Self-Assembled Multinuclear Complexes Incorporating ^99m Tc

Multinuclear complexes or clusters are rarely investigated in medicinal inorganic chemistry although they represent structural intermediates between molecules and nanomaterials. We present in this report two strategies towards ^99m Tc-containing clusters. In a pre-assembly approach, the preformed but incomplete cluster fragment [Re₃ (μ₂ -OH)₃ (μ₃ -OH)(CO)₉ ]^- reacts with [^99m Tc(CO)₃ ]⁺ to the highly stable [^99m TcRe₃ (μ₃ -OH)₄ (CO)₁₂ ] cube. The same structure self-assembles when reacting the mononuclear Re and ^99m Tc precursors in one pot. Integrating the coordinating OH groups from Schiff bases in this concept leads straight to dinuclear, mixed-metal complexes of the type [^99m TcRe(μ₂ -O^N-R¹ )₂ (CO)₆ ] in quantitative yields. Both strategies are unprecedented and open a future path towards clusters, incorporating a ^99m Tc radiolabel while being decorated with targeting or cytotoxic moieties.