Ferric ferrocyanide (Prussian blue) and its analogues are renowned for the variety of properties and applications associated with them. At the same time, however, they suffer from issues related to their variable composition and poor crystallinity. As a result, we are preparing discrete cyanide-bridged clusters both to mimic these materials and to search for properties unique to the molecule, such as single molecule magnetism. The work in this dissertation has focused on the expansion of series of trigonal bipyramidal (TBP) cyanide-bridged clusters, [M(tmphen)2]3[M′(CN)6]2, that exhibit a variety of properties including spin crossover, charge-transfer-induced spin transition, and photomagnetism. One goal of the work was focused on the preparation of new paramagnetic TBP clusters incorporating various 3d metal ion combinations. Nine new clusters were prepared and characterized, including several “model compounds” with only one type of paramagnetic metal ion. The magnetic properties of these model compounds were combined to better explain the coupling through the cyanide ligands in clusters with two paramagnetic metal centers. An additional two clusters were also prepared that were found to exhibit a thermally induced LS Fe^II -> HS Fe^II transition. The spin crossover event was confirmed by magnetic susceptibility and Mössbauer spectroscopy, and variable temperature X-ray crystallography revealed the transitions to be distinct for each FeII center and dependant on the interstitial solvent. Another major goal of the work was to investigate the TBP clusters for their potential to be used as building-blocks to prepare 1-D extended structures of linked clusters, such as a {[Co(tmphen)2]3[Fe(CN)6]2[Mn(MeOH)4]}∞(ClO4)3 chain. A final research goal was a search for photomagnetic behavior, the change in magnetic properties with irradiation, related to spin transitions in several key TBP clusters. The Fe3Fe2 and Fe3Co2 TBP clusters were found to exhibit a light-induced excited spin state trapping (the LIESST effect) similar to that observed in mononuclear FeII compounds, and the photo-induced charge transfer that has been observed in Co-Fe Prussian blue materials is mimicked by the Co3Fe2 TBP molecular analogue.

This study focuses on investigating the effect of the electronic spin transition of iron on the elasticity of the candidate lower mantle ferropericlase (Mg,Fe)O. This may be relevant to our understanding of the seismic velocity structures of the Earth’s lower mantle. The elastic constants of (Mg₀.₉₂Fe₀.₀₈)O at high-spin (HS) state, low-spin (LS) state, and through the pressure-induced HS-to-LS transition has been measured using both Brillouin Light Scattering (BLS) and Impulsive Stimulated Scattering (ISS). There is a large pressure range in which c₁₁ and c₁₂ exhibit a softening, while c₄₄ does not register such an anomaly. Compared with previously published data of ferropericlase with similar compositions ([Marquardt et al., 2009b], BLS measurement of (Mg₀.₉Fe₀.₁)O and [Crowhurst et al., 2008], ISS measurement of (Mg₀.₉₄Fe₀.₀₆)O), this study provides more reliable elastic constants measurements by taking the advantage of simultaneous measurements on Vp and Vs using both BLS and ISS. Our results show that bulk sound velocity of ferropericlase has a large but smooth softening in the spin transition pressure region. The elastic constants of ferropericlase at the spin transition region and the LS state have been well studied in this thesis, and a relaxation behavior has also been observed in this study. Those two subjects are not well documented in literature. The temperature effect of the spin state transition and its consequential effect on mineral’s elastic properties have not been studied in this project, but further research on this subject will follow. However, even in the room temperature, our results don’t show sudden changes in seismic velocities. Moreover, current theoretical and experimental studies [Sturhahn et al., 2005, Tsuchiya et al., 2006, Lin et al., 2007] indicate that the spin transition takes place over an extended range of depth along an expected lower-mantle geotherm, where sudden changes in compressional and bulk sound velocity are not expected. / text

