Abstract
There is considerable interest in the development of bifunctional ligand scaffolds for the group 7 metals due to potential biological applications. Building on our recent work in the development of "click" ligands and macrocycles, we show that a CuAAC "click" approach can be exploited for the synthesis of a small family of bioconjugated tridentate pyridyl-1,2,3-triazole macrocycles. These bioconjugated tridentate macrocycles form stable [Re(CO)3]+ complexes, and this could facilitate the development of [M(CO)3]+ (M = Mn, Tc, Re) targeted agents. The parent macrocycle, bioconjugates, and [Re(CO)3]+ complexes were characterized by elemental analysis and HR-ESI-MS, 1H and 13C NMR, and IR spectroscopy, and the molecular structures of the alcohol-functionalized macrocycle and two of the Re(I) complexes were confirmed by X-ray crystallography. The electronic structure of the parent [Re(CO)3]+ macrocycle complex was examined using UV-vis, Raman, and emission spectroscopy and density functional theory calculations. The complex exhibited intense absorptions in the UV region which were modeled using time-dependent density functional theory (TD-DFT). The calculations suggest that the lower energy part of the absorption band is MLCT in nature and additional higher energy π-π∗ transitions are present. The complex was weakly emissive at room temperature in methanol with a quantum yield of 5.1 × 10-3 and correspondingly short excited state lifetime (τ ≈ 20 ns). The family of macrocycles and the corresponding Re(I) complexes were tested for antimicrobial activity in vitro against both Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) microorganisms. Agar-based disk diffusion assays indicated that two of the Re(I) complexes displayed antimicrobial activity but the minimum inhibitory concentrations (MIC) for these compounds proved to be extremely modest (MIC > 256 μg/mL).
Original language | English |
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Pages (from-to) | 7031-7043 |
Number of pages | 13 |
Journal | Organometallics |
Volume | 33 |
Issue number | 24 |
DOIs | |
Publication status | Published - 22 Dec 2014 |
Bibliographical note
Publisher Copyright:© 2014 American Chemical Society.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry