Shehadeh Mizyed

Synthesis of New Azacrown Ether Schiff-Bases and their Complexes with C60

A series of novel azacrown ether Schiff bases 2-5 have been synthesized and their host-guest interaction with C60, have been studied in toluene using absorption spectroscopic method. All complexes are found to be stable with 1:1 stoichiometry. Compound 2 Complex has the highest logk value, probably due to the electronic effect of the four methyl groups attached to the phenyl

A conductance study of the binding of benzo-15-crown-5 with alkali cations in acetonitrile

The decrease in the molar electrolytic conductance of Na+, K+, Rb+, and Cs+ tetraphenylborates, caused by the addition of benzo-15-crown-5 in acetonitrile at constant ionic strength, is analyzed according to a model involving 1:1 stoichiometry. The stability constant,K, and the limiting molar conductivity, Λc, for each 1:1 complex are determined from the conductance measurements by using a nonlinear least squares curve fitting procedure. The stability sequence of the 1:1 complexes, as deduced from data at 288, 293, 298, 303, and 308 K, has the order Na+>K+>Rb+>Cs+. Values of ΔH0, ΔS0, and Λc at 298 K are reported and their significance is discussed.

The kinetics and molecular modeling of the complexation of tenoxicam with cyclodextrins in solution

The effect of cyclodextrins on photodegradation of tenoxicam (TEN) was studied at pH 4, 7 and 10. After 60 min of irradiation with UV light, the photodegradation was extensive. All cyclodextrins (alpha, beta, or gamma) stabilize TEN and reduce the rate of photodegradation. The largest effect of cyclodextrins is at pH 7. Molecular modeling results help to explain and manipulate the results. The results are discussed and compared with other results from previous studies.

A thermodynamic study of the association of alkali metal cations with dicyclohexano-18-crown-6

A thermodynamic study of the association of Na+, K+, Rb+, and Cs+ with dicyclohexano-18-crown-6 in acetonitrile has been carried out at 308, 303, 298, 293, and 288 K using a conductometric technique. The observed molar conductivities, A, were found to decrease significantly for mole ratios less than unity. A model involving 1∶1 stoichiometry has been used to analyze the conductivity data. The stability constant,K, and the limiting molar conductivity, Ac, for each 1∶1 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of logK at 298 K, as derived from this study is K+>Na+>Rb+>Cs+. Values of ΔHo and ΔSo are reported and their significance is discussed.

Synthesis of novel p-tert-butylcalix[4]arene Schiff bases and their complexes with C60, potential HIV-Protease inhibitors.

Some p-tert-butylcalix[4]arene Schiff base crown ethers were synthesized, characterized using (1)H, (13)C-NMR, DEPT 135 and Mass spectrometry. Their complexes with C60 were isolated and characterized. The inhibition effect of these complexes on HIVP was studied and found that complexes of 9 and 10 have comparable Ki values to Pepstatine which is known as HIVP inhibitor and used as a control. The synthesis of the ligands, complexes and the inhibition behavior are discussed in this article.

Naphthaldehyde-derived ligands: synthesis and their Ni(II) ion complexation

Three novel diazacrown ether ligands, namely 17-, 18-, and 20-membered O2N2-donor macrocycles derived from 3,3′-[butane-1,4-diylbis(oxy)]bis(2-naphthalenecarbaldehyde), were prepared and characterized by 1H and 13C NMR spectroscopy and mass spectra. Their host–guest interaction with Ni(II) was studied in DMSO-d6 using 1H NMR spectroscopy. The stoichiometry of the complex in each case in the concentration range examined was determined to be 1:1 using the continuous variation method (Job’s plot). The 17-membered O2N2-donor macrocycle in which the two nitrogen atoms are tethered by three methylene units binds Ni(II) more strongly than the other two macrocycles do.Graphical abstract

Synthesis and biological activities of new azacrown ether Schiff bases and spectrophotometric studies of their complexation with (60)fullerene

A series of novel azacrown ether Schiff bases 1–3 have been synthesized in good yield and in a simple way. Their host–guest interaction with [60]fullerene has been studied in toluene by absorption spectroscopic method. All the complexes are found to be stable with 1:1 stoichiometry. Because of their potential applications in industry, agriculture and medicine, they were investigated for their mutagenic and antimutagenic activities using the spot test and the plate incorporation assay of Ames. Compounds 1, 2 and 3 were found to be nonmutagenic in the Ames test using strains TA 1535, TA100 and TA97a of Salmonella typhimurium. However, using strain TA102 revealed that, although both compounds 1 and 2 were nonmutagenic, compound 2 gave a positive response indicating that it acts as an oxidative mutagen. The structure-activity relationship may throw some light on the biological activity of such series of compounds.

