33 research outputs found
Exploring cosmic origins with CORE: Cosmological parameters
We forecast the main cosmological parameter constraints achievable with the
CORE space mission which is dedicated to mapping the polarisation of the Cosmic Microwave
Background (CMB). CORE was recently submitted in response to ESA’s fifth call for mediumsized mission proposals (M5). Here we report the results from our pre-submission study of the
impact of various instrumental options, in particular the telescope size and sensitivity level,
and review the great, transformative potential of the mission as proposed. Specifically, we
assess the impact on a broad range of fundamental parameters of our Universe as a function
of the expected CMB characteristics, with other papers in the series focusing on controlling
astrophysical and instrumental residual systematics. In this paper, we assume that only a
few central CORE frequency channels are usable for our purpose, all others being devoted
to the cleaning of astrophysical contaminants. On the theoretical side, we assume ΛCDM as
our general framework and quantify the improvement provided by CORE over the current
constraints from the Planck 2015 release. We also study the joint sensitivity of CORE and
of future Baryon Acoustic Oscillation and Large Scale Structure experiments like DESI and
Euclid. Specific constraints on the physics of inflation are presented in another paper of the
series. In addition to the six parameters of the base ΛCDM, which describe the matter content
of a spatially flat universe with adiabatic and scalar primordial fluctuations from inflation, we
derive the precision achievable on parameters like those describing curvature, neutrino physics,
extra light relics, primordial helium abundance, dark matter annihilation, recombination
physics, variation of fundamental constants, dark energy, modified gravity, reionization and
cosmic birefringence. In addition to assessing the improvement on the precision of individual
parameters, we also forecast the post-CORE overall reduction of the allowed parameter space
with figures of merit for various models increasing by as much as ∼ 107 as compared to Planck
2015, and 105 with respect to Planck 2015 + future BAO measurements
Microwave-Assisted Solvothermal Synthesis and Optical Properties of Tagged MIL-140A Metal–Organic Frameworks
A series
of tagged MIL-140A-R frameworks have been synthesized using a microwave-assisted
solvothermal method. Compared with their UiO-66-R polymorphs, the
absorption energies in the MIL-140A-R series (R = NH<sub>2</sub>,
NO<sub>2</sub>, Br, Cl, and F) are extended toward the visible region
because of the spatial arrangement of the linkers
In Situ Spectroelectrochemical Investigations of the Redox-Active Tris[4-(pyridin-4-yl)phenyl]amine Ligand and a Zn<sup>2+</sup> Coordination Framework
An investigation
of the redox-active trisÂ[4-(pyridin-4-yl)Âphenyl]Âamine (NPy<sub>3</sub>) ligand in the solution state and upon its incorporation into the
solid-state metal–organic framework (MOF) [ZnÂ(NPy<sub>3</sub>)Â(NO<sub>2</sub>)<sub>2</sub>·<i>x</i>MeOH·<i>x</i>DMF]<sub><i>n</i></sub> (MeOH = methanol and
DMF = <i>N</i>,<i>N</i>-dimethylformamide) was
conducted using in situ UV/vis/near-IR, electron paramagentic resonance
(EPR), and fluorescence spectroelectrochemical experiments. Through
this multifaceted approach, the properties of the ligand and framework
were elucidated and quantified as a function of the redox state of
the triarylamine core, which can undergo a one-electron oxidation
to its radical cation. The use of pulsed EPR experiments revealed
that the radical generated was highly delocalized throughout the entire
ligand backbone. This combination of techniques provides comprehensive
insight into electronic delocalization in a framework system and demonstrates
the utility of in situ spectroelectrochemical methods in assessing
electroactive MOFs
In Situ Spectroelectrochemical Investigations of the Redox-Active Tris[4-(pyridin-4-yl)phenyl]amine Ligand and a Zn<sup>2+</sup> Coordination Framework
An investigation
