Hydrogen Bonds Of Moderate Strength Research Articles

2H NMR Line Shapes and Spin−Lattice Relaxation in Ba(ClO3)2·2H2O

Solid-state deuterium NMR measurements were used to characterize the flipping motion of the water molecule in barium chlorate monohydrate, Ba(ClO3)2·2H2O. In particular, temperature-dependent quadrupole echo line shapes, their τ dependence and spectral intensities, and the anisotropy of the spin−lattice relaxation observed in inversion recovery experiments permit measurement of the 2-fold flipping rates. These were studied as a function of temperature and yield an activation energy Ea = 30 kJ/mol and pre-exponential factor A0 = 1.5 × 1014, which are typical for molecular motion constrained by hydrogen bonds of moderate strength. A discussion of experimental considerations is also presented.

Vibrational spectra of tris(methylammonium) cyclotriphosphate

AbstractIR and Raman spectra of (CH3NH3)3P3O9 were recorded and analysed. The vibrational bands due to P3O and (CH3NH3)+ groups are identified. From the spectral analysis, it is inferred that the P3O ion has a ring structure in the compound. Hydrogen bonds of moderate strength are observed between the external oxygen atoms of P3O and NH3+ groups.

The Raman spectrum of boric acid

The Raman spectrum of crystalline boric acid is recorded using mercuryλ2537 excitation. Fifteen Raman lines, three of them belonging to the lattice spectrum, are reported. Satisfactory assignments of all the observed Raman frequencies are made using the available X-ray crystal structure data. From the presence of a new high frequency Raman band at about 3420 cm.−1 it is suggested that there might be a small number of long, weak O-H....O hydrogen bonds in the crystal, in addition to the hydrogen bonds of moderate strength reported from X-ray diffraction data.