c was synthesized when a film was produced from the above prepared compound and irradiated with light for 30 seconds in the same manner as in example 1 a deep blue color developed the u03bb max was 628 nm the change in absorbance at the u03bb max is shown in the table below in the same manner as in example 1 but replacing 1 2 3 3 tetramethylindole iodide with 1 isopropyl 2 3 3 trimethylindole iodide example 6 1 hexadecyl 2 3 3 trimethylindole iodide example 7 or 1 octadecyl 2 3 3 trimethylindole iodide example 8 the respective compound of the formula i wherein x 1 x 2 x 3 x 4 and r are as shown in the table below was synthesized when a film produced from each of the resulting compounds was irradiated with light in the same manner as in example 1 a deep blue color developed in each case the u03bb max was 618 nm 617 nm or 617 nm respectively in 250 ml of methyl alcohol was dissolved 24 6 g of sodium 1 nitroso 2 naphthol 6 sulfonate and the solution was heated to 65 u00b0 c to the resulting solution was added dropwise 100 ml of a methyl alcohol solution containing 10.