Abstract
Aggregates of pyrrole with nitrogen are studied by Fourier transform infrared spectroscopy in supersonic jet expansions as well as in neon, argon and nitrogen cryomatrices. The NH stretching vibration undergoes a significant downshift upon switching from isolated gas phase conditions to bulk nitrogen matrices, which can be reconstructed incrementally by stepwise cluster formation with an increasing number of nitrogen molecules both in supersonic expansions and neon or argon matrices. The modelling of the bulk matrix shift by finite cluster theory remains an interesting challenge. Self-aggregation of pyrrole also yields the first spectra of the homodimer and -trimer in a neon matrix, showing particularly small (up to 10 cm-1) deviations from the isolated gas phase values.
Highlights
Isolation of transient species or weakly bound molecular aggregates in cryogenic matrices provides one of the most powerful and sensitive methods for subsequent spectroscopic studies of their structure and dynamics.[1]
Stepwise nanocoating of hydrogenbonded organic compounds with matrix host molecules in supersonic expansions is a useful tool in understanding gas-to-matrix shifts[8,9,10] and may enable a more rigorous comparison of matrix isolation spectra to theoretical predictions
Additional conformers which are more than 1.0 kJ molÀ1 less stable than the respective minimum energy structures can be found in Fig. S1–S5 and the respective spectroscopic predictions are summarised in Table S2 in the Electronic supplementary information (ESI).† In the absence of detailed interconversion barrier analyses, it remains unclear which of the higher energy structures may contribute to the kinetically controlled jet experiments
Summary
Isolation of transient species or weakly bound molecular aggregates in cryogenic matrices provides one of the most powerful and sensitive methods for subsequent spectroscopic studies of their structure and dynamics.[1] spectral shifts and splittings from unperturbed gas phase values due to the bulk environment are frequently observed even for light, soft and less perturbative matrix hosts such as parahydrogen[2] or neon.[3] The significant electric quadrupole moment of molecular nitrogen[4] results in a comparatively strong perturbation found in corresponding matrices.[5] Partial positive charges at the centre and negative charges at the molecule ends[6] lead to a more specific and directional guest–host interaction than for the large argon host.[7] Stepwise nanocoating of hydrogenbonded organic compounds with matrix host molecules in supersonic expansions is a useful tool in understanding gas-to-matrix shifts[8,9,10] and may enable a more rigorous comparison of matrix isolation spectra to theoretical predictions. Corresponding infrared spectra in neon matrices provided in this work facilitate previously uncertain trimer band assignments in argon matrix.[7]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