The work presented herein describes efforts to synthesize and characterize cyanide-bridged molecular compounds with high-spin ground states. This investigation focused primarily on the assembly of hexacyanometallate units with convergent cationic metal complexes that are coordinated to capping ligands. In this manner, a family of related compounds was developed that serve as models for understanding the role of magnetic exchange interactions and anisotropy in nanomagnetic materials. The work presented in Chapter II describes the successful incorporation of the [Fe(CN)6]3- building block into planar geometries with nuclearities ranging from three to ten metal centers. In Chapter III, this methodology was optimized to yield two pentanuclear FeIII/NiII clusters, namely, the trigonal bipyramidal unit, {[Ni(tmphen)2]3[Fe(CN)6]2}, and the extended square, {[Ni(bpy)2(H2O)][Ni(bpy)2]2-[Fe(CN)6]2}. Magnetic measurements on pure phases of these samples revealed that each system exhibits ferromagnetic coupling between the L.S. FeIII and NiII centers, but neither exhibits slow paramagnetic relaxation effects down to T=2K. In Chapter IV, this chemistry was extended to the [Mn(CN)6]3-building block in order to increase magnetic exchange coupling and anisotropy in this cluster type, efforts that resulted in the isolation of the molecule, {[Mn(tmphen)2]3[Mn(CN)6]2}. This cluster exhibits intramolecular antiferromagnetic exchange interactions between the Mn centers which lead to an S=11/2 ground state and a negative ZFS value (D=-0.348 cm-1), parameters that support the experimental observation of Single-Molecule Magnet (SMM) behavior at low temperatures. A detailed investigation of the physical and structural properties of {[Co(tmphen)2]3[Fe(CN)6]2} in Chapters V and VI led to the realization that the cluster exhibits sensitivity to temperature and humidity. The molecule exists in three different electronic isomeric forms in the solid state and undergoes a charge-transfer induced spin-transition (CTIST) under the influence of temperature. The results presented in Chapter VI describe the behavior of this same cluster in solution, the highlight of which is the discovery that water reacts with the cluster to form a fourth electronic isomer. Finally, it is described in Chapter VII that this Co/Fe trigonal bipyramidal unit can be used as a building block for systematically incorporating three metal types into a family of 1-D chain and cluster compounds.

The work presented herein describes efforts to synthesize and characterize cyanide-bridged molecular compounds with high-spin ground states. This investigation focused primarily on the assembly of hexacyanometallate units with convergent cationic metal complexes that are coordinated to capping ligands. In this manner, a family of related compounds was developed that serve as models for understanding the role of magnetic exchange interactions and anisotropy in nanomagnetic materials. The work presented in Chapter II describes the successful incorporation of the [Fe(CN)6]3- building block into planar geometries with nuclearities ranging from three to ten metal centers. In Chapter III, this methodology was optimized to yield two pentanuclear FeIII/NiII clusters, namely, the trigonal bipyramidal unit, {[Ni(tmphen)2]3[Fe(CN)6]2}, and the extended square, {[Ni(bpy)2(H2O)][Ni(bpy)2]2-[Fe(CN)6]2}. Magnetic measurements on pure phases of these samples revealed that each system exhibits ferromagnetic coupling between the L.S. FeIII and NiII centers, but neither exhibits slow paramagnetic relaxation effects down to T=2K. In Chapter IV, this chemistry was extended to the [Mn(CN)6]3-building block in order to increase magnetic exchange coupling and anisotropy in this cluster type, efforts that resulted in the isolation of the molecule, {[Mn(tmphen)2]3[Mn(CN)6]2}. This cluster exhibits intramolecular antiferromagnetic exchange interactions between the Mn centers which lead to an S=11/2 ground state and a negative ZFS value (D=-0.348 cm-1), parameters that support the experimental observation of Single-Molecule Magnet (SMM) behavior at low temperatures. A detailed investigation of the physical and structural properties of {[Co(tmphen)2]3[Fe(CN)6]2} in Chapters V and VI led to the realization that the cluster exhibits sensitivity to temperature and humidity. The molecule exists in three different electronic isomeric forms in the solid state and undergoes a charge-transfer induced spin-transition (CTIST) under the influence of temperature. The results presented in Chapter VI describe the behavior of this same cluster in solution, the highlight of which is the discovery that water reacts with the cluster to form a fourth electronic isomer. Finally, it is described in Chapter VII that this Co/Fe trigonal bipyramidal unit can be used as a building block for systematically incorporating three metal types into a family of 1-D chain and cluster compounds.

