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Competitive Potentiometric study of a Series of 18-Crown-6 with Pb2+, Ag+, and Tl+ Ions in Methanol Using Ag+/Ag Electrode

Zolgarnein J., Azimi G., Habibi M.

Polish Journal of Chemistry

2004

Vol. 78 / nr 6

795-802

The complexation of Ag+, Tl+ and Pb2+ with 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), dicyclohexyl-18-crown-6 (DCY18C6), and dibenzopyridino-18-crown-6 (DBPY18C6) in methanol solution have been studied by a competitive potentiometry, using Ag+/Ag electrode as a sensor. The stoichiometry and stability constants of resulting complexes have been evaluated by MINIQUAD program. The stoichiometry for all resulting complexes was 1:1. The order of stability of Ag+ complexes with used crown ethers varied as DBPY18C6 > DCY18C6 > 18C6 > DB18C6. For Pb2+, and Tl+ , the sequence of stability of complexes with each of these crown ethers (except of DBPY18C6) varied in the order Pb2+>Ag+>Tl+ . The major trend of stability of resulting complexes of these macrocycle with Pb2+ and Tl+ varied in the order DCY18C6 > 18C6 > DBPY18C6 > DB18C6 with few exceptions.

Competitive Spectrophotometrc Study of Complexation of Dibenzopyridino-18-crown-6 with Ca2+, Sr2+, and Ba2+ in Binary Dimethylsulphoxide-Acetonitrile Solutions

Zolgharnein J., Zahirredini F., Azimi G.

Polish Journal of Chemistry

2003

Vol. 77 / nr 7

813-820

The complexation of dibenzopyridino-18-crown-6 (DBPY18C6) with Ca2+, Sr2+ and Ba2+ has been studied in binary dimethylsulphoxide - acetonitrile mixtures at 25_C by a competitive spectrophotometric technique, using murexide as a metal ion indicator. Stoichiometry and stability of the resulting complexes were evaluated by KINFIT program. The stability of 1:1 complexes prepared were found strongly solvent dependent. There is an inverse linear relationship between log Kf and mole fraction of dimethylsulphoxide (DMSO) in the solvent. In all these solvents the increase of %AN increases the stability of DBPY18C6 complexes with alkaline earth cations in the sequence Ba2+ > Sr2+ > Ca2+.