Search

Your search keyword '"Krivokapic, Alexander"' showing total 38 results
Start Over Author "Krivokapic, Alexander"
38 results on '"Krivokapic, Alexander"'

4. Adding a new dimension to the investigation of platinum-mediated arene C-H activation reactions using 2D NMR exchange spectroscopy: Dynamics of Pt(II) phenyl/benzene site exchange

Author

Wik, Bror Johan, Lersch, Martin, Krivokapic, Alexander, and Tilset, Mats

Subjects
Nuclear magnetic resonance spectroscopy -- Usage, Platinum compounds -- Chemical properties, Benzene -- Chemical properties, Chemistry
Abstract

The low-temperature protonation chemistry of (N-N)PtPh2 complexes, where a choice between Pt(II) and Pt(IV) products is available depending on the reaction conditions is described. In the absence of strongly bonded ligands, Pt(II) phenyl/pi-benzene complexes (N-N)Pt(C6H5)-(eta(super 2)-C6H6)(super +) are formed.

Published
2006

9. Ligand-field dependence of the excited state dynamics of hangman bisporphyrin dyad complexes

Author

Hodgkiss, Justin M., Krivokapic, Alexander, and Nocera, Daniel G.

Subjects
Porphyrins -- Structure, Porphyrins -- Chemical properties, Zinc compounds -- Structure, Zinc compounds -- Chemical properties, Energy transformation -- Analysis, Electron transport -- Research, Chemicals, plastics and rubber industries
Abstract

The first transient kinetic studies of Hangman porphyrin dyads which is was developed to interrogate the ligand-field dependent of photoinduced PCET versus excitation energy transfer and intersystem crossing in P[Zn.sup.II]-P[Fe.sup.III]-OH dyads where (P = porphyrin) is reported.

Published
2007

10. Contracted and expanded meso-alkynyl porphyrinoids: from triphyrin to hexaphyrin

Author

Krivokapic, Alexander, Cowley, Andrew R., and Anderson, Harry L.

Subjects
Chemistry, Organic -- Research, Porphyrins -- Composition, Organic compounds -- Composition, Methylene chloride, Fluorides -- Composition, Biological sciences, Chemistry
Abstract

Research has been conducted on triisopropylsilyl propynal. The authors report that boron trifluoride-catalyzed Rothemund condensation of this compound with 3,4-diethylpyrrole in dichloromethane produce chromophores with special spectroscopic characteristics.

Published
2003

12. Synthesis and crystal structure of a meso-trialkynyl[28]hexaphyrin

Author

Harry L. Anderson and Krivokapic Alexander Krivokapic Alexander

Subjects
Crystallography, Chemistry, General Medicine, Crystal structure
Abstract

A 5,15,25-trialkynyl [28]hexaphyrin(1.1.1.1.1.1) is the main product of the boron trifluoride-catalysed condensation of meso-anthryl dipyrromethane and triisopropylsilylpropynal; it absorbs strongly in the near-infrared, out to 1093 nm.

Published
2003

34. L-Isoleucyl-L-serine 0.33-hydrate, L-phenylalanyl-L-serine and L-methionyl-L-Serine 0.34-hydrate.

Author

Görbitz, Carl Henrik, Bruvoll, Marius, Dizdarevic, Selma, Fimland, Nina, Hafizovic, Jasmina, Kalfjøs, Helen Therese, Krivokapic, Alexander, and Vestli, Kristian

Subjects
PEPTIDES, SERINE, CRYSTALS, HYDROPHOBIC surfaces, HYDROGEN bonding, BED sheets, INTERMOLECULAR forces
Abstract

The structures of the title dipeptides, C9H18N2O4·0.33H2O, C12H16N2O4 and C8H16N2O4S·0.34H2O, complete a series of investigations focused onl-Xaa-l-serine peptides, where Xaa is a hydro­phobic residue. All three structures are divided into hydro­philic and hydro­phobic layers. The hydro­philic layers are thin forl-phenyl­alanyl-l-serine, rendered possible by an unusual peptide conformation, and thick forl-isoleucyl-l-serine andl-methionyl-l-serine, which include cocrystallized water mol­ecules on the twofold axes. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

