Ümit Çakır

SYNTHESIS, SPECTRAL AND BIOLOGICAL STUDIES OF Mn(II), Ni(II), Cu(II), AND Zn(II) COMPLEXES WITH A TETRADENTATE SCHIFF BASE LIGAND. COMPLEXATION STUDIES AND THE DETERMINATION OF STABILITY CONSTANTS (Ke)

The complexes Mn(II), Ni(II), Cu(II) and Zn(II) ions with a N2O2 Schiff base derived from 1,4-diaminobutane and salicylaldehyde, N,N′-bis(salicylidene)-1,4-diaminobutane (LH2), have been prepared and characterized by elemental analyses, molar conductivities, spectral (IR, NMR, visible, UV) and magnetic moment measurements. Stability constants were measured by means of a conductometric method. Furthermore, the stability constants for complexation between ZnCl2, Cu(NO3)2 and AgNO3 salts and the ligand in 80% dioxane-water and pure methanol were determined by conductance measurements. The magnitudes of these ion association constants are related to the nature of the solvation of the cation and the complexed cation. The mobilities of the complexes are also dependent, in part, upon solvation effects. The complexes Mn(II), Ni(II), Cu(II) and Zn(II) ions with the Schiff base have been evaluated for their antibacterial activity against rec − and rec + stains of Bacillus subtilis.

THE SYNTHESIS, CHARACTERIZATION AND CONDUCTANCE STUDIES OF NEW Cu(II), Ni(II) AND Zn(II) COMPLEXES WITH THE SCHIFF BASE DERIVED FROM 1,2-BIS-(o-AMINOPHENOXY)ETHANE AND SALICYLALDEHYDE

Cu(II), Ni(II) and Zn(II) complexes with the Schiff base derived from 1,2-bis-(o-aminophenoxy)ethane with salicylaldehyde have been prepared. The complexes have been characterized by elemental analysis, magnetic measurements, 1H NMR, 13C NMR, UV, visible and IR spectra as well as conductance measurements. The ligand is coordinated to the central metal as a tetradentate ONNO ligand. The four bonding sites are the central azomethine nitrogen and aldehydic OH groups. The ligand was used for complexation studies. Stability constants were measured by a conductometric method. Furthermore, the stability constants for complexation between ZnCl2 and Cu(NO3)2 salts and N,N′-bis(salicylidene)-1,2-bis-(o-aminophenoxy)ethane (H2L) in 80% dioxane/water and pure methanol were determined from conductance measurements. The magnitudes of these ion association constants are related to the nature of the solvation of the cation and the complexed cation. The mobilities of the complexes are also dependent, in part, upon solvation effects.

Synthesis and Characterization of a Novel Oxovanadium(IV) Complex and Conductometric Studies with N,N′‐bis(Salicylidene)‐1,2‐bis‐(p‐aminophenoxy)ethane

Abstract A new oxovanadium complex of the Schiff base obtained by the condensation of 1,2‐bis(p‐aminophenoxy)ethane with salicylaldehyde was synthesized. The complex has been characterized by elemental analyses, magnetic measurements, UV‐VIS and IR spectra. Stability constants and thermodynamic values for complexation between Cu(NO3)2, Zn(NO3)2 · 6H2O, and VOSO4 · 5H2O salts and the ligand synthesized by the method described in the literature in 80% dioxane–water and pure methanol were determined by conductance measurements. The stability constants (log K e) in 80% dioxane/water decrease in the order Cu(II) > (Zn(II). However, just the opposite behavior has been obtained for these metal complexes with the ligand in methanol (Zn(II) > (Cu(II)). The magnitudes of these ion association constants are related to the nature of solvation of the cation and of the complexed cation. The mobility of the complexes is also dependent, in part, upon solvation effects. Since the mobility of the VO(IV)L complex has been found to be higher than that of VO(IV) ion, assuming that the complex–solvent interaction in the VO(IV)‐L systems is comparatively weak. A major consequence of the complexation is the increase in the molar conductivity of the complex and a corresponding large decrease in κ values. For this reason, it was not obtained any stability constant values for VO(IV)‐L systems in two type of solvents.

