Journal of Chemical Crystallography, Vol. 31, No. 6, June 2001 ( C  2002) Crystal structure, thermal analysis, and IR spectrometric investigation of 1,2-diammonium-2-methyl propane sulfate monohydrate Taha Guerfel (1) and Amor Jouini (1) * Received October 9, 2000 Chemical preparation, X-ray single crystal, thermal analysis, and IR spectrometric inves- tigation of C 4 H 14 N 2 SO 4 ·H 2 O (denoted DAMPS) are described. DAMPS crystallizes in the orthorhombic system with P2 1 2 1 2 1 space group, a = 9.2726(4) ˚ A, b = 9.5227(2) ˚ A, c = 10.3807(4) ˚ A, V = 916.62(6) ˚ A 3 , and Z = 4. The DAMPS structure is built up from inorganic chains parallel to the b axis and linked via Ow H···O hydrogen bonds. These chains are interconnected by organic groups so as to build a three-dimensional arrangement. KEY WORDS: Organic sulfate; crystal structure; DTA/TG/DSC; vibrational spectra. Introduction Chemists and physicists of the solid state have shown an increasing interest in the study of the efficient and highly transparent nonlinear optical crystal. 1,2 The approach which combines the high cohesion of sulfate host-matrices with the enhanced polarizability of organic molecules was clearly illustrated with organic sulfates be- cause some of them exhibit nonlinear optical coefficients. 3 Our own work has focused on study- ing the interaction between sulfuric acid and 1,2-diamino-2-methyl propane. This study al- lowed the finding of a new noncentrosymmetric crystal whose chemical preparation, crystal struc- ture, thermal behavior, and IR spectrum are dis- cussed here. (1) Laboratoire de Chimie du Solide, D´ epartement de Chimie, Facult´ e des Sciences de Monastir, Universit´ e du centre, 5019 Monastir, Tunisia. *To whom correspondence should be addressed; e-mail: amor. jouini@fsm.rnu.tn. Experimental Crystals of DAMPS are prepared at room temperature by slow evaporation of 400 mL of aqueous solution of H 2 SO 4 (10 −1 M) neutral- ized by a stoichiometric amount of 1,2-diamino-2- methyl propane. During this operation the solution was stirred vigorously. The synthesis reaction is C 4 H 12 N 2 + H 2 SO 4 H 2 O −→ (C 4 H 14 N 2 ) SO 4 ·H 2 O. When most of the solution is evaporated, cubic crystals appear deep down the vessel. Preliminary photographs indicated ortho- rhombic symmetry, and systematically absent re- flections showed the space group to be P2 1 2 1 2 1 . The crystal structure was carried out with direct methods from the SHELXS-97, 4 which permit- ted the location of the SO 4 group and the oxy- gen of the water molecule to be deduced from the TG curve. The other non-hydrogen atoms were rapidly located after subsequent cycles of re- finement and difference Fourier synthesis, using 333 1074-1542/01/0600-0333/0 C  2002 Plenum Publishing Corporation