of the redox-active trisÂ[4-(pyridin-4-yl)Âphenyl]Âamine (NPy<sub>3</sub>) ligand in the solution state and upon its incorporation into the
solid-state metal–organic framework (MOF) [ZnÂ(NPy<sub>3</sub>)Â(NO<sub>2</sub>)<sub>2</sub>·<i>x</i>MeOH·<i>x</i>DMF]<sub><i>n</i></sub> (MeOH = methanol and
DMF = <i>N</i>,<i>N</i>-dimethylformamide) was
conducted using in situ UV/vis/near-IR, electron paramagentic resonance
(EPR), and fluorescence spectroelectrochemical experiments. Through
this multifaceted approach, the properties of the ligand and framework
were elucidated and quantified as a function of the redox state of
the triarylamine core, which can undergo a one-electron oxidation
to its radical cation. The use of pulsed EPR experiments revealed
that the radical generated was highly delocalized throughout the entire
ligand backbone. This combination of techniques provides comprehensive
insight into electronic delocalization in a framework system and demonstrates
the utility of in situ spectroelectrochemical methods in assessing
electroactive MOFs
In Situ Spectroelectrochemical Investigations of the Redox-Active Tris[4-(pyridin-4-yl)phenyl]amine Ligand and a Zn<sup>2+</sup> Coordination Framework
An investigation
of the redox-active trisÂ[4-(pyridin-4-yl)Âphenyl]Âamine (NPy<sub>3</sub>) ligand in the solution state and upon its incorporation into the
solid-state metal–organic framework (MOF) [ZnÂ(NPy<sub>3</sub>)Â(NO<sub>2</sub>)<sub>2</sub>·<i>x</i>MeOH·<i>x</i>DMF]<sub><i>n</i></sub> (MeOH = methanol and
DMF = <i>N</i>,<i>N</i>-dimethylformamide) was
conducted using in situ UV/vis/near-IR, electron paramagentic resonance
(EPR), and fluorescence spectroelectrochemical experiments. Through
this multifaceted approach, the properties of the ligand and framework
were elucidated and quantified as a function of the redox state of
the triarylamine core, which can undergo a one-electron oxidation
to its radical cation. The use of pulsed EPR experiments revealed
that the radical generated was highly delocalized throughout the entire
ligand backbone. This combination of techniques provides comprehensive
insight into electronic delocalization in a framework system and demonstrates
the utility of in situ spectroelectrochemical methods in assessing
electroactive MOFs
Thermal spin crossover behaviour of two-dimensional Hofmann-type coordination polymers incorporating photoactive ligands
Two spin crossover (SCO)-active 2D Hofmann-type framework materials, [Fe(3-PAP)2Pd(CN)4] (A) and [Fe(4-PAP)2Pd(CN)4] (B) containing the photoactive azo-benzene-type ligands 3-phenylazo-pyridine (3-PAP) and 4-phenylazo-pyridine (4-PAP) were prepared. These materials form non-porous Hofmann-type structures whereby 2D [FeIIPd(CN)4] grids are separated by 3- or 4-PAP ligands. The iron(ii) sites of both materials (A and B) undergo abrupt and hysteretic spin transitions with characteristic transition temperatures T1/2↓,↑: 178, 190 K (ΔT: 12 K) and T1/2↓,↑: 233, 250 K (ΔT: 17 K), respectively. Photo-magnetic characterisations reveal light-induced excited spin state trapping (LIESST) activity in both A and B with characteristic T(LIESST) values of 45 and 40 K. Although both free ligands show trans- to-cis isomerisation in solution under UV-irradiation, as evidenced via absorption spectroscopy, such photo-activity was not observed in the ligands or complexes A and B in the solid state. Structural analysis of a further non-SCO active isomer to B, [Fe(4-PAP)2Pd(CN)4]·1/2(4-PAP) (B·(4-PAP)), which contains free ligand in the pore space is reported
Untangling Complex Redox Chemistry in Zeolitic Imidazolate Frameworks Using Fourier Transformed Alternating Current Voltammetry
Two zeolitic imidazolate
frameworks, ZIF-67 and ZIF-8, were interrogated
for their redox properties using Fourier transformed alternating current
voltammetry, which revealed that the 2-methylimidazolate ligand is
responsible for multiple redox transformations. Further insight was
gained by employing discrete tetrahedral complexes, [MÂ(DMIM)<sub>4</sub>]<sup>2+</sup> (DMIM = 1,2-dimethylimidazole, M = Co<sup>II</sup> or Zn<sup>II</sup>) which have similar structural motifs to ZIFs.
