Salicylaldehyde thiazolyl hydrazones as ligands

Novel bidentate Schiff base ligands, 2‐(2‐hydroxy‐5‐chloro/nitro)benzaldehyde‐[4‐(3‐methyl‐3‐mesitylcyclobutyl)‐1,3‐thiazol‐2‐yl]hydrazone, and their metal complexes have been prepared and characterized by elemental analyses, IR, ¹³C and ¹H NMR spectra, and magnetic susceptibility measurements. All the complexes were found to be mononuclear. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:617–621, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10201     

Synthesis,crystal and molecular structure of trans‐bis(2‐pyridinepropanol)bis(saccharinato)nickel(II)

Trans‐bis(2‐pyridinepropanol)bis(saccharinato)nickel(II), [Ni(sac)₂(pypr)₂], where sac and pypr are the saccharinate anion and the 2‐pyridinepropanol molecule, respectively, crystallizes in the triclinic space group P (No. 2) with a = 8.1981(8), b = 9.9680(10), c = 10.4956(10) Å, α = 90.740(3)° β = 108.142(3)°, γ = 111.025(3)°, Z = 1, V = 1.537 ų. The structure of the nickel(II) complex consists of neutral molecules in which the nickel(II) ion sits on a center of symmetry and is octahedrally coordinated by two sac ligands, and two neutral pypr ligands. The pypr acts as a bidentate N‐ and O‐donor ligand forming a seven‐membered chelate ring, while sac behaves as a monodentate O‐donor ligand via the carbonyl O atom. The Ni‐N bond distance is 2.1016(15) Å, whereas the Ni‐O_pypr and Ni‐O_sac bond distances are 2.1280(12) and 2.0792(11) Å, respectively. The individual molecules are held together with a strong hydrogen bond between the hydroxyl O atom of pypr and N atom of sac and the C‐H…O type weak hydrogen bonds between some ring hydrogen atoms of pypr and sac, and the carbonyl and sulfonyl O atoms of sac in the neighbouring molecules. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and Characterization of α,ω‐Heterofunctional Poly(ethylene oxide) Macromonomers

A novel α,ω‐heterofunctional poly(ethylene oxide) (PEO) macromonomer possessing methacryloyl and thienyl end groups was prepared by ring‐opening polymerization of ethylene oxide initiated by potassium thienylethoxide and termination of the living PEO ends with methacryloyl chloride. Incorporation of methacryloyl and thienyl groups was confirmed by free‐radical and oxidative polymerization processes, respectively, and by means of ¹H NMR analysis.

     

Computer-simulation analysis of the ESR spectra of mechanoradicals in PMMA

In this study, initially, we tried to obtain the mechanoradicals of PMMA (poly(methyl methacrylate)). For this purpose, we designed a simple drilling apparatus. Using this apparatus, we prepared some PMMA samples at 77 K in vacuum. Later, by using an ESR (electron spin resonance spectrometer), we observed ESR signals for these samples at 77 K. This means that mechanoradicals have been successfully produced by mechanical fracture in PMMA using our drilling apparatus. Secondly, we tried to identify the radicals from these spectra through using theoretical analyses and, some computer simulations have been done by suggesting two different theoretical models for these ESR signals. Finally, by using experimental and theoretical data, we showed that our simple apparatus could be used to obtain mechanoradicals from polymers. Results were seen to be in very good agreement with the literature. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2195–2200, 1997     

Synthesis,Crystal and Molecular Structure of 2‐Pyridylethanolbis(saccharinato)mercury(II)

2‐Pyridylethanolbis(saccharinato)mercury(II), [Hg(sac)2(pyet)], where sac and pyet are the saccharinate anion and the 2‐pyridylethanol molecule, respectively, crystallizes in the triclinic space group P (No. 2) with a = 10.4518(6), b = 11.3796(6) (5), c = 19.9945(12) Å, a = 102.758(3)° b = 98.146(3)°, g = 104.751(3)°, Z = 4, V = 2193.0(2) ų. The unit cell contains two crystallographically independent [Hg(sac)2(pyet)] units in which the mercury(II) ion is tetrahedrally coordinated by two nitrogen atoms of two sac ligands, and one nitrogen and one oxygen atoms of one neutral pyet ligands. The pyet acts as a bidentate N‐ and O‐donor ligand forming a six‐membered chelate ring, while sac behaves as a monodentate N‐donor ligand. The average bite angle of the pyet ligand is 75.8(5)°. The Hg‐N_sac bond distances are in the range 2.0874(18) and 2.1931(18) Å, whereas the Hg‐N_pyet and Hg‐O_pyet bond distances are 2.2452(19)‐2.3202(19) and 2.6036(17)‐2.5902(16) Å, respectively. The crystal exhibits two strong hydrogen bonds between the hydroxyl O atom of pyet and sulfonyl O atoms of sac and the C‐H…O type weak hydrogen bonds between H atoms of the aromatic rings of the pyet and the sulfonyl O atoms of the sac ligands. Furthermore, packing of the molecules in the solid‐state results in aromatic π‐π interactions associated with the aromatic rings of sac‐sac and py‐py.     

