Publications by authors named "Kees Goubitz"

15 Publications

  • Page 1 of 1

Reassessment of paracetamol orthorhombic Form III and determination of a novel low-temperature monoclinic Form III-m from powder diffraction data.

Acta Crystallogr C Struct Chem 2018 Mar 28;74(Pt 3):392-399. Epub 2018 Feb 28.

University of Amsterdam, Faculty of Humanities, Conservation and Restoration of Cultural Heritage, Johannes Vermeerplein 1, 1071DV Amsterdam, The Netherlands.

Paracetamol [N-(4-hydroxyphenyl)acetamide, CHNO] has several polymorphs, just like many other drugs. The most stable polymorphs, denoted Forms I and II, can be obtained easily and their crystal structures are known. Crystals of the orthorhombic, less stable, room-temperature Form III are difficult to grow; they need a special recipe to crystallize and suffer from severe preferred orientation. A crystal structure model of Form III has been proposed and solved from a combination of structure prediction and powder X-ray diffraction (PXRD) [Perrin et al. (2009). Chem. Commun. 22, 3181-3183]. The final R value of 0.138 and the corresponding considerable residual trace were reasons to check its validity. A new structure determination of Form III using new high-resolution PXRD data led to a final R value of 0.042 and an improvement of the earlier proposed model. In addition, a reversible phase transition was found at 170-220 K between the orthorhombic Form III and a novel monoclinic Form III-m. The crystal structure of Form III-m has been determined and refined from PXRD data to a final R value of 0.059.
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http://dx.doi.org/10.1107/S2053229618002619DOI Listing
March 2018

Nature of Li2O2 oxidation in a Li-O2 battery revealed by operando X-ray diffraction.

J Am Chem Soc 2014 Nov 5;136(46):16335-44. Epub 2014 Nov 5.

Fundamental Aspects of Materials and Energy, Department of Radiation Science and Technology, Faculty of Applied Sciences, Delft University of Technology , Mekelweg 15, 2629 JB, Delft, The Netherlands.

Fundamental research into the Li-O2 battery system has gone into high gear, gaining momentum because of its very high theoretical specific energy. Much progress has been made toward understanding the discharge mechanism, but the mechanism of the oxygen evolution reaction (OER) on charge (i.e., oxidation) remains less understood. Here, using operando X-ray diffraction, we show that oxidation of electrochemically generated Li2O2 occurs in two stages, but in one step for bulk crystalline (commercial) Li2O2, revealing a fundamental difference in the OER process depending on the nature of the peroxide. For electrochemically generated Li2O2, oxidation proceeds first through a noncrystalline lithium peroxide component, followed at higher potential by the crystalline peroxide via a Li deficient solid solution (Li(2-x)O2) phase. Anisotropic broadening of the X-ray Li2O2 reflections confirms a platelet crystallite shape. On the basis of the evolution of the broadening during charge, we speculate that the toroid particles are deconstructed one platelet at a time, starting with the smallest sizes that expose more peroxide surface. In the case of in situ charged bulk crystalline Li2O2, the Li vacancies preferentially form on the interlayer position (Li1), which is supported by first-principle calculations and consistent with their lower energy compared to those located next to oxygen (Li2). The small actively oxidizing fraction results in a gradual reduction of the Li2O2 crystallites. The fundamental insight gained in the OER charge mechanism and its relation to the nature of the Li2O2 particles is essential for the design of future electrodes with lower overpotentials, one of the key challenges for high performance Li-air batteries.
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http://dx.doi.org/10.1021/ja508794rDOI Listing
November 2014

New furanoditerpenoids from Croton jatrophoides.

Planta Med 2009 Feb 17;75(3):262-7. Epub 2008 Dec 17.

Institute of Traditional Medicine, Muhimbili University of Health and Allied Sciences, Dar es Salaam, Tanzania.