In this work we demonstrate a multidirectional approach that enables
the complex electrochemical behavior of ZIFs to be unraveled
Dinuclear Ruthenium Complex Based on a π-Extended Bridging Ligand with Redox-Active Tetrathiafulvalene and 1,10-Phenanthroline Units
The synthesis of
a π-extended bridging ligand with both redox-active tetrathiafulvalene
(TTF) and 1,10-phenanthroline (phen) units, namely, bisÂ(1,10-phenanthroÂ[5,6-<i>b</i>])Âtetrathiafulvalene (BPTTF), was realized via a self-coupling
reaction. Using this ligand and RuÂ(tbbpy)<sub>2</sub>Cl<sub>2</sub> (tbbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine),
the dinuclear rutheniumÂ(II) compound [{RuÂ(tbbpy)<sub>2</sub>}<sub>2</sub>(BPTTF)]Â(PF<sub>6</sub>)<sub>4</sub> (<b>1</b>) has
been obtained by microwave-assisted synthesis. Structural characterization
of <b>1</b> revealed a crossed arrangement of the TTF moieties
on adjacent dimers within the crystal structure. The optical and redox
properties of <b>1</b> were investigated using electrochemical,
spectroelectrochemical, electron paramagnetic resonance (EPR), and
absorption spectroscopic studies combined with theoretical calculations.
One exhibits a rich electrochemical behavior owing to the multiple
redox-active centers. Interestingly, both the ligand BPTTF and the
ruthenium compound <b>1</b> are EPR-active in the solid state
owing to intramolecular charge-transfer processes. The results demonstrate
that the TTF-annulated bisÂ(phen) ligand is a promising bridging ligand
to construct oligomeric or polymeric metal complexes with multiple
redox-active centers
[V<sub>16</sub>O<sub>38</sub>(CN)]<sup>9–</sup>: a soluble mixed-valence redox-active building block with strong antiferromagnetic coupling
A new discrete [V16O38(CN)]9- cluster, which displays the hitherto unknown 8- charge on the duster shell and is the first to encapsulate the cyanide anion, has been synthesized and characterized by IR and UV/vis/near-IR spectroscopy, electrochemistry, and magnetic susceptibility measurements. Bond valence sum calculations conducted on the basis of the crystal structure analysis of K9[V16O38(CN)]·13H2O confirm that this new member of the polyoxovanadate series is a mixed-valence complex. The intervalence charge transfer bands arising from intrametal interactions reveal that a localized (class II) assignment is appropriate for the duster; however, a small degree of electronic delocalization is present. Interesting possibilities exist for the incorporation of this unit into higher dimensionality framework structures, where the redox, optical, and magnetic properties can be exploited and tuned
Electronic, Optical, and Computational Studies of a Redox-Active Napthalenediimide-Based Coordination Polymer
The new one-dimensional coordination
framework (ZnÂ(DMF)ÂNO<sub>3</sub>)<sub>2</sub>(NDC)Â(DPMNI), where NDC
= 2,6-naphthalenedicarboxylate
and DPMNI = <i>N</i>,<i>N</i>′-bisÂ(4-pyridylmethyl)-1,4,5,8-naphthalenetetracarboxydiimide,
which has been crystallographically characterized, exhibits two redox-accessible
states due to the successive reduction of the naphthalenediimide (NDI)
ligand core. Solid-state electrochemical and vis–near-IR spectroelectrochemical
measurements coupled with density functional theory (DFT) calculations
enabled the origins of the optical transitions in the spectra of the
monoradical anion and dianion states of the material to be assigned.
Electron paramagnetic resonance (EPR) spectroscopy revealed that the
paramagnetic radical anion state of the DPMNI core could be accessed
upon broad-spectrum white light irradiation of the material, revealing
a long-lived excited state, possibly stabilized by charge delocalization
which arises from extensive π<i>–</i>π*
stacking interactions between alternating NDC and NDI aromatic cores
which are separated by a distance of 3.580(2) Ã…