New bis(azobenzocrown)s with dodecylmethylmalonyl linkers as ionophores for sodium selective potentiometric sensors.

Novel biscrowns 1 and 2 were synthesized from 13-membered azobenzocrown ethers containing bromoalkylenoxy chains in para position relative to the azo group. The synthesized diester molecules are dodecylmethylmalonic acid derivatives differing by the linker length. The synthesized compounds have the potential of being used as sodium ionophores in ion-selective electrodes. They were characterized and used as ionophores in classic and miniature, solid contact (screen-printed and glassy carbon) membrane ion-selective electrodes. Compound 3, a similar monoester derivative of 13-membered azobenzocrown, was synthesized and used in membrane electrodes for comparison. Lipophilicity of new ionophores was determined by TLC. Lipophilicity of bis(azobenzocrown)s was found to be within the range of logPTLC = 12-13. It was observed that the particularly important selectivity coefficients logKNa,K determined for new electrodes, being logKNa,K = -2.5 and -2.6 (SSM, 0.1 M), are better than those of the electrodes featuring seven out of the nine commercially available sodium ionophores. It was concluded that the ionophore 1 creates, in acetone, with sodium iodide, complex of 1:1 stoichiometry (sandwich complex) with stability constant (logK) ca. 3.0.

Synthesis of thiol derivatives of azobenzocrown ethers. The preliminary studies on recognition of alkali metal ions by gold nanoparticles functionalized with azobenzocrown and lipoic acid.

The article presents the synthesis of novel 13- and 16-membered azobenzocrown derivatives with peripheral thiol moieties and preliminary studies assessing their possible application in plasmonic sensors based on gold nanoparticles. The effect of the length of the chain connecting the macrocycle with the thiol group and the effect of the presence of the additional functional compound, i.e. lipoic acid, on the sensor response was analyzed. Colloidal gold nanoparticles modified with a 16-membered crown with a thiol group on oxyethylene (compound 12) or oxybutylene (compound 13) linker was found to have good properties, allowing for detection of potassium ions in aqueous solutions at concentrations 8-20 mM for bifunctionalized nanogold and 4-26 mM for less stable, colloidal gold modified only with thiol derivatives of azobenzocrowns. The response towards potassium cations of bifunctionalized nanogold modified with compound 13 was more stable in time than for the system incorporating compound 12. Compound 13, obtained with the highest yield among all presented thiol derivatives of azobenzocrowns, was selected for further, more detailed, studies.