L'objectif central de cette thèse est l'évaluation de la possibilité d'utilisation de complexes moléculaires à transitions de spin pour des applications en nano-électronique. Dans un premier temps, les propriétés électriques du complexe [Fe(Htrz)2(trz)](BF4) et de ces analogues [Fe1-xZnx(Htrz)2(trz)](BF4) ont été analysées sous forme de poudres au moyen de la spectroscopie diélectrique. Il a été montré que les conductivités AC et DC aussi bien que la constante diélectrique et que la fréquence de relaxation diélectrique subissent une baisse importante lors de la transition de l'état bas spin (BS) vers l'état haut spin (HS). Les molécules à base de cations de fer gardent leurs propriétés de transition de spin dans les échantillons dilués de Zn, mais les courbes de transition de spin sont considérablement altérées. La substitution par Zn des centres de fer actifs mène à une importante baisse de la conductivité électrique d'environ 6 ordres de grandeur (pour Zn/Fe = 0.75). Nous concluons de ces résultats que les ions Fe(II) participent directement au processus de transport des charges, qui a été analysé dans le cadre d'un modèle de conductivité par saut de porteurs de charge activé thermiquement. Des particules micrométriques de [Fe(Htrz)2(trz)](BF4) ont été alors intégrées par diélectrophorèse entre des électrodes d'or. Ainsi, nous avons obtenu un dispositif montrant un phénomène de bistabilité lors de la caractérisation I-V, T. La stabilité du matériau initial et le dispositif électronique ont été contrôlés avec précision et les effets concomitants de changements de températures, d'irradiation lumineuse et du champ électrique sur l'intensité du courant ont été analysés en détail. D'une part, nous avons montré que le dispositif peut être adressé de manière préférentielle par une irradiation lumineuse en fonction de son état de spin, et d'autre part, nous avons démontré la commutation de l'état métastable HS vers l'état stable BS par application d'un champ électrique à l'intérieur du cycle d'hystérésis. Les effets de champ ont été discutés dans le cadre de modèles de type Ising statiques et dynamiques, tandis que les phénomènes photo-induits étaient attribués à des effets de surface. Le complexe [Fe(H2B(pz)2)2(phen)] a également été caractérisé par spectroscopie diélectrique sous forme de poudre et ensuite intégré par évaporation thermique sous vide au sein d'un dispositif vertical entre les électrodes en Al et ITO. Cette approche nous a permis de sonder la commutation de l'état de spin dans la couche de [Fe(bpz)2(phen)] par des moyens optiques tout en détectant les changements de résistance associés, à la fois dans les régimes à effet tunnel (jonction de 10 nm) et dans les régimes à injection (jonctions de 30 et 100 nm). Le courant tunnel dans les jonctions à transition de spin diminue durant la commutation de l'état BS vers l'état HS, tandis que le comportement de rectification des jonctions " épaisses " ne révélait aucune dépendance significative à l'état de spin. L'ensemble de ces résultats ouvre la voie à de nouvelles perspectives pour la construction de dispositifs électroniques et spintroniques incorporant des matériaux à transition de spin. / The central theme of this thesis is the evaluation of potential interest and applicability of molecular spin crossover (SCO) complexes for nanoelectronic applications. The electrical properties of the [Fe(Htrz)2(trz)](BF4) complex and its Zn substituted analogues were analyzed first in the bulk powder form using broadband dielectric spectroscopy. It has been shown that the ac and dc conductivities as well as the dielectric constant and the dielectric relaxation frequency exhibit an important drop when going from the low spin (LS) to the high spin (HS) state. The iron ions kept their spin transition properties in the Zn diluted samples, but the SCO curves were significantly altered. The Zn substitution of active iron centers led to an important decrease of the electrical conductivity of ca. 6 orders of magnitude (for Zn/Fe = 0.75). We concluded from these results that the ferrous ions directly participate to the charge transport process, which was analyzed in the frame of an activated hopping conductivity model. Micrometric particles of [Fe(Htrz)2(trz)](BF4) were then integrated by dielectrophoresis between interdigitated gold electrodes leading to a device exhibiting bistability