Self‐Assembled Multinuclear Complexes Incorporating ^99mTc

Abstract

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 Tc-containing clusters. In a pre-assembly approach, the preformed but incomplete cluster fragment [Re (μ -OH) (μ -OH)(CO) ] reacts with [ Tc(CO) ] to the highly stable [ TcRe (μ -OH) (CO) ] cube. The same structure self-assembles when reacting the mononuclear Re and 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 [ TcRe(μ -O^N-R ) (CO) ] in quantitative yields. Both strategies are unprecedented and open a future path towards clusters, incorporating a Tc radiolabel while being decorated with targeting or cytotoxic moieties.

Chemistry at High Dilution: Dinuclear 99 mTc Complexes

“…Reactionof1 + + (Re) and 1 + + ( 99m Tc )w ith 2-mercapto-ethanol yields the dinuclear heterometallic (Re/ 99m Tc )complex 2 À À (top). HPLC traces of 2 À À (g-detection,red trace, R t = 18.6 min) and Re 2 (m 2 -S(CH 2 ) 2 OH) 3 (CO) 6 ] À (UV-detection, black trace, R t = 17.7 min)c onfirm the structurali dentity of the two homologues. The signals at longer retention times are complexes of higher nuclearity.…”

“…We recently showed that multinuclear complexes comprising one 99m Tc moiety are accessible either by a pre‐ or a self‐assembly approach . Extending this concept from oxygen‐ to sulfur bridging ligands, we found that [Re(OH 2 ) 3 (CO) 3 ] + ( 1 + (Re)) together with [ 99m Tc(OH 2 ) 3 (CO) 3 ] + ( 1 + ( 99m Tc)) and 2‐mercaptoethanol HS(CH 2 ) 2 OH rapidly led to quantitative consumption of 1 + ( 99m Tc) and the formation of 2 − as the major product (Figure , top), besides higher molecular clusters as minor products.…”

“…Crystals were grown using nano-crystallization screening experiments. [8] (19), Re1-S1-Re2 86.27 (5),R e1-S2-Re2 86.32 (6), Re1-S3-Re2 86.31 (6). and with a 99m Tc-concentration of about 100 nm,o ne main radioactive species was observed as as ingle peak on HPLC (R t = 18.4 min, g-channel, Figures S3 and S4).…”

“…We recently showedt hat multinuclear complexesc omprising one 99m Tc moiety are accessible either by apre-or as elf-assembly approach. [6] Extending this concept from oxygen-to sulfur bridging ligands, we found that [Re(OH 2 ) 3 (CO) 3 ] + (1 + + (Re)) togetherw ith [ 99m Tc (OH 2 ) 3 (CO) 3 ] + (1 + + ( 99m Tc )) and2 -mercaptoethanol HS(CH 2 ) 2 OH rapidly led to quantitative consumption of 1 + + ( 99m Tc )a nd the formationof2 À À as the major product (Figure 1, top), besides higherm olecular clusters as minor products.P erforming the synthesis with microwave assisted heating, insteado fs tirring at room temperature, diminished the formation of higher molecular clusters and thus led to better yields of 2 À À .F igure 1b ottom shows the HPLC traces in the UV/Vis and g-channel of such am icrowavea ssisted reaction (for the r.t. experiment see Figure S2).…”

Formation of a highly dense tetra-rhenium cluster in a protein crystal and its implications in medical imaging

“…This has been followed by two strategies which can prepare multinuclear rhenium(I) and technetium(I) tricarbonyl complexes, either di-or tetranuclear clusters, in a one-pot reaction. Furthermore, it allows for a tetranuclear cluster containing both rhenium and technetium metal centres to be a model theranostic agent (Frei et al, 2018).…”