Ayten Göçmen

Synthesis and characterization of coumarin-crown ethers

Improving the preparation methods of some common dihydroxycoumarins, coumarin derivatives of the macrocyclic ethers were obtained in good yields. Dihydroxycoumarins reacted with dichlorides or ditosylates of polyethyleneglycols in the presence of DMF/H,O/K,CO, and macrocyclic ethers with a coumarin moiety were obtained with satisfactory yields. The structures of molecules obtained were proved with common methods of NMR, El mass spectra and elemental analysis. Optical properties in acetonitrile and the association constants, Ka of Na+ ion with such molecules were now determined in water with a Na+ ion selective electrode.

Cation complexing of crown ethers using fluorescence spectroscopy, part II☆

The complex formations of benzo[12]crown-4, benzo[15]crown-5 and benzo[18]crown-6 with perchlorate salts of Mg(2+), Li(+) and Na(+) were investigated using the steady state fluorescence emission spectroscopy in acetonitrile. The complexation enhanced quenched fluorescence spectra, (CEQFS) exhibited the ion complexation role of the macrocyclic ethers and equilibrium constant, K(e) of 1:1 stoichiometry were estimated. The K(e) were found in the order of Mg(+)>Na(+)>Li(+) for benzo[15]crown-5 whilst Na(+)>Mg(+)>Li(+) order was found with benzo[12]crown-4 at 298 K.

The potentiometric determination of stability constants of macrocyclic ethers using linear regression techniques

SummaryThe stability constants of various stoichiometries of NaCl complexes of the macrocyclic ethers of 15-crown-5, benzo-15-crown-5, 18-crown-6 and benzo-18-crown-6 were measured by maintaining identical initial ion-ligand concentrations [A0+]=[Lo] and using the expression of the stability constant βi of a complex formation, 1/βi[Lo]n+m−1=(1−nP′)n(1−mP′)m/P′ where P′=PAL/[1+PAL(m−1)]. The potentiometric measurements were carried out in water with a glass membrane electrode in a computer-ion meter system.

The Synthesis of Novel Crown Ethers. Part IV. Coumarin Derivatives of [18]crown-6 and Cation Binding from Fluorescence Spectra

Abstract4-H, 4-methyl and 4-phenyl-1-benzopyran-2-one derivatives of [18]crown-6 derivatives were synthesised from 6,7- and 7,8-dihydroxy-1-benzopyran-2-one reacting with pentaethylene glycol ditosylate in K2CO3/DMF/water. The products were identified by elemental analysis, EI-GC-mass spectra and 1H-NMR spectroscopy. The Na+ association constants of some coumarin derivatives were determined with an ion selective electrode in water. The Na+ , K+, Ba2+ and Sr2+ binding role of such compounds were particularly observed as remarkable alterations in acetonitrile. The 1 : 1 associations constants of K+ and Na+ with some coumarin-[18]crown-6 derivatives estimated by this way in acetonitrile exhibited the utility of complexing enhanced quenching fluorescence spectra for the ion binding power of the such macrocycles.

Fluorescence Spectra of Salt Solutions of Coumarin Crown Ethers

Abstract The fluorescence spectra of the coumarin derivatives of crown ethers obtained from 7,8-dihydroxycoumarins were studied in the presence of some alkali and alkaline earth cations in acetonitrile. The altered fluorescence spectra were examined qualitatively from the point of enhancement of fluorescent quantum yields as well as a resonance. Heavy metal effects were eliminated since there is no influence of the metal salts on the spectra of the initial coumarin derivatives. However, both the complexation-enhanced fluorescence and complexation-enhanced quenching spectra is observed in the fluorescence emission and excitation spectra of macrocyclic ether-coumarin / metal salt systems. The origin of results are briefly discussed in terms of crown ether complexation. In water solutions almost no such effects were observed.

THE CATION BINDING OF BENZO CROWN ETHERS IN ACETONITRILE USING FLUORESCENCE SPECTROSCOPY

The effects of Na+, K+ and Li+ cations on the fluorescence spectra of benzo[15]crown-5, benzo[18]crown-6 and dibenzo[18]crown-6 were investigated in acetonitrile. The alkali cation role observed was usually the complexation-enhanced quenching fluorescence effect (CEQF) in acetonitrile due to the increased fluorescence quenching rate of the complexed fluoroionophore. The association constants for 1 :1 stoichiometry InKa have been obtained using the relationship 1/Ka[L0] = (1 −P)2/P. It was shown that the preferential interaction rule of compatibility of cationic radii and macrocyclic ring size is in excellent agreement with the association constants obtained by fluorescence spectroscopy. The order of InKa found for benzo[15]crown-5 complexation was Li+ > Na+ > K+ and K+ > Na+ > Li+ for benzo[18]crown-6 in acetonitrile.

Thermodynamics of benzoate complexes of cobalt(II), nickel(II) and manganese(II) in aqueous solution

Abstract The thermodynamic functions for the formation of benzoate complexes of cobalt(II), nickel(II) and manganese(II) have been determined by measuring the pertinent stability constants potentiometrically at temperatures within the range 25–40 ° C. From the enthalpy changes evaluated, and the free energy changes calculated from the stability constants, the entropy changes were found. All data refer to a sodium perchlorate medium of ionic strength 1.0 M.

Effect of acrylamide concentration on the kinetics of oxidation of tartaric acid by cerium(IV) in sulfuric-perchloric acid media

The kinetics of oxidation of tartaric acid by Ce(IV) in the absence and presence of acrylamide has been investigated spectrophotometrically in aqueous H2SO4−HClO4 media at a constant ionic strength 2.0M and 25°C. Oxidation of tartaric acid in both cases was first order with respect to Ce(IV). Kinetic data showed that the reaction involves the formation of an unstable complex and an intermediate free radical. The activation parameters were calculated to be Ea=91.3±0.4 kJ-mol−1, ΔSΔ=20.2±1.0 J-mol−1-K−1, ΔHΔ=88.8±0.4 kJ-mol−1. A polymerization mechanism is discussed.

Cation Binding of Benzo Crown Ethers in acetonitrile using Fluorescence Spectroscopy, Part II

The effects of Na+, K+, Li+ and Mg2+ cations on the fluorescence spectra of benzo[12]Crown-4, benzo[15]Crown-5, and benzo[18]Crown-6 were investigated in dry acetonitrile. The alkali cation coused the complexation enhanced quenched fluorescence (CEQF) by increasing the fluorescence quenching rates of the cationic fluoroionophores. The 1:1 stoichiometry of ion association constants, lnKa have been obtained. The results were ruled out by compatibility of cationic radii and macrocycle size. The order of lnKa found for benzo[15]crown-5 was Mg+>Na+>Li+ for the cations and the Na+>Li+ was found for benzo[18]crown-6. The most of the cations have slight effects on the fluorescence spectra of benzol[12]crown-4 in acetonitrile.

The thermodynamics of benzoate complexes of copper(II) and iron(III) in aqueous solution

Abstract The thermodynamics of the complex formation reactions of copper(II) and iron(III) with benzoate ions have been determined by measuring the formation constants at different temperatures. The benzoate complexes of fairly hard acceptors, like Fe(III), are characterized by highly positive entropy changes. All measurements were carried out potentiometrically at 25, 35 and 40°C and in an ionic medium of 1 M, with sodium perchlorate as the background electrolyte.