H/D Isotopic and Temperature Effects in the Polarized IR Spectra of Hydrogen-Bond Cyclic Trimers in the Crystal Lattices of Acetone Oxime and 3,5-Dimethylpyrazole

Abstract

Polarized IR spectra of hydrogen-bonded acetone oxime and 3,5-dimethylpyrazole crystals were measured at 293 and 77 K in the ν(X-H) and ν(X-D) band frequency ranges. These crystals contain molecular trimers in their lattices. The individual crystal spectral properties remain in a close relation with the electronic structure of the two different molecular systems. We show that a vibronic coupling mechanism involving the hydrogen-bond protons and the electrons on the π-electronic systems in the molecules determines the way in which the vibrational exciton coupling between the hydrogen bonds in the trimers occurs. A strong coupling in 3,5-dimethylpyrazole trimers prefers a "tail-to-head"-type Davydov coupling widespread via the π-electrons. A weak through-space exciton coupling in acetone oxime trimers involves three adjacent hydrogen bonds in each cycle. The relative contribution of each exciton coupling mechanism in the trimer spectra generation is temperature and the molecular electronic structure-dependent. This explains the observed difference in the temperature-induced evolution of the compared spectra. The mechanism of the H/D isotopic "self-organization" processes in the crystal hydrogen bonds was also analyzed. The two types of the hydrogen-bond trimers exhibit the same way, in which the H/D isotopic recognition mechanism occurs. In acetone oxime and 3,5-dimethylpyrazole trimers, identical hydrogen isotope atoms exist in these entire hydrogen-bond systems.

Car–Parrinello Molecular Dynamics Simulations of Infrared Spectra of Crystalline Vitamin C with Analysis of Double Minimum Proton Potentials for Medium-Strong Hydrogen Bonds

“…Spectral changes accompanying hydrogen bond formation are especially pronounced in the region of the X–H stretching bands (ν s ): decrease in the frequency of the ν s stretching mode, increase of its intensity, and broadening of the bands and appearance of a complex fine structure. These features of the infrared and Raman bands of the ν s mode have been a subject of many theoretical studies. − As the hydrogen bond is one of the most important interactions in all biochemical systems, its dynamics is of great importance.…”

Biochemical Capacitance of Geobacter Sulfurreducens Biofilms

“…The oxime moiety represents a supramolecular connector that can generate hydrogen‐bonded networks through complementary hydrogen bonds or involving a dimeric R 2 2 (6) motif 16–18. Because an oxime‐oxygen atoms contains two lone pairs of electrons and one of them is connected to a hydrogen atom, the oxime moiety can be a supramolecular synthon involved in hydrogen bonds with up to its neighboring molecules 19.…”

anti-Ethyl acetohydroximate

“…For related structures, see: Kjaer et al (1977); Larsen (1971). For studies of the IR spectra of hydrogen bonding in oxime derivatives, see: Flakus et al (2012). For typical bond distances, see: Allen et al (1987).…”

“…Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al, 2006); software used to prepare material for publication: publCIF (Westrip, 2010). (Flakus et al, 2012). In order to study interactions occurring via hydrogen bonds and molecular packing in this compound, we have now determined the structure of (I) using diffraction data collected at 100 K. Until now, the structures of syn-methyl acetohydroximate and syn-and antiethyl benzohydroximate were determined (Kjaer et al, 1977;Larsen et al, 1971).…”