16 research outputs found
Hierarchically Structured Porous Spinels via an Epoxide-Mediated SolāGel Process Accompanied by Polymerization-Induced Phase Separation
Enhancing the activity
and stability of catalysts is a major challenge
in scientific research nowadays. Previous studies showed that the
generation of an additional pore system can influence the catalytic
performance of porous catalysts regarding activity, selectivity, and
stability. This study focuses on the epoxide-mediated solāgel
synthesis of mixed metal oxides, NiAl<sub>2</sub>O<sub>4</sub> and
CoAl<sub>2</sub>O<sub>4</sub>, with a spinel phase structure, a hierarchical
pore structure, and Ni and Co contents of 3 to 33 mol % with respect
to the total metal content. The solāgel process is accompanied
by a polymerization-induced phase separation to introduce an additional
pore system. The obtained mixed metal oxides were characterized with
regard to pore morphology, surface area, and formation of the spinel
phase. The BrunauerāEmmettāTeller surface area ranges
from 74 to 138 m<sup>2</sup>Ā·g<sup>ā1</sup> and 25 to
94 m<sup>2</sup>Ā·g<sup>ā1</sup> for Ni and Co, respectively.
Diameters of the phase separation-based macropores were between 500
and 2000 nm, and the mesopore diameters were 10 nm for the Ni-based
system and between 20 and 25 nm for the cobalt spinels. Furthermore,
NiāAl spinels with 4, 5, and 6 mol % Ni were investigated in
the dry reforming of CH<sub>4</sub> (DRM) with CO<sub>2</sub> to produce
H<sub>2</sub> and CO. CH<sub>4</sub> conversions near the thermodynamic
equilibrium were observed depending on the Ni content and reaction
temperature. The Ni catalysts were further compared to a noble metal-containing
catalyst based on a spinel system showing comparable CH<sub>4</sub> conversion and carbon selectivity in the DRM
Synthesis, Crystal Structure and Catalytic Behavior of Homo- and Heteronuclear Coordination Polymers [M(tdc)(bpy)] (M<sup>2+</sup> = Fe<sup>2+</sup>, Co<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; tdc<sup>2ā</sup> = 2,5-thiophenedicarboxylate)
A series of isostructural
3D coordination polymers <sup>3</sup><sub>ā</sub>[MĀ(tdc)Ā(bpy)]
(M<sup>2+</sup> = Zn<sup>2+</sup>, Cd<sup>2+</sup>, Co<sup>2+</sup>, Fe<sup>2+</sup>; tdc<sup>2ā</sup> = 2,5-thiophenedicarboxylate;
bpy = 4,4ā²-bipyridine) was synthesized and characterized by
X-ray diffraction, thermal analysis, and gas adsorption measurements.
The materials show high thermal stability up to approximately 400
Ā°C and a solvent induced phase transition. Single crystal X-ray
structure determination was successfully performed for all compounds
after the phase transition. In the zinc-based coordination polymer,
various amounts of a second type of metal ions such as Co<sup>2+</sup> or Fe<sup>2+</sup> could be incorporated. Furthermore, the catalytic
behavior of the homo- and heteronuclear 3D coordination polymers in
an oxidation model reaction was investigated
Synthesis, Crystal Structure and Catalytic Behavior of Homo- and Heteronuclear Coordination Polymers [M(tdc)(bpy)] (M<sup>2+</sup> = Fe<sup>2+</sup>, Co<sup>2+</sup>, Zn<sup>2+</sup>, Cd<sup>2+</sup>; tdc<sup>2ā</sup> = 2,5-thiophenedicarboxylate)
A series of isostructural
3D coordination polymers <sup>3</sup><sub>ā</sub>[MĀ(tdc)Ā(bpy)]
(M<sup>2+</sup> = Zn<sup>2+</sup>, Cd<sup>2+</sup>, Co<sup>2+</sup>, Fe<sup>2+</sup>; tdc<sup>2ā</sup> = 2,5-thiophenedicarboxylate;
bpy = 4,4ā²-bipyridine) was synthesized and characterized by
X-ray diffraction, thermal analysis, and gas adsorption measurements.
