Electrochromic behaviour and x-ray structure analysis of a Pechmann dye, (E)-5,5′-diphenyl-3,3′-bifuranylidene-2,2′-dione

Studies on the title compound have established that, although it could be oxidised with a concomitant change in its visible spectrum, this process is not reversible. This is discussed in the light of the crystal structure which is also reported in this paper. The title compound crystallises in the monoclinic space group P2₁/n, a = 27.033(6) Å, b = 4.988(2) Å, c = 5.372(2) Å, β =94.59(2)°. The molecules have close intermolecular contacts along stacks packing in the c direction. The packing is compared to that found in two other Pechmann dyes.