Bis-thiourea receptors

Ion-Selective Electrodes based on Bis-Thiourea Receptors. Bis-thiourea derivatives 14, 15, and 17, which have a good membrane solubility, sufficient lipophilicity to prevent leaching into the aqueous sample solution, and a low tendency for self-aggregation in nonpolar solvents, were incorporated into PVC matrix liquid membranes for ISEs. While membrane electrodes based on the dibutyl derivative 14 gave a phosphate response almost identical to that of a conventional anion-exchanger electrode, a membrane electrode based on the phenyl-substituted bis-thiourea 15 exhibited a slightly improved phosphate response, which seems to be the result of improved complexation of phosphate in the sensor membrane. 

ICSs have also been successfully employed for anion sensing. For instance, Umezawa et al. prepared an ion-channel sensor that is selective for phosphate ion in aqueous solution by surface functionalization of a gold electrode with a SAM of a bis-thiourea receptor. They studied the behavior of the material in the presence of several inorganic anions by cyclic voltammetry with [Fe(CN)g] as the redox marker. In the absence of anions, the surface... 

Figure 5. Suggested structure of 1 1 complex between dihydrogenphosphate (H2PO4) and bis-urea (X = O) and bis-thiourea (X = S) receptors.

Tozawa, T., Misawa, Y., Tokita, S., Kubo, Y., A regioselectively bis (thiourea)-substituted dibenzo-diaza-30-crown-10 a new strategy for the development of multi-site receptors. Tetrahedron Lett. 2000, 41, 5219-5223. 

Further, multitopic anion receptors 10-12 (Fig. 5), containing thiourea functionalities embedded into an oligosaccharide structure, were designed. The p-iylene bis(thiourea) was used as an aromatic framework to construct the binding site of proper geometry for dicarboiylates. 

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