Intermolecular hydrogen bonding of N-methylformamide in aqueous environment: A theoretical study

The intermolecular hydrogen bonding of N-methylformamide (NMF) in water is investigated. Ground-state geometry optimizations and binding energies were calculated with density functional theory (DFT). Electronic transition energies, and corresponding oscillator strengths of low-lying electronically excited states of free NMF monomers and hydrogen-bonded NMF–(H2O)2,3 complexes were calculated with time-dependent density functional theory (TDDFT). Electronic absorption spectra red-shift occurs due to the formation of the intermolecular hydrogen bonds ONMF⋯HOwater and NH⋯Owater. Larger electronic absorption spectrum red-shift in trans-NMF–(H2O)2,3 than in cis-NMF–(H2O)2,3 can be attributed to stronger excited state hydrogen bond strengthening in trans-NMF–(H2O)n complexes.