The materials show high thermal stability up to approximately 400
Ā°C and a solvent induced phase transition. Single crystal X-ray
structure determination was successfully performed for all compounds
after the phase transition. In the zinc-based coordination polymer,
various amounts of a second type of metal ions such as Co<sup>2+</sup> or Fe<sup>2+</sup> could be incorporated. Furthermore, the catalytic
behavior of the homo- and heteronuclear 3D coordination polymers in
an oxidation model reaction was investigated
Antagonists for the Orphan GāProtein-Coupled Receptor GPR55 Based on a Coumarin Scaffold
The
orphan G-protein-coupled receptor GPR55, which is activated by 1-lysophosphatidylinositol
and interacts with cannabinoid (CB) receptor ligands, has been proposed
as a new potential drug target for the treatment of diabetes, Parkinsonās
disease, neuropathic pain, and cancer. We applied Ī²-arrestin
assays to identify 3-substituted coumarins as a novel class of antagonists
and performed an extensive structureāactivity relationship
study for GPR55. Selectivity versus the related receptors CB<sub>1</sub>, CB<sub>2</sub>, and GPR18 was assessed. Among the 7-unsubstituted
coumarins selective, competitive GPR55 antagonists were identified,
such as 3-(2-hydroxybenzyl)-5-isopropyl-8-methyl-2<i>H</i>-chromen-2-one (<b>12</b>, PSB-SB-489, IC<sub>50</sub> = 1.77
Ī¼M, p<i>A</i><sub>2</sub> = 0.547 Ī¼M). Derivatives
with long alkyl chains in position 7 were potent, possibly allosteric
GPR55 antagonists which showed ancillary CB receptor affinity. 7-(1,1-Dimethyloctyl)-5-hydroxy-3-(2-hydroxybenzyl)-2<i>H</i>-chromen-2-one (<b>69</b>, PSB-SB-487, IC<sub>50</sub> = 0.113 Ī¼M, <i>K</i><sub>B</sub> = 0.561 Ī¼M)
and 7-(1,1-dimethylheptyl)-5-hydroxy-3-(2-hydroxybenzyl)-2<i>H</i>-chromen-2-one (<b>67</b>, PSB-SB-1203, IC<sub>50</sub> = 0.261 Ī¼M) were the most potent GPR55 antagonists of the
present series
Association between Serum Insulin-Like Growth Factor (IGF) I and IGF Binding Protein-3 and Lung Function
Network Flexibility: Control of Gate Opening in an Isostructural Series of Ag-MOFs by Linker Substitution
An isostructural series of 15 structurally
flexible microporous
silver metalāorganic frameworks (MOFs) is presented. The compounds
with a dinuclear silver core as secondary building unit (Ag<sub>2</sub>N<sub>4</sub>) can be obtained under solvothermal conditions from
substituted triazolyl benzoate linkers and AgNO<sub>3</sub> or Ag<sub>2</sub>SO<sub>4</sub>; they exhibit 2-fold network interpenetration
with <b>lvt</b> topology. Besides the crystal structures, the
calculated pore size distributions of the microporous MOFs are reported.
Simultaneous thermal analyses confirm the stability of the compounds
up to 250 Ā°C. Interconnected pores result in a three-dimensional
pore structure. Although the porosity of the novel coordination polymers
is in the range of only 20ā36%, this series can be regarded
as a model system for investigation of network flexibility, since
the pore diameters and volumes can be gradually adjusted by the substituents
of the 3-(1,2,4-triazol-4-yl)-5-benzamidobenzoates. The pore volumes
of selected materials are experimentally determined by nitrogen adsorption
at 77 K and carbon dioxide adsorption at room temperature. On the
basis of the flexible behavior of the linkers a reversible framework
transformation of the 2-fold interpenetrated network is observed.
The resulting adsorption isotherms with one or two hysteresis loops
are interpreted by a gate-opening process. Due to external stimuli,
namely, the adsorptive pressure, the materials undergo a phase transition
confirming the structural flexibility of the porous coordination polymer
Bis(carboxyphenyl)-1,2,4-triazole Based MetalāOrganic Frameworks: Impact of Metal Ion Substitution on Adsorption Performance
This work presents
the syntheses and comprehensive characterization of six paddlewheel
based metalāorganic frameworks (MOFs) with the general formula <sub>ā</sub><sup>3</sup>[M<sub>2</sub>L<sub>2</sub>] (M = Cu, Co, Zn; L = bisĀ(carboxyphenyl)-1,2,4-triazole)
forming an isoreticular series with rutile (<b>rtl</b>) topology.