Four furanoditerpenoids were isolated from roots of Croton jatrophoides (Euphorbiaceae) collected in Tanzania. In addition to the known compounds penduliflaworosin and teucvin (mallotucin A), a new teucvin isomer, which was named isoteucvin, and a furanoditerpenoid with a new skeleton, for which the name jatrophoidin was adopted, were isolated. Their structures were elucidated by spectroscopic methods such as ESI-MS and NMR, including (1)H-, (13)C-, and two-dimensional NMR. The crystal structures of isoteucvin and jatrophoidin were solved using single-crystal X-ray diffraction, by which we also established the absolute configuration of jatrophoidin. The refined crystal structure of isoteucvin has the same (absolute) configuration as jatrophoidin, although the X-ray diffraction data of isoteucvin were not conclusive with respect to the absolute configuration.
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http://dx.doi.org/10.1055/s-0028-1088383DOI Listing
February 2009

Structures of mono-unsaturated triacylglycerols. V. The beta'(1)-2, beta'-3 and beta(2)-3 polymorphs of 1,3-dilauroyl-2-oleoylglycerol (LaOLa) from synchrotron and laboratory powder diffraction data.

Acta Crystallogr B 2008 Dec 8;64(Pt 6):771-9. Epub 2008 Nov 8.

University of Amsterdam, HIMS/FNWI/Kristallographie, Valckenierstraat 65, 1018 Xe Amsterdam, The Netherlands.

The crystal structures of the beta'(1)-2, the beta'-3 and the beta(2)-3 polymorphs of 1,3-dilauroyl-2-oleoylglycerol have been solved from powder diffraction data. The packing of the beta(2)-3 polymorph is similar to that of other cis mono-unsaturated triacylglycerols. Both the beta' polymorphs are crystallized in a novel type of packing in which one of the saturated lauroyl chains is packed side-by-side with part of the unsaturated oleoyl chain.
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http://dx.doi.org/10.1107/S0108768108031601DOI Listing
December 2008

Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen.

J Phys Chem A 2005 Oct;109(42):9443-55

Molecular Photonic Materials, van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WS Amsterdam, The Netherlands.

The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1'H-indol-3'-yl)maleimide and 4-methyl-3-(1'H-indol-3'-yl)maleimide, are investigated. The bromo derivative was crystallized and its X-ray structure was determined. Both compounds are strongly colored while their separate components (indole and maleimide) absorb in the UV region only. To understand the ground- and excited-state behavior, the photophysical properties of the two compounds were studied in detail by steady state and time-resolved absorption and emission spectroscopy. Their solvatochromic behavior was investigated by using the Kamlet-Taft approach, which indicates some charge transfer (CT) character in the excited state. Nano- and femtosecond transient absorption spectroscopy was used for the identification and investigation of the CT state. Furthermore, the effect of the complexation with zinc(II) 1,4,7,11-tetraazacyclododecane (Zn-cyclen) on the photophysical properties of these two compounds was studied. An enhancement of the fluorescence intensity upon self-assembly (up to 90 times) and high association constants were observed, which illustrate the potential use of these compounds as luminescent sensors. DFT calculations indicate that HOMO-1 to LUMO excitation is mainly responsible for the charge transfer character and that this transition changes its character drastically when Zn-cyclen complexation occurs, thus giving it sensor properties.
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http://dx.doi.org/10.1021/jp054651zDOI Listing
October 2005

A Staudinger approach towards binol-derived MAP-type bidentate P,N ligands.

Angew Chem Int Ed Engl 2004 Jun;43(26):3471-3

Van't Hoff Institute of Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands.

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http://dx.doi.org/10.1002/anie.200454146DOI Listing
June 2004

Synthesis of the cyclobutanone core of solanoeclepin A intramolecular allene butenolide photocycloaddition.

Org Biomol Chem 2003 Dec 29;1(24):4364-6. Epub 2003 Oct 29.

Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands.

