From 1966 to 1968 he set up the organic chemistry X-ray crystallography department at the University of Heidelberg at the invitation of Heinz Staab.
There he developed and installed computer programs using the direct method of Nobel Laureates Herbert Hauptman and Jerome Karle.
Back at the Weizmann Institute, Leiserowitz worked on the synthesis of molecules for the investigation of various molecular interactions using X-ray crystallography (crystal engineering).
In collaboration with Danish scientists, he also used X-ray diffraction to investigate thin molecular films with synchrotron radiation at DESY in Hamburg.
He and Meir Lahav have been working together for many years on the stereochemical control of crystal formation and growth with targeted impurities.