Intramolecular hydrogen bonding and tautomerism in Schiff bases. Part II. Structures of 1-[N-(2-pyridyl)aminomethylidene}-2(1H)-naphtalenone (1) and bis[2-hydroxy-kappa O-N-(2-pyridyl)-1-naphthaldiminato-kappa N]zinc(II) (2)

Hokelek, Tuncer/0000-0002-8602-4382WOS: 000086678200005The Schiff base ligand (1) and its Zn(II) complex (2) have been synthesized and their crystal structures have been determined. Compound (1) crystallizes in the monoclinic space group C2/c with a = 26.993(2), b = 5.891(1), c = 16.000(2) W, P = 103.29(1)degrees, V = 2476.0(6) Angstrom(3), Z = 8 and D-x = 1.332 g cm(-3) Compound (2) crystallizes in the orthorhombic space group Pbca with a = 19.580(3), b = 9.416(2), c = 27.801(2) Angstrom, V = 5125.5(6) Angstrom(3), Z = 8 and D-x = 1.451g cm(-3) In the crystal structure of the free Schiff base ligand (1), the existence of a strong intramolecular N-H...O hydrogen bond INO = 2.572(4), N-H = 0.90(4), H...O = 1.759(4) Angstrom, N-H...O = 149.6(3)degrees] is observed. The C-N amine bond and C-N-C bond angle are 1.345(4)Angstrom and 124.4(3)degrees, respectively. The C3 = O1 and C4 = C5 bond lengths [1.274(4) and 1.351(5) Angstrom] are shortened by the pronounced quinoidal effect. In solution, compound (1) is in tautomeric equilibria (phenol-imine, O-H ... N keto-amine, O ... H-N forms), as supported by H-1 NMR and UV-visible data. In the crystal structure of the Zn(II) complex (2), zinc atom has a distorted tetrahedral coordination. One of the pyridine N atom of the ligands is in close contact with the Zn(II) atom [Zn1 ... N4 = 2.864(5) Angstrom].It is interesting that the C-N amine bond [1.345(4) Angstrom] in compound (1) changes to the imine bond [1.27(5) Angstrom] in the Zn(TI) complex (2). (C) 2000 Elsevier Science B.V. All rights reserved

Phosphorus-nitrogen compounds. Part VI. Aminolysis of octachlorocyclotetraphosphazatetraene and the crystal structure of 2-trans-6-bis(n-propylamino)-2,4,4,6,8,8-hexakis-tert-butylaminocyclo-2 lambda(5), 4 lambda(5), 6 lambda(5), 8 lambda(5)-tetraphosphazatetraene

Hokelek, Tuncer/0000-0002-8602-4382WOS: 000186239600017The reactions of 2-trans-6-N4P4(NBPrn)(2)CI6 (2), which was obtained from N4P4Cl8 (1) and n-propylamine, with pyrrolidine and t-butylamine in different solvents have been studied. Compound (2) gave two different products, namely monocyclic (3 and 5) and bicyclic (4 and 6) phosphazenes. Compounds (2-6) have been characterized by elemental analysis, IR, H-1-, C-13-, P-31 NMR, HETCOR and MS and the structure of compound (5) has been examined crystallographically. The bicyclic phosphazene (6) is the first exciting example of bicyclic phosphazenes containing chlorine atoms, in the literature. The formation mechanisms of bicyclic phosphazenes are re-considered by taking into account the synthesis of compound (6), which contains three stereogenic phosphorus atoms. Compound (5) crystallizes in the monocyclic space group P2(1) In with a = 13.974(2), b = 17.836(5), and c = 18.683(4) Angstrom, beta = 98.50(1)degrees, V = 4605.4(2) Angstrom(3), Z = 4 and D-x = 1.051 g cm(-3). It consists of a non-centrosymmetric, nonplanar phosphazene ring in a saddle conformation, with two n-propylamino (in 2-trans-6 positions) and six bulky t-butylamino side groups. The bulky substituents are instrumental in determining the molecular geometry. (C) 2003 Elsevier B.V. All rights reserved

Corrosion inhibition of brass in presence of terdentate ligands in chloride solution

WOS: 000228625600015The inhibition of two terdentate ligands, 2-[(E)-pyridin-2-ylimino)methyl)]phenol and 2-[(pyridin-2-ylamino)methyl]phenol, abbreviated L, and L, respectively, on the corrosion of brass in 0.10 M NaCl solution under various conditions, has been studied by means of the potentiostatic polarization and AC impedance methods. The studies show that terdentate ligands, L-1 and L-2 inhibit the corrosion of brass in chloride solution and that the inhibiting efficiency increases with an increase in their concentrations. Self-assembled films of these substances were also prepared on the brass surface. These films improved significantly the protecting ability of brass surface to corrosion in 0.10 M NaCl solution. When the films were modified with benzotriazole (BTA), the quality and corrosion resistance of films improved markedly. (c) 2004 Elsevier Ltd. All rights reserved

4,4,6,6-tetrachloro-4a ',8 '-dihydrodinaphtho[2,1-c ';2,1-g ']-2 lambda(5),4 lambda(5),6 lambda(5)-cyclotriphosphazene-1-spiro-1 '-[2,5,8a,1]dioxazaphosphanaphthalene

Hokelek, Tuncer/0000-0002-8602-4382WOS: 000222371200091The title compound, C22H15Cl4N4O2P3, is a spiro phosphazene derivative with two bulky naphthalene rings. The phosphazene and the two six-membered N/O rings are not planar. The aliphatic C atom (in ArCH-OAr) and the N atom (in ArCH2-N), which has a pyramidal geometry, are capable of representing stereogenic centres

