Antibacterial agents are widely used, today, for treatment of many different bacterial infections. The most common strains of bacteria are, however, growing resistance towards these available agents rapidly. The bacterial resistance is the most important cause of constant need for new antibacterial agents. Metallohelicates as a branch of supramolecular chemistry are the primary topic of this study. Due to the success of silver as an antimicrobial agent, here the synthesis of silver(I)-based helicates of the type [Ag2(N4-TL)2](PF6)2 using symmetrical pyridine based N4-tetradentate ligands (N4-TL) such as, (N1E,N2E)-N1,N2-bis(pyridin-2-ylmethylene)-1,2-diaminoethane (picen), (N1E,N2E)-N1,N2-bis((6-methylpyridin-2-yl)methylene)-1,2-diaminoethane (6-Mepicen), (N1E,N2E)- N1,N2-bis(pyridine-2-ylmethylene)-1,2R-diaminopropane (Pic-1,2R-pn), N1,N3-bis(pyridin-2-ylmethyl)propane-1,3-diamine (Pic-1,3-pnh), N1,N4-bis(pyridin-2-ylmethylene) 1,4-diaminobutane (pic-1,4-bn), (1S,2S,N1E,N2E)- 1,2-diphenyl-N1,N2-bis(pyridine-2-ylmethylene)-1S,2S-diaminoethane (S,S-picenph2) and (1R,2R,N1E,N2E)-1,2-diphenyl-N1,N2-bis(pyridine-2-ylmethylene)-1R,2Rdiaminoethane (R,R-picenph2), are presented. N4-TLs were synthesised and coordinated to silver(I) to determine the effects that modifications to the diamine linker may have on the configuration of the silver(I) helicates. An increase is size of the linker chain of the silver(I) helicates is expected to proportionally increase the biological activity of these compounds. Also an increase in the size of the linker chain may result in helicates to bind at different positions to DNA. The ligands and their resulting silver(I) helicates have been characterised using 1H and 13C Nuclear Magnetic Resonance (NMR), Infrared (IR), Ultraviolet-Visible (UV-Vis), Electrospray Ionisation Mass spectrometry (ESI-Mass) and X-ray crystallography. Crystal structures of [Ag2(picen)2](PF6)2, [Ag2(picen)2](ClO4)2, [Ag2(6-Mepicen)2](PF6)2 and [Ag2(pic-1,4-bn)2](PF6)2 were obtained and confirmed that helicates were formed. Subsequently these silver(I) helicates were examined for their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. 2 Also their interactions with DNA were investigated using circular dichroism (CD), linear dichroism (LD) and Isothermal Titration Calorimetry (ITC).
Date of Award | 2014 |
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Original language | English |
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