Intermolecular Hydrogen Bonding and Vibrational Analysis of N,N-Dimethylformamide Hexamer Cluster

Abstract

Hexamer cluster of N,N-dimethylformamide(DMF) based on the crystal structure was investigated for the equilibrium structure, the stabilization energies, and the vibrational properties in the density functional force field. The geometry (point group Ci) of fully optimized hexamer clustered DMF shows quite close similarity to the crystal structure weakly intermolecular hydrogen bonded each other. Stretching force constants for intermolecular hydrogen bonded methyl and formyl hydrogen atoms with nearby oxygen atom, methyl C-H···O and formyl C-H···O, were obtained in 0.055 ~ 0.11 and ~ 0.081 mdyn/Å, respectively. In-plane bending force constants for hydrogen bonded methyl hydrogen atoms were in 0.25 ~ 0.33, and for formyl hydrogen ~ 0.55 mdynÅ. Torsion force constants through hydrogen bonding for methyl hydrogen atoms were in 0.038 ~ 0.089, and for formyl hydrogen atom ~ 0.095 mdynÅ. Calculated Raman and infrared spectral features of single and hexamer cluster represent well the experimental spectra of DMF obtained in the liquid state. Noncoincidence between IR and Raman frequency positions of stretching C=O, formyl C-H and other several modes was interpreted in terms of the intermolecular vibrational coupling in the condensed phase.

Weak Interactions in Dimethyl Sulfoxide (DMSO)–Tertiary Amide Solutions: The Versatility of DMSO as a Solvent

“…In DMF, the first solvation shell shows the expected preference for antiparallel dipole orientation between molecules, while in DMAc, parallel dipoles maximize dispersion forces between the π-delocalized OC–N backbones and methyl groups . These results are consistent with Raman and IR spectroscopy and molecular dynamics studies of liquid DMF, all of which reported a highly structured first solvation shell with weak hydrogen bonding from carbonyl and methyl H atoms, in line with the “relatively short” C–H···OC contacts seen earlier by gas-phase electron diffraction. − …”

Rich Capping Ligand–Ag Colloid Interactions

“…However, strong vibrational features arising from adsorbed PVP or DMF were observed for all Ag colloids, demonstrating the strong surface-enhanced Raman scattering (SERS) effect of Ag surfaces. Their assignments (Table ) were made on the basis of previous Raman spectra of pure PVP and DMF, PVP and DMF in complexes, and PVP and DMF on metal colloids. , − Ag–DMF particles exhibit the Ag–N and/or Ag–O Raman shift features at 222 cm –1 , while Ag–PVP cubes and Ag–PVP + DMF plates exhibit the same Ag–N and/or Ag–O vibrational features at 245 cm –1 . These results indicate that the interactions between the Ag surface and adsorbed capping ligands are similar for Ag–PVP cubes and Ag–PVP + DMF plates, in agreement with the above Ag 3d XPS results that Ag–PVP cubes and Ag–PVP + DMF plates exhibit similar Ag 3d binding energies.…”