51
|
Lin F, Meng X, Kukueva E, Altantzis T, Mertens M, Bals S, Cool P, Van Doorslaer S. Direct-synthesis method towards copper-containing periodic mesoporous organosilicas: detailed investigation of the copper distribution in the material. Dalton Trans 2015; 44:9970-9. [DOI: 10.1039/c4dt03719g] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A direct synthesis method to incorporate Cu in ethane-bridged PMOs is presented. EPR and TEM reveal the immobilization and distribution of Cu in the material.
Collapse
|
52
|
Peys N, Maurelli S, Reekmans G, Adriaensens P, De Gendt S, Hardy A, Van Doorslaer S, Van Bael MK. Chemical composition of an aqueous oxalato-/citrato-VO(2+) solution as determinant for vanadium oxide phase formation. Inorg Chem 2014; 54:69-78. [PMID: 25517211 DOI: 10.1021/ic5015779] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aqueous solutions of oxalato- and citrato-VO(2+) complexes are prepared, and their ligand exchange reaction is investigated as a function of the amount of citrate present in the aqueous solution via continuous-wave electron paramagnetic resonance (CW EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopy. With a low amount of citrate, monomeric cis-oxalato-VO(2+) complexes occur with a distorted square-pyramidal geometry. As the amount of citrate increases, oxalate is gradually exchanged for citrate. This leads to (i) an intermediate situation of monomeric VO(2+) complexes with a mix of oxalate/citrate ligands and (ii) a final situation of both monomeric and dimeric complexes with exclusively citrato ligands. The monomeric citrato-VO(2+) complexes dominate (abundance > 80%) and are characterized by a 6-fold chelation of the vanadium(IV) ion by 4 RCO2(-) ligands at the equatorial positions and a H2O/R-OH ligand at the axial position. The different redox stabilities of these complexes, relative to that of dissolved O2 in the aqueous solution, is analyzed via (51)V NMR. It is shown that the oxidation rate is the highest for the oxalato-VO(2+) complexes. In addition, the stability of the VO(2+) complexes can be drastically improved by evacuation of the dissolved O2 from the solution and subsequent storage in a N2 ambient atmosphere. The vanadium oxide phase formation process, starting with the chemical solution deposition of the aqueous solutions and continuing with subsequent processing in an ambient 0.1% O2 atmosphere, differs for the two complexes. The oxalato-VO(2+) complexes turn into the oxygen-deficient crystalline VO2 B at 400 °C, which then turns into crystalline V6O13 at 500 °C. In contrast, the citrato-VO(2+) complexes form an amorphous film at 400 °C that crystallizes into VO2 M1 and V6O13 at 500 °C.
Collapse
|
53
|
Ling Y, Van Mierloo S, Schnegg A, Fehr M, Adriaensens P, Lutsen L, Vanderzande D, Maes W, Goovaerts E, Van Doorslaer S. Electronic structure of positive and negative polarons in functionalized dithienylthiazolo[5,4-d]thiazoles: a combined EPR and DFT study. Phys Chem Chem Phys 2014; 16:10032-40. [PMID: 24488368 DOI: 10.1039/c3cp54635g] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
2,5-Dithienylthiazolo[5,4-d]thiazole (DTTzTz) derivatives have high potential for solution-processed organic field-effect transistors and solar cells, both as electron acceptors and donors. Here, the electronic structure of positive and negative radicals (polarons) of two functionalized DTTzTz materials is studied using multi-frequency and multi-resonance electron paramagnetic resonance (EPR) in combination with density functional theory (DFT). It is shown that the negative and positive DTTzTz polarons can be distinguished on the basis of their characteristic EPR parameters. The chemically induced polarons are compared to light-generated states observed in a blend of one of the DTTzTz derivatives with a donor polymer. The study gives in-depth information about the spread of the electron or hole in the DTTzTz molecules.
Collapse
|
54
|
Van Doorslaer S, Trandafir F, Harmer JR, Moens L, Dewilde S. EPR analysis of cyanide complexes of wild-type human neuroglobin and mutants in comparison to horse heart myoglobin. Biophys Chem 2014; 190-191:8-16. [DOI: 10.1016/j.bpc.2014.03.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 03/21/2014] [Accepted: 03/28/2014] [Indexed: 02/05/2023]
|
55
|
Lin F, Meng X, Mertens M, Cool P, Van Doorslaer S. Probing framework–guest interactions in phenylene-bridged periodic mesoporous organosilica using spin-probe EPR. Phys Chem Chem Phys 2014; 16:22623-31. [DOI: 10.1039/c4cp03778b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Spin-probe EPR reveals significant differences in the adsorption of probe molecules in benzene-bridged periodic mesoporous silica with crystal-like or amorphous walls.