These microporous materials are suitable for a systematic investigation
of structureāproperty relationships based on the impact of
the metal ion. Depending on
the metal ion, the calculated porosities and the pore diameters reach
from 58% to 61% and 300 to 750 pm, respectively. Simultaneous thermal
analysis and temperature dependent PXRD studies reveal varying thermal
behavior with stabilities up to 400 Ā°C. In the case of syntheses
with various Co<sup>2+</sup>/Cu<sup>2+</sup>, Co<sup>2+</sup>/Zn<sup>2+</sup>, and Cu<sup>2+</sup>/Zn<sup>2+</sup> ratios, ICP-OES analyses
and SEM-EDX studies confirm the formation of mixed metal MOFs and
the metal ion distribution in the bulk samples as well as within the
crystals. For the systematic investigation of CO<sub>2</sub> (298
K) and N<sub>2</sub> (77 K) adsorption properties, all materials were
previously subjected to extraction with supercritical CO<sub>2</sub>. Depending on the metal ion, this procedure causes different phase
transitions for each compound. As a result, adsorption studies reveal
varying network flexibility for these MOFs. This study is one of the
rare examples demonstrating that targeted modification of gate opening
pressure, hysteresis shape, and adsorbed amounts of CO<sub>2</sub> or N<sub>2</sub> are possible by choice of the metal ion. This finding
is supported by adsorption studies on the mixed metal MOF <sub>ā</sub><sup>3</sup>[(Cu<sub>0.48</sub>Co<sub>0.52</sub>)<sub>2</sub>(<i>p</i>-L)<sub>2</sub>)], showing CO<sub>2</sub> adsorption/desorption characteristics
of both homonuclear copper and cobalt materials, whereas N<sub>2</sub> does not induce gate opening of the framework, as observed for the
cobalt MOF. Furthermore, catalytic studies reveal that <sub>ā</sub><sup>3</sup>[Cu<sub>2</sub>(<i>p</i>-L)<sub>2</sub>)] is a suitable catalyst
for the oxidation of cyclohexene with <i>tert</i>-butylhydroperoxide
(TBHP) with high conversion of the starting materials and good selectivity.
Its robustness under the applied catalysis conditions leads to similar
conversions in repetition measurements
Improved Isolation of Microbiologically Produced (2<i>R</i>,3<i>S</i>)āIsocitric Acid by Adsorption on Activated Carbon and Recovery with Methanol
A new,
efficient method for the isolation of (2<i>R</i>,3<i>S</i>)-isocitric acid (ICA) from its fermentation
solution was developed. It is noteworthy that this method is based
on selective adsorption directly from the fermentation solution on
activated carbon, followed by the release of both ICA and citric acid
by means of elution with methanol and their final separation by known
methods. Thereby, several disadvantages were overcome: Electrodialysis
is no longer necessary to remove cations such as Na<sup>+</sup> from
the fermentation solution. Also, several hitherto accompanying dyestuffs
were not observed with this method. Furthermore, removal of water
by distillation is expendable. Eventually, the new crude product is
of a quality that also avoids the use of a tedious slide vane rotary
vacuum pump distillation of the trimethyl esters of both acids, which
hitherto was the basis for the separation of ICA. In summary, the
new method distinctly spares energy as well as time
Co-Registered Molecular Logic Gate with a CO-Releasing Molecule Triggered by Light and Peroxide
Co-registered molecular logic gates
combine two different inputs
and outputs, such as light and matter. We introduce a biocompatible
CO-releasing molecule (CORM, <b>A</b>) as MnĀ(I) tricarbonyl
complex with the ligand 5-(dimethylamino)-<i>N</i>, <i>N</i>-bisĀ(pyridin-2-ylmethyl) naphthalene-1-sulfonamide (<b>L</b>). CO release is chaperoned by turn-on fluorescence and can
be triggered by light (405 nm) as well as with hydrogen peroxide in
aqueous phosphate buffer. Complex <b>A</b> behaves as a logic
āORā gate via co-registering the inputs of irradiation
(light) and peroxide (matter) into the concomitant outputs fluorescence
(light) and CO (matter). Cell viability assays confirm the low toxicity
of <b>A</b> toward different human cell lines. The CORM has
been used to track the inclusion of <b>A</b> into cancer cells
Platinum Group Metal Phosphides as Heterogeneous Catalysts for the Gas-Phase Hydroformylation of Small Olefins
A method
for the synthesis of highly crystalline Rh<sub>2</sub>P nanoparticles
on SiO<sub>2</sub> support materials and their use
as truly heterogeneous single-site catalysts for the hydroformylation
of ethylene and propylene is presented. The supported Rh<sub>2</sub>P nanoparticles were investigated by transmission electron microscopy
and by infrared analysis of adsorbed CO. The influence of feed gas
composition and reaction temperature on the activity and selectivity
in the hydroformylation reaction was evaluated by using high throughput
experimentation as an enabling element; core findings were that beneficial
effects on the selectivity were observed at high CO partial pressures
and after addition of water to the feed gas. The analytical and performance
data of the materials gave evidence that high temperature reduction
leading to highly crystalline Rh<sub>2</sub>P nanoparticles is key
to achieving active, selective, and long-term stable catalysts