The unequivocal solid-state structure and stereochemistry of the hetaryl leuco-TAM dye, 2,2'-(2-phenyl propane-1,3-diylidene) bis(1,3,3-trimethylindoline) derivatives were established using X-ray single crystal analysis. The X-ray crystal analysis showed that the (Z, E)-isomers only formed stereoselectively, with a so-called "threebladed propeller" conformation, from the reaction of a Fischer base and benzaldehyde derivatives. These isomers were stacked in a juxtaposition to form a dimer or a double dimer, adopting either a triclinic, with P-1, or monoclinic crystal system with a space group P21/n in the unit cell of the crystal.