35. Synthesis, Characterization, and Protonation Reactions of ArBIAN and ArBICAT Diimine Platinum Diphenyl Complexes

Author

Parmene, Jerome, Krivokapic, Alexander, and Tilset, Mats

Abstract

PtIIdiphenyl complexes N–NPtPh2[N–N = diimines Ar–N=CAnC=N–Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar–N=CMe–CMe=N–Ar, the electronwithdrawing ability of the ArBIAN ligand and the electrondonating ability of the O,Oheterocyclic ArBICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the NAryl groups. Protonation of N–NPtPh2in dichloromethaneacetonitrile at –78 °C furnishes the corresponding PtIVhydrides N–NPtPh2HNCMe+. The PtIVhydrides liberate benzene with the formation of N–NPtPhNCMe+when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtIIspecies N–NPtNCMe22+at approximately 50 °C. Protonation of N–NPtPh2in the absence of acetonitrile results in the clean formation of N–NPtPhη2C6H6+at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine Naryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonationinduced reactions of diiminePtPh2complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the ArBICAT system has a weaker transinfluence than the ArBIAN and ArDAB systems.

Published
2010
Full Text
View/download PDF

36. Synthesis of polypara-phenylenevinylene rotaxanes by aqueous Suzuki couplingElectronic supplementary information (ESI) available: details of analytical ultracentrifuge measurements; experimental synthetic procedures. See http://www.rsc.org/suppdata/cc/b3/b311762f/

Author

Terao, Jun, Tang, Andrew, Michels, Jasper J., Krivokapic, Alexander, and Anderson, Harry L.

Abstract

PPV-based polyrotaxanes have been prepared by coupling vinyl boronic acids to aryl iodides in the presence of cyclodextrins, and the crystal structure of a 2rotaxane of this type has been determined.

Published
2003
Full Text
View/download PDF

37. Design of Multi-Luminescent Silica-Based Nanoparticles for the Detection of Liquid Organic Compounds.

Author

Delic A, Lindgren M, Psarrou M, Economopoulos S, Mariussen E, Krivokapic A, Torsæter O, Omran M, and Einarsrud MA

Abstract

Tracer testing in reservoir formations is utilised to determine residual oil saturation as part of optimum hydrocarbon production. Here, we present a novel detection method of liquid organic compounds by monodisperse SiO 2 nanoparticles (NPs) containing two luminophores, a Eu III :EDTA complex and a newly synthesised fluorophore based on the organic boron-dipyrromethene (BODIPY)-moiety. The particles exhibited stable Eu III PL emission intensity with a long lifetime in aqueous dispersion. The fluorescence of the BODIPY was also preserved in the aqueous environment. The ratiometric PL detection technique was demonstrated by using toluene and 1-octanol as model compounds of crude oil. The optimal synthesis conditions were found to give NPs with a diameter of ~100 nm, which is suitable for transport through porous oil reservoir structures. The cytotoxicity of the NPs was confirmed to be very low for human lung cell and fish cell lines. These findings demonstrate the potential of the NPs to replace the hazardous chemicals used to estimate the residual oil saturation. Moreover, the ratiometric PL detection technique is anticipated to be of benefit in other fields, such as biotechnology, medical diagnostics, and environmental monitoring, where a reliable and safe detection of a liquid organic phase is needed., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Published
2024
Full Text
View/download PDF

38. Highly cis-selective cyclopropanations with ethyl diazoacetate using a novel Rh(I) catalyst with a chelating N-heterocyclic iminocarbene ligand.

Author

Rosenberg ML, Krivokapic A, and Tilset M

Subjects
Alkenes chemistry, Catalysis, Chelating Agents, Molecular Structure, Organometallic Compounds chemistry, Stereoisomerism, Cyclopropanes chemistry, Diazonium Compounds chemistry, Organometallic Compounds chemical synthesis, Rhodium chemistry
Abstract

A structurally characterized Rh(I) iminocarbene complex (N,C)Rh(CO)Cl is activated with AgOTf to act as a highly cis-selective catalyst for the cyclopropanation of substituted styrenes and other alkenes with ethyl diazoacetate (11 examples, 10-99% yield, up to >99% cis-selectivity).

Published
2009
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results