Investigation of the electrochemical reduction mechanism of 1-[N-(2-pyridyl)aminomethylidene]-2(1H)-naphthalenone (PN)

WOS: 000230360900007The electrochemical reduction mechanism of 1-[N-(2-pyridyl)aminomethylidene]-2(1H)-naphthalenone (PN) was investigated by using various electrochemical techniques in 0.1 M tetrabutylammonium tetrafluoroborate (TBATFB) in acetonitrile at glassy carbon (GC) electrode. The number of electrons transferred and diffusion coefficient of the compound were estimated by using an ultra-microelectrode (UME). PN has two reduction peaks in a cyclic voltammogram. Each of them corresponds to a one-electron transfer. In this medium and at the GC electrode surface, the first peak was observed at about - 1.8 V (vs. Ag/Ag+) which is more stable and well defined compared to the second peak. It was determined by using cyclic voltammetry that PN is electroreduced by an EC mechanism. It was also explained by multicycle CV experiments and a dopamine test as well as by Raman spectroscopy that the homogenous chemical reaction is dimerization. The EC mechanism was also examined and the kinetics of this process were calculated by digital simulation. (c) 2005 Elsevier B.V. All rights reserved

Phosphorus-nitrogen compounds. spiro- and crypta-phosphazene derivatives: synthesis and spectral investigations. Structure of butane-N,N '-bis(1,4-oxybenzyl)-spiro(propane-1,3-diamino) tetrachlorocyclo-2 lambda(5), 4 lambda(5), 6 lambda(5),-triphosphazatriene. Part VII

Hokelek, Tuncer/0000-0002-8602-4382; Asmafiliz, Nuran/0000-0002-9335-4101WOS: 000222521900015The condensation reactions between trimer, N3P3Cl6, and diamines, 2 and 4 and {1-{N-[1-(2-hydroxynaphthylmethyl)aminomethylidene]}-2(1H)-naphthalenone, 3, yielded the new spiro-cyclic- (5 and 8) and the novel spiro-phosphazene (7) derivatives, respectively. The fully substituted phosphazene (6) was also obtained from the reaction of 5 with the excess of pyrrolidine. Compounds (4-8) have been characterized by elemental analyses, FTIR, H-1-, C-13-, P-31-NMR, HETCOR, COSY and MS. The structure of crypta-phosphazene, 8, has been examined crystallographically. Compound 8 is the first example of the crypta-phosphazene derivatives. The P-31-NMR spectra of compounds 7 and 8 indicate that, both of the compounds have anisochronism because of the stereogenic centers. The pyramidal geometry of two spiro-cyclic nitrogen atoms in compound 8, gives rise to stereogenic property. The sums of the bond angles around N-4 and N-5 nitrogens are 350.6(2) and 349.6(3)degrees, respectively. Compound 8 crystallizes in the triclinic space group P (1) over bar with a = 8.798(3), b = 10.498(3) and c = 15.689(4) Angstrom; alpha = 91.35(2), beta = 103.39(4) and gamma = 102.88(4)degrees; V = 1369.9(7) Angstrom(3), Z = 2 and D-x = 1.491 g cm(-3). It consists of a non-centrosymmetric, non-planar phosphazene ring with a bulky dibenzo-diazacrown etheric side group. (C) 2004 Elsevier B.V. All rights reserved

Stereogenic Centers upon the Addition of Chiral Solvating Agents

The reactions of hexachlorocyclotriphosphazatriene, N3P3Cl6, with N/O-donor-type N-alkyl (or aryl)-o-hydroxybenzylamines (la-le) produce mono- (2a-2e), di- (3a-3d), and tri- (4a and 4b) spirocyclic phosphazenes. The tetrapyrrolidino monospirocyclic phosphazenes (2f-2i) are prepared from the reactions of partly substituted compounds (2a-2d) with excess pyrrolidine. The dispirodipyrrolidinophosphazenes (3e-3h) and trispirophosphazenes (3i-3k) are obtained from the reactions of trans-dispirophosphazenes with excess pyrrolidine and sodium (3-amino-1-propanoxide), respectively. Compounds 3a-3d have cis and trans geometric isomers. Only the trans isomers of these compounds are isolated. Compounds 3a-3h have two stereogenic P atoms. They are expected to be in cis (meso) and trans (racemic) geometric isomers. In the trans trispiro compounds (3i-3k), there are three stereogenic P atoms. They are expected to be in racemic mixtures. The stereogenic properties of 3a-3k are confirmed by P-31 NMR spectroscopy upon the addition of the chiral solvating agent; (S)-(+)-2,2,2-trifluoro-1-(9'-anthryl)ethanol. The molecular structures of 3i-3k, 4a, and 4b look similar to a propeller, where the chemical environment of one P atom is different from that of others. Additionally, 4a and 4b are also expected to exist as cis-trans-trans and cis-cis-cis geometric isomers, but both of them are found to be in cis-trans-trans geometries. The solid-state structures of 2a, 2e, 2f, 3e, and 31 are determined by X-ray crystallography. The compounds 2f-2i, 3e-3i, and 3k are screened for antibacterial activity against Gram-positive and Gram-negative bacteria and for antifungal activity against yeast strains. These compounds (except 3f) have shown a strong affinity against most of the bacteria. Minimum inhibitory concentrations (MIC) are determined for 2f-2i, 3e-3i, and 3k. DNA binding and the nature of interaction with pUC18 plasmid DNA are studied. The compounds 2f-2i, 3e-3i, and 3k induce changes on the DNA mobility. The prevention of BamHI and HindIII digestion (except 2g) with compounds indicates that the compounds bind with nucleotides in DNA