David Kitko - Academia.edu (original) (raw)

Papers by David Kitko

Inorganic Chemistry, Nov 1, 1998

A phenol-based "end-off" compartmental ligand, 2-[N,N-di(2-pyridylmethyl)aminomethyl]-6-{N-[2-(di... more A phenol-based "end-off" compartmental ligand, 2-[N,N-di(2-pyridylmethyl)aminomethyl]-6-{N-[2-(dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL), having an iminic bidentate and an aminic tridentate chelating arms on the 2-and 6-positions of the phenolic ring, respectively, forms dinuclear nickel complexes [Ni 2 (L)-(AcO)(NCS) 2 ] (1), [Ni 2 (L)(AcO) 2 (MeOH)]PF 6 (2), and [{Ni 2 (L)(OH)(MeOH)} 2 (CO 3)](PF 6) 2 (3). Complex 1 crystallizes in the monoclinic space group P2 1 /c, a) 14.165(5) Å, b)15.198(4) Å, c) 17.395(8) Å,) 100.62-(4)°, V) 3680(2) Å 3 , and Z) 4. The pair of Ni ions present are bridged by the phenolic oxygen of Land an acetate group in syn-syn mode (Ni-Ni: 3.373(3) Å). An isothiocyanate nitrogen atom coordinates to each Ni providing an asymmetric dinuclear core with a mixed {5/6} coordination number set. Complex 2 crystallizes in the monoclinic space group P2 1 /c, a) 13.505(5) Å, b) 12.028(4) Å, c) 22.774(9) Å,) 103.78(3)°, V) 3592(2) Å 3 , and Z) 4. It has a dinuclear core bridged by the phenolic oxygen of Land two acetate groups in syn-syn mode, providing a µ-phenoxo-bis(µ-carboxylato)dinickel(II) core (Ni-Ni: 3.396(6) Å). A methanol molecule coordinates to the Ni bound to the bidentate arm, forming a dinuclear core having a {6/6} coordination number set and an asymmetric donor atom environment. Complex 3 crystallizes in the orthorhombic space group Pbcn, a) 19.056(5) Å, b) 18.997(4) Å, c) 19.919(6) Å, R)) γ) 90°, V) 7211(5) Å 3 , and Z) 8. In each dinuclear unit a pair of Ni ions are bridged by the phenolic oxygen of Land a hydroxo oxygen (Ni-Ni: 3.087(2) Å). A carbonate further bridges two of the dinuclear units to present a composite dimer. The Ni bound to the bidentate arm attains six-coordinate geometry by further interaction with two oxygens of the bridging carbonato group. The Ni bound to the tridentate arm assumes six-coordinate geometry by further coordination of a methanol oxygen. Complexes 1-3 react with urea in ethanol to form the isocyanate complexes [Ni 2 (L)-(AcO)(NCS)(NCO)] (1′), [Ni 2 (L)(AcO)(NCO)(EtOH)]PF 6 (2′), and [{Ni 2 (L)(NCO)(EtOH)} 2 (CO 3)](PF 6) 2 (3′), respectively. Complex 3′ crystallizes in the triclinic space group P1 h, a) 20.072(7) Å, b) 21.145(6) Å, c) 18.688(6) Å, R) 106.20(2)°,) 90.01(3)°, γ) 88.73(3)°, V) 7614(4) Å 3 , and Z) 4. It has a dimeric structure very similar to that of 3, except for the replacement of the hydroxy bridge and the methanol ligand in 3 by isocyanate bridge and ethanol ligand, respectively, in 3′.

