Formation of Diazepam–Lanthanides(III) Complexes in the 50–50 Volume % Ethanol–Water Solvent System and Study of the Effect of Temperature on the Complex Formation Constants
- 121 Downloads
Diazepam (7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one) is an important derivative of the 1,4-benzodiazepine compound commercially distributed as Valium. The complex formation constants of diazepam with some light lanthanide(III) metal ions have been studied by potentiometric measurements. All titrations were performed in 50–50% (volume/volume) ethanol–water solvent mixtures at constant ionic strength (0.10 mol⋅dm−3). The ionic strength was maintained by using sodium perchlorate. The complex formation constants were determined at 25.00, 35.00 and 45.00 °C. With increasing temperature, a decrease was observed in the protonation constant (pK) of diazepam.
KeywordsDiazepam Complex formation constant Temperature Lanthanides Mixed solvent
The authors thank the late Prof. V.G. Dongre, Department of Chemistry, University of Mumbai for his precious guidance.
- 3.El-Hawary, W.F., Issa, Y.M., Talat, A.: Spectrophotometric determination of diazepam in pure form, tablets and ampoules. Int. J. Biomed. Sci. 3, 50–55 (2007) Google Scholar
- 7.Cinellu, M.A., Stoccoro, S., Minghetti, G., Bandini, A.L., Demartin, F.: Mono and dinuclear gold(I) complexes with neutral and deprotonated 1,4-benzodiazepin-2-ones. Crystal and molecular structure of (L–H) Au(PPh3)⋅Et2O, where L = 1,3-dihydro-7-nitro-5-phenyl-2H-1,4-benzodiazepin-2-one, nitrazepam. Inorg. Chim. Acta 168, 33–41 (1990) CrossRefGoogle Scholar
- 21.Irving, H., Rossotti, H.: Methods for computing successive stability constants from experimental formation curves. J. Chem. Soc. 3397–3405 (1953) Google Scholar
- 22.Irving, H., Rossotti, H.: The calculation of formation curves of metal complexes from pH titration curves in mixed solvents. J. Chem. Soc. 2904–2910 (1954) Google Scholar
- 23.Irving, H., Rossotti, H.: The stabilities of some metal complexes of 8-hydroxyquinoline and related substances. J. Chem. Soc. 2910–2918 (1954) Google Scholar