The compact tricyclic substructure of solanoeclepin A containing the cyclobutanone ring was prepared by using as the key step a highly regioselective intramolecular [2 + 2]-photocycloaddition reaction between one of the [small pi]-bonds of an allene and the CC double bond of a butenolide.
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http://dx.doi.org/10.1039/b311415eDOI Listing
December 2003

KHCoP2O7.2H2O: a novel acidic pyrophosphate.

Acta Crystallogr C 2003 Jun 31;59(Pt 6):i57-8. Epub 2003 May 31.

Laboratory of Spectroscopy, Department of Chemistry, Faculty of Sciences, University Ibn Tofail, BP 133, 14000 Kenitra, Morocco.

Potassium cobalt hydrogenpyrophosphate dihydrate, KHCoP(2)O(7).2H(2)O, crystallizes in the orthorhombic space group Pnma. This salt is isotypic with KHMP(2)O(7).2H(2)O (M = Mn and Zn). The structure consists of alternating layers, built from HP(2)O(7)(3-) acidic pyrophosphate groups and CoO(6) octahedra, joined by potassium ions and bridging hydrogen bonds. The Co, K and water O atoms lie on mirror planes. The pyrophosphate group consists of two symmetry-related PO(4) groups, with the bridging O atom on a mirror plane.
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http://dx.doi.org/10.1107/s0108270103010084DOI Listing
June 2003

Alcoholysis of acylpalladium(II) complexes relevant to the alternating copolymerization of ethene and carbon monoxide and the alkoxycarbonylation of alkenes: the importance of Cis-coordinating phosphines.

J Am Chem Soc 2003 May;125(18):5523-39

Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV, Amsterdam, The Netherlands.

The mechanism and kinetics of the solvolysis of complexes of the type [(L-L)Pd(C(O)CH(3))(S)](+)[CF(3)SO(3)](-) (L-L = diphosphine ligand, S = solvent, CO, or donor atom in the ligand backbone) was studied by NMR and UV-vis spectroscopy with the use of the ligands a-j: SPANphos (a), dtbpf (b), Xantphos (c), dippf (d), DPEphos (e), dtbpx (f), dppf (g), dppp (h), calix-6-diphosphite (j). Acetyl palladium complexes containing trans-coordinating ligands that resist cis coordination (SPANphos, dtbpf) showed no methanolysis. Trans complexes that can undergo isomerization to the cis analogue (Xantphos, dippf, DPEphos) showed methanolyis of the acyl group at a moderate rate. The reaction of [trans-(DPEphos)Pd(C(O)CH(3))](+)[CF(3)SO(3)](-) (2e) with methanol shows a large negative entropy of activation. Cis complexes underwent competing decarbonylation and methanolysis with the exception of 2j, [cis-(calix-diphosphite)Pd(C(O)CH(3))(CD(3)OD)](+)[CF(3)SO(3)](-). The calix-6-diphosphite complex showed a large positive entropy of activation. It is concluded that ester elimination from acylpalladium complexes with alcohols requires cis geometry of the acyl group and coordinating alcohol. The reductive elimination of methyl acetate is described as a migratory elimination or a 1,2-shift of the alkoxy group from palladium to the acyl carbon atom. Cis complexes with bulky ligands such as dtbpx undergo an extremely fast methanolysis. An increasing steric bulk of the ligand favors the formation of methyl propanoate relative to the insertion of ethene leading to formation of oligomers or polymers in the catalytic reaction of ethene, carbon monoxide, and methanol.
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http://dx.doi.org/10.1021/ja029341yDOI Listing
May 2003

SPANphos: a C2-symmetric trans-coordinating diphosphane ligand.

Angew Chem Int Ed Engl 2003 Mar;42(11):1284-7

Institute of Molecular Chemistry, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.

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http://dx.doi.org/10.1002/anie.200390330DOI Listing
March 2003

Lead tartrate from X-ray powder diffraction data.