A Thermodynamic Study of the Charge Transfer Complexes of Iodine with Different tert-Butylcalix(4)crowns

Formation of the charge-transfer complexes between calix[4]crowns (1 - 4) and iodine in chloroform solution was studied using UV-vis spectrophotometry. The stability constants and the thermodynamic data of the resulting 1 : 1 complexes were determined and was found to decrease with increasing the size of the crown moiety of the calixcrown. All complexes formed were found to be enthalpy stabilized, and all except the complex of 2 were entropy destabilized.

Synthesis, metal ion complexation and antibacterial activities of some thiapodands with lipophilic amide and ester end groups

A series of acyclic analogues of thiacrown ethers (podands) 7–12 with lipophilic amide and ester end groups were synthesized in high yield and in a simple way. Their transition metal ions complexation was studied using a conductometric method in acetonitrile at 25°C. Podands 7 and 11 showed a continuous decrease in the molar conductances in their complexation with Ag+, Cu2+, Cd2+, Hg2+, Zn2+ and Pb2+ which begins to level off at a mole ratio of 1:1 podand to metal indicating the formation of a stable 1:1 complexes. On the other hand, podand 9 also showed the formation of 1:1 complexes with above metal cations except with Hg2+ ion, which formed a 1:2 podand-to-metal ratio complex. An influence of end groups on metal ion selectivity is evident. Podands having ethoxy end groups (podands 8, 10 and 12 exhibit pronounced metal ion selectivity over podands having amino end groups (podands 7, 9 and 11). Compounds 10 and 12 with dithiaethylene units and ethoxy end groups provide the best selectivity for Hg2+ and Ag+ ions. These results suggest that podands 10 and 12 could be useful for the selective removal of Hg2+ and Ag+ ions from industrial waste that may contain a variety of toxic heavy and transition metal ions. The in vitro antibacterial activity of the investigated compounds was tested against several microorganisms such as Bacillus subtilis (ATCC 6633), Micrococcus luteus (ATCC 10240), Staphylococcus aureus (ATCC 43300), Escherichia coli (ATCC 25922) and Enterobacter aerogenes (ATCC 13048). The antibacterial activity of podand 10 is significant for M. luteus and B. subtilis compared with other podands under investigation.

Genotoxicity of different tert-butylcalix[4]crowns.

The ability of two calix[4]arene derivatives, namely 25,27-p-tert-butylcalix[4]dithiooxabenzocrown (1) and 25,27-p-tert-butylcalix[4]trithiooxabenzocrown (2), to produce chromosomal aberrations in root meristematic cells of Allium cepa and micronuclei (MN) in normochromatic erythrocytes (NCE) of Balb/c mice was investigated. NCE are normal mature red blood cells with a full complement of hemoglobin but lack ribosomes. In the first test, the root tips were treated with a series of concentrations of the two test chemicals ranging from 10 - 7 to 10 - 4 M for 24 or 48 h. Both compounds caused concentration-dependent increases in the percentage of aberrant cells and reductions in the mitotic index. These effects depended, to some extent, on the duration of the treatment. The most conspicuous chromosomal abnormalities were c-mitosis, chromosome bridges, chromosome breaks, chromosome lags as well as micronuclei and multinuclei. In the second test, acridine orange fluorescent staining was applied to evaluate the incidence of MN in NCE of mice intraperitoneally injected with varying contents of the two test chemicals (0.02 - 0.08 mg/mouse). The two chemicals induced dose-dependent MN formation as compared to the negative control. The second compound had more pronounced cytogenetic influence than the first one. Mitomycin C (MMC, 14 mg/kg body weight), employed as positive control, produced more obvious effects on the parameters investigated.