Chemischer Informationsdienst, May 24, 1977

Chemischer Informationsdienst, Jun 24, 1980

ChemInform Abstract Die Co-Komplexe (I), (IIc) und (III) wurden durch Reaktion der wasserfreien C... more ChemInform Abstract Die Co-Komplexe (I), (IIc) und (III) wurden durch Reaktion der wasserfreien Co-halogenide mit den Phosphinen in CH2Cl2 dargestellt. (Ic) wurde nur ESR-spektroskopisch nachgewiesen. Die Cyanokomplexe (IIa) und (IIb) erhielt man durch säulenchromatographischen Cyanid-Ionenaustausch aus (I), Elektronenstrukturen wurden mittels EPR-Spektroskopie ermittelt. Während Chloro-und Bromo-Komplexe keine Reaktion mit O2 zeigen, reagieren dieübrigen Verbindungen, wie am Beispiel von (IIb) gezeigt wird, mit O2 zu EPR-spektroskopisch identifizierten Addukten, in denen nach Abgabe von einem Phosphinliganden der Disauerstoff zunächst einzähnig gebunden ist und aus denen dann ein Produkt des Typs (IV) entsteht, in dem O2 ringförmig in Peroxoform gebunden ist.

Inorganic Chemistry, Jun 1, 2007

Journal of the Chemical Society D Chemical Communications, 1969

Journal of the American Chemical Society, Nov 17, 2005

Quantitative epoxidation of norbornylene with [Mn IV (Me 2 EBC)(OH) 2 ](PF 6) 2 •H 2 O. In a typi... more Quantitative epoxidation of norbornylene with [Mn IV (Me 2 EBC)(OH) 2 ](PF 6) 2 •H 2 O. In a typical reaction, 0.3255 g (0.5 mmol) of [Mn IV (Me 2 EBC)(OH) 2 ](PF 6) 2 •H 2 O was dissolved in a 5 ml of acetone/water (ratio 4:1) solvent mixture. After 1 mmol of norbornylene was added, the reaction mixture was stirred in a controlled atmosphere wet box at room temperature for at least 2 days in the absence of oxygen. Quantitative analysis of products was performed using gas chromatography. Catalytic epoxidation of olefins. In a typical reaction, a solution of 0.1 ml of 50 mM (0.005 mmol) Mn II (Me 2 EBC)Cl 2 was prepared in 5 ml of acetone/water (ratio 4:1). After 0.2 ml of 2.5 M (0.5 mmol) norbornylene in acetone was added to the solvent mixture containing the catalyst, 1 mL of 50% H 2 O 2 was added stepwise (0.2 mL per half hour). The reaction mixture was stirred for an additional 1h at room temperature. The quantitative analysis of products was performed using chromatography by the internal standard method and the identities of the products were confirmed by GC-MS. A parallel experiment without catalyst was run as a control.

Journal of the American Chemical Society, Nov 11, 2008

Clarifying the difference in redox reactivity between the metal oxo and metal hydroxo moieties fo... more Clarifying the difference in redox reactivity between the metal oxo and metal hydroxo moieties for the same redox active metal ion in identical structures and oxidation states, that is, M n+ dO and M n+-OH, contributes to the understanding of nature's choice between them (M n+ dO or M n+-OH) as key active intermediates in redox enzymes and electron transfer enzymes, and provides a basis for the design of synthetic oxidation catalysts. The newly synthesized manganese(IV) complex having two hydroxide ligands, [Mn(Me 2 EBC) 2 (OH) 2 ](PF 6) 2 , serves as the prototypic example to address this issue, by investigating the difference in the hydrogen abstracting abilities of the Mn IV dO and Mn IV-OH functional groups. Independent thermodynamic evaluations of the O-H bond dissociation energies (BDE OH) for the corresponding reduction products, Mn III-OH and Mn III-OH 2 , reveal very similar oxidizing power for Mn IV dO and Mn IV-OH (83 vs 84.3 kcal/mol). Experimental tests showed that hydrogen abstraction proceeds at reasonable rates for substrates having BDE CH values less than 82 kcal/mol. That is, no detectable reaction occurred with diphenyl methane (BDE CH) 82 kcal/mol) for both manganese(IV) species. However, kinetic measurements for hydrogen abstraction showed that at pH 13.4, the dominant species Mn(Me 2 EBC) 2 (O) 2 , having only Mn IV dO groups, reacts more than 40 times faster than the Mn IV-OH unit in Mn(Me 2 EBC) 2 (OH) 2 2+ , the dominant reactant at pH 4.0. The activation parameters for hydrogen abstraction from 9,10-dihydroanthracene were determined for both manganese(IV) moieties: over the temperature range 288-318 K for Mn IV (OH) 2 2+ , ∆H q) 13.1 (0.7 kcal/mol, and ∆S q)-35.0 (2.2 cal K-1 mol-1 ; and the temperature range 288-308 K for for Mn IV (O) 2 , ∆H q) 12.1 (1.8 kcal/mol, and ∆S q)-30.3 (5.9 cal K-1 mol-1 .

