Trimorphism of a model carcinogen 4-nitroquinoline-N-oxide

Abstract

Three polymorphs of a model carcinogen 4-nitroquinoline-N-oxide were crystallized from its solutions in various organic solvents using either (i) slow cooling or evaporation (form I), (ii) moderate rate of cooling (form II) or (iii) flash cooling (form III). These polymorphs are characterized by distinct crystal morphologies, powder diffractions and IR spectra. Single-crystal X-ray analysis of forms I and II revealed essentially the same geometries of 4-nitroquinoline-N-oxide molecules (with the exception of the nitrogroup characteristics), and distinct patterns of multiple hydrogen bonds, electrostatic interactions and π-stacking in their crystal structures.