Acta Crystallogr C 2002 Dec 20;58(Pt 12):m596-8. Epub 2002 Nov 20.

Laboratory for Crystallography, Institute of Molecular Chemistry, Universiteit van Amsterdam, Nieuwe Achtergracht 166, NL-1018 WV Amsterdam, The Netherlands.

The structure of lead tartrate, Pb(2+).C(4)H(4)O(6)(2-), has been solved from X-ray powder diffraction data. The cation exhibits ninefold coordination and the tartrate groups are linked through Pb.O contacts to form a three-dimensional network.
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http://dx.doi.org/10.1107/s0108270102019637DOI Listing
December 2002

Crystal structure of the inclusion complex of beta-cyclodextrin with mefenamic acid from high-resolution synchrotron powder-diffraction data in combination with molecular-mechanics calculations.

Acta Crystallogr B 2002 Dec 28;58(Pt 6):1036-43. Epub 2002 Nov 28.

University of Amsterdam, Faculty of Science, Laboratory for Crystallography, Institute of Molecular Chemistry, Nieuwe Achtergracht 166, The Netherlands.

The crystal structure of the inclusion complex of beta-cyclo-dextrin with mefenamic acid has been determined from a combination of high-resolution synchrotron powder-diffraction data and molecular-mechanics calculations. A grid search indicates two possible solutions, which are corroborated by molecular-mechanics calculations, while Rietveld-refinement results suggest the crystal structure that is more likely to be formed in the solid state. Mefenamic acid is partially included in beta-cyclodextrin with either the xylyl or the benzoic-acid moiety being inside its cavity. In both solutions mefenamic acid and beta-cyclodextrin form a monomeric complex in a herringbone packing scheme.
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http://dx.doi.org/10.1107/s010876810201947xDOI Listing
December 2002

Novel selective phosphodiesterase (PDE4) inhibitors. 4. Resolution, absolute configuration, and PDE4 inhibitory activity of cis-tetra- and cis-hexahydrophthalazinones.

J Med Chem 2002 Jun;45(12):2526-33

Leiden/Amsterdam Center for Drug Research, Division of Medicinal Chemistry, Department of Pharmacochemistry, Vrije Universiteit, De Boelelaan 1085c, 1081 HV Amsterdam, The Netherlands.

Recently, we reported that 4-catechol-substituted cis-(+/-)-4a,5,6,7,8,8a-hexa- and cis-(+/-)-4a,5,8,8a-tetrahydro-2H-phthalazin-1-ones show potent inhibition of phosphodiesterase (PDE4) activity, while the corresponding trans racemic mixtures exhibit only weak to moderate activity. To determine the absolute configuration and PDE4 inhibitory activity of the individual cis-enantiomers, several optically active phthalazinones have been synthesized. The enantiomers of the various gamma-keto acids, used as starting materials, were resolved in a classical way by the formation of diastereomeric salts, and each was converted to optically active phthalazinone in an enantioselective manner. The absolute configuration of the (+)-enantiomer of cis-hexahydrophthalazinone (+)-12 was determined by X-ray crystallography. The carbon atoms at the 4a and 8a positions were found to have the S- and R-configuration, respectively. In the present series of hexa- and tetrahydrophthalazinones, stereoselectivity for PDE4 inhibition is observed; the cis-(+)-enantiomers of the phthalazinones display high inhibitory activity, whereas their (-)-counterparts exhibit only weak to moderate activity. It is likely that all cis-(+)-phthalazinones have a (4aS,8aR)-configuration and vice versa for the cis-(-)-analogues. In the current series, the N-adamantan-2-yl analogue (+)-14 shows the most potent inhibition of PDE4 (pIC(50) = 9.3); the corresponding (-)-enantiomer is 250-fold less active. In addition, the N-substituted tetrahydrophthalazinones under study were investigated for their in vivo antiinflammatory activities by examining the suppression of arachidonic acid (AA) induced mouse ear edema formation. In this assay analogues (+)-14 and (+)-15 were found to be potent antiinflammatory agents showing about 50% inhibition at 30 micromol/kg po.
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http://dx.doi.org/10.1021/jm0110338DOI Listing
June 2002

5,5-Dimethyl-2-[6-methyl-2-(methylsulfanyl)pyrimidin-4-yloxy]-1,3,2-dioxaphosphorinane-2-thione.

