A novel approach to robust Tc(III) mixed-ligand chelates as tools for conjugating biologically active molecules


A novel approach to robust Tc(III) mixed-ligand chelates as tools for conjugating biologically active molecules

Pietzsch, H.-J.; Spies, H.

To meet the need for small and "robust" chelates we focussed our recent investigations on new types of technetium(III) chelates, their synthesis and evaluation of molecular properties. Here we report on five-coordinated compounds with "3+1+1", "3+2", and "4+1" donor arrangements.
Such species, all belonging to the family of "n+1"mixed-ligand technetium complexes, were developed and characterized towards versatility, lipophilicity and stability.
The "3+2" approach make use of the combination of a tridentate HS-E-SH ligands with a PR2-SH chelator, common action of the tripodal nitrilotris(ethanethiol) with isocyanide co-ligands leads to
trigonal-bipyramidal "4+1" Tc(III) complexes.
Both types enables easy functionalization and thus a fine-tuning of physicochemical properties of the complexes or to link the chelate unit to biomolecules.
The sterically well shielded oxo-free species are non-polar, showing higher logP values as the "3+1" oxotechnetium(V) compounds. The "3+2" and "4+1" complexes are stable towards re-oxidation and transchelation in challenge experiments with glutathione. The "3+2" type is the most versatile one while the compact "4+1" seems to be the most stable arrangement.
The presented "3+2" and "4+1" complex types are useful tools in designing of 99mTc or 186/188Re radiopharmaceuticals.

  • Lecture (Conference)
    Meeting der COST B12 Action, WG 5, Rom, 29.05.2000

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Publ.-Id: 3380