Proton NMR relaxation in albumin solutions doped with Mn(II)

The aim of this study is to obtain further information about the source of proton relaxation in the Mn(II)-human serum albumin complex. For this purpose, proton relaxation rates in albumin solutions 1/T ₁ and 1/T ₂ were measured versus increasing amounts of manganese [Mn_t]. The fractions of manganese bound to albumin [Mn_b] and free manganese [Mn_f] were then determined from proton relaxation rate enhancement data. Paramagnetic contributions of bound manganese to the observed relaxation rates (1/T _1p^*)_b and (1/T _2p^*)_b were also determined. Finally, the (1/T _2p^*)_b/(1/T _1p^*)_b ratio was used in a derived equation to estimate an effective correlation time τ. Mean τ value of the complex was found to be in the order of 3 ns, while the hydration number of bound manganese q was estimated to be about 4. The 1/τ was found to be the sum of the inverse values of rotational correlation time 1/τ _r, mean residence time of water in hydration spheres of the complex 1/τ _m, and longitudinal electronic relaxation time of manganese 1/τ _s in the complex. In conclusion, the relaxation mechanism in albumin solutions containing Mn(II) can be interpreted through dipolar and scalar interactions modulated by τ _r, τ _m and τ _s. This analysis enables one to get reasonable figures for the τ _r and q of Mn(II) in albumin solution.     

4,4,6,6‐Tetra­chloro‐2,2‐(ethyl­ene­di­oxy­di‐o‐phenyl­enedi­imino)‐2λ5,4λ5,6λ5‐cyclo­triphosphazene

The title ligand, C₁₄H₁₄Cl₄N₅O₂P₃, is a cyclo­phosphazene lariat (PNP pivot) ether with a spiro‐cyclic 11‐membered macrocyclic ring containing two ether O and two N atoms; the phosphazene ring is nearly planar. The macrocyclic ring contains a four‐centred (trifurcate) N—H⋯O/N—H⋯N hydrogen bond, and the relative inner‐hole size of the macrocycle is ∼1.14 Å in radius. The mol­ecules are linked about inversion centres by N—H⋯N hydrogen bonds into centrosymmetric dimers.     

Investigation of DNA cleavage activities of new oxime-type ligand complexes and molecular modeling of complex-DNA interactions

Nucleolytic activities of some new oxime-type ligand complexes were investigated by neutral agarose gel electrophoresis. Analysis of the cleavage products in agarose gel indicated that all complexes used converted supercoiled pUC18 plasmid DNA to its nicked or linear form. It was found that nucleolytic activities of the complexes depend on the complex concentration, reaction time and the presence of a cooxidant (magnesium monoperoxyphthalate, MMPP) in the reaction mixture. However, the complexes cleaved pUC18 plasmid DNA at all investigated pH values. Nucleolytic activities of complexes were investigated for different complex concentrations (0.1–100 μmol L⁻¹), pH values (6.0–10.0) and reaction times (0–60 min). Molecular modeling studies performed by the Hyperchem Software together with DNA-binding studies showed that planar sites of the complexes intercalated into double stranded DNA. It can be concluded that all oxime-type ligand complexes used can be evaluated as nuclease mimics.     

Synthesis of two new p-tert-butylcalix[4]arene β-ketoimin derivatives for extraction of dichromate anion

In this study the selective derivatization of p-tert-butylcalix[4]arene was carried out and two new p-tert-butylcalix[4]arene β-ketoimin, 5,11,17,23-tetra-tert-butyl-25,27-bis-3-methyl-[(β-ketoimine)-ethoxy]-26,28-dihydroxycalix[4]arene (4), and 5,11,17,23-tetra-tert-butyl-25,27-bis-3-chloro-[(β-ketoimine)-ethoxy]-26,28-dihydroxycalix[4]arene (5) have been synthesized. In the synthesis, the lower rim of p-tert-butylcalix[4]arene was modified in order to acquire binding site for the recognition of dichromate anion. It was observed that these ionophores 4 and 5 showed high affinity towards dichromate anion. The protonated Schiff-base forms of the receptors were effective for transferring the HCr₂O₇ ^? anion from aqueous phase to a dichloromethane phase.     

Analysis of permethrin isomers in composite diet samples by molecularly imprinted solid-phase extraction and isotope dilution gas chromatography–ion trap mass spectrometry

Determination of an individual's aggregate dietary ingestion of pesticides entails analysis of a difficult sample matrix. Permethrin-specific molecularly imprinted polymer (MIP) solid-phase extraction cartridges were developed for use as a sample preparation technique for a composite food matrix. Vortexing with acetonitrile and centrifugation were found to provide optimal extraction of the permethrin isomers from the composite foods. The acetonitrile (with 1% acetic acid) was mostly evaporated and the analytes reconstituted in 90:10 water/acetonitrile in preparation for molecularly imprinted solid-phase extraction. Permethrin elution was accomplished with acetonitrile and sample extracts were analyzed by isotope dilution gas chromatography–ion trap mass spectrometry. Quantitation of product ions provided definitive identification of the pesticide isomers. The final method parameters were tested with fortified composite food samples of varying fat content (1%, 5%, and 10%) and recoveries ranged from 99.3% to 126%. Vegetable samples with incurred pesticide levels were also analyzed with the given method and recoveries were acceptable (81.0–95.7%). Method detection limits were demonstrated in the low ppb range. Finally, the applicability of the MIP stationary phase to extract other pyrethroids, specifically cyfluthrin and cypermethrin, was also investigated.