Inorganic Chemistry, Aug 26, 2006

A nonionic surfmer (MAA-EO 23 C 12) was prepared and reacted with acrylamide, acrylic acid, and a... more A nonionic surfmer (MAA-EO 23 C 12) was prepared and reacted with acrylamide, acrylic acid, and a double tailed hydrophobic monomer (BTMAM) to synthesize a surface-active hydrophobically associating copolymer (SHAP) through photoinitiated free radical copolymerization in aqueous solution. Fourier transform infrared and 1 H-nuclear magnetic resonance spectroscopy were used to characterize the functional monomer and the SHAP. Several performance evaluations, such as viscosification property, temperature resistance, salt tolerance, and shear resistance, were also conducted. Experiment results demonstrated that the introduced nonionic surfmer and hydrophobic monomer could endow the copolymer with excellent temperature resistance, salt tolerance, and shear resistance capability at low concentration.

Journal of the American Chemical Society, Jan 24, 2007

Bond dissociation energy (BDE) calculations. The BDE OH calculations were performed by the method... more Bond dissociation energy (BDE) calculations. The BDE OH calculations were performed by the method introduced by Bordwell 1 and adapted by Mayer 2 (See Scheme 1S and 2S). Hydrogen abstraction reaction-small synthetic scale. All reagents were obtained from Aldrich and used as received except 1,4-cyclohexadiene which was distilled before use. In a typical reaction, 0.25 mmol of the manganese(IV) complex was added to 0.5 mmol of 1,4-cyclohexadiene in 5 mL of acetone/water (ratio 4:1) solvent in a controlled atmosphere wet box. The reaction mixture was stirred until the purple color of the manganese(IV) species turned to the red brown color of the corresponding manganese(III) species. Quantitative analysis of products was performed by GC using an internal standard, and the identities of the reaction products were confirmed by GC-MS. Hydrogen abstraction reaction in base-analytical scale. In 8 mL of acetone/water (ratio 4:1), 0.063 g (0.1 mmol) of manganese(IV) complex was dissolved. The pH value of the resulting solution was adjusted by NaOH to pH 8.6 before adding 0.4 mL (2.4 mmol mmol) of diphenylmethane to initiate the reaction. After stirring overnight, the manganese(IV) in the complex was reduced to the corresponding manganese(III) derivative and the pH value of the solution had changed to 7.6. GC and GC/MS analysis of the reaction mixture showed that no hydrogen abstraction product was formed. Rate Measurements (a) In a typical kinetic experiment, a 20 fold excess of substrate was used. Excess 1,4-cyclohexadiene (CHD, 40 mM) and 2 mM of the manganese(IV) complex were dissolved in 10 mL of acetone/water solvent (ratio 4:1, initial pH 6.1), at r.t. The disappearance of the manganese(IV) species was monitored by UV-visible spectrophotometry and the pseudo first order rate constant (k 1) was calculated. The same procedure was used in rate determinations for the other substrates listed in Table 1. (b) To determine the influence of pH on the rates of the hydrogen abstraction reactions, the oxidations of different substrates by our Mn(IV) complex were studied in solutions having different selected initial pH values. pH values of 4.0 and 8.4 were chosen to reveal the relative reactivities of the two distinct catalyst species capable of performing hydrogen abstractions, LMn IV (OH) 2 2+ and LMn IV (O)OH +. These pH values were chosen on the basis of a well defined pK value of 6.86 relating these two species and approximate values of ~2 and ~10 representing, for pKa

