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New approach for the synthesis of water soluble fac-[MI(CO)3]+ bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re)


Kama, Dumisani V; Frei, Angelo; Brink, Alice; Braband, Henrik; Alberto, Roger; Roodt, Andreas (2021). New approach for the synthesis of water soluble fac-[MI(CO)3]+ bis(diarylphosphino)alkylamine complexes (M = 99Tc, Re). Dalton Transactions, 50(47):17506-17514.

Abstract

A novel proof-of-concept is reported to modify the water solubility and potential biological effects of a bis(diphenylphosphino)alkylamine (PNP) ligand and the corresponding metal complex, by introducing an amine group on the outer periphery of the pendant ligand arm. Thus, a tertiary butoxycarbonyl protected N’-Boc-ethylenediamine-N,N-bis(diphenylphosphino) (N‘-Boc-PNP) ligand (1) was synthesized by reacting the protected ethylenediamine and chlorodiphenylphosphine in a 1 : 2 molar ratio. The corresponding fac-[Re(CO)3(N‘-Boc-PNP)Br] (1A) complex was then obtained by reacting N‘-Boc-PNP (1) with (Et4N)2fac-[Re(CO)3Br3] in equimolar amounts in DCM at 50 °C. De-protection of the N‘-Boc pendant amine group in 1A with TFA leads to fac-[Re(NH3+-PNP)(CO)3Br]·CF3COO− (1B) which is soluble in D2O (>0.05 M). Treating 1B with saturated aqueous NaHCO3 yields fac-[Re(NH2-PNP)(CO)3Br]·MeOH (1C) in near quantitative yield. Although both 1A and 1C are not soluble in D2O, addition of TFA easily generates 1B (31P NMR), confirming the formation of the protonated amine. Isolation of fac-[99Tc(CO)3(N-Boc-PNP)(Cl)] (1D) confirmed that the rhenium and technetium (99Tc) can be easily interchanged in this process. Reported are hence the unique rhenium series of compounds 1A, 1B and 1C and the corresponding technetium complex 1D, unequivocally characterized by single crystal XRD, as well as IR and 1H NMR spectroscopy. Preliminary antimicrobial evaluation indicates that ligand 1 and its respective rhenium complexes (1A–1C) were not active against selected fungi (Candida albicans and Cryptococcus neoformans) and bacteria (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus). These types of ligands and complexes therefore present themselves as excellent radio models for further evaluation using 186Re, 188Re and 99mTc to potentially study the radiotoxicity of appropriately designed complexes.

Abstract

A novel proof-of-concept is reported to modify the water solubility and potential biological effects of a bis(diphenylphosphino)alkylamine (PNP) ligand and the corresponding metal complex, by introducing an amine group on the outer periphery of the pendant ligand arm. Thus, a tertiary butoxycarbonyl protected N’-Boc-ethylenediamine-N,N-bis(diphenylphosphino) (N‘-Boc-PNP) ligand (1) was synthesized by reacting the protected ethylenediamine and chlorodiphenylphosphine in a 1 : 2 molar ratio. The corresponding fac-[Re(CO)3(N‘-Boc-PNP)Br] (1A) complex was then obtained by reacting N‘-Boc-PNP (1) with (Et4N)2fac-[Re(CO)3Br3] in equimolar amounts in DCM at 50 °C. De-protection of the N‘-Boc pendant amine group in 1A with TFA leads to fac-[Re(NH3+-PNP)(CO)3Br]·CF3COO− (1B) which is soluble in D2O (>0.05 M). Treating 1B with saturated aqueous NaHCO3 yields fac-[Re(NH2-PNP)(CO)3Br]·MeOH (1C) in near quantitative yield. Although both 1A and 1C are not soluble in D2O, addition of TFA easily generates 1B (31P NMR), confirming the formation of the protonated amine. Isolation of fac-[99Tc(CO)3(N-Boc-PNP)(Cl)] (1D) confirmed that the rhenium and technetium (99Tc) can be easily interchanged in this process. Reported are hence the unique rhenium series of compounds 1A, 1B and 1C and the corresponding technetium complex 1D, unequivocally characterized by single crystal XRD, as well as IR and 1H NMR spectroscopy. Preliminary antimicrobial evaluation indicates that ligand 1 and its respective rhenium complexes (1A–1C) were not active against selected fungi (Candida albicans and Cryptococcus neoformans) and bacteria (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Staphylococcus aureus). These types of ligands and complexes therefore present themselves as excellent radio models for further evaluation using 186Re, 188Re and 99mTc to potentially study the radiotoxicity of appropriately designed complexes.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Scopus Subject Areas:Physical Sciences > Inorganic Chemistry
Uncontrolled Keywords:Inorganic Chemistry
Language:English
Date:1 January 2021
Deposited On:16 Feb 2022 15:19
Last Modified:28 Jan 2024 02:44
Publisher:Royal Society of Chemistry
ISSN:1477-9226
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1039/d1dt03234h
Project Information:
  • : FunderSNSF
  • : Grant IDIZLSZ2_149029
  • : Project TitleMulti-functional Cyclopentadienyl and Carbonyl Complexes for Theranostic Applications