The Infrared Spectrum Between 4000 and 200 cm⁻¹ and the X-Ray Powder Diffraction Pattern of Hexamethylenetetramine Hexahydrate in Four Isotopic Forms at 100 K

Abstract

The X-ray diffraction pattern of powdered hexamethylenetetramine hexahydrate (HMT-h12·6H2O ) at 120 K has been recorded and analyzed. The thermal contraction occurs primarily along the trigonal axis. The infrared spectra of polycrystallineHMT-h12·6H2O, HMT-h12·6D2O, HMT-d12·6H2O, and HMT-d12·6D2O at 95 K have been recorded. The most sensitive test for ice impurity is obtained from the OD stretching bands of HDO molecules in dilute solution in the hydrate, vOD(HDO), but ice impurity also affects the OH and OD stretching bands of H2O and D2O, vOH(H2O) and vOD(D2O). The absorption by HMT can be assigned to the single HMT molecule per diffraction unit cell. The symmetries of the vibrations under the C3v diffraction site symmetry cannot be determined from this data, so the absorption is assigned to the parent vibration of pure HMT.Three peaks arise from vOH(HDO) and vOD(HDO), at 2464 2369, and 2295 cm−1 for vOD(HDO). They can, with considerable uncertainty, be assigned to the three nonequivalent hydrogen bond lengths in the structure. An alternative assignment uses the hypothesis that the frequency of an O—D … O bond of given length is abnormally low when a three-coordinated oxygen atom is the base. A partial interpretation of the vOH(H2O) and vOD(D2O) bands is presented. It is quite clear that a large part of their breadth is due to Fermi resonance with the continuum of overtone and combination levels that lie close to the fundamental levels. Several fairly sharp features due to rotational vibrations of H2O and D2O, vR(H2O) and vR(D2O), provide the only evidence of the partial order in the positions of the hydrogen atoms. Three vR(HDO) frequencies have been detected, 860, 570, and 490 cm−1. Their ratios agree well with the ratios of the square roots of the reciprocal moments of inertia, but not with the ratios of frequencies calculated following Blue's arguments.

Photophysical Characterization of Er3+ doped and Er3+/Nd3+ co-doped Gd(OH)3 Nanocrystals: the Impact of Hexamethylenetetramine utilization for Morphology Engineering

“…Therefore, we conclude that the HMTA played a key role in forming the nanorod morphology of the samples prepared in this work. The weak vibration peaks at wavenumber of 2930 cm -1 and 2852 cm -1 are attributed to symmetric and asymmetric stretching vibrations of -CH2 and OHbending, respectively [51]. The vibration band at 705.4 cm -1 is assigned to Gd-OH bond confirming that Gd(OH)3 is formed [47].…”

Photophysical Characterization of Er3+ doped and Er3+/Nd3+ co-doped Gd(OH)3 Nanocrystals: the Impact of Hexamethylenetetramine utilization for Morphology Engineering

“…Therefore, we conclude that the HMTA played a key role in forming the nanorod morphology of the samples prepared in this work. The weak vibration peaks at wavenumber of 2930 cm -1 and 2852 cm -1 are attributed to symmetric and asymmetric stretching vibrations of -CH2 and OHbending, respectively [51]. The vibration band at 705.4 cm -1 is assigned to Gd-OH bond confirming that Gd(OH)3 is formed [47].…”