An embodiment of the invention comprises a ligand of Formula I wherein R1 and R2 are independently an alkyl or cycloalkyl R3 is and alkyl X is CO or SO2 Y is (CH2)n, C6H4, (OCH2CH2)n(NHCH2CH2)n and (OCH2CH2CH2)n, or a combination thereof Z is linker group capable of conjugating to a vector and n is an integer between 0 and 10. Also included are an imaging agent comprising a compound of Formula I complexed to 99mTc and their method of use to image a subject having a target site using single photon emission computed tomography (SPECT).
