Solvatochromic and Photochromic behavior of 1',3',3'-trimethyl-8-nitrospiro[chromene-2,2'-indoline]

1',3',3'-trimethyl-8-nitrospiro[chromene-2,2'-indoline] is one of the spiropyran derivatives. In recent years,  the  spiropyran  derivatives  have  been  studied  numerously  for  their  photochromic properties.We know these compounds as an isomeric system. The closed-ring spiropyran (SP) could be  converted  into  the  open-ring  merocyanine  (MC) upon  UV  irradiation.  In  this  work,  1',3',3'-trimethyl-8-nitrospiro[chromene-2,2'-indoline] is prepared, and subsequently, characterized by the FT-IR, 1H-NMR,  and 13C-NMR  spectroscopic  techniques.  In  order  to  confirm  its  molecular structure, the UV–visible spectroscopic analysis of its solutions is studied in different solvents in the spectral range of 250-750 nm before and after exposure to a UV lamp. The 1',3',3'-trimethyl-8-nitrospiro[chromene-2,2'-indoline]chromophore shows a solvatochromism behavior: the spiropyran solution  in  acetonitrile  is completely  colorless, while  its  solution  is pale  blue  in  DMF  and  dark purple  in  ethanol  and  methanol.  The  visible  spectra  of  the  spiropyran  solutions  show  that the solvents methanol and ethanol are capable of stabilizing the MC form better than the solvents DMF and  acetonitrile,  and that  this  photochromic  compound  has  a  higher  absorption  intensity  in  the visible region.