A New Binding Mode in the Dynamic Coordination Chemistry of Porphyrins

In our on-going research program dedicated to the coordination of various cations of medical interests, we have been studying different types of porphyrinic architectures.¹ Among these cations, bismuth appears as a plausible candidate for alpha-radiotherapy.² Considering the decay scheme of its 213 isotope, it is obvious that the coordination chemistry of bismuth³ and lead⁴ and to some extent, thallium are somehow related and exhibit some similarities.

For instance, we have shown that an unprecedented transmetalation mechanism involving a daughter radionuclide is expected to increase the rate of ²¹³Bi incorporation leading to 1Bi.⁵

Moreover, we will detail and demonstrate that this peculiar behaviour is rationalized by a translocation-coupled transmetalation mechanism, leading to the formation of a dinuclear complex in which coexist the long-known out-of-plane (OOP) coordination mode and the newly reported hanging-atop (HAT) coordination mode.⁶

 This HAT binding mode is found in both homo- and heterobimetallic complexes with lead and bismuth (see both X-ray structures above) and represents the prerequisite for metal migration processes according to which these dinuclear complexes behave as allosteric Newton’s Cradle-like devices (NCD).⁷ This NCD behaviour can be extended to other metal complexes and controlled and/or initiated in different ways.⁸

 

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4. Halime Z; Michaudet L; Lachkar M; Brossier P; Boitrel B. Bioconjugate Chem., 2004, 15, 1193-1200.

5. Le Gac, S.; Najjari, B.; Motreff, N.; Remaud-Le Saec, P.; Faivre-Chauvet, A.; Dimanche-Boitrel, M.-T.; Morgenstern, A.; Bruchertseifer, F.; Lachkar, M.; Boitrel, B. Chem. Commun. 2011, 47, 8554 - 8556.

6. Le Gac S.; Najjari B.; Fusaro L.; Roisnel T.; Dorcet V.; Luhmer M.; Furet E.; Halet J.-F.; Boitrel B. Chem. Commun., 2012, 48, 3724-3726.

7. Najjari B.; Le Gac S.; Roisnel T.; Dorcet V.; Boitrel B. J. Am. Chem. Soc., 2012, 134, 16017-16032.

8. a) Le Gac, S.; Dorcet, V.; Fusaro, L.; Boitrel, B., Chem. Eur. J. 2013, 19, 13376-13386.  b) Le Gac, S.; Najjari, B.; Dorcet, V.; Roisnel, T.; Fusaro, L.; Luhmer, M.; Furet, E.; Halet, J.-F.; Boitrel, B., Chem. Eur. J. 2013, 19, 11021-11038. c) Le Gac, S.; Fusaro, L.; Roisnel, T.; Boitrel, B., J. Am. Chem. Soc. 2014, 136, 6698-6715.