PURPOSE: To provide a photochromic substance consisting of a specific halogen- containing metal diaryl thiocarbazonate, exhibiting distinct color change, having excellent solubility in organic solvents, and durable to weathering and repeated color changes.

CONSTITUTION: The objective photochromatic substance is represented by the formula [M is HgII, PdII, PtII, NiII, AgI, ZnII, GdII, PbII, BiIII or TiI; m is 1W3; R and R1 are group of formula IIWV (X and X1 are halogen); R2 and R3 are 1W4C alkyl, 2W6C alkoxycarbonyl, 6W10C aryl, nitro, sulfonyl, sulfo, 6W10C arylamino, 1W4C alkylamino, 1W4C alkoxy, 6W10C allyloxy, amino, 2W11C acyl, hydroxy, 1W11C acylamino, or trifluoromethyl].

USE: Recording memory, copying material, recording material such as photo-sensitive material for laser, photo-sensitive material for holography, etc., optical filter, displaying material, actinometer, decorative material, etc.