New thermally irreversible photochromic methyl cyanoacetate-condensed fulgide derivatives were prepared and their photochromic properties were investigated. Coloured form of methyl cyanoacetate-condensed derivatives C-4(a-d) show large bathochromic shifts of their long wavelength absorption bands compared to the coloured form of corresponding fulgides Z-1(a-d). Solvent effects on the compound ZZ-4a and its ring-closed form C-4a were investigated. The polarity of the solvent caused a bathochromic shift of both coloured and uncoloured forms. (C) 2007 Elsevier B.V. All rights reserved.