Acid Dissociation Constants of 5,5-Diphenylpyrrolidine N-Aroylthioureas and Stability Constants of their Pt(II) and Ni(II) Complexes in Acetonitrile-Water Hydroorganic Solvent

Year 2017, Volume: 13 Issue: 1, 125 - 138, 30.03.2017

Duygu Ersen Müge Gemili Hayati Sarı Yahya Nural

https://doi.org/10.18466/cbayarfbe.302657

Abstract

In this study, acid dissociation constants
of 5,5-diphenylpyrrolidine N-aroylthiourea
derivatives, exhibiting anti(myco)bacterial activity, were determined by
potentiometric titration in 30% (v/v)
acetonitrile-water hydroorganic solventat
25 ± 0.1 °C,
at an ionic background of 0.1 mol / L of NaCl using the HYPERQUAD computer
program. Three acid dissociation constants were determined for each compound 1a-e and we suggest that these acid
dissociation constants are related to the carboxyl, enol and enthiol groups. Stability constants of their Pt(II) and
Ni(II) complexes were also determined by potentiometric titration under the
same conditions stated above using the HYPERQUAD computer program. The ligands
behave as bidentate and bind to the metal atom via the S and O atoms. In various pH conditions, the different
complex forms were formulated as ML₂, MHL₂, MH₂L₂,
MH₃L₂, MH₄L₂, MH₅L₂
and MH_-4L₂ between Pt²⁺/Ni²⁺ ions
and 5,5-diphenylpyrrolidine N-aroylthioureas. Stability
constants of the complexes show that the ligands 1a-e form complexes with Pt(II) and Ni(II) metals as 2:1. The
stability of the complexes formed by the ligands and platinum were found to
follow the order: 3d > 3a > 3e > 3c > 3b. The stability of the complexes
formed by the ligands and nickel were found to follow the order: 4d > 4c > 4a > 4b > 4e. As a result, generally the platinum complexes formed with these
ligands are more stable than their nickel complexes.

Keywords

Acid dissociation constant, Aroylthiourea, 5, 5-Diphenylpyrrolidine, Nickel, Platinum, Stability constant

References

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