in the I-V,T characteristics. The stability of the starting material and the electronic device were carefully controlled and the concomitant effect of temperature changes, light irradiation and voltage bias on the current intensity were analyzed in detail. We showed that the device can be preferentially addressed by light stimulation according to its spin state and the switching from the metastable HS to the stable LS state was also demonstrated by applying an electric field step inside the hysteresis loop. The field effects were discussed in the frame of static and dynamic Ising-like models, while the photo-induced phenomena were tentatively attributed to surface phenomena. The [Fe(bpz)2(phen)] complex was also investigated by dielectric spectroscopy in the bulk powder form and then integrated by high vacuum thermal evaporation into a large-area vertical device with Al (top) and ITO (bottom) electrodes. This approach allowed us to probe the spin-state switching in the SCO layer by optical means while detecting the associated resistance changes both in the tunneling (10 nm junction) and injection-limited (30 and 100 nm junctions) regimes. The tunneling current in the thin SCO junctions showed a drop when going from the LS to the HS state, while the rectifying behavior of the 'thick' junctions did not reveal any significant spin-state dependence. The ensemble of these results provides guidance with new perspectives for the construction of electronic and spintronic devices incorporating SCO molecular materials.

Cette thèse concerne les études théoriques et expérimentales de composés à transition de spin (SCO: “spin crossover”) menées pour déterminer la possibilité de les implémenter dans des capteurs de température et/ou de pression. L’analyse théorique a été effectuée en utilisant les deux modèles les plus utilisés dans ce domaine de recherche notamment: le modèle équivalent d’Ising et le modèle de couplage Atom-Phonon. Pour générer les états des systèmes SCO, les méthodes d’échantillonnage entropique de Monte Carlo (MCES : « Monte Carlo Entropic Sampling ») et de Monte Carlo Metropolis (MCM) ont été utilisées. La méthode MCES a été utilisée pour étudier les systèmes à basse dimensions réduites et la méthode MCM pour les systèmes de grande taille. Ainsi le rôle de la coopérativité dans un système SCO a été analysé et l’influence des interactions des molécules de surface avec leur environnement local a été étudiée. Il a été montrée qu’une transition procédant par plusieurs étapes (« multi step transition ») est pilotée par trois types d’interactions: celles à courte portée, celles à longue portée et celles entre les molécules de surface avec leur environnement. Ces résultats peuvent être utilisés pour assembler les matériaux de type SCO dans des dispositifs technologiques parce-que, comme il a été montré, il est nécessaire de tenir compte des interactions qui peuvent exister entre les molécules de surface et leur environnement. De plus, des résultats importants ont été obtenus en analysant le rôle de l’architecture du système. Les résultats obtenus en appliquant le modèle de couplage Atom-Phonon ont été comparés en utilisant trois méthodes différentes pour résoudre le Hamiltonien du système: l’approximation du champ moyen, la matrice dynamique et l’approximation parabolique. Ainsi il a été montré que la méthode de l’approximation parabolique est meilleure que la méthode de l’approximation du champ moyen et que les résultats obtenus avec cette méthode sont très proches de ceux obtenus avec des calculs exacts. Ceci est du au fait que cette méthode est très proche de la méthode de calculs exacts. Les études expérimentales des composés SCO Fe(hyptrz)]A2∙H2O et [Fe(hyetrz)3]I2∙H2O ont révélées leur propriété thermo- et piézo-chromique. Une grande variété de techniques a été employée pour la caractérisation des deux composés. Ainsi les analyses thermiques du premier composé sous l’action d’une pression externe ont été réalisées avec une cellule de pression à gaz. Ce type de cellule a l’avantage de maintenir le caractère hydrostatique sur le domaine entier de température. Le deuxième composé a été caractérisé en utilisant des techniques telles que: caractérisation optique, DSC, spectroscopie Mössbauer et un dispositif micromécanique pour l’application de la pression. Les résultats ont démontré la faisabilité de détection