TY - JOUR
A1 - Schenk, Jonas
A1 - Batzdorf, Lisa
A1 - Emmerling, Franziska
A1 - Kneipp, Janina
A1 - Panne, Ulrich
A1 - Buurman, Merwe
T1 - Simultaneous UV/Vis spectroscopy and surface enhanced raman scattering of nanoparticle formation and aggregation in levitated droplets
N2 - The formation and growth of hydroxylamine reduced silver nanoparticles were investigated by simultaneous Raman and UV/Vis spectroscopy coupled to an acoustic levitator as a sample holder. Based on the UV/Vis spectra, a two step particle formation mechanism with fast initial formation and adjacent coalescence can be proposed for the reduction of silver nitrate with hydroxylamine. The presence of the analyte adenine during particle formation resulted in differences in the adenine SERS signature compared to experiments, where adenine was added after particle synthesis. It was possible to monitor the adenine and sodium chloride induced aggregation of the nanoparticles and its dynamics based on both the extinction spectra and the SERS data. Correlating the information from the extinction spectra with the SERS intensity, the maximum SERS signals were observed at maximum extinction of the aggregated nanoparticle solution at the Raman excitation wavelength.
PY - 2012
DO - https://doi.org/10.1039/c2ay05744a
SN - 1759-9660
SN - 1759-9679
N1 - Geburtsname von Batzdorf, Lisa: Tröbs, L. - Birth name of Batzdorf, Lisa: Tröbs, L.
N1 - Geburtsname von Buurman, Merwe: Albrecht, M. - Birth name of Buurman, Merwe: Albrecht, M.
VL - 4
IS - 5
SP - 1252
EP - 1258
PB - RSC Publ.
CY - Cambridge
AN - OPUS4-25742
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Scheurrell, Kerstin
A1 - B. Martins, Inês C.
A1 - Murray, Claire
A1 - Emmerling, Franziska
T1 - Exploring the role of solvent polarity in mechanochemical Knoevenagel condensation: in situ investigation and isolation of reaction intermediates
N2 - Mechanochemistry has proven to be a highly effective method for the synthesis of organic compounds. We studied the kinetics of the catalyst-free Knoevenagel reaction between 4-nitrobenzaldehyde and malononitrile, activated and driven by ball milling. The reaction was investigated in the absence of solvents (neat grinding) and in the presence of solvents with different polarities (liquid-assisted grinding). The reaction was monitored using time-resolved in situ Raman spectroscopy and powder X-ray diffraction (PXRD). Our results indicate a direct relationship between solvent polarity and reaction kinetics, with higher solvent polarity leading to faster product (2-(4-nitrobenzylidone)malononitrile) formation. For the first time, we were able to isolate and determine the structure of an intermediate 2-(hydroxy(4-nitrophenyl)methyl)malononitrile based on PXRD data.
KW - Physical and Theoretical Chemistry
KW - General Physics and Astronomy
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-588071
DO - https://doi.org/10.1039/D3CP02883F
SN - 1463-9076
VL - 25
IS - 35
SP - 23637
EP - 23644
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-58807
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schiffmann, J.
A1 - Emmerling, Franziska
A1 - Martins, Ines
A1 - Van Wüllen, L.
T1 - In-situ reaction monitoring of a mechanochemical ball mill reaction with solid state NMR
N2 - We present an approach towards the in situ solid state NMR monitoring of mechanochemical reactions in a ball mill. A miniaturized vibration ball mill is integrated into the measuring coil of a home-built solid state NMR probe, allowing for static solid state NMR measurements during the mechanochemical reaction within the vessel. The setup allows to quantitatively follow the product evolution of a prototypical mechanochemical reaction, the formation of zinc phenylphosphonate from zinc acetate and phenylphosphonic acid. MAS NMR investigations on the final reaction mixture confirmed a reaction yield of 89% in a typical example. Thus, NMR spectroscopy may in the future provide complementary information about reaction mechanisms of mechanochemical reactions and team up with other analytical methods which have been employed to follow reactions in situ, such as Raman spectroscopy or X-ray diffraction.
KW - Mechanochemistry
KW - Solid state NMR
KW - NMR probe Development
PY - 2020
DO - https://doi.org/10.1016/j.ssnmr.2020.101687
VL - 109
SP - 101687
PB - Elsevier Inc.
AN - OPUS4-51283
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, M.C.