Archives of Dermatological Research, Nov 1, 1988

Sheets of porcine stratum corneum were dispersed into individual corneocytes after 4 h in a solut... more Sheets of porcine stratum corneum were dispersed into individual corneocytes after 4 h in a solution consisting of 8 mM N,N-dimethyldodecylamine oxide and 2 mM sodium dodecylsuifate in phosphate-buffered isotonic saline, at 45 ~ C. With continued detergent treatment and moderate sonication, most of the cells lost their keratin contents and were then separated from the remaining intact cells by centrifugation in cesium chloride solution of density 1.280. Electron microscopy showed that the cell envelopes retained both the crosslinked protein envelope and its attached lipid envelope. The dry weight of envelopes was approximately 7% of the estimated dry weight of the original stratum corneum, while the corneocytes surviving intact also amounted to 7% of the starting weight. Mild alkaline hydrolysis of the corneocyte envelopes allowed the extraction of hydroxyceramides amounting to 10% of the dry weight of the envelopes. The procedure therefore provides isolated corneocyte envelopes suitable for studying both the protein and lipid components of this compound sheath.

Journal of Investigative Dermatology, Feb 1, 1989

Journal of Coordination Chemistry, Dec 12, 2007

Two ultra rigid, o-xylylene cross-bridged macrobicyclic ligands, 1, 10, 13, 19-tetraazatricyclo [... more Two ultra rigid, o-xylylene cross-bridged macrobicyclic ligands, 1, 10, 13, 19-tetraazatricyclo [8.6. 6.03, 8] docosa-3, 5, 7-triene (H2XBC), and 13, 19-dimethyl-1, 10, 13, 19-tetraazatricyclo [8.6. 6.03, 8] docosa-3, 5, 7-triene (Me2XBC), have been synthesized and ...

166 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1976.U of I OnlyRestricted to t... more 166 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1976.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Chemischer Informationsdienst, 1979

NOVELTY - A laundry and cleaning composition comprises metal complex (1-99.9 pts.wt.), an oxygen ... more NOVELTY - A laundry and cleaning composition comprises metal complex (1-99.9 pts.wt.), an oxygen bleaching agent, and adjunct materials. The metal complex comprises a transition metal atom including manganese, iron, cobalt, chromium, nickel, copper, vanadium, molybdenum, tungsten, palladium, ruthenium; and a cross-bridged macropolycyclic ligand comprising an organic macrocycle ring comprising greater than or equal to 4 donor atoms. USE - A laundry and cleaning composition for fabric washing, and for hard surfaces (including interiors of ovens, kitchen surfaces, or bathroom surfaces). ADVANTAGE - The composition has superior bleaching compared to compositions not having the selected transition-metal bleach catalyst. The superiority in bleaching is obtained using very low levels of transition-metal bleach catalyst. It controls or kills microorganisms including bacteria, viruses, sub-viral particles, and molds; and destroys objectionable non-living proteins and/or peptides. DETAILED DE...

L'invention concerne des compositions pharmaceutiques et des procedes d'utilisation de ce... more L'invention concerne des compositions pharmaceutiques et des procedes d'utilisation de ces dernieres qui comprennent a) une quantite efficace d'un agent d'imagerie par resonance magnetique, par exemple, un complexe de formule (I) et b) les excipients d'equilibrage et d'autre ingredients ajoutes.

NOVELTY - A laundry and cleaning composition comprises metal complex (1 ppb to 99.9%), oxygen ble... more NOVELTY - A laundry and cleaning composition comprises metal complex (1 ppb to 99.9%), oxygen bleaching agent, and additives (balance). The metal complex comprises transition metal and cross-bridge macropolycyclic ligand comprising organic macrocycle ring and moiety comprising cross-bridged chain that covalently connects non-adjacent donor atoms of organic macrocycle ring. The organic macrocycle ring comprises donor atoms that are coordinated to transition metal; and non-donor atoms to separate the donor atoms from each other by covalent linkages of non-donor atom. USE - For use as laundry composition and automatic dishwashing detergents. ADVANTAGE - The composition provides enhanced cleaning/bleaching benefits through the use of transition-metal bleach catalyst. DETAILED DESCRIPTION - A laundry and cleaning composition comprises metal complex (1 ppb to 99.9%), oxygen bleaching agent, and additives (balance). The metal complex comprises transition metal and cross-bridge macropolycyc...

Inorganic Chemistry, 2006