Photofragmentation dynamics of N,N-dimethylformamide following excitation at 193 nm

Abstract

N,N-dimethylformamide, HCON(CH), is a useful model compound for investigating the peptide bond photofragmentation dynamics. We report data from a comprehensive experimental and theoretical study into the photofragmentation dynamics of N,N-dimethylformamide in the gas phase at 193 nm. Through a combination of velocity-map imaging and hydrogen atom Rydberg tagging photofragment translational spectroscopy we have identified two primary fragmentation channels, namely, fission of the N-CO "peptide" bond and N-CH bond fission leading to the loss of CH. The possible fragmentation channels leading to the observed products are rationalised with recourse to CASPT2 calculations of the ground and first few excited-state potential energy curves along the relevant dissociation coordinates, and the results are compared with the data from previous experimental and theoretical studies on the same system.

Stability of the Monoelectronic Reduction Product from 1,2,5‐Thiadiazole S,S‐Dioxides. Electrochemical, Chemical, and Photoinduced Doping

“…A proposed reaction mechanism for the photoinduced reaction of 1 a ‐ c in DMF solution is shown in Scheme . A similar mechanism of radical production was proposed by J. H. DeLap and H. H. Dearman as the initial steps in the photo‐oxidation of 4‐amino‐4‐nitroazobenzene in DMF, for Sharkey and Mochell as the initial steps in the photo‐oxidation of amides, and by M. L. Lipciuc as the results from an experimental and theoretical study about the photofragmentation of DMF in the gas phase, at 193 nm. Also, essentially the same mechanism apparently applies to the secondary processes in the radiolysis of DMF .…”

Primary and Secondary Loss of CO and NO Ligands in the Ultraviolet Photodissociation of the Heteroleptic Co(CO)3NO Complex

“…The momentum distributions of the CO ( v = 0, low J ≈ 0 and high J = 39) fragments (black solid lines) and Co­(CO) 2 NO intermediates (red broken lines) are shown in Figure for discriminating the primary CO photofragment from the secondary CO fragments by momentum-matching . The CO (low J and high J ) fragments exhibited broad momentum distributions, whose peaks and widths are dependent on the rotational states; the peak momenta are 3.7 × 10 –23 kg m/s for J ≈ 0 (upper in Figure ) and 5.5 × 10 –23 kg m/s for J = 39 (lower in Figure ).…”

Multi-mass velocity-map imaging studies of photoinduced and electron-induced chemistry

“…Photodissociation studies on amides provide a stepping stone to understanding the behaviour of energised peptide bonds within proteins, providing insight into photostability and photodamage mechanisms in biomolecules. N,N-dimethylformamide (N,N-DMF), N(CH3)2CHO, provides a useful model for investigating peptide bond fragmentation dynamics, and had been studied by a number of other authors 34,35,36,37 prior to our recent multimass VMI study 38 . Figure 8(a) shows cuts through the first few adiabatic potential energy surfaces for dissociation of N,N-DMF along the C-N, N-CH3 and C-H bond coordinates.…”