A1 - Stroh, Julia
A1 - Malaga, K.
A1 - Meng, Birgit
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - Pathway of a damaging mechanism - Analyzing chloride attack by synchrotron based X-ray diffraction
N2 - Typically, the changes of the phase compositions due to the chemical attack are studied in-situ only by chemical analysis or microscopy. In this study, the chloride transport and binding in the cement matrix in different cementitious materials was analyzed by synchrotron based X-ray diffraction (SyXRD) and energy dispersive X-ray spectroscopy (EDX). Sample materials consisting of cement paste were embedded in high concentrated sodium chloride solution over different time spans. Afterwards, the phase and chemical compositions were determined. The high spatial resolution and the information about the chloride distribution offer a detailed view of chloride binding in the cement matrix and allow the conclusions about the degradation mechanisms. The results are discussed related to the influence of different supplementary cementitious materials on the damaging mechanism.
KW - Portland cement
KW - In-situ
KW - X-Ray diffraction
KW - EDX
KW - Durability
KW - Chloride attack
PY - 2015
DO - https://doi.org/10.1016/j.solidstatesciences.2015.03.021
SN - 1293-2558
SN - 1873-3085
VL - 44
SP - 45
EP - 54
PB - Elsevier Masson SAS
CY - Amsterdam
AN - OPUS4-33171
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, Moritz-Caspar
A1 - Müller, Urs
A1 - Malaga, Katarina
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - Spatially resolved investigation of complex multi-phase systems using muXRF, SEM-EDX and high resolution SyXRD
N2 - Spatially resolved analysis of complex multi-phase systems can be validated through different analytical methods. This study compares investigations by scanning electron microscopy coupled with energy dispersive X-ray fluorescence analysis and high resolution X-ray diffraction. The studied sulfate attacked cement paste containing fly ashes consists of different interacting crystalline and amorphous phases. The complementary methods revealed in detail changes in phase composition due to the chemical attack. The advantages and disadvantages of both methods are discussed and suggestions are given for combining them with additional methods to maximize the information content.
KW - EDX-SEM
KW - SyXRD
KW - Spatial investigations
KW - Comparison
KW - High resolution
KW - Cement paste
KW - Sulfate attack
KW - Damaging mechanism
PY - 2013
DO - https://doi.org/10.1016/j.cemconcomp.2012.08.018
SN - 0958-9465
SN - 1873-393X
VL - 37
SP - 241
EP - 245
PB - Elsevier Ltd.
CY - Barking, Essex
AN - OPUS4-29111
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, Moritz-Caspar
A1 - Müller, Urs
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - Deciphering the sulfate attack of cementitious materials by high-resolution micro-x-ray diffraction
N2 - The durability of cementitious materials depends, among others, on their resistance against chemical attack during the service life of a building. Here, we present an approach to analyze changes in the phase composition due to chemical attack in the form of sulfate ingress within the microstructure. Micro-X-ray (µX-ray) diffraction using synchrotron radiation in Debye–Scherrer (transmission) geometry allowed a spatial resolution of 10 µm. Phase transformations in the wake of damaging processes were observed in a detailed high-resolution imaging study. In comparison, samples containing supplementary cementitious materials were investigated and used to reconstruct the influence of different degeneration processes in detail. Additionally, reaction fronts within the bulk were localized by micro-X-ray fluorescence analysis. The experimental setup provided the possibility for analyzing the phase assemblage of a given sample without destroying the microstructure. The specimens for phase analysis are thick sections of the primary material and can be used for further microscopic analysis of the microstructure and microchemistry, e.g., scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM–EDX) or Raman spectroscopy.
PY - 2011
DO - https://doi.org/10.1021/ac200181g
SN - 0003-2700
SN - 1520-6882
VL - 83
IS - 10
SP - 3744
EP - 3749
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-23669
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, Moritz-Caspar
A1 - Sarfraz, Adnan
A1 - Müller, Urs
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - First seconds in a building's life - In situ synchrotron X-ray diffraction study of cement hydration on the millisecond timescale
N2 - Setting cement: Highly dynamic hydration processes that occur during the first seconds of cement hydration were studied by time-resolved synchrotron X-ray diffraction. Polycarboxylate ether additives were found to influence the formation of the initial crystalline hydration products on a molecular level.
