Four N-7-benzyl-substituted 4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1 '-cyclohexane-2 ',6 '-diones as ethanol hemisolvates: similar molecular constitutions but different crystal structures

3-tert-Butyl-7-(4-chlorobenzyl)-4 ',4 '-dimethyl-1-phenyl4,5,6,7-tetrahydro-1H-pyrazolo[3,4-b]pyridine-5-spiro-1 ' cyclohexane-2 ',6 '- dione ethanol hemisolvate, C30H34ClN3O2 center dot 0.5C(2)H(6)O, (I), its 7-(4-bromobenzyl)-analogue, C30H34BrN3O2 center dot 0.5C(2)H(6)O, (II), and its 7-(4-methylbenzyl)-analogue, C31H37N3O2 center dot 0.5C(2)H(6)O, (III), are isomorphous, with the ethanol component disordered across a twofold rotation axis in the space group C2/c. In the corresponding 7-[4-( trifluoromethyl) benzyl]-compound, C31H34F3N3O2 center dot 0.5C(2)H(6)O, (IV), the ethanol component is disordered across a centre of inversion in the space group P (1) over bar. In each of (I)-(IV), the reduced pyridine ring adopts a half- chair conformation. The heterocyclic components in (I)-(III) are linked into centrosymmetric dimers by a single C-H center dot center dot center dot pi interaction, with the half-occupancy ethanol component linked to the dimer by a combination of C-H center dot center dot center dot O and O-H center dot center dot center dot pi (arene) hydrogen bonds. The heterocyclic molecules in (IV) are linked into chains of centrosymmetric rings by C-H center dot center dot center dot O and C-H center dot center dot center dot pi hydrogen bonds, again with the half- occupancy ethanol component pendent from the chain. The significance of this study lies in the isomorphism of the related derivatives (I)-(III), in the stoichiometric hemisolvation by ethanol, where the disordered solvent molecule is linked to the heterocyclic component by a two-point linkage, and in the differences between the crystal structures of (I)-(III) and that of (IV).