Pressure-Induced Phase Transition in N–H···O Hydrogen-Bonded Molecular Crystal Oxamide

Abstract

The effect of high pressure on the structural stability of oxamide has been investigated in a diamond anvil cell by Raman spectroscopy up to ∼14.6 GPa and by angle-dispersive X-ray diffraction (ADXRD) up to ∼17.5 GPa. The discontinuity in Raman shifts around 9.6 GPa indicates a pressure-induced structural phase transition. This phase transition is confirmed by the change of ADXRD spectra with the symmetry transformation from P1 to P1. On total release of pressure, the diffraction pattern returns to its initial state, implying this transition is reversible. We discuss the pressure-induced variations in N-H stretching vibrations and the amide modes in Raman spectra and propose that this phase transition is attributed to the distortions of the hydrogen-bonded networks.

Pressure-induced phase transition in N–H⋯O hydrogen-bonded crystalline malonamide

“…27 Similarly, oxamide transitions into a high-pressure phase at pressures above 9.6 GPa. 28 Moreover, acrylamide polymerizes under pressures that exceed 4 GPa; the strong N-H/O bond of the initial phase breaks and the relatively weak N-H/O bond in the new phase forms under high pressure. 29 Therefore, studies on hydrogen bonds in amides under high pressure are fundamental to pave a new way for molecular construction in crystal engineering.…”

Hydrogen bonds and polymerization in acrylamide under pressure

“…Single crystal x‐ray diffraction study of formamide suggests a new β phase with denser packing but same space group at pressure ~0.88 GPa by reconstruction of N‐H‐‐‐O hydrogen bond along with the formation of new C‐H‐‐‐O type hydrogen bonds. Acetamide, Polyamide PA 66 and oxamide are other amides in which changes in the hydrogen bonding networks are indicated by Raman or infrared spectroscopic studies. Variations in the hydrogen bonds of acrylamide are also reported in brief by an infrared absorption study carried out up to 5 GPa .…”

Pressure Induced Topochemical Polymerizationof Solid Acryalmide Facilitated by Anisotropic Response of Hydrogen Bond Network

“…The study of materials under pressure has attracted much attention in recent years, as it provides access to structural and dynamical information not available at ambient conditions. [1][2][3][4][5][6][7][8][9][10][11] Hydrogen bonded molecular crystals, in particular, exhibit very interesting properties under pressure. [12][13][14][15][16][17][18][19][20] Among the various phenomena seen in these systems, pressure induced polymerization is very appealing.…”

“…[1][2][3][4][5][6][7][8][9][10][11] Hydrogen bonded molecular crystals, in particular, exhibit very interesting properties under pressure. [12][13][14][15][16][17][18][19][20] Among the various phenomena seen in these systems, pressure induced polymerization is very appealing. This is because unlike chemical, [21][22][23][24] and radiationinitiated [25][26][27][28] routes to polymerization, hydrostatic pressure needs no initiating catalyst and can yield pure a polymer phase.…”