KW - Cement hydration
KW - Colloidal suspensions
KW - In situ analysis
KW - X-ray diffraction
KW - SyXRD
KW - High resolution
KW - In-situ
PY - 2012
DO - https://doi.org/10.1002/anie.201200993
SN - 1433-7851
SN - 1521-3773
SN - 0570-0833
VL - 51
IS - 20
SP - 4993
EP - 4996
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-26287
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, Moritz-Caspar
A1 - Sarfraz, Adnan
A1 - Müller, Urs
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - Erste Sekunden im Leben eines Bauwerks - In-situ-Synchrotron-Röntgenbeugungsuntersuchungen der Zementhydratation mit Millisekunden-Auflösung
N2 - Höchst dynamische Hydratationsprozesse in den ersten Sekunden bei der Entstehung eines Bauwerkes lassen sich mithilfe von Synchrotron-Röntgenbeugung mit einer sehr hohen Zeitauflösung nachverfolgen. Der Schwerpunkt lag dabei auf der Beeinflussung der Bildung erster kristalliner Hydratationsprodukte während des Frühstadiums der Zementhydratation.
KW - SyXRD
KW - High resolution
KW - In-situ
KW - Colloidal suspension
KW - Cement hydration
KW - In-situ-Analyse
KW - Kolloidale Suspensionen
KW - Röntgenbeugung
KW - Zementhydratation
PY - 2012
DO - https://doi.org/10.1002/ange.201200993
SN - 0044-8249
SN - 0932-2140
SN - 1521-3757
VL - 124
IS - 20
SP - 5078
EP - 5081
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-26284
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlegel, Moritz-Caspar
A1 - Wenzel, Klaus-Jürgen
A1 - Sarfraz, Adnan
A1 - Panne, Ulrich
A1 - Emmerling, Franziska
T1 - A wall-free climate unit for acoustic levitators
N2 - Acoustic levitation represents the physical background of trapping a sample in a standing acoustic wave with no contact to the wave generating device. For the last three decades, sample holders based on this effect have been commonly used for contact free handling of samples coupled with a number of analytical techniques. In this study, a wall-free climate unit is presented, which allows the control of the environmental conditions of suspended samples. The insulation is based on a continuous cold/hot gas flow around the sample and thus does not require any additional isolation material. This provides a direct access to the levitated sample and circumvents any influence of the climate unit material to the running analyses.
KW - Acoustic levition
PY - 2012
DO - https://doi.org/10.1063/1.4705968
SN - 0034-6748
SN - 1089-7623
VL - 83
IS - 5
SP - 055101-1 - 055101-3
PB - American Institute of Physics
CY - Melville, NY
AN - OPUS4-25881
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlögl, Johanna
A1 - Goldammer, Ole
A1 - Bader, Julia
A1 - Emmerling, Franziska
A1 - Riedel, Sebastian
T1 - Introducing AFS ([Al(SO3F)3]x) – a thermally stable, readily available, and catalytically active solid Lewis superacid
N2 - This paper introduces the thermally stable, solid Lewis superacid aluminium tris(fluorosulfate) (AFS), that is easy-to-synthesize from commercially available starting materials. Its applicability, e.g. in catalytic C–F bond activations, is shown.
KW - Lewis Acid
KW - C-F activation
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-601001
DO - https://doi.org/10.1039/D4SC01753F
SN - 2041-6520
SP - 1
EP - 7
PB - Royal Society of Chemistry (RSC)
AN - OPUS4-60100
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Scholz, G.
A1 - Emmerling, Franziska
A1 - Dreger, M.
A1 - Kemnitz, E.
T1 - Mechanochemical synthesis and characterization of hydrated and dehydrated crystalline strontium terephtalates
N2 - A successful mechanochemical synthesis of strontium terephthalate trihydrate is described for the first time. The dehydration of Sr(C8H4O4)·3H2O occurs at about 100 °C and results in a well-defined strontium terephtalate, Sr(C8H4O4), thermally stable up to 550 °C. Both compounds are not described so far in the literature. Their structures were solved by ab initio structure determination and subsequent Rietveld refinement of the powder diffraction data. Further methods like DTA-TG, MAS NMR and FT-IR spectroscopy, and BET measurements were used to characterize these compounds.
