Çakil Erk

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.

Improved synthesis of some hydroxycoumarins

Abstract An improved synthesis of some 7-hydroxycoumarin derivatives is reported. Hydroxybenzenes reacted with β-ketoesters or d,l-malic acid in HClO4 to give good yields of 7-hydroxycoumarins. IR and 1H NMR data for the products are also reported.

Synthesis and fluorescence spectroscopy of bis(ortho- and para-carbonyl)phenyl glycols

Abstract Bis-(2′- or 4′-carbonyl)phenyl glycols (podands) were synthesized by reacting ortho - and para -vanillin and 2′- and 4′-hydroxy acetophenone with mono or diethylene glycol dihalides. The products were characterised using IR, 1 H-NMR, 13 C-NMR spectroscopy and mass spectrometry. Aromatic carbonyl derivatives of glycols were investigated to determine the role of Na + ions, using steady state fluorescence spectroscopy.

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.

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.

The complexation of cyclic polyethers and a series of equations for determination of equilibrium constants

Abstract An outstanding and compact formalism was established to estimate the equilibrium constants K e of essential ligands with well-known structures like crown ethers, or unknown complexing stoichiometries. The application of the general formula ⧸ K e [L 0 ] m + n -1 = (⧸ P L −1)(1- P L ) m + n −1 is described by the computer-simulated plots, where m / n is the complexing ligand/cation ratio, P L is the mole fraction of the complexed ligand and [L 0 ] is the initial ligand concentration of the complex solution.

Eu(fod)3 binding on the 1H-NMR spectra of some benzo[3n]crown-n and dibenzo[3n+2]crown-n

The complexing of Eu(fod)(3) with macrocyclic ethers, benzo[15]crown-5, benzo[12]crown-4, dibenzo[20]crown-6, dibenzo[23]crown-7 and dibenzo[26]crown-8 was observed on their (1)H-NMR spectra and the selective binding constants at 400 MHz and 305 K in CDCl(3) were reported. The Eu(fod)(3) interaction displayed the selective binding role of oxygen on macrocyclic, H(2)COCH(2), backbones with o- or m-dioxyphenyl groups referring the (1)H chemical shifts. The estimated equilibrium constants, K(a) of 1:1 ratio of interactions were in accordance with the Eu(3+) ionic radii to bind the oxygen sites depending on the macrocyclic size and conformation of the ethers. The minimum lanthanide-macrocyclic ether distance displayed the maximum stability so that benzo[3n]crown-n (n=4, 5) group was found to bind the Eu(fod)(3) moderately whilst dibenzo[3n+2]crown-n (n=6-8) oligomer chemical shifts were induced largely since the such Eu(3+) complexes are more stable with larger ethyleneoxy groups.

The Synthesis of Dibenzo[3n]crown-n by Novel Methods and their Cation Binding Studied by Fluorescence Spectroscopy. Part IV

AbstractThe dibenzo[3n]crown-n were synthesised from1,2-bis(o-hydroxyphenoxy)ethane obtained from 1,2-bis(o-formylphenoxy)ethane via Bayer-Willigeroxidations with H2O2/CH3COOH in good yields. The cyclic condensation of 1,2-bis(o-hydroxyphenoxy)ethanewith dichlorides, and ditosylates of polyethylene glycols in DMF/Me2CO3 gave the macrocyclesdibenzo[15]crown-5, dibenzo[18]crown-6, dibenzo[21]crown-7 anddibenzo[24]crown-8. The structures were identified using IR, mass, 1H and 13C NMR spectroscopy. Therecognition of the molecules for the cations, Li+, Na+, K+, Rb+ and Zn2+were conducted quantitatively with steady state fluorescencespectroscopy. The 1:1 association constants in acetonitrileshowed a good relation of the appropriate size of the macrocyclic ether towards the fitting cationradii. Namely, dibenzo[15]crown-5 was the best for Li+ binding and more than 100 times better thanNa+ and K+. Dibenzo[21]crown-7 was excellent for Rb+ binding while K+ is 100 timesless preferred. The largest crown ether studied, dibenzo[24]crown-8, exhibited the order of binding power,Rb+ > K+ > Na+. Zn2+ displayed, however, a marked binding with only dibenzo[18]crown-6.p>

Ion-dipole interactions of macrocyclic ethers using13C dipole-dipole relaxation time measurements. Part XI: The complexation of 1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane with Ca2+ in CD3OH

The association constants,Ka, of Ca2+ complexes with the nonequivalent binding site macrocycle,1,4,7,10,13,16-hexaoxa-2,6-dioxocyclooctadecane, were determined in CD3OH solution using13C dipole-dipole relaxation time,T1DD, studies. The measurements ofT1DD of the macrocyclic backbone for different stoichiometries (n:m) of complex formation were conducted under extreme narrowing experimental NMR conditions. The general equilibria given with 1/Ka[L0]n+m−1 = (1-nP′)n (1-mP′)m/P′ was used for identical cation and macrocyclic ether-ester concentrations in CD3OH and the association constants found were comparatively small depending on the cyclic ether-ester segments. The logKa values varied from 1.09 to 0.231 for 1 :1 and from 2.43 to 3.61 for 1 : 2 and from 2.29 to 4.24 for 2 : 1 ligand to cation complex stoichiometries.

Cation Complexation and Stereochemistry of Macrocycles Studied by 13C NMR Relaxation-Time Measurements

Cation binding by macrocycles was studied using 13C NMR dipole-dipole relaxation measurements in solution. The association constants of [3n]Crown-n and its cyclohexyl, benzo and dioxo derivatives with Li+, Na+, K+ and Ca2+ cations were studied in polar solvents. The relaxation times, T1 obs and NOE factors (η) of 13C atoms in the backbone of free and complex macrocycles were estimated in the extreme narrowing NMR conditions and gave T0 DD and T10 DD dipolar relaxation times. The internal motions coupled with the dipolar relaxation times are influenced by cation binding characterized by the association constants, Ka. The experimental results showed the effect of ionic radii and macrocycle size on ion selectivity as well as on the selectivity between non equivalent binding sites. The energy barriers of the preferential a, ±g,a conformational sequences present in the bound oxyethylene backbone were examined by molecular dynamics simulations using the MM+ force field in commercial software.