Chromogenic macrocyclic derivatives of azoles—synthesis and properties

Chromogenic azole diazothiacrown ethers

“…In the case of alkali and alkaline earth metal ions no spectral changes were found. This is on the contrary to previously described [8] rather high stability constants for Ca 2+ , Sr 2+ and Ba 2+ complexes with 18-membered pyrrole oxa-analog 8a. On the other hand the 21-membered pyrrole analog 8b selectively forms complexes with potassium (log K K =~4) and barium (log K Ba = 4.59).…”

“…6.7]. Considering earlier studies of the respective oxaanalogues (8-9, Figure 1) [6,12], we expected wider variety of complexed ions, especially transition/heavy metal ions. …”

“…Stability constants for Pb 2+ , Cu 2+ and Ag + complexes with 2 are listed in Table 1. Analogously to compound 1, ionophore 2 reacts too slowly with nickel and cobalt ions to determine of log K. The 18-membered imidazole azocrown ether 9a selectively forms complexes with Na + , Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ in a selective manner [8]. Compound 3, the thia-analog of 9a is spectroscopically insensitive towards alkali and alkaline earth cations.…”

“…It was proved that membrane electrodes containing pyrrole derivatives 8 are potassium selective, whereas the respective imidazole derivative 9 shows good selectivity for sodium over potassium with pot K Na K , log = -1.77 [8]. With reference to this investigation, potentiometric studies of ion-selective electrodes with membranes doped with azothiacrown ethers 1 -7 were performed under identical conditions.…”

Pyrrole Azocrown Ethers. Synthesis, Complexation, Selective Lead Transport and Ion-Selective Membrane Electrode Studies

“…Recently, we have described the synthesis and properties of 18-and 21-membered azomacrocyclic chromoionophores (compounds 1 and 2) that contain a pyrrole residue [2]. In these compounds the pyrrole moiety replaces the phenol residue used previously [3,4].…”