scholarly journals Increasing spin crossover cooperativity in 2D Hofmann-type materials with guest molecule removal

2018 ◽  
Vol 9 (25) ◽  
pp. 5623-5629 ◽  
Author(s):  
Katrina A. Zenere ◽  
Samuel G. Duyker ◽  
Elzbieta Trzop ◽  
Eric Collet ◽  
Bun Chan ◽  
...  
Keyword(s):  
Ambient Temperature ◽  
Guest Molecule ◽  
Spin Crossover ◽  
Guest Molecules ◽  
Ligand Interactions ◽  
Wide Hysteresis

Ambient temperature spin crossover with wide hysteresis has been achieved in 2D Hofmann-type materials, where removal of guest molecules optimises ligand–ligand interactions, resulting in increased cooperativity.

scholarly journals Guest-Dependent Stabilization of the Low Spin State in Spin-Crossover Metal-Organic Frameworks

2018 ◽  
Author(s):  
C. Huy Pham ◽  
Francesco Paesani
Keyword(s):  
Spin State ◽  
Guest Molecule ◽  
Spin Crossover ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Gas Detection ◽  
Rotational Mobility ◽  
Guest Molecules ◽  
In Silico Modeling ◽  
Metal Organic

<div> <div> <div> <p>Computer simulations are carried out to characterize the variation of spin crossover (SCO) behavior of the prototypical {Fe(pz)[Pt(CN)4]} metal-organic framework (MOF) upon adsorption of chemically and structurally different guest molecules. A detailed analysis of both strength and anisotropy of guest molecule-framework interactions reveals direct correlations between the mobility of the guest molecules inside the MOF pores, the rotational mobility of the pyrazine rings of the framework, and the stabilization of the low-spin state of the material. Based on these correlations, precise molecular criteria are established for predicting the spin state of {Fe(pz)[Pt(CN)4]} upon guest adsorption. Finally, predictions of the SCO temperature upon adsorption of various toxic gases demonstrate that in silico modeling can provide fundamental insights and design principles for the development of spin-crossover MOFs for applications in gas detection and chemical sensing. </p> </div> </div> </div>

scholarly journals Guest-Dependent Stabilization of the Low Spin State in Spin-Crossover Metal-Organic Frameworks

2018 ◽  
Author(s):  
C. Huy Pham ◽  
Francesco Paesani
Keyword(s):  
Spin State ◽  
Guest Molecule ◽  
Spin Crossover ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
Gas Detection ◽  
Rotational Mobility ◽  
Guest Molecules ◽  
In Silico Modeling ◽  
Metal Organic

<div> <div> <div> <p>Computer simulations are carried out to characterize the variation of spin crossover (SCO) behavior of the prototypical {Fe(pz)[Pt(CN)4]} metal-organic framework (MOF) upon adsorption of chemically and structurally different guest molecules. A detailed analysis of both strength and anisotropy of guest molecule-framework interactions reveals direct correlations between the mobility of the guest molecules inside the MOF pores, the rotational mobility of the pyrazine rings of the framework, and the stabilization of the low-spin state of the material. Based on these correlations, precise molecular criteria are established for predicting the spin state of {Fe(pz)[Pt(CN)4]} upon guest adsorption. Finally, predictions of the SCO temperature upon adsorption of various toxic gases demonstrate that in silico modeling can provide fundamental insights and design principles for the development of spin-crossover MOFs for applications in gas detection and chemical sensing. </p> </div> </div> </div>

scholarly journals Hydrogen Inter-Cage Hopping and Cage Occupancies inside Hydrogen Hydrate: Molecular-Dynamics Analysis

2020 ◽  
Vol 11 (1) ◽  
pp. 282
Author(s):  
Yogeshwaran Krishnan ◽  
Mohammad Reza Ghaani ◽  
Arnaud Desmedt ◽  
Niall J. English
Keyword(s):  
Molecular Dynamics ◽  
Energy Barrier ◽  
Guest Molecule ◽  
Arrhenius Equation ◽  
Dynamics Simulation ◽  
Type Ii ◽  
Large Cage ◽  
Guest Molecules ◽  
Simulation Time ◽  
Average Occupancy

