The merocyanine form of DIPS and three of its nitro derivatives were studied by surface-enhanced Raman spectroscopy. It was found that in case of the nitro derivates, the SERS spectra originated from the unprotonated open merocyanine forms, even if the solution was acidified. In case of 6-nitro BIPS, there exist two enantiomers of the closed spiro form with different properties. The photoinduced merocyanine form of the photoactive enantiomer is different from the thermal ring opening product of the photoinactive enantiomer.