Abstract: It is an object of the present invention to provide a compound that has absorption in a near infrared region, has high efficiency of singlet oxygen generation (quantum yield), and also has high tumor toxicity when it is combined with an immunotoxin. According to the present invention, provided is a compound represented by the following formula (1) or a salt thereof: wherein L1 and L2 each independently represent a single bond, —O—, —CO—, an alkylene group containing 1 to 8 carbon atoms, a sugar chain, or a combination thereof; R1 and R2 each independently represent an alkyl group containing 1 to 8 carbon atoms, a carboxylic acid group, an amino group, a hydroxyl group, a thiol group, or a biotin residue; R3, R4, R5, R6, R7 and R8 each independently represent an alkyl group containing 1 to 8 carbon atoms, a phenyl group, a carboxylic acid group, an amino group, a hydroxyl group, a thiol group, or a biotin residue; and M represents Mg, Zn, Fe, P, Si, Cu, Sn, Al, Ti, Mo, or Ni.