Two azafulgides were synthesized and their crystal structures determined by a single crystal X‐ray diffraction analysis. The substances crystallized in the following symmetries and cell parameters. C23H19NO3(2): triclinic space group P&1bar; with a = 7.243(2). b = 10.981(6) and c = 12.672(8)Å, α = 80.40(5)°, β = 75.58(4)° and γ = 77.32(3)° Z = 2; C19H19NO3(1): orthogonal space group C2v9‐Pmc21 with a = 8.079(8), b = 12.752(9) and c = 15.752(13)Å, Z=4. The calculated densities are 1.26 and 1.27 g/cm3 respectively for 2 and 1. The crystal structures were determined by direct methods. The least‐squares refinement led to R values of 0.044 and 0.058 for 2 and 1 for 2738 and 952 reflections with I > 3σ‐(I) respectively.

Six fulgides of indole series are prepared. Three of them are photochromic. The others in which R1 is hydrogen atom do not show photochromism. Only Z‐E isomerizations occur on irradiation at 365 nm. The effects of molecular structural modifications on photochromic properties are also discussed.