Stability constants of adducts of succinate copper(II) complexes with β‐cyclodextrin determined by capillary electrophoresis

Abstract

Cyclodextrins (CD) form inclusion complexes with different "guests" owing to the fact that the shape of the CD molecule is a truncated cone with a hydrophobic cavity. The adducts of CD with metal complexes remain scantily explored. In this study, the stability constants of the adducts between succinate copper(II) complexes and β-CD was determined using capillary electrophoresis. The β-CD concentration in background electrolytes (BGE) was found to influence on the effective electrophoretic mobility of the copper(II) complexes in succinate BGEs. It was shown that succinic acid and its anions and copper(II) ions did not form a significant amount of the inclusion complexes with β-CD and the mobility change was caused by the adduct formation between succinate copper(II) complexes and β-CD. The stability constants of these adducts were determined at 25°С and ionic strength of 0.100 M: log β(CuL /β-CD) = 1.76 ± 0.06, log β(CuL /β-CD) = 0.98 ± 0.09. The [CuHL] and [CuHL ] species were found to do not form adducts with β-CD.

Thermodynamic parameters for the complexation of water-soluble betulin derivatives with (2-hydroxypropyl)-β-cyclodextrin determined by affinity capillary electrophoresis

“…The factor allowing the corrections for viscosity change, υ, for each BGE was calculated by eq. 10 For a case when the studied compound D forms 1:1 and 1:2 complexes with CD, the system is described using following equations [27,35]:…”

“…To determine stability constants and thermodynamic parameters, a number of techniques are used [6,7], including UV-Vis [8][9][10] and fluorescence [8,9,11] spectroscopy, conductometry [12,13], isothermal calorimetry [14][15][16][17], phase solubility study with UV-Vis spectroscopy [14,18,19] or high-performance liquid chromatography [20], potentiometry [21], capillary electrophoresis [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], and other techniques. Capillary electrophoresis (CE) has advantages such as rapidity, high selectivity, a small value of samples, and low-cost of analysis.…”

“…Kinetically labile complexes give one peak in electropherograms, the effective electrophoretic mobility of which, µ eff , is the average weighted over the mole fractions of species [27]:…”

Thermodynamic parameters for the complexation of water‐insoluble betulin derivatives with (2‐hydroxypropyl)‐γ‐cyclodextrin determined by phase‐solubility technique combined with capillary zone electrophoresis

“…CE has advantages such as rapidity, high selectivity, small value of samples, and low operating costs. The most used approach is mobility shift ACE [22][23][24][25][26][27][28][29][30][31][32][33]. In this method, binding constants are determined based on the change in electrophoretic mobilities of the studied compounds with varying the ligand content in BGE.…”

“…The study of complexation in solutions requires knowledge of its thermodynamic parameters . A number of techniques are used to determine the thermodynamic parameters , including NMR , UV/Vis , fluorescence spectroscopy , calorimetry , phase‐solubility (PS) method with HPLC , and with UV/Vis spectrophotometry , RP–LC , CE , and others. CE is one of the modern techniques that allow studying the complexes into solutions.…”