KW - Mechanochemical synthesis
KW - Ab initio structure determination
KW - MAS NMR spectroscopy
KW - Strontium
PY - 2013
DO - https://doi.org/10.1002/zaac.201200550
SN - 0044-2313
SN - 1521-3749
SN - 0372-7874
SN - 0863-1786
SN - 0863-1778
VL - 639
IS - 5
SP - 689
EP - 693
PB - Wiley-VCH
CY - Weinheim
AN - OPUS4-29117
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schulz, K.
A1 - Schmack, R.
A1 - Klemm, H. W.
A1 - Kabelitz, Anke
A1 - Schmidt, T.
A1 - Emmerling, Franziska
A1 - Kraehnert, R.
T1 - Mechanism and kinetics of hematite crystallization in air: Linking bulk and surface models via mesoporous films with defined nanostructure
N2 - Iron can form numerous oxides, hydroxides, and oxide−hydroxides. Despite their relevance, many of the transformation processes between these phases are still poorly understood. In particular the crystallization of quasi-amorphous hydroxides and oxide−hydroxides is difficult to assess, since typical diffraction and scattering methods provide only sampleaveraged information about the crystallized phases. We report a new approach for the investigation of the crystallization of oxide−hydroxides. The approach relies on model-type films that comprise a defined homogeneous nanostructure. The nanostructure allows quantitative linking of Information obtained by bulk-averaging diffraction techniques (XRD, SAXS) with locally resolved information, i.e., Domain sizes (SEM, TEM, LEEM) and phase composition (SAED). Using time-resolved imaging and diffraction we deduce mechanism and kinetics for the crystallization of ferrihydrite into hematite. Hematite forms via nucleation of hematite domains and subsequent Domain growth that terminates only upon complete transformation. A Johnson−Mehl−Avrami−Kolmogorov model describes the kinetics over a wide temperature range. The derived understanding enables the first synthesis of ferrihydrite films with ordered mesoporosity and quantitative control over the films’ hematite and ferrihydrite content.
KW - Iron oxide
KW - Crystallization
KW - Mesoporous films
KW - Nanostructure
PY - 2017
DO - https://doi.org/10.1021/acs.chemmater.6b05185
SN - 0897-4756
SN - 1520-5002
VL - 29
IS - 4
SP - 1724
EP - 1734
AN - OPUS4-39690
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Seidel, R.
A1 - Kraffert, K.
A1 - Kabelitz, Anke
A1 - Pohl, M.N.
A1 - Kraehnert, R.
A1 - Emmerling, Franziska
A1 - Winter, B.
T1 - Detection of the electronic structure of iron-(III)-oxo oligomers forming in aqueous solutions
N2 - The nature of the small iron-oxo oligomers in iron-(III) aqueous solutions has a determining effect on the chemical processes that govern the formation of nanoparticles in aqueous phase. Here we report on a liquid-Jet photoelectron-spectroscopy experiment for the investigation of the electronic structure of the occurring iron-oxo oligomers in FeCl3 aqueous solutions. The only iron species in the as-prepared 0.75 M solution are Fe3+ monomers. Addition of NaOH initiates Fe3+ hydrolysis which is followed by the formation of iron-oxo oligomers. At small enough NaOH concentrations, corresponding to approximately [OH]/[Fe] = 0.2–0.25 ratio, the iron oligomers can be stabilized for several hours without engaging in further aggregation. Here, we apply a combination of non-resonant as well as iron 2p and Oxygen 1s resonant photoelectron spectroscopy from a liquid microjet to detect the electronic structure of the occurring species. Specifically, the oxygen 1s partial electron yield X-ray absorption (PEY-XA) spectra are found to exhibit a peak well below the onset of liquid water and OH (aq) absorption. The iron 2p absorption gives rise to signal centered between the main absorption bands typical for aqueous Fe3+. Absorption bands in both PEY-XA spectra are found to correlate with an enhanced photoelectron Peak near 20 eV binding energy, which demonstrates the sensitivity of resonant photoelectron (RPE) spectroscopy to mixing between iron and ligand orbitals. These various signals from the iron-oxo oligomers exhibit Maximum intensity at [OH]/[Fe] = 0.25 ratio. For the same ratio, we observe changes in the pH as well as in complementary Raman spectra, which can be assigned to the Transition from monomeric to oligomeric species. At approximately [OH]/[Fe] = 0.3 we begin to observe particles larger than 1 nm in radius, detected by small-angle X-ray scattering.