Synthesis and carbonic anhydrase inhibitory properties of novel coumarin derivatives

A newly series of water-soluble 1-alkyl-3-(4-methyl-7, 8-dihydroxy-2H-chromen-2-one) benzimidazolium chloride salts (3a-j) were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and II were evaluated. hCA I and II from human erythrocytes were purified by a simple one step procedure by using Sepharose 4B-L-tyrosine-sulphanilamide affinity column. The result showed that all the synthesized compounds were inhibited the CA isoenzymes activity. Among them, 3g and 3j were found to be most active (IC50 = 22.09 µM and 20.33 µM) for hCA I and hCA II, respectively.

Complexation and mutagenicity potential studies with N, N′- bis (2-hydroxynaphthalin-1-carbaldehydene)-1,2- bis -(P-aminophenoxy)ethane and a novel oxovanadium(IV) complex

A new oxovanadium(IV) complex of the Schiff base obtained by condensation of 1,2-bis(p-aminophenoxy)ethane with 2-hydroxynaphthalin-1-carbaldehyde was synthesized. The complex was characterized by elemental analysis, magnetic measurements, mass spectral data, UV–visible and IR spectra. Stability constants and thermodynamic values for complexation between Cu(NO3)2, Zn(NO3)2·6H2O, Ni(NO3)2·6H2O and VOSO4·5H2O and the ligand in 80% dioxane/water were determined by conductance measurements. Ni(II) and Cu(II) complexes of the ligand synthesized by a previously described method were found to be mutagens on strain TA 100 in the presence and absence of S9 mix. These compounds are classified as mutagenic in the Ames test.

The Determination of Crown-Cation Complexation Behavior in Dioxane/ Water Mixtures by Conductometric Studies

Using conductance measurements, an attempt has been made to gain detailed information about the specific molecular interactions of crown compounds with metal ions in a 1,4-dioxane/water binary system. Analyses of the transport data of dioxane/water mixtures yielded the mobility of the crown compound action complexes and the ion-pair dissociation constant of the crown compound–electrolyte complex. Binary mixed aqueous solvents are frequently employed in broad areas of chemistry. Their applicability ranges from synthetic and mechanistic studies in organic chemistry to biophysical chemistry, with emphasis on molecular interactions in biologically significant structures. Stability constants of crown compound complexes are determined by various methods, such as potentiometry (with ion selective electrodes), polarography, voltammetry, spectrophotometry, nuclear magnetic resonance, calorimetry and solubility. In this study the conductometry measurements have been carried out with high precision at optimal concentrations in dioxane/water systems. Structures of crown–cation complexes in dioxane/water mixtures are estimated from the conductance parameters (κ, Λ and α) as well as the complex formation constant, Ke = (ΛMAm − Λ) / (Λ − ΛMaLbAm) [L]. The conductance behavior of Na+, K+ chlorides and Na+ perchlorates with 18-crown-6, 15-crown-5, and 12-crown-4 have been studied in various dioxane/water systems (50%, 80%, and 85%) at 25°C. The all experimental studies have been made by the ratio 1 : 1 of the metal-ion and the crown ether, Ke. For the calculations, Excel. 5.0 was used as an application program. Copyright

Spectroscopic and Conductance Studies of New Transition Metal Complexes with a Schiff Base Derived from 4-Methoxybenzaldehyde and 1,2-bis( p-Aminophenoxy)ethane

Four new metal complexes of Cu(II), Ni(II), Zn(II) and Co(III) with Schiff base derived from 4‐methoxybenzaldehyde and 1,2‐bis(p‐aminophenoxy)ethane have been prepared and characterized by magnetic susceptibility, conductance measurements, elemental analyses, UV–Vis, 1H NMR and IR spectra studies. The magnetic and spectroscopic data indicate an octahedral geometry for the six‐coordinate complexes. The ligand was used for complexation studies. Stability constants were measured by means of a conductometric method. Furthermore, the stability constants for complexation between ZnCl2, Cu(NO3)2 and AgNO3 salts and ligand (L) in 80% dioxane–water and pure methanol were determined from conductance measurements. In 80% dioxane–water, he stability constants (log Ke) increase inversely with the crystal radii in the order Ag(I) < Zn(II) < Cu(II).

