STRUCTURE OF 2,4-DIMETHYL-1H-NAPHTHO[2,3-B][1,4]DIAZEPINE HYDROPICRATE - SOLID-STATE ASSEMBLY VIA C-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-O HYDROGEN-BONDING

Crystal structure determination, semiempirical AM1 and PM3 calculation s have been performed on 2,4-dimethyl-1H-naphtho[2,3-b][1,4]diazepine hydropicrate. The two molecules are almost planar apart from two NO2 a nd CH3 groups. The NO2 pls> and 44.3 degrees with the least squares pl ane of the 'phenyl' ring. The naphthodiazepine molecule and the picrat e acid molecule are intermolecularly linked by one N-H...O and four C- H...O hydrogen bonds and form polar ribbons parallel to the [110] dire ction. The ribbons are linked by intermolecular C-H...O hydrogen bonds about a centre of inversion and the ensemble forms layers. These laye rs are weakly bound by van der Waals' interactions and undergo a rever sible martensitic-type transition upon heating. During this transition the colour of the crystal changes from dark orange to yellow. AM1 and PM3 calculations on the dimers reproduce, with acceptable approximati on, the main features of the structure.