Methoxy-substituted derivatives of 1,4-bis(2-phenylethenyl)benzene and of 1,4-bis(2-phenylethyl)benzene as ligands in ion-selective electrodes for lead ions

We report the potentiometric responses towards lead ions of liquid membrane electrodes containing 1,4-bis[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene (1),2,5-dimethoxy-1,4-bis[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene (2),1,4-bis[2-(3,4,5-trimethoxyphenyl)ethyl]benzene (3) and 2,5-dimethoxy-1,4-bis[2-(3,4,5-trimethoxyphenyl)ethyl]benzene (4). All ligands strongly respond to lead ions in the activity range 10−6–10−3 M and three show high selectivity against common interfering mono- and doubly charged cations. The new ligands demonstrate low affinity for protonation. Addition of 1 mol% of potassium tetrakis(p-chlorophenyl)borate as a lipophilic anionic salt significantly increases the selectivity of ligands 2, 3 and 4. The ligands show potential as sensory elements of liquid membrane electrodes destined for determination of lead ions.