Extraction-ability and -selectivity of tetra-aza-crown ethers for transition metal cations

In order to investigate the relative effects of the differences between the structures and lipophilicities of 1, 10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TA-18-crown-6) and the tetrabenzyl derivative of 1,10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TBTA-18-crown-6) on their extraction-abilities and -selectivities for transition metal cations, constants of the overall extraction (logKex) of 1:1 (M:L) complexes, the distribution (KD) for two diluents (CH2Cl2 and CHCl3) with different dielectric constants have been determined at 25 ± 0.1 °C. The magnitude of logKex is largely determined by that of KD. The equilibrium constants of TA-18-crown-6 have been compared with those of TBTA-18-crown-6. It is found that:(i) logKex sequences of TA-18-crown-6 and TBTA-18-crown-6 for transition metals in CH2Cl2 lie in order: Fe3+ > Cu2+ > Mn2+ > Co2+ > Cd2+ > Ni2+ > Zn2+ and Fe3+ > Cu2+ > Co2+ > Mn2+ > Ni2+ > Cd2+ > Zn2+ respectively; (ii) the stability sequences of two types of tetra-aza-crown ethers with the transition metal cations in CHCl3 are the same as follows: Fe3+ > Ni2+ > Cu2+ > Co2+ > Zn2+ > Cd2+ > Mn2+, and (iii) unusual selectivities are observed for transition metal-tetra-aza-crowns, e.g. the high Fe3+/Mn+ selectivity factors (Sf) of TA-18-crown-6, except for the competitive-extractions for the special case in CHCl3 of TBTA-18-crown-6, it was found that the Mn2+/Mn+ values were relatively higher according to the other transition metal cations. A systematic sequence in these two types of solvents is not found for a given transition metal cation in terms of the variation of selectivity with the tetra-aza-crown ethers. The results provide alternatives for the rational design of other specific ligands on the transition metal cations.

In vitro inhibition of cytosolic carbonic anhydrases I and II by some new dihydroxycoumarin compounds

A new series of 6, 7-dihydroxy-3-(methylphenyl) chromenones, including three new derivatives, i.e. 6,7-dihydroxy-3-(2-methylphenyl)-2H-chromen-2-one (OPC); 6,7-dihydroxy-3-(3-methylphenyl)-2H-chromen-2-one (MPC); 6,7-dihydroxy-3-(4-methylphenyl)-2H-chromen-2-one (PPC) and one previously described, namely 6,7-dihydroxy-3-phenyl-2H-chromen-2-one (DPC), were synthesized. These compounds were investigated as inhibitors of human carbonic anhydrase I (hCA-I) and human carbonic anhydrase II (hCA-II) which had been purified from human erythrocytes on an affinity gel comprised of L-tyrosine-sulfonamide-Sepharose 4B.

New coumarin derivatives as carbonic anhydrase inhibitors

Abstract In the current study, a series of 4-chloromethyl-7-hydroxy-coumarin derivatives containing imidazolium, benzimidazolium, bisbenzimidazolium and quaternary ammonium salts were synthesized, characterized and the inhibition effects of the derivatives on human carbonic anhydrases (hCA I and hCA II) were investigated as in vitro. Structures of these coumarins were confirmed by FT-IR, (1)H NMR, (13)C NMR and LC–MS analyses. Structure activity relationship study showed that 3d (IC50: 79 μM for hCA I and 88 μM for hCA II) performed higher inhibitory activity than others.