Two isomeric 10-methyl-8-phenyl-11-pyridyl-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinolines: cyclic hydrogen-bonded tetramers versus isolated molecules.

The molecules of 10-methyl-8-phenyl-11-(3-pyridyl)-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, C26H20N4, (I), are linked by a single C-H...N hydrogen bond into cyclic R(4)(4)(12) tetramers generated by a -4 axis. In isomeric 10-methyl-8-phenyl-11-(4-pyridyl)-6,8-dihydro-5H-benzo[f]pyrazolo[3,4-b]quinoline, (II), which crystallizes with Z' = 2 in space group P2(1)2(1)2, the two independent molecules are nearly enantiomeric but there are no direction-specific interactions between them.