Low inversion energy barrier of cytisine NH group—an explanation for the FT-IR bands splitting

Characterization of indigo carmine with surface‐enhanced resonance Raman spectroscopy (SERRS) using silver colloids and island films, and theoretical calculations

“…66 -68 The band at 868 cm 1 increases in relative intensity as compared to the RR spectrum of the solution and appears as a C-N stretching contribution. 68,69 In the same way, the band at 768 cm 1 can be due to the out-of-plane C-C/C-H bending modes and to the pyrrolidone rings' breathing modes. The very weak peak at 667 cm 1 in the solution becomes very strong in the SERR spectra (673 cm 1 , Fig.…”

“…62,66 -68 The strong band at 1630 cm 1 (slightly red shifted from the RR spectrum of the solution, 1632 cm 1 ) and its shoulder at 1650 cm 1 , which is absent in the solution, are assigned to the C C/C O stretching modes and to the in-plane C-H bending mode, whereas the strong signal at 1245 cm 1 (slightly blue shifted from the solution, 1241 cm 1 ) can be seen as C-H/C O bending contributions. The peak at 1475 cm 1 increases in relative intensity as compared to the solution and can be due to the phenyl and pyrrolidone ring stretching modes, 65 while the new weak peak at 1188 cm 1 appears as a stretching contribution of the N-C bonds 69,70 and of the C9 C9 0 bridge bond. 66,68 In the low wavenumber region of the SERRS spectra (Fig.…”

“…4) in the RR spectrum of the solution and which decreases in relative intensity, is attributed to the N-C stretching and to the in-plane C-H bending modes. 69,70 The weak peak at 1444 cm 1 is attributed to the C-C and N-C C-N stretching contributions, the in plane N-H bending mode and the in plane C-H bending mode of the phenyl rings, being the main contributions in the band's shape. In the RR spectrum of the solution, this band has almost the same position and relative intensity (Fig.…”

“…4). 43,68,69 The out-of-plane C-H deformation mode of the phenyl rings is observed in the solid state at 1036/997 cm 1 and in the solution at 1029/990 cm 1 . The very weak band at 967 cm 1 in the Raman spectrum of the solid state (968 cm 1 in the solution) is assigned to the out-of-plane C-H bending mode and to the O12-S10-O13/O12 0 -S10 0 -O13 0 deformation modes.…”

“…On the other hand, the very weak peaks at 895 cm 1 (solid state) and 896 cm 1 (solution) correspond to the symmetrical C2-N1-C9/C2 0 -N1 0 -C9 0 stretching modes. 69 The next bands in the Raman spectrum of E132 in the solid state are attributed as follows: the weak peak at 833 cm 1 (839 cm 1 in the solution) to the C5-S10/C5 0 -O10 0 stretching modes 40 and to the C-C out-of-plane bending mode of the five-membered rings; the band at 764 cm 1 (768 cm 1 in the solution, increased in relative intensity) to the breathing mode of the pyrrolidone rings and to the out-of-plane C-H and C-C bending modes; the peak at 722 cm 1 (increased in the RR spectrum of the solution) to the C2-N1-C9/C2 0 -N1 0 -C9 0 bending modes. The weak peak at 672 cm 1 in the Raman spectrum of the solid, which is slightly blue shifted in the RR spectrum of the solution (667 cm 1 ) and highly increased in relative intensity, is assigned to the outof-plane N-H and C-C bending modes of both pyrrolidone rings.…”