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This work describes the fabrication and applications of potentiometric silver-selective sensors, based on the use of a newly synthesized p-tert-butylthiacalix [4]arene comprising two triazole rings, as a novel neutral ionophore in plasticized poly(vinyl chloride) (PVC) membranes. The effect of lipophilic anionic additives on the voltammetric responses of the sensors was investigated in details. The constructed sensors exhibited a Nernstian behavior with 53 ± 0.9 mV per decade change in Ag + activity over the range from 7.0x10 -6 to 8.0x10-3 , with a repetitive detection limit of 0.421 µg mL -1 . Moreover, the effect of lipophilic salts, plasticizers and various interfering ions were probed. Importantly, validation of the method is achieved in terms of good performance characteristics, including good selectivity for Ag + over alkali, alkaline earth and transition metal ions (e.g. Na + , K + , Pb 2+ , Mg 2+ , Co 2+ Ni 2+ , and Cu 2+ ) together with long life span. Other important characteristics such as low detection limit, acceptable accuracy and precision, long term stability, reproducibility were also demonstrated. On the application side, the sensors were utilized for facile potentiometric measurements of iodide ions (I -) over the concentration range of 0.749 to 856 µg mL −1 and also employed for probing sequential titration of some importantly relevant anions (e.g. Cl -, Br -, I-, SCN -and N -3 ). Significantly, sequential binding of these anions with Ag + cations produces sharp stepwise titration curves with consecutive end point breaks at the equivalent points.

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In the title compound, C13H13N3O, the phenyl ring makes a dihedral angle of 47.0 (1)° with the mean plane of the –NC(=O)N– unit, while the dihedral angle between the latter mean plane and the amino­phenyl ring is 84.43 (7)°. In the crystal, mol­ecules are linked via N—H⋯O hydrogen bonds involving the central –NHC(=O)NH– units, forming chains running parallel to the b axis. These chains associate with one another via N—H⋯O and N—H⋯N hydrogen bonds, from the pendant amino groups to the –NHC(=O)NH– units of adjacent mol­ecules, forming columns propagating along [010]. The structure was refined as a two-component twin with a 0.933 (3):0.067 (3) domain ratio.

Novel quinoxaline derivatives (2a–d, 3, 4a, 4b, 5–15) have been synthesized and screened for their in vitro anticancer and COX-2 inhibitory activities. Compounds 4a, 5, 11 and 13 proved to be the most potent anticancer and COX-2 inhibitors.

The asymmetric unit of the title compound, C48H54O5S4·N(C2H5)4 +·Cl−, contains two tetra-tert-butyl-[(benzo­yl)meth­oxy]-trihy­droxy-tetra­thia­calix[4]arene mol­ecules, two tetra­ethyl­ammonium cations and two chloride anions. The two calixarene molecules in the asymmetric unit each display a cone conformation. There are no significant differences between the two independent molecules. The guest species do not sit within the calixarene ‘buckets’. In the crystal, extensive O—H⋯O, O—H⋯S and O—H⋯Cl hydrogen bonds and weak C—H⋯O, C—H⋯S and C—H⋯Cl inter­actions link the thia­calixarene mol­ecules, tetra­ethyl­ammonium cations and chloride anions, forming a three-dimensional network encompassing channels running parallel to the a-axis direction. The structure contains a solvent-accessible void of 76 (3) Å3, but no solvent mol­ecule could reasonably be located. The crystal studied was an inversion twin with a 0.57 (8):0.43 (8) domain ratio.