Collapse
|
56
|
Moons H, Loas A, Gorun SM, Van Doorslaer S. Photoreduction and light-induced triplet-state formation in a single-site fluoroalkylated zinc phthalocyanine. Dalton Trans 2014; 43:14942-8. [DOI: 10.1039/c4dt00621f] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Anaerobic red-light illumination leads to reduction of perfluoroisopropyl-substituted zinc(ii) phthalocyanine in ethanol, while low power UV illumination favours the formation of a triplet excited state.
Collapse
|
57
|
Caretti I, Zamani S, Beyers E, Cool P, Van Doorslaer S. Effects of copper and vanadium deposition in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes. Dalton Trans 2013; 42:12148-56. [PMID: 23609025 DOI: 10.1039/c3dt00061c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Metal incorporation and doping is one of the routes commonly explored to improve visible light photocatalytic activity of titania and related materials. In this work, we explore the effect of copper and vanadium deposition and incorporation in multi-walled hydrogen trititanate and mixed-phase anatase/trititanate nanotubes. The molecular designed dispersion method is used to introduce the metals in the materials. Electron paramagnetic resonance facilitates a full characterization of the metal sites before and after calcination and allows determining the UV- and visible-light-induced formation of paramagnetic intermediates. Vanadium or copper deposition on the tubes leads to increased formation of F(+) centres under visible or UV illumination. The EPR results are linked to the activity towards rhodamine 6G photobleaching of the different materials.
Collapse
|
58
|
Van Leuven W, Cuypers B, Desmet F, Giordano D, Verde C, Moens L, Van Doorslaer S, Dewilde S. Is the heme pocket region modulated by disulfide-bridge formation in fish and amphibian neuroglobins as in humans? BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1757-63. [PMID: 23403147 DOI: 10.1016/j.bbapap.2013.01.042] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 01/25/2013] [Accepted: 01/29/2013] [Indexed: 12/17/2022]
Abstract
Neuroglobin, a globin characterized by a bis-histidine ligation of the heme iron, has been identified in mammalian and non-mammalian vertebrates, including fish, amphibians and reptiles. In human neuroglobin, the presence of an internal disulfide bond in the CD loop (CD7-D5) is found to modulate the ligand binding through a change in the heme pocket structure. Although the neuroglobin sequences mostly display conserved Cys at positions CD7, D5 and G18/19, a number of exceptions are known. In this study, neuroglobins from amphibian (Xenopus tropicalis) and fish (Chaenocephalus aceratus, Dissostichus mawsoni and Danio rerio) are investigated using electron paramagnetic resonance and optical absorption spectroscopy. All these neuroglobins differ from human neuroglobin in their Cys-positions. It is demonstrated that if disulfide bonds are formed in fish and amphibian neuroglobins, the reduction of these bonds does not result in alteration of the heme pocket in these globins. Furthermore, it is shown that mutagenesis of the Cys residues of X. tropicalis neuroglobin influences the protein structure. The amphibian neuroglobin is also found to be more resistant to H2O2-induced denaturation than the other neuroglobins under study, although all show an overall large stability in high concentrations of this oxidant. This article is part of a Special Issue entitled: Oxygen Binding and Sensing Proteins.
Collapse
|
59
|
Peys N, Ling Y, Dewulf D, Gielis S, De Dobbelaere C, Cuypers D, Adriaensens P, Van Doorslaer S, De Gendt S, Hardy A, Van Bael MK. V6O13films by control of the oxidation state from aqueous precursor to crystalline phase. Dalton Trans 2013; 42:959-68. [DOI: 10.1039/c2dt31857a] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
60
|
Smits M, Ling Y, Lenaerts S, Van Doorslaer S. Photocatalytic removal of soot: unravelling of the reaction mechanism by EPR and in situ FTIR spectroscopy. Chemphyschem 2012; 13:4251-7. [PMID: 23150192 DOI: 10.1002/cphc.201200674] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 10/19/2012] [Indexed: 11/07/2022]
Abstract
Photocatalytic soot oxidation is studied on P25 TiO(2) as an important model reaction for self-cleaning processes by means of electron paramagnetic resonance (EPR) and Fourier transform infrared (FTIR) spectroscopy. Contacting of carbon black with P25 leads on the one hand to a reduction of the local dioxygen concentration in the powder. On the other hand, the weakly adsorbed radicals on the carbon particles are likely to act as alternative traps for the photogenerated conduction-band electrons. We find furthermore that the presence of dioxygen and oxygen-related radicals is vital for the photocatalytic soot degradation. The complete oxidation of soot to CO(2) is evidenced by in situ FTIR spectroscopy, no intermediate CO is detected during the photocatalytic process.
