Formation Constants of Dibenzo-18-crown-6 Complexes with Alkali Metal Ions in DMSO, DMF, and PC at 25°C

Abstract

The formation constants (Kf) for the 1 : 1 complexes of dibenzo-18-crown-6 (DBG) with alkali metal ions in DMSO (dimethyl sulfoxide), DMF (N,N-dimethyl formamide), and PC (propylene carbonate) have been determined conductometrically. The formation constant sequences of the alkali metal ions with DBG in DMSO, DMF, and PC are K+>Rb+>Cs+≅Na+>>Li+, K+>Rb+>Cs+>Na+>Li+, and K+>>Na+>Rb+>Cs+>Li+ respectively. The Kf value series about the same alkali metal ion among these nonaqueous solvents are given in the order of DMSO<DMF<PC. These results show that the selectivity of DBC toward the alkali metal ions is dependent on the ionic diameter and the ring-hole size of DBC, and that the donor number of the organic solvent as a component factor is important in determining the process of the formation of the DBC complexes constant.

Facilitated Transfer of Alkali-Metal Cations by Dibenzo-18-crown-6 across the Electrochemically Polarized Interface between an Aqueous Solution and a Hydrophobic Room-Temperature Ionic Liquid

“…The stoichiometry of the complex formed in RTIL, i.e., the number of n in a 1: n complex, can be evaluated by changing the initial concentration of M in W, , or that of L in RTIL, . ,, When is sufficiently greater than , the Nernst-type equation for FIT (eq 2) can be written as, where φ is the phase-boundary potential across the RTIL|W interface, is the formal potential for FIT, R is the gas constant, T is the temperature, z M is the charge with signed unit of an electron charge, F is the Faraday constant, and is the surface concentration of component i (M, L, or ML) at α (W or R) side of the RTIL|W interface. When a 1:1 complex is formed in RTIL, as is frequently seen in the case of complexation between alkali-metal cations and DB18C6 in molecular solvents, ,,,− the peak potential of FIT should show a Nernstian response to and the peak current for FIT should be proportional to , according to eq 3.…”

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

“…The cell constant was determined using 0.1N and 0.01 N analytical grade KCl in deionized water and the mean value was used. The specific conductance of this solution at various temperatures has been reported in the literature [1].…”

“…In this case the complex has less mobility in the solution than the uncomplexed metal cation, resulting in the diminished capacity of charge transfer and hence the conductivity of the solution decreases. Since the ligand coordinates to the metal ion, leaving the anion undisturbed, dissociation of the metal salt increases and hence the conductivity of the solution increased [1]. In some cases, in spite of increase in the ligand concentration the change in conductance is negligible; consequently, determination of the formation constant by conductometric method becomes difficult.…”

“…Metal complex study is well established area of research work. To study the formation constant of ligand with metal ions in solution conductometric method is widely used because of its various advantages such as low cost, eco-friendly, less time consuming, proper thermodynamic calculation with different parameters and most important easy to operate [1][2][3]. Using conductometric method, researcher can calculate all thermodynamic parameters for specific reactions and also investigate stability constant.…”

Thermodynamic studies on metal complexes of Cd2+, Ni2+, Cu2+ AND Co2+ with pyridine-2,6-dicarboxylic acid in water, methanol and water-methanol binary solvent systems at 298.15 , 308.15 and 318.15 K by conductometric method

“…Researcher can also calculate thermodynamic parameters like enthalpy, entropy and Gibb's free energy (G. A. Lawrance, 2010;N. Matsuura et al, 1976;Francis and Shrivastav, 2011).…”