Spin Crossover MaterialsSpin Crossover Materials



Postgraduate students will also find this book useful as a comprehensive introduction to the field.

Author: Malcolm A. Halcrow

Publisher: John Wiley & Sons

ISBN: 9781118519318

Category:

Page: 568

View: 591

The phenomenon of spin-crossover has a large impact on the physical properties of a solid material, including its colour, magnetic moment, and electrical resistance. Some materials also show a structural phase change during the transition. Several practical applications of spin-crossover materials have been demonstrated including display and memory devices, electrical and electroluminescent devices, and MRI contrast agents. Switchable liquid crystals, nanoparticles, and thin films of spin-crossover materials have also been achieved. Spin-Crossover Materials: Properties and Applications presents a comprehensivesurvey of recent developments in spin-crossover research, highlighting the multidisciplinary nature of this rapidly expanding field. Following an introductory chapter which describes the spin-crossover phenomenon and historical development of the field, the book goes on to cover a wide range of topics including Spin-crossover in mononuclear, polynuclear and polymeric complexes Structure: function relationships in molecular spin-crossover materials Charge-transfer-induced spin-transitions Reversible spin-pairing in crystalline organic radicals Spin-state switching in solution Spin-crossover compounds in multifunctional switchable materials and nanotechnology Physical and theoretical methods for studying spin-crossover materials Spin-Crossover Materials: Properties and Applications is a valuable resource for academic researchers working in the field of spin-crossover materials and topics related to crystal engineering, solid state chemistry and physics, and molecular materials. Postgraduate students will also find this book useful as a comprehensive introduction to the field.

Synthesis and Applications of New Spin Crossover CompoundsSynthesis and Applications of New Spin Crossover Compounds



The crystal chemistry of spin crossover (SCO) behavior in coordination compounds can potentially be in association with smart materials—promising materials for applications as components of memory devices, displays, sensors and mechanical ...

Author: Takafumi Kitazawa

Publisher: MDPI

ISBN: 9783039213610

Category:

Page: 254

View: 451

The crystal chemistry of spin crossover (SCO) behavior in coordination compounds can potentially be in association with smart materials—promising materials for applications as components of memory devices, displays, sensors and mechanical devices and, especially, actuators, such as artificial muscles. This Special Issue is devoted to various aspects of SCO and related research, comprising 18 interesting original papers on valuable and important SCO topics. Significant and fundamental scientific attention has been focused on the SCO phenomena in a wide research range of fields of fundamental chemical and physical and related sciences, containing the interdisciplinary regions of chemical and physical sciences related to the SCO phenomena. Coordination materials with bistable systems between the LS and the HS states are usually triggered by external stimuli, such as temperature, light, pressure, guest molecule inclusion, soft X-ray, and nuclear decay. Since the first Hofmann-like spin crossover (SCO) behavior in {Fe(py)2[Ni(CN)4]}n (py = pyridine) was demonstrated, this crystal chemistry motif has been frequently used to design Fe(II) SCO materials to enable determination of the correlations between structural features and magnetic properties.

Spin States in Biochemistry and Inorganic ChemistrySpin States in Biochemistry and Inorganic Chemistry



Topics covered include: • DFT and ab initio wavefunction approaches to spin states • Experimental techniques for determining spin states • Molecular discovery in spin crossover • Multiple spin state scenarios in organometallic ...

Author: Marcel Swart

Publisher: John Wiley & Sons

ISBN: 9781118898314

Category:

Page: 472

View: 145

It has long been recognized that metal spin states play a central role in the reactivity of important biomolecules, in industrial catalysis and in spin crossover compounds. As the fields of inorganic chemistry and catalysis move towards the use of cheap, non-toxic first row transition metals, it is essential to understand the important role of spin states in influencing molecular structure, bonding and reactivity. Spin States in Biochemistry and Inorganic Chemistry provides a complete picture on the importance of spin states for reactivity in biochemistry and inorganic chemistry, presenting both theoretical and experimental perspectives. The successes and pitfalls of theoretical methods such as DFT, ligand-field theory and coupled cluster theory are discussed, and these methods are applied in studies throughout the book. Important spectroscopic techniques to determine spin states in transition metal complexes and proteins are explained, and the use of NMR for the analysis of spin densities is described. Topics covered include: DFT and ab initio wavefunction approaches to spin states Experimental techniques for determining spin states Molecular discovery in spin crossover Multiple spin state scenarios in organometallic reactivity and gas phase reactions Transition-metal complexes involving redox non-innocent ligands Polynuclear iron sulfur clusters Molecular magnetism NMR analysis of spin densities This book is a valuable reference for researchers working in bioinorganic and inorganic chemistry, computational chemistry, organometallic chemistry, catalysis, spin-crossover materials, materials science, biophysics and pharmaceutical chemistry.