KW - Iron-oxo oligomers
KW - XPS
KW - Electronic structure
PY - 2017
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-433468
DO - https://doi.org/10.1039/c7cp06945f
SN - 1463-9076
SN - 1463-9084
VL - 19
IS - 48
SP - 32226
EP - 32234
AN - OPUS4-43346
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Siegel, David
A1 - Blaske, Franziska
A1 - Koch, Matthias
A1 - Emmerling, Franziska
A1 - Nehls, Irene
T1 - Deacetyl tenuazonic acid p-toluenesulfonylhydrazone
KW - Deacetyl tenuazonic acid
KW - Toluenesulfonylhydrazine
KW - Hydrazone
KW - Crystal structure
PY - 2009
DO - https://doi.org/10.1107/S1600536809048958
SN - 1600-5368
VL - E65
IS - 12
SP - o3136 Sup-1 - o3136 Sup-8
PB - Munksgaard
CY - Copenhagen
AN - OPUS4-20608
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Siegel, David
A1 - Koch, Matthias
A1 - Emmerling, Franziska
A1 - Nehls, Irene
T1 - Deacetyl tenuazonic acid
KW - Deacetyl tenuazonic acid
KW - X-ray single crystal diffraction
KW - Crystal structure
PY - 2009
DO - https://doi.org/10.1107/S1600536809015372
SN - 1600-5368
VL - 65
IS - 6
SP - o1201
PB - Munksgaard
CY - Copenhagen
AN - OPUS4-19429
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Siegel, David
A1 - Merkel, Stefan
A1 - Koch, Matthias
A1 - Emmerling, Franziska
A1 - Nehls, Irene
T1 - 3-{1-[(2,4-Dinitrophenyl)hydrazino]ethylidene}-5-(1-methylpropyl)pyrrolidine-2,4-dione
KW - Tenuazonic acid 2,4-dinitrophenylhydrazone
KW - X-ray single crystal diffraction
KW - Crystal structure
PY - 2009
DO - https://doi.org/10.1107/S1600536809012458
SN - 1600-5368
VL - 65
IS - 5
SP - o988
EP - o989
PB - Munksgaard
CY - Copenhagen
AN - OPUS4-19736
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Siegel, David
A1 - Troyanov, S.
A1 - Noack, J.
A1 - Emmerling, Franziska
A1 - Nehls, Irene
T1 - Alternariol
N2 - In the title compound (systematic name: 3,7,9-trihydroxy-1-methyl-6H-benzo[c]chromen-6-one), C14H10O5, the methyl group is shifted out of the molecular plane due to a steric collision, thus causing a slight twist of the benzene rings. The molecular structure is stabilized by an intramolecular O-H...O hydrogen bond, generating an S(6) ring. In the crystal, molecules are connected by intermolecular O-H...O hydrogen bonds into a three-dimensional network.
KW - Alternariol
KW - Kristallstruktur
PY - 2010
DO - https://doi.org/10.1107/S1600536810017502
SN - 1600-5368
VL - 66
IS - 6
SP - o1366
PB - Munksgaard
CY - Copenhagen
AN - OPUS4-21400
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Simo, A.
A1 - Polte, Jörg
A1 - Pfänder, N.
A1 - Vainio, U.
A1 - Emmerling, Franziska
A1 - Rademann, K.
T1 - Formation mechanism of silver nanoparticles stabilized in glassy matrices
N2 - In any given matrix control over the final particle size distribution requires a constitutive understanding of the mechanisms and kinetics of the particle evolution. In this contribution we report on the formation mechanism of silver nanoparticles embedded in a soda-lime silicate glass matrix. For the silver ion-exchanged glass it is shown that at temperatures below 410 °C only molecular clusters (diameter <1 nm) are forming which are most likely silver dimers. These clusters grow to nanoparticles (diameter >1 nm) by annealing above this threshold temperature of 410 °C. It is evidenced that the growth and thus the final silver nanoparticle size are determined by matrix-assisted reduction mechanisms. As a consequence, particle growth proceeds after the initial formation of stable clusters by addition of silver monomers which diffuse from the glass matrix. This is in contrast to the widely accepted concept of particle growth in metal–glass systems, in which it is assumed that the nanoparticle formation is predominantly governed by Ostwald ripening processes.