Collapse
|
61
|
Tanner P, Ezhevskaya M, Nehring R, Van Doorslaer S, Meier W, Palivan C. Specific His6-tag Attachment to Metal-Functionalized Polymersomes Relies on Molecular Recognition. J Phys Chem B 2012; 116:10113-24. [DOI: 10.1021/jp305544v] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
|
62
|
Van Doorslaer S, Tilleman L, Verrept B, Desmet F, Maurelli S, Trandafir F, Moens L, Dewilde S. Marked difference in the electronic structure of cyanide-ligated ferric protoglobins and myoglobin due to heme ruffling. Inorg Chem 2012; 51:8834-41. [PMID: 22877248 DOI: 10.1021/ic3007074] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Electron paramagnetic resonance experiments reveal a significant difference between the principal g values (and hence ligand-field parameters) of the ferric cyanide-ligated form of different variants of the protoglobin of Methanosarcina acetivorans (MaPgb) and of horse heart myoglobin (hhMb). The largest principal g value of the ferric cyanide-ligated MaPgb variants is found to be significantly lower than for any of the other globins reported so far. This is at least partially caused by the strong heme distortions as proven by the determination of the hyperfine interaction of the heme nitrogens and mesoprotons. Furthermore, the experiments confirm recent theoretical predictions [Forti, F.; Boechi, L., Bikiel, D., Martí, M.A.; Nardini, M.; Bolognesi, M.; Viappiani, C.; Estrin, D.; Luque, F. J. J. Phys. Chem. B 2011, 115, 13771-13780] that Phe(G8)145 plays a crucial role in the ligand modulation in MaPgb. Finally, the influence of the N-terminal 20 amino-acid chain on the heme pocket in these protoglobins is also proven.
Collapse
|
63
|
Vinck E, Carter E, Murphy DM, Van Doorslaer S. Observation of an Organic Acid Mediated Spin State Transition in a Co(II)–Schiff Base Complex: An EPR, HYSCORE, and DFT Study. Inorg Chem 2012; 51:8014-24. [DOI: 10.1021/ic300058p] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
64
|
Abbruzzetti S, Tilleman L, Bruno S, Viappiani C, Desmet F, Van Doorslaer S, Coletta M, Ciaccio C, Ascenzi P, Nardini M, Bolognesi M, Moens L, Dewilde S. Ligation tunes protein reactivity in an ancient haemoglobin: kinetic evidence for an allosteric mechanism in Methanosarcina acetivorans protoglobin. PLoS One 2012; 7:e33614. [PMID: 22479420 PMCID: PMC3313925 DOI: 10.1371/journal.pone.0033614] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 02/13/2012] [Indexed: 11/19/2022] Open
Abstract
Protoglobin from Methanosarcina acetivorans (MaPgb) is a dimeric globin with peculiar structural properties such as a completely buried haem and two orthogonal tunnels connecting the distal cavity to the solvent. CO binding to and dissociation from MaPgb occur through a biphasic kinetics. We show that the heterogenous kinetics arises from binding to (and dissociation from) two tertiary conformations in ligation-dependent equilibrium. Ligation favours the species with high binding rate (and low dissociation rate). The equilibrium is shifted towards the species with low binding (and high dissociation) rates for the unliganded molecules. A quantitative model is proposed to describe the observed carbonylation kinetics.
Collapse
|
65
|
Finazzo C, Doorslaer SV, Schweiger A. Solvent effects of cobalt(II) phthalocyanine in sulfuric acid: a continuous wave and pulse EPR study. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424603000124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Products based on metal phthalocyanines are widely used in industry. In the processing of these materials it is essential to control the conditions of the matrix the metal phthalocyanines are embedded in. Using the example of cobalt(II) phthalocyanine in sulfuric acid we show that continuous wave and pulse electron paramagnetic resonance and electron nuclear double resonance spectroscopy provide excellent tools to monitor the influence of the matrix on paramagnetic phthalocyanines. The g values, the cobalt hyperfine values, and the hyperfine and nuclear quadrupole couplings of the isoindole nitrogens, as well as the hyperfine interactions of the surrounding protons allow for a detailed assessment of the electronic structure of cobalt(II) phthalocyanine in sulfuric acid. Subtle differences between the system under study and related Co ( II ) porphyrin and corrin systems could be traced.
