SYNTHESIS, H-1-NMR AND ELECTRONIC ABSORPTION-SPECTRA OF 2,6-DISUBSTITUTED DERIVATIVES OF 2,6-DIHYDROBENZ (1,2-C-4,5-C')DIPYRAZOL-3,7-DIONE, A NEW CROSS-CONJUGATED CHROMOPHORE

The synthesis of a series of 2,6-substituted 2,6-dihydrobenz[1,2-c:4,5-c']dipyrazol-3,7-diones is described and their postulated structures confirmed by means of H-1-NMR and mass spectroscopy. The electronic absorption spectra and the changes of bond and charge orders upon electronic excitation are discussed on the basis of Variable-Electronegativity PPP-CI calculations.