INFRARED AND RAMAN SPECTRA OF MAGNESIUM AMMONIUM PHOSPHATE HEXAHYDRATE (STRUVITE) AND ITS ISOMORPHOUS ANALOGUES II. The O-H/N-H stretching region Bojan Soptrajanov l ,2, Viktor Stefov l , Heinz Dieter Lutz 3 and Bernward Engelen 3 1 Institut za hemija, PMF', Un,iverzitet "Sv. Kiril i Metodij", Skopje, Macedonia 2 Makedonska akademija na naukite i umetnostite, Skopje, Macedonia J Anorganische Chemie, Universitiit Siegen, 57068 Siegen, Deutschland e-mail: bojan@manu.edu.mk Abstract: The three investigated comp.ounds KMgP0 4 · 6H 2 0 (KMP), NH 4 MgP0 4 . 6H 2 0 (NMP) and NH 4 MgAs0 4 ' 6H 2 0 (NMA) - are characte- rized by the existence, in their structure, of quite strong 0",'0 hydrogen bonds (of which some are among the shortest of this type ever found in crystalline hydrates, the Ow ... 0 distances being slightly above 260 pm). Reflecting the strength of the hydrogen bonds, a broad and structured feature extending from "" 4000 down to "" 2000 cm -I is found in the infrared spectra. Although not as rich in detail as the infrared spectra, the Raman ones are similar in appearance. Rather surprisingly, the spectral picture is not very different in the case of the two phosphate compounds (KMgP0 4 ' 6H 2 0 and NH 4 MgP0 4 . 6H 2 0) although N-H stretching bands are expected in the same region of the spectrum of NMP. Thus, obviously, the intensity of the feature in the O-H/N-H stretching region is due mainly to modes of the water molecules whereas the stretches contribute to a lesser degree to the shape and intensity. The com- parison of the spectra in the O-D/N-D stretching region confirms this. Key words: metal(I) magnesium phosphate hexahydrates; ammonium magnesium arsenate hexahydrate, infrared spectra, Raman spectra, potential protonic conductors. 299 E. C. Faulques et al. (eds.), Spectroscopy o/Emerging Materials, 299-308. © 2004 Kluwer Academic Publishers. Printed in the Netherlands.