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    STUDIA CHEMIA - Issue no. 1-2 / 1999  
         
  Article:   POLYMETHINE DYES. PART II*. THE PHOTOCHROMIC BEHAVIOUR OF SOME CATIONIC DIMETHINE DYES.

Authors:  IOAN BÂLDEA, IOAN PANEA, ADRIAN CONSTANTIN APETRI.
 
       
         
  Abstract:  The photochromic behaviour of some 1-H-indazolo-3dimethine dyes (1-3) in dimethylformamide and 5-chloro-1,3,3.trimethyl-2-[2-(4-oxo-4-H-1-benzopyran-3-yl)ethenyl]-3-H-indolium perchlorate (4) in 1,2 dichloroethane, acetone and acetic acid has been studied. The reason for the photochromism consists of the Z/E or cis/trans isomerisation reaction. The formation of Z configuration at light exposure and thermal re-formation of E configuration at dark is supported by spectroscopic data (UV-VIS, IR and 1H- NMR) and kinetic data. Activation parameters for the cis-trans isomerisation have been determined.  
         
     
         
         
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