The synthesis of a bis(Thiosemicarbazone) macrocyclic ligand and the Mn(II), Co(II), Zn(II) and 68Ga(III) complexes

Melyssa L. Grieve, Patrick R.W.J. Davey, Craig M. Forsyth, Brett M. Paterson

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A 1,4,7,10-tetraazacyclododecane (cyclen) variant bearing two thiosemicarbazone pen-dant groups has been prepared. The ligand forms complexes with Mn2+, Co2+ and Zn2+. X-ray crystallography of the Mn2+, Co2+ and Zn2+ complexes showed that the ligand provides a six-coordinate environment for the metal ions. The Mn2+ and Zn2+ complexes exist in the solid state as racemic mixtures of the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,λ)/Λ(δ,δ,δ,δ) diastereomers, and the Co2+ complex exists as the Δ(δ,δ,δ,δ)/Λ(λ,λ,λ,λ) and Δ(λ,λ,λ,δ)/Λ(δ,δ,δ,λ) diastereomers. Density functional theory calculations indicated that the relative energies of the diastereomers are within 10 kJ mol−1. Magnetic susceptibility of the complexes indicated that both the Mn2+ and Co2+ ions are high spin. The ligand was radiolabelled with gallium-68, in the interest of developing new positron emission tomography imaging agents, which produced a single species in high radiochemical purity (>95%) at 90 °C for 10 min.

Original languageEnglish
Article number3646
Number of pages18
Issue number12
Publication statusPublished - 2 Jun 2021


  • Coordination chemistry
  • Cyclen
  • Gallium-68
  • Macrocycle
  • Radiochemistry
  • Thiosemicarbazone
  • Transition metal

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