Imidazole Trimer-Water Complexes in Superfluid Helium Nanodroplets: Water Stretching Modes

摘要

Imidazole (IM) is an important moiety, having a proton donor and acceptor, in nucleic acid bases, i.e., adenine and guanine, and plays an important role in the intermolecular interactions of biological processes so that many theoretical and experimental studies of IM and its clusters have been investigated. Previously, we have presented and characterized the high-resolution infrared laser spectra of IM, imidazole dimer (IMD) and two isomers of DVI- and IMD-water complexes (IMW and IMDW) formed in helium nanodroplets. Recently, we have extended the study of imidazole clusters to imidazole trimer (IMT) reporting the vibrational spectra of IMT in the free NH spectral region and found out that the IM molecules tend to form linear structures due to their dipole-dipole interactions in helium nanodroplets. The unambiguous free NH band assignment was made by the experimental techniques, such as pick-up oven temperature dependence and vibrational transition moment angle (VTMA), and density functional theory (DFT) calculations.