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Abstract. The interaction of CT DNA by two anionic Ru(III) complexes with N-substituted salicylidenimine ligands was investigated by spectroscopic titration and cyclic voltammetry. The result gives a surprising evidence for intercalation of DNA by the negatively charged complex species containing non typical intercalating ligands with K b of order 10 4 M −1 . Na[RuCl 2 (N-R-5-X-salim) 2 ], where R represents butyl or phenyl and X = H, Cl, were characterized on the basis of elemental analysis, MALDI-TOF mass spectrometry, infrared, UV / visible spectroscopic measurements and cyclic voltammetry. (doi: 10.5562/cca2216)

A simple biosensor constructed by bulk-modification of carbon ink with manganese dioxide as a mediator was investigated for its ability to serve as amperometric detector for L-ascorbic acid in hydrodynamic mode. The sensor could be operated at pH 5.0 (0.05 M phosphate buffer) and exhibited excellent reproducibility and stability. Optimization of measurement parameters such as applied working potential and pH value were studied in detail. The screen printed electrode exhibited a linear amperometric increase with the concentration of L-ascorbic acid from 50 mg L(-1) to 250 mg L(-1) and gave a (LOD = 3sigma) detection limit of 0.2 mg L(-1) (1.172 micromol L(-1)). The manganese dioxide modified screen printed electrode shows long term stability.

A dinuclear Schiff base RuII complex derived from 5‐chlorosalicylaldehyde and 2‐aminopyridine was synthesized. The structure of the compound was analyzed by mass spectrometry as well as IR, UV/Vis, and 1H NMR spectroscopy, along with chemical analysis,as well as magnetic, cyclovoltammetric and conductivity measurements. Two RuII atoms are octahedrally coordinated by azomethine and pyridine nitrogen atoms from two tridentate monobasic Schiff bases and bridging phenol oxygen atoms. The formula of the complex is [Ru2L2Cl2(Et2NH)(H2O)] [L = N‐(2‐pyridyl)‐5‐chlorosalicylideneimine and Et2NH = isodiethylamine]. The RuII atoms in the dinuclear neutral complex species have different coordination environments, RuN3O2Cl and RuN2O3Cl. Interaction with CT DNA showed moderate hydrophobic binding. The compound demonstrates strong activity against methicillin‐resistant Staphylococcus aureus, methicillin‐sensitive Staphylococcus aureus, and especially Enterococcus faecalis. Microbiological tests showed significant inhibition of growth and ability to kill pathogens, similar or even improved compared to reference antibiotics vancomycin.

A simple glucose biosensor has been developed by bulk modification of a carbon paste electrode with glucose oxidase as a biocomponent and manganese dioxide as a mediator. The sensor was employed as amperometric detector in a flow-injection system at 21 °C in 0.2 M phosphate buffer (pH 7.5). At an applied working potential of 0.48 V vs Ag/AgCl and a flow rate of 0.2 ml min-1, the sensor exhibited well reproducible amperometric response to glucose. A linear relation between the peak current and the analyte concentration was found between 20 and 500 mg l-1 glucose with a detection limit (3σ) of 10.5 mg l-1 glucose. The sensor can be operated continuously for 12 h without any loss in the signal height and can be used for the determination of glucose in white wine samples.

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