The inter-cage hopping in a type II clathrate hydrate with different numbers of H2 and D2 molecules, from 1 to 4 molecules per large cage, was studied using a classical molecular dynamics simulation at temperatures of 80 to 240 K. We present the results for the diffusion of these guest molecules (H2 or D2) at all of the different occupations and temperatures, and we also calculated the activation energy as the energy barrier for the diffusion using the Arrhenius equation. The average occupancy number over the simulation time showed that the structures with double and triple large-cage H2 occupancy appeared to be the most stable, while the small cages remained with only one guest molecule. A Markov model was also calculated based on the number of transitions between the different cage types.

scholarly journals Spin-state-dependent electrical conductivity in single-walled carbon nanotubes encapsulating spin-crossover molecules

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Julia Villalva ◽  
Aysegul Develioglu ◽  
Nicolas Montenegro-Pohlhammer ◽  
Rocío Sánchez-de-Armas ◽  
Arturo Gamonal ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Spin State ◽  
Spin Crossover ◽  
Single Walled Carbon Nanotubes ◽  
Guest Molecules ◽  
Spintronic Devices ◽  
Single Walled Carbon ◽  
State Dependent ◽  
Lack Of Control ◽  
Walled Carbon Nanotubes

AbstractSpin crossover (SCO) molecules are promising nanoscale magnetic switches due to their ability to modify their spin state under several stimuli. However, SCO systems face several bottlenecks when downscaling into nanoscale spintronic devices: their instability at the nanoscale, their insulating character and the lack of control when positioning nanocrystals in nanodevices. Here we show the encapsulation of robust Fe-based SCO molecules within the 1D cavities of single-walled carbon nanotubes (SWCNT). We find that the SCO mechanism endures encapsulation and positioning of individual heterostructures in nanoscale transistors. The SCO switch in the guest molecules triggers a large conductance bistability through the host SWCNT. Moreover, the SCO transition shifts to higher temperatures and displays hysteresis cycles, and thus memory effect, not present in crystalline samples. Our results demonstrate how encapsulation in SWCNTs provides the backbone for the readout and positioning of SCO molecules into nanodevices, and can also help to tune their magnetic properties at the nanoscale.

Inclusion compounds of plant growth regulators in cyclodextrins. V. 4-Chlorophenoxyacetic acid encapsulated in β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin

2005 ◽  
Vol 61 (2) ◽  
pp. 207-217 ◽  
Author(s):  
Frantzeska Tsorteki ◽  
Kostas Bethanis ◽  
Nikos Pinotsis ◽  
Petros Giastas ◽  
Dimitris Mentzafos
Keyword(s):  
Guest Molecule ◽  
Crystal Packing ◽  
Host Molecule ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
Space Group ◽  
X Ray ◽  
Dimeric Complexes ◽  
The Mean ◽  
Chlorophenoxyacetic Acid

The crystal structures of 4-chlorophenoxyacetic acid (4CPA) included in β-cyclodextrin (β-CD) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMβCD) have been studied by X-ray diffraction. The 4CPA/β-CD complex crystallizes as a head-to-head dimer in the space group C2 in the Tetrad packing mode. The packing modes of some β-CD dimeric complexes, having unique stackings, are also discussed. The 4CPA/TMβCD inclusion complex crystallizes in the space group P21 and its asymmetric unit contains two crystallographically independent complexes, complex A and complex B, exhibiting different conformations. The host molecule of complex A is significantly distorted, as a glucosidic residue rotated about the O4′—C1 and C4—O4 bonds forms an aperture where the guest molecule is accommodated. The phenyl moiety of the guest molecule of complex B is nearly perpendicular to the mean plane of the O4n atoms. The conformations of the guest molecules of the two complexes are similar. The crystal packing consists of antiparallel columns as in the majority of the TMβCD complexes published so far.