PY - 2012
DO - https://doi.org/10.1021/ja309034n
SN - 0002-7863
SN - 1520-5126
VL - 134
IS - 45
SP - 18824
EP - 18833
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-27539
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Simoes, R.
A1 - Bernades, C.
A1 - Joseph, A.
A1 - Piedade, F.
A1 - Kraus, Werner
A1 - Emmerling, Franziska
A1 - Diogo, H.
A1 - da Piedade, M.
T1 - Polymorphism in simvastatin: Twinning, disorder, and enantiotropic phase transitions
N2 - : Simvastatin is one of the most widely used active pharmaceutical ingredients for the treatment of hyperlipidemias. Because the compound is employed as a solid in drug formulations, particular attention should be given to the characterization of different polymorphs, their stability domains, and the nature of the phase transitions that relate them. In this work, the phase transitions delimiting the stability domains of three previously reported simvastatin forms were investigated from structural, energetics, and dynamical points of view based on single crystal X-ray diffraction (SCXRD), hot stage microscopy (HSM), and differential scanning calorimetry (DSC) experiments (conventional scans and heat capacity measurements), complemented with molecular dynamics (MD) simulations. Previous assignments of the crystal forms were confirmed by SCXRD: forms I and II were found to be orthorhombic (P212121, Z′/Z = 1/4) and form III was monoclinic (P21, Z′/Z = 2/4). The obtained results further indicated that (i) the transitions between different forms are observed at 235.9 ± 0.1 K (form III → form II) and at 275.2 ± 0.2 K (form II → form I) in DSC runs carried out at 10 K min−1 and close to these values when other types of techniques are used (e.g., HSM). (ii) They are enantiotropic (i.e., there is a transition temperature relating the two phases before fusion at which the stability order is reversed), fast, reversible, with very little hysteresis between heating and cooling modes, and occur under single crystal to single crystal conditions. (iii) A nucleation and growth mechanism seems to be followed since HSM experiments on single crystals evidenced the propagation of an interface, accompanied by a change of birefringence and crystal contraction or expansion (more subtle in the case of form III → form II), when the phase transitions are triggered. (iv) Consistent with the reversible and small hysteresis nature of the phase transitions, the SCXRD results indicated that the molecular packing is very similar in all forms and the main structural differences are associated with conformational changes of the “ester tail”. (v) The MD simulations further suggested that the tail is essentially “frozen” in two conformations below the III → II transition temperature, becomes progressively less hindered throughout the stability domain of form II, and acquires a large conformational freedom above the II → I transition. Finally, the fact that these transitions were found to be fast and reversible suggests that polymorphism is unlikely to be a problem for pharmaceutical formulations employing crystalline simvastatin because, if present, the III and II forms will readily convert to form I at ambient temperature.
KW - Polymorphism
KW - Twinning
KW - Disorder
KW - Simvastatine
PY - 2018
DO - https://doi.org/10.1021/acs.molpharmaceut.8b00818
SN - 1543-8384
SN - 1543-8392
VL - 15
IS - 11
SP - 5349
EP - 5360
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-46927
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Simões, R. G.
A1 - Melo, P. L. T.
A1 - Bernardes, C. E. S.
A1 - Heilmann, Maria
A1 - Emmerling, Franziska
A1 - Minas da Piedade, M. E.
T1 - Linking Aggregation in Solution, Solvation, and Solubility of Simvastatin: An Experimental and MD Simulation Study
N2 - The solubility is generally thought to be higher if the solvent effectively solvates solute molecules that are well-separated from each other. The present work suggests, however, that the formation of large solute aggregates does not necessarily imply less effective solvation and lower solubility. Measurements of the solubility of simvastatin (one of the most commonly prescribed antihyperlipidemic drugs) in three solvents with different polarities and protic characters, led to the solubility order acetone > ethyl acetate > ethanol, in the full temperature range covered by the experiments (283–308 K). An analysis of the structures of the different solutions on the basis of molecular dynamics simulation results indicated that this trend seems to be determined by a balance between the solute tendency toward aggregation and the ability of the solvent to efficiently solvate it, by integrating the cluster structures, regardless of their size, and effectively establishing solvent–solute interactions.
KW - Simvastatin
KW - Solubility
KW - API
KW - Aggregation
PY - 2021
DO - https://doi.org/10.1021/acs.cgd.0c01325
VL - 21
IS - 1
SP - 544
EP - 551
AN - OPUS4-52185
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -