Conformational Changes upon S1 Yields S0 Excitation in 4-Dimethylaminobenzonitrile and Some of Its Chemical Analogs

摘要

One color time of flight mass spectra (mass resolved excitation spectra) for jet cooled 4-dimethylaniline (DMA), 3-dimethylamino-obenzonitrile (3-DMABN), N,N-dimethyl-4-(trifluoromethyl) benzoamine (4-CF3-DMA) and 4-(d6-dimethylamino)benzonitrile (4-d6-DMABN), are presented and analyzed. Near the origin of the S1-S0 transition the low frequency modes can be assigned to motions of the dimethylamino group and the dimethylamino group torsion about the motion of the dimethylamino group and the dimethylamino group torsion about the C-ipso-N bond (the twist coordinate) in S1 give rise to the most prominent peaks in this spectrum. The potential parameters for the twist coordinate of 4-DMABN and DMA are quite similar in S1: B = 0.546, V2 = 175, and V4 = 525/cm for 4-DMABNand B = 0.546, V2 = 175, and V4 = 515/cm for DMA. The V2 and V4 terms are slightly larger for 3-DMABN and 4-CF3-DMA. The inversion motion is also similar for these molecules but is more anharmonic for the para-substituted dimethylanilines, 4-DMABN and 4-CF3-DMA, than for the meta and unsubstituted molecules. Keywords: Mass spectra, Twist coordinate, Amines, Nitriles, Compounds, Methyl radicals, Anilines. (MJM)