An iron(ii) complex exhibiting five anhydrous phases, two of which interconvert by spin-crossover with wide hysteresis

2012 ◽  
Vol 3 (2) ◽  
pp. 349-354 ◽  
Author(s):  
Thomas D. Roberts ◽  
Floriana Tuna ◽  
Tamsin L. Malkin ◽  
Colin A. Kilner ◽  
Malcolm A. Halcrow
Keyword(s):  
Spin Crossover ◽  
Wide Hysteresis

Investigation of the disorder of dibromo- and dichloromethane in their tri-ortho-thymotide clathrates using X-ray diffraction and solid-state 2H NMR spectroscopy

2011 ◽  
Vol 89 (7) ◽  
pp. 854-862
Author(s):  
Glenn A. Facey ◽  
Ilia Korobkov
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Guest Molecule ◽  
Type B ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Twofold Axis ◽  
H Nmr ◽  
Heavy Atoms

The tri-ortho-thymotide (TOT) clathrates of dibromo- and dichloromethane were characterized by single crystal X-ray diffraction at 200 K and solid-state 2H NMR spectroscopy as a function of temperature. The host structure was found to be typical of other cage-type TOT clathrates. The X-ray results showed a substantial amount of disorder among the guest molecules. In both clathrates, multiple guest molecule positions could be modeled. The heavy atoms of all the guest molecule positions lie approximately in the same plane, with some out-of-plane distortion. The guest molecules were of two different types in positions symmetric about the crystallographic twofold rotation axis: type A guests, with carbon atoms well removed from the crystallographic twofold axis, and type B guests, with carbon atoms very close to the twofold axis. The 2H NMR spectra for the guests confirmed that the disorder was dynamic. The experimental results could be accounted for by the presence of three simultaneous types of molecular motion, all fast with respect to the 2H quadrupolar interaction: (i) twofold molecular flips about the molecular C2 symmetry axis, (ii) exchange between the type A and type B sites in a single plane, and (iii) a two-site libration of the plane containing the heavy atoms of the A and B guest sites with a temperature-dependent amplitude.

Hysteretic spin crossover driven by anion conformational change

2017 ◽  
Vol 53 (70) ◽  
pp. 9801-9804 ◽  
Author(s):  
Natnaree Phukkaphan ◽  
Dyanne L. Cruickshank ◽  
Keith S. Murray ◽  
Wasinee Phonsri ◽  
Phimphaka Harding ◽  
...  
Keyword(s):  
Conformational Change ◽  
Room Temperature ◽  
Spin Crossover ◽  
Wide Hysteresis

An air stable FeIII complex showing a wide hysteresis near room temperature is described. The origin of the cooperativity is an unprecedented anion conformational change.

Determination of Relative Stability of Urea Complexes from X-Ray Powder Diffraction Data

1960 ◽  
Vol 4 ◽  
pp. 140-150 ◽  
Author(s):  
Jack Radell ◽  
J.W. Connolly
Keyword(s):  
Dissociation Constant ◽  
Guest Molecule ◽  
Interplanar Spacing ◽  
Dynamic Equilibrium ◽  
Crystalline Complex ◽  
Guest Molecules ◽  
X Ray ◽  
Host Molecules ◽  
The Stability

AbstractUrea complexes consist of a channel made up of hydrogen-bonded urea host molecules into which a variety of guest molecules can fit to form a crystalline complex. The urea host can accommodate, one at a time, a variety of guests having the requisite size and shape. The stability of the resulting complex is a function of the properties of the guest molecule. A procedure has been devised which produces pure complex free of any uncomplexed urea or host molecules in solution. The insoluble crystalline complexes formed from the solution of urea and guest molecule in methanol established a dynamic equilibrium. When the crystals of complex are removed from the solution, dissociation to urea and guest occurs to an extent, depending upon the dissociation constant of the complex. If the dissociation constant, KD, is very low, undetectable quantities of uncomplexed urea form along with complex. If the dlissoclation constant is high, extensive amounts of urea form in the presence of complex. Characteristic interplanar spacing s are obtained for a urea complex irrespective of the guest molecule present. The pattern obtained for the hexagonal complex is completely different from the pattern obtained for tetragonal urea. X-ray examination of a homologous series of compounds gives, for each partially dissociated complex, spacings for both urea and complex. The relative intensities of urea and complex spacings permit the estimation of the stability of such a complex compared to that of other homologues.

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