Configuration dynamic outgoing from the photochemically and thermally stimulated E-Z isomerization of the C=N bond is a characteristic feature of studied isatin diphenylhydrazones. Thermally more stable E-isomers (due to the dimerization process) isomerize to the bathochromically shifted Z-isomers. Although the shift in absorption maximum is not large, the absorbance changes are sufficient for potential practical use of these compounds as photochromic switches when the readout wavelength is optimally selected. The process is reversible and switching cycles can be repeated many times in both directions.Due to the Vis-Vis character of molecular photoswitching and significant geometry changes during the switching process, isatin diphenylhydrazones are suitable candidates for reversible photocontrol of both biological and technological systems. Moreover, the interaction with strongly basic anion leads to the unique photochemical switching between two stable tautomeric forms of organic amide anion and forms thus the four-state molecular switch.¹