Synthesis and Characterization of FE II Spin Crossover Complexes Containing the Organic Donor TetrathiafulvaleneSynthesis and Characterization of FE II Spin Crossover Complexes Containing the Organic Donor Tetrathiafulvalene



The future work will be directed at electrooxidizing the complex to generate the conductive pathways within the TTF substructure.

Author: Jordan Hoyt

Publisher:

ISBN: OCLC:643107484

Category:

Page: 36

View: 517

Two novel spin crossover complexes with TTF containing ligands were synthesized. Both of them were modeled after the well studied spin crossover compound Fe II (phen)2(NCS)2. The first of these complexes, containing the TTF-annulated 1, 10-phenanthroline, exhibits spin transition which is strongly dependent on the nature of interstitial solvent molecules. When the sample was prepared in CH2Cl2, a gradual, incomplete spin transition was observed with indications of a metastable high spin state that could be stabilized by rapid cooling of the sample. The sample prepared in CHCl3 undergoes spin transition only above 300 K. An examination of the crystal structure obtained for the complex prepared in CH2Cl2 shows packing of interstitial solvent molecules in one-dimensional channels within the structure. The second spin crossover complex is similar to the first, but hexyl groups were added to the TTF-ligand in order to increase the solubility of the complex. The obtained complex exhibits gradual spin crossover and is soluble in CHCl3 and CH2Cl2. Electrochemical studies revealed two reversible oxidations, which makes this complex a promising precursor for the preparation of conducting spin-crossover materials. The future work will be directed at electrooxidizing the complex to generate the conductive pathways within the TTF substructure. Along with the preparation of these complexes, some insights and preliminary data towards the preparation of a spin crossover complex containing a tetradentate capping ligand and a single bidentate ligand functionalized with TTF were generated.

High Spatial Resolution Investigation of Spin Crossover Phenomena Using Scanning Probe MicroscopiesHigh Spatial Resolution Investigation of Spin Crossover Phenomena Using Scanning Probe Microscopies



Recently a variety of nanoscale objects, including nanoparticles, thin films and nanometric assemblies, exhibiting molecular spin-state switching phenomena have been developed for applications in sensors, nanophotonic, nanoelectronic and ...

Author: Edna Magdalena Hernandez Gonzalez

Publisher:

ISBN: OCLC:931619054

Category:

Page: 208

View: 954

Recently a variety of nanoscale objects, including nanoparticles, thin films and nanometric assemblies, exhibiting molecular spin-state switching phenomena have been developed for applications in sensors, nanophotonic, nanoelectronic and nanomechanical systems. These spin crossover nanomaterials have been also reported to exhibit interesting size-dependent properties. Indeed, even if the origin of the spin crossover phenomenon is purely molecular, the macroscopic behavior of these systems in the solid state is strongly influenced by elastic interactions between the molecules. These cooperative properties and, in general, the phase diagram are expected to depend strongly on the size of the material. Beyond the phase stability, the transformation kinetics is likely to display also size dependence. Indeed, the strong elastic interactions in these materials lead, in many cases, to first-order phase transitions and phase separation phenomena. Details of the associated spatio-temporal dynamics of spin crossover systems remain largely unexplored. All these size dependent and spatially heterogeneous phenomena in spin crossover materials call for appropriate characterization methods with high spatial resolution imaging capability, but to date only far-field optical microscopy has been used to this aim. Hence, the overall objective of this PHD thesis was to develop new approaches allowing to trigger and detect the spin crossover phenomenon with nanometric spatial resolution. For the detection of the thermally induced spin crossover in thin films, we used for the first time Near-Field Scanning Optical Microscopy (NSOM) and Atomic Force Microscopy (AFM) in conjunction with an original nano-heater device, based on Joule-heated metallic nanowires. Using these techniques the spin-state change in the films was inferred with sub-wavelength resolution through the associated optical and mechanical property changes of the material. Apertured NSOM used either in luminescence or reflectivity mode provided useful signal for detecting the spin-state switching phenomena, but rather limited quantification was possible due to sample stability issues (photobleaching, etc). On the other hand, AFM mechanical modes, including fast force spectroscopy and multifrequency analysis, allowed for quantitative and well-reproducible measurements with nanometric resolution. In particular, we have measured for the first time the increase of the Young's modulus (ca. 25-30 %) when going from the high spin to the low spin state and used this property for quantitative imaging of the spin transition. AFM measurements were also performed on spin crossover single crystals. We have shown that probe-sample thermal interactions can be used to manipulate the nucleation and propagation of the high spin and low spin phases in the crystals. On the other hand, these interactions make for difficulties for the AFM imaging of these phenomena. Nevertheless changes of the surface topography during the spin transition can be observed and discussed in conjunction with far-field optical microscopy and Raman spectroscopy data. The ensemble of these results open up new possibilities for the investigation and manipulation of these bistable objects at the nanoscale.

