A compound having formula: wherein: - X is a radioisotope chosen from the group consisting of: 125 I, 123 I, 124 I, 131 I, and 211 At; - R 1 and R' 1 are independently from each other chosen from the group consisting of: nitro, acyl, formyl, sulfonyl, trifluoromethyl, cyano, chloride, bromide, fluoride, OAc and alkyl groups, or R 1 and R' 1 may form together with the adjacent carbon atom carrying them a C=O group; - R 2 is chosen from the group consisting of: H, alkyl groups, functional groups being able to bind a vector selected from the group consisting of maleimide, N-hydroxysuccinimide ester, tetrafluorophenyl ester, isothiocyanate, isocyanate, anhydride, alkyne and azide groups, and functional groups having targeting properties which make the compound of the invention a vector itself selected from the group consisting of biotine, haptens, antibodies, antibodies fragments, peptides, drugs and nanocarriers; - R 8 and R 9 are independently from each other chosen from the group consisting of H, OH, NH 2, halogen, alkyl groups, alkoxy groups, amine groups, amide groups, and ester groups; - Z is a heteroatom, - R 5 is H or is a -C(R 6)(R 7)- radical forming together with Y and X a five-membered heterocycle when Y is a heteroatom having the same definition as Z, R 6 and R 7 being as defined above for R 1 and R' 1; and - Y is an electron-withdrawing group selected from the group consisting of: nitro, acyl, formyl, sulfonyl, trifluoromethyl, cyano, chloride, bromide, fluoride and OAc, or Y is an heteroatom Z forming a five-membered heterocycle together with X and R 5 being a radical -C(R 6)(R 7)-, wherein "alkyl" means a saturated or unsaturated aliphatic hydrocarbon group which may be straight or branched having 1 to 12 carbon atoms in the chain. - X is a radioisotope chosen from the group consisting of: 125 I, 123 I, 124 I, 131 I, and 211 At; - R 1 and R' 1 are independently from each other chosen from the group consisting of: nitro, acyl, formyl, sulfonyl, trifluoromethyl, cyano, chloride, bromide, fluoride, OAc and alkyl groups, or R 1 and R' 1 may form together with the adjacent carbon atom carrying them a C=O group; - R 2 is chosen from the group consisting of: H, alkyl groups, functional groups being able to bind a vector selected from the group consisting of maleimide, N-hydroxysuccinimide ester, tetrafluorophenyl ester, isothiocyanate, isocyanate, anhydride, alkyne and azide groups, and functional groups having targeting properties which make the compound of the invention a vector itself selected from the group consisting of biotine, haptens, antibodies, antibodies fragments, peptides, drugs and nanocarriers; - R 8 and R 9 are independently from each other chosen from the group consisting of H, OH, NH 2, halogen, alkyl groups, alkoxy groups, amine groups, amide groups, and ester groups; - Z is a heteroatom, - R 5 is H or is a -C(R 6)(R 7)- radical forming together with Y and X a five-membered heterocycle when Y is a heteroatom having the same definition as Z, R 6 and R 7 being as defined above for R 1 and R' 1; and - Y is an electron-withdrawing group selected from the group consisting of: nitro, acyl, formyl, sulfonyl, trifluoromethyl, cyano, chloride, bromide, fluoride and OAc, or Y is an heteroatom Z forming a five-membered heterocycle together with X and R 5 being a radical -C(R 6)(R 7)-,