Effect of rhenium(i) complexation on aza-Michael additions to 5-amino-1,10-phenanthroline with [18F]ethenesulfonyl fluoride towards PET optical tracer development
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Date
2019-01-14
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Publisher
CSIRO Publishing
Abstract
Conjugations with the recently developed [18F]ethenesulfonyl fluoride ([18F]ESF) were performed on 5-amino-1,10-phenanthroline, in its free form and coordinated to a rhenium(i) tricarbonyl complex, as a means of radiosynthesizing dual-modal optical and positron emission tomography (PET) tracers. The Michael-donating ability of the aromatic amine was noticeably perturbed on coordination with the rhenium(i) centre, resulting in decreased radiochemical yields from 34 %, in the case of the free ligand, to 1 %. We attribute the decreased nucleophilicity of the amine to metal deactivation from the electron-withdrawing feature of the rhenium(i) tricarbonyl centre, based on spectroscopic and computational evidence, thus highlighting this effect as a crucial parameter in designing late-stage metal coordination methods employing related aza-Michael additions. Photophysical analyses were also performed on the ESF-conjugated rhenium(i) complex, exhibiting a longer decay lifetime from the triplet metal-to-ligand charge transfer excited state when compared with the non-conjugated analogue. © CSIRO 1996-2021
Description
Keywords
Fluorine 18, Phenanthrolines, Rhenium, Positron computed tomography, Emission computed tomography, Tracer techniques, Radiochemical analysis, Ligands, Decay
Citation
Klenner, M. A., Pascali, G., Zhang, B., Ciancaleoni, G., Massi, M., & Fraser, B. H. (2019). Effect of rhenium(i) complexation on aza-Michael additions to 5-amino-1,10-phenanthroline with [18F]ethenesulfonyl fluoride towards PET optical tracer development. Australian Journal of Chemistry, 72(4), 288-294. doi:10.1071/CH18512