Collapse
|
66
|
Nagy NV, Doorslaer SV, Szabó-Plánka T, Rompaey SV, Hamza A, Fülöp F, Tóth GK, Rockenbauer A. Copper(II)-Binding Ability of Stereoisomeric cis- and trans-2-Aminocyclohexanecarboxylic Acid–l-Phenylalanine Dipeptides. A Combined CW/Pulsed EPR and DFT Study. Inorg Chem 2012; 51:1386-99. [DOI: 10.1021/ic2016116] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
67
|
Nevil N, Ling Y, Mierloo SV, Kesters J, Piersimoni F, Adriaensens P, Lutsen L, Vanderzande D, Manca J, Maes W, Doorslaer SV, Goovaerts E. Charge transfer in the weak driving force limit in blends of MDMO-PPV and dithienylthiazolo[5,4-d]thiazoles towards organic photovoltaics with high VOC. Phys Chem Chem Phys 2012; 14:15774-84. [DOI: 10.1039/c2cp42399e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
68
|
Zamani S, Carter E, Murphy DM, Van Doorslaer S. Probing differences in binding of methylbenzylamine enantiomers to chiral cobalt(ii) salen complexes. Dalton Trans 2012; 41:6861-70. [DOI: 10.1039/c2dt30207a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
69
|
Murphy DM, Caretti I, Carter E, Fallis IA, Göbel MC, Landon J, Doorslaer SV, Willock DJ. Visualizing Diastereomeric Interactions of Chiral Amine–Chiral Copper Salen Adducts by EPR Spectroscopy and DFT. Inorg Chem 2011; 50:6944-55. [DOI: 10.1021/ic200113u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
70
|
Ding F, Doorslaer SV, Cool P, Verpoort F. Olefin isomerization reactions catalyzed by ruthenium hydrides bearing Schiff base ligands. Appl Organomet Chem 2011. [DOI: 10.1002/aoc.1808] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
71
|
Maurelli S, Vishnuvarthan M, Chiesa M, Berlier G, Van Doorslaer S. Elucidating the Nature and Reactivity of Ti Ions Incorporated in the Framework of AlPO-5 Molecular Sieves. New Evidence from 31P HYSCORE Spectroscopy. J Am Chem Soc 2011; 133:7340-3. [DOI: 10.1021/ja202210g] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
72
|
Maurelli S, Livraghi S, Chiesa M, Giamello E, Van Doorslaer S, Di Valentin C, Pacchioni G. Hydration Structure of the Ti(III) Cation as Revealed by Pulse EPR and DFT Studies: New Insights into a Textbook Case. Inorg Chem 2011; 50:2385-94. [DOI: 10.1021/ic1021802] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
|
73
|
Ling Y, Kozakiewicz P, Blockhuys F, Biesemans M, Van Alsenoy C, Moons H, Goovaerts E, Willem R, Van Doorslaer S. The solid-state organization of ‘self-doped’ PPV oligomers. Phys Chem Chem Phys 2011; 13:18516-22. [DOI: 10.1039/c1cp21786k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
74
|
Caretti I, Carter E, Fallis IA, Murphy DM, Van Doorslaer S. Interactions of an asymmetric amine with a non-C2 symmetric Cu–salen complex: An EPR/ENDOR and HYSCORE investigation. Phys Chem Chem Phys 2011; 13:20427-34. [DOI: 10.1039/c1cp22522g] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
75
|
Sala LF, González JC, García SI, Frascaroli MI, Van Doorslaer S. Detection and structural characterization of oxo-chromium(V)-sugar complexes by electron paramagnetic resonance. Adv Carbohydr Chem Biochem 2011; 66:69-120. [PMID: 22123188 DOI: 10.1016/b978-0-12-385518-3.00002-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This article describes the detection and characterization of oxo-Cr(V)-saccharide coordination compounds, produced during chromic oxidation of carbohydrates by Cr(VI) and Cr(V), using electron paramagnetic resonance (EPR) spectroscopy. After an introduction into the main importance of chromium (bio)chemistry, and more specifically the oxo-chromium(V)-sugar complexes, a general overview is given of the current state-of-the-art EPR techniques. The next step reviews which types of EPR spectroscopy are currently applied to oxo-Cr(V) complexes, and what information about these systems can be gained from such experiments. The advantages and pitfalls of the different approaches are discussed, and it is shown that the potential of high-field and pulsed EPR techniques is as yet still largely unexploited in the field of oxo-Cr(V) complexes. Subsequently, the discussion focuses on the analysis of oxo-Cr(V) complexes of different types of sugars and the implications of the results in terms of understanding chromium (bio)chemistry.
Collapse
|