Diastereomeric isomerization of hetaryl leuco-TAM dyes, (2Z, 2′E)-2,2′-(2-phenyl propane-1,3-diylidene)bis(1,3,3-trimethylindoline) derivatives in various organic solvents

The diastereomeric isomerization of the ZE isomers of (2Z, 2′E)-2,2′-(2-phenyl propane-1,3-diylidene) bis(1,3,3-trimethylindoline) derivatives were examined by ¹H NMR spectroscopy in various organic solvents. In non-polar solvents, such as benzene, THF, and chloroform, the ZE isomers of these molecules equilibrated into a mixture of ZE/EE or ZE/EE/ZZ isomers with time, whereas the isomers were inert in polar organic solvents, such as acetone and DMSO. Theoretical calculations of the energies and dipole moments of the diastereomers in different media were performed using the Jaguar program.