Vibrational overtone spectroscopy of pyrrole and pyrrolidine

Abstract

The gaseous near-infrared and visible absorption spectra of pyrrole and pyrrolidine have been measured for the first through fourth N-H stretch vibrational overtones and the second through fourth C-H stretch overtones. The C-H overtone features follow the simple local mode expression with anharmonicities of 53.9 f 0.5 cm-' for pyrrole and 60 f 2 cm-' for pyrrolidine. Multiple transitions observed in the N-H stretching regions indicate the presence of vibrational coupling to other vibrational modes. This assignment is confirmed by the first and third N-H vibrational overtone spectrum of gaseous pyrrole-d4. For comparison, the visible spectra of neat liquid pyrrole, dilutions of pyrrole in carbon tetrachloride, and neat liquid pyrrolidine were obtained by direct absorption spectroscopy. The pattern of multiple peaks for the N-H absorption region also appears (shifted 200 cm-l to the red) in solution-phase pyrrole. This shift of all the peaks results from the intermolecular interactions of the N-H in the liquid; however, the preservation of the peak splittings indicates that this splitting is a result of intramolecular vibrational coupling. The spectrum of pyrrolidine is remarkably similar to that of pyrrole, suggesting the same vibrational coupling exists for both compounds.

Self-Aggregation in Pyrrole: Matrix Isolation, Solid State Infrared Spectroscopy, and DFT Study

“…23,24,49,50,52,58 In the recent years, the emphasis was put on the study of anharmonicity and assignment of overtones and combination tones. 16,17,20,47,51 Very interestingly, despite the previous extensive investigation of the vibrational spectra of pyrrole, this molecule has not been studied by matrix isolation spectroscopy yet. The high tendency of pyrrole to aggregate is, without any doubt, the main factor responsible for the difficulty in isolating the molecule in matrixes.…”

Left main dissection: A time bomb?

“…To get an insight into the reliability of the optimized geometries of this heterodimer at the employed level of theory, the optimized geometry parameters of the two monomeric units were compared with the available experimental data 14–19 (the complete results are available from the author upon request); the agreement of the presently applied level of theory with the experimental data is good. In the case of free pyrrole, the results from the present study are of essentially identical quality with the MP2 ones reported recently for this system 35.…”

“…All in all, studies of π‐type hydrogen bonding interaction between aromatic domains containing heteroatoms are of special importance for a number of chemical and biochemical phenomena. Because, to the best of our knowledge, no experimental data are available for the heterodimer considered in the this article, the obtained theoretical results were compared with the available data for the (pyrrole) 2 and (indole) 2 homodimers 7, 15, as well as with the data for free monomeric units 14, 16–19. Conclusions regarding experimental detection of the π‐bonded dimers are also derived that are expected to be helpful for further experimental studies.…”

Physical, Spectroscopic and Thermal Characterization of Biofield Treated Fish Peptone

“…Similarly, the -C-O-Cstretching peak of the lactone ring was observed at 1245 and 1247 cm -1 in the control and treated samples, respectively [28]. Besides, the N-H bending peak of pyrrole ring C-N stretching peak of pyrazole ring present in proteins was appeared at 1151 cm -1 in the control sample [29,30]; whereas at 1118 cm -1 in the treated sample. The C-OH stretching peak of carbohydrates was observed at 1072 cm -1 in the control and 1085 cm -1 in the treated sample.…”