Figure 3:

a) Radiolabelling reaction of ligand 9 with a highly reactive [^99mTc(CO)₃(H₂O)₃]⁺-complex in aqueous solution. b) Overview of the HPLC-trace of Re-complex 10 as a non-radioactive surrogate [UV, 254 nm] with a retention time of 12.5 min and the radio-HPLC-trace of the technetium-99m complex 11 [$\text{γ}$-detector, radioactive counts] with a retention time of 12.6 min. 11 was obtained in a radiochemical yield of 59% with a radiochemical purity of >98% after purification on an analytical HPLC with deionized water and acetonitrile containing 0.1% TFA each.