and density functional theory methods. The formation of (DME) n (nZ2-4) complexes lead to the contraction of methyl C-H bond and elongation of C-O bond, when these two bonds form the hydrogen bonding. The contraction of C-H bond gives a blue shift in the C-H stretching frequency. The interaction of water molecules with the (DME) n (nZ1-4) complexes lead to the elongation of O-H bonds. The elongation of O-H bond gives the red shift in the O-H stretching frequency. The length of the C-H/O hydrogen bond is longer than the length of the R(O/H) hydrogen bond, which gives the standard O-H/O H-bond interaction. Interaction energies were calculated after eliminating basis set superposition error by using full counterpoise correction method. Interaction energy for the C-H/O hydrogen bond is less than that for the O-H/O hydrogen bond. Natural bond orbital analysis reveals that the increase of electron density in the s* antibonding orbitals of the O-H bond in water yield its weakening. The contractions of C-H bond in the (DME) clusters have been analyzed using the concept of charge density transfer and rehybridization mechanisms. The charge density (r), and Laplacian of charge density (V 2 r), were also calculated for both C-H/O and O-H/O interactions, which are used for the classification of improper (blue shifted) and proper (red shifted) hydrogen bonds.