COMPLEXES OF THE PROTON SPONGE 1,8-BIS(DIMETHYLAMINO)NAPHTHALENE (DMAN) .5. THE STRUCTURE AT 100-K OF [DMANH]+BULLET[DIHYDROGEN HEMIMELLITATE-ASTERISK]-HEMIHYDRATE

Crystallisation of the "proton sponge" 1,8-bis(dimethylamino)naphthalene (DMAN) in the presence of hemimellitic acid (1,2,3-benzenetricarboxylic acid, BTA) resulted in the salt [DMANH]+.[BTA]-.1/2 H2O. The structure analysis was performed at liquid nitrogen temperature (100 K). The space group is C2/c with Z = 8. The cell dimensions are: a = 20.085(1), b = 8.557(1), c = 25.429(1) angstrom, beta = 105.01(1)-degrees, V = 4221.3(6) angstrom3. The structure was solved by direct methods and refined to R = 0.0363 for 4131 unique reflections with I greater-than-or-equal-to 2.5-sigma(I). The proton sponge DMAN accepts a proton from one of the carboxyl groups of BTA with the formation of a strong intramolecular hydrogen bond. Electron-density difference maps in the plane of this [N-H...N]+ hydrogen bond reveal a disordering of the hydrogen atom in a 70:30 ratio over two positions at distances of approximately 0.9 angstrom from the pertaining nitrogen atoms. The water molecule is disordered over two positions at distances of 1.203(3) angstrom from the twofold axis.