Magnetic MaterialsMagnetic Materials



G. Felix, W. Nicolazzi, M. Mikolasek, G. Molnar, A. Bousseksou, Non-extensivity of thermodynamics at the nanoscale in molecular spin crossover materials: A ...

Author: Khan Maaz

Publisher: BoD – Books on Demand

ISBN: 9789535124276

Category:

Page: 278

View: 216

This book reports on the recent progresses in theory, application, and characterization of magnetic materials. It covers a broad spectrum of topics on magnetic materials with different shapes and morphologies such as transition metals, cylindrical and 2D ferromagnetic nanowires, core-shell nanowires, monoatomic-layered nanostructures, and nanocrystals. This book addresses diverse groups of readers with general background in physics and material science and also covers topics for the specialists in the field of magnetism. It is believed that this book will be interesting for the readers and will provide a solid foundation about the topic for the students, scientists, and engineers working in the field of material science and condensed matter physics.

Spin Crossover in Iron II and Cobalt II Complexes Including Multifunctional MaterialsSpin Crossover in Iron II and Cobalt II Complexes Including Multifunctional Materials



Structure-function correlations for this work were vital to further the understanding of the factors influential in determining the magnetic properties of crystalline SCO compounds, by varying the nature of the ligand, solvent or counter ...

Author: Hayley Sue Scott

Publisher:

ISBN: OCLC:1011512506

Category:

Page: 652

View: 677

At the outset, the primary focus of this Ph.D. project has been directed towards the synthesis of new 2,2'-dipyridylamino(dpa)- and 1,2,4-triazole(trz)- based ligands to be incorporated into spin crossover (SCO) iron(II) complexes.Initial aims sought the synthesis of a wide and diverse range of SCO compounds containingnovel dpa- and trz-based ligands in order to determine what sort of control could be exercised over magnetic properties. New ligands synthesised for the project incorporated a range of nondpa- or trz-substituents with, for example, different capacities to participate in hydrogen bonding or aryl interactions (such as !-stacking), with different degrees of bulkiness, flexibility, or additional binding sites, for metals or other guests, that are distinct and separate from the dpa or trz coordination sites. This fundamental study also probed the influence of second coordination sphere entities, including the effects of solvation and counter ion species, upon the spin transition. Structure-function correlations for this work were vital to further the understanding of the factors influential in determining the magnetic properties of crystalline SCO compounds, by varying the nature of the ligand, solvent or counter-ion.As there is currently great interest in the study of multifunctional ('hybrid') molecular materials, a further aspect of this Ph.D. project was aimed towards the synthesis of ligands incorporating a moiety capable of a secondary function, in addition to SCO. This led to two main areas of study, the first of which consisted of the synthesis and coordination of a number of ferrocene-appended ligands and attempts have been made to analyse how one-electron changes at the ferrocene group (located external to the coordination site) influences the spin transition. This includes a system in which a new ferrocene-trz ligand and its 1-D polynuclear complexes were studied using magnetic, electrochemical and Mössbauer measurements (Chapter 6), as well as synthesis of discrete FeII and CoII complexes incorporating ferrocene-based ligands (Chapter 7).Our second approach at obtaining multifunctional SCO materials has led us to pursue the synthesis and coordination of crown-appended dpa-based ligands which have the potential to show, in addition to SCO, encapsulation of alkali metal ions in the aza-crown ether, which ideally would result in guest dependent magnetic properties. This work appears in Chapter 4.Throughout this study, where possible, all complexes have been comprehensively characterised, primarily using single crystal X-ray structural determination and variable temperature magneticsusceptibility measurements, although the vast array of complexes appearing in this thesis have been characterised using a number of other techniques including PXRD, Mössbauer spectroscopy, electrochemical studies, magnetic- and photo-magnetic measurements and to a lesser extent heat-capacity measurements.