PURPOSE: To provide a new compd. as a complexing agent for nuclides which can be used for nuclear medicine.

CONSTITUTION: This compd. is expressed by formula I, wherein T is S, O; R1 is O or S bonded with R2; R1 to R4 are H, -(CH2)a-CH3, -COOR', -SO3R', etc.; R' is H, phenyl, p-hydroxyphenyl, etc.; W is H, -COCH3, -CH2C6H5, etc.; (m), (n), (o) are 0 to 2; (a) is 0 to 20. The compd. of formula I is obtd. by adding pertechnetic acid salt-99mTC to 10-benzoyl-8-keto-7-aza-2-amino-4,10-dithiadecanoic acid expressed by formula II and removing protective groups. The obtd. complex is suitable for medical diagnosis, especially to display the blood supply state in heart and brain.