Acta Crystallogr C 2002 May 19;58(Pt 5):o280-1. Epub 2002 Apr 19.

Faculty of Physics, Babes-Bolyai University, M. Kogalniceanu No. 1, 3400 Cluj-Napoca, Romania.

The title compound, C(11)H(17)N(2)O(3)PS(2), is a cyclic thiophosphoryl pyrimidine derivative exhibiting insecticidal properties. The crystal structure determination gives evidence for the presence of the thione isomer of the compound. The pyrimidine nucleus is planar and its substituents have small deviations from the least-squares plane. The dioxaphosphorinane ring adopts a chair conformation. The lack of classical hydrogen bonds and the weak intermolecular interactions lead to a 'loose' packing characterized by channels in the structure.
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http://dx.doi.org/10.1107/s0108270102005218DOI Listing
May 2002

Bonding Properties of a Novel Inorganometallic Complex, Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) (iPr-DAB = N,N'-Diisopropyl-1,4-diaza-1,3-butadiene), and its Stable Radical-Anion, Studied by UV-Vis, IR, and EPR Spectroscopy, (Spectro-) Electrochemistry, and Density Functional Calculations.

Inorg Chem 1996 Sep;35(19):5468-5477

Anorganisch Chemisch Laboratorium, J. H. van 't Hoff Research Institute, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Amsterdam Institute for Molecular Studies, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands, Afdeling Theoretische Chemie, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands, J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 3, 182 23 Prague, Czech Republic.

Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) was synthesized and characterized by UV-vis, IR, (1)H NMR, (13)C NMR, (119)Sn NMR, and mass (FAB(+)) spectroscopies and by single-crystal X-ray diffraction, which proved the presence of a nearly linear Sn-Ru-Sn unit. Crystals of Ru(SnPh(3))(2)(CO)(2)(iPr-DAB).3.5C(6)H(6) form in the triclinic space group P&onemacr; in a unit cell of dimensions a = 11.662(6) Å, b = 13.902(3) Å, c = 19.643(2) Å, alpha = 71.24(2) degrees, beta = 86.91(4) degrees, gamma = 77.89(3) degrees, and V = 2946(3) Å(3). One-electron reduction of Ru(SnPh(3))(2)(CO)(2)(iPr-DAB) produces the stable radical-anion [Ru(SnPh(3))(2)(CO)(2)(iPr-DAB)](*-) that was characterized by IR, and UV-vis spectroelectrochemistry. Its EPR spectrum shows a signal at g = 1.9960 with well resolved Sn, Ru, and iPr-DAB (H, N) hyperfine couplings. DFT-MO calculations on the model compound Ru(SnH(3))(2)(CO)(2)(H-DAB) reveal that the HOMO is mainly of sigma(Sn-Ru-Sn) character mixed strongly with the lowest pi orbital of the H-DAB ligand. The LUMO (SOMO in the reduced complex) should be viewed as predominantly pi(H-DAB) with an admixture of the sigma(Sn-Ru-Sn) orbital. Accordingly, the lowest-energy absorption band of the neutral species will mainly belong to the sigma(Sn-Ru-Sn)-->pi(iPr-DAB) charge transfer transition. The intrinsic strength of the Ru-Sn bond and the delocalized character of the three-center four-electron Sn-Ru-Sn sigma-bond account for the inherent stability of the radical anion.
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http://dx.doi.org/10.1021/ic960042hDOI Listing
September 1996
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