Crystallographic studies of (Z) and (E) isomers of 2-amino-5-(2-chlorobenzylidene)-1-methyl-1H-imidazol-4(5H)-one

The X-ray structures of two geometric isomers of 5-(2-chlorobenzylidene)-creatinine (1) are reported. In the crystal of almost planar 1-(E) hydrogen bonded centrosymmetric dimmers dominate, while in the structure of 1-(Z), adopting the twisted conformation, helical chains motifs, subsequently intertwined in braids, are preferred. Both creatinine analogs were found to crystallize in the 2-amino tautomeric form. X-ray investigations have been supported with 1H and 13C NMR data that confirmed 2-amino form also in DMSO solutions of (E)- and (Z)-5-(2-chlorobenzylidene)-creatinine.