Synthesis, characterisation and in vitro cytotoxicity of mixed ligand Pt(ii) oxadiazoline complexes with hexamethylenetetramine and 7-nitro-1,3,5-triazaadamantane.

trans-Platinum(ii) oxadiazoline complexes with 7-nitro-1,3,5-triazaadamantane (NO2-TAA) or hexamethylenetetramine (hmta) ligands have been synthesised from trans-[PtCl2(PhCN)2] via cycloaddition of nitrones to one of the coordinated nitriles, followed by exchange of the other nitrile by NO2-TAA or hmta. Stoichiometric control allows for the selective synthesis of mono- and dinuclear complexes where 7-NO2TAA and hmta act as mono- and bidentate ligands, respectively. Precursors and the target complexes trans-[PtCl2(hmta)(oxadiazoline)], trans-[PtCl2(NO2-TAA)(oxadiazoline)] and trans-[{PtCl2(oxadiazoline)}2(hmta)] were characterised by elemental analysis, IR and multinuclear (1H, 13C, 195Pt) NMR spectroscopy. DFT (B3LYP/6-31G*/LANL08) and AIM calculations suggest a stronger bonding of hmta with the [PtCl2(oxadiazoline)] fragment, in agreement with the experimentally observed reactivity in the ligand exchange (hmta > 7-NO2TAA). Replacement of the nitrile by hmta is predicted to be more exothermic than that with 7-NO2-TAA, although the activation barriers are similar. Protonation of the non-coordinated N atoms is anticipated to weaken the Pt-N bond and lower the activation barrier for ligand exchange. This effect might help activate these compounds in a slightly acidic environment such as some tumour tissues. Ten of the new compounds were tested for their in vitro cytotoxicity in the human cancer cell lines HeLa and A549. Some of the mononuclear complexes are more potent than cisplatin, and their activity is still high in A549 where cisplatin shows little effect. The dinuclear complexes are inactive, presumably due to their lipophilicity and reduced solubility in water.

Conducting core-shell nanowires by amyloid nanofiber templated polymerization.

The preparation of conducting polymer nanowires in aqueous solutions is a challenging goal, especially for applications in nanobioelectronics. Here, we show that amyloid nanofibers template the formation of conducting polyaniline nanowires with a core-shell architecture. The nanofibers exhibit hydrophobic pockets that presumably preassemble the aniline monomers. The template directs polymer morphology as it favors the formation of linear polymer chains, suppresses defects in the polymer chain which are detrimental to charge transport and induces chiral helicity into the polymer. This strategy has the potential of being applied to other polymers than polyaniline and might open up new possibilities to synthesize biocompatible and conducting polymer nanowires with prospects for applications in, for example, sensing, neuronal tissue engineering, and electrostimulated stem cell differentiation.