de la pression en utilisant un capteur ou marqueur basé sur un composé SCO fonctionnant à température ambiante. Pour le composé SCO [Fe(hyetrz)3]I2∙H2O, une valeur seuil de la pression de contact autour de 30 MPa a été obtenue qui induit de manière irréversible un changement de couleur du matériau moléculaire. Ceci résulte de la transition de l’état HS vers l’état BS. De plus, la possibilité d’une transition qui induit un changement de couleur en sens inverse en utilisant un autre stimulus (température) a été démontrée, ce qui permet de réutiliser le capteur. A partir de ces résultats, un nouveau type de capteur fonctionnant sur le principe d’une détection optique a été proposé qui permettrait la détection concomitante à la fois de la température et de la pression. Ce nouveau type de capteur est basé sur deux composés SCO qui sont caractérisés par des transitions progressives. En considérant les développements récents dans le domaine SCO cet objectif pourrait être très bientôt atteint. / This thesis is about the theoretical and experimental studies carried on spin crossover compounds (SCO) in order to investigate the possibility of their implementation in temperature and/or pressure sensors. The theoretical analysis was performed using two of the most applied models in the field namely: the Ising-like model and the Atom Phonon coupling model. To generate the states of SCO systems the Monte Carlo Entropic Sampling (MCES) and Monte Carlo Metropolis (MCM) methods were used. The MCES method was used for small systems and the MCM method for large systems. Thus, we analyzed the role of cooperativity of a SCO system and studied the influence of interactions of the surface molecules with their local environment. We have shown that a multi step transition is driven by three types of interactions: the short-range interactions, long-range interactions and interactions of surface molecules with their environment. These results can be applied to assemble SCO materials based devices because, as we have shown, it is necessary to account for the interactions that may occur between the molecules on the surface and their environment. Moreover, important results were obtained by analyzing the role of the system’s architecture. Considering equal number of molecules systems, we have shown that a square system is more cooperative than a ladder type system which in turn is more cooperative than a chain-type system. The results obtained using the Atom Phonon coupling model were compared using three different methods to solve the Hamiltonian system: mean field approximation, dynamic matrix and parabolic approximation. Thus it was shown that the parabolic approximation method is better than that of the mean field approximation method and that the results obtained by this method are very close to those obtained by exact calculations. This is because this method is very close to exact calculation. The experimental studies on SCO compounds Fe(hyptrz)]A2∙H2O and [Fe(hyetrz)3]I2∙H2O revealed their thermo- and piezo-chromic character. A variety of techniques have been employed for the characterization of the two compounds. Thus the thermal analysis of the first mentioned compound under the action of external pressure was carried out using a gas pressure cell. This type of cell has the advantage of maintaining the hydrostatic character over the entire range of temperature. The second compound was characterized using techniques such as: optical characterization, DSC, Mössbauer spectroscopy and a micromechanical home-made device for the application of pressure. The results demonstrated the feasibility of pressure detection using a molecular spin crossover based sensor/marker operating at ambient temperature. For the SCO compound [Fe(hyetrz)3]I2∙H2O, we obtained a threshold value of the contact pressure of about 30 MPa to irreversibly induce the color change of the molecular material, due to the spin state switching from HS to LS state. Moreover, the possibility of switching back the color using another stimulus (temperature) was demonstrated, making this sensor reusable. Taking into account the above mentioned results we proposed a new type of sensor with optical detection that would allow the concomitant detection of both temperature and pressure. This new type of sensor is based on two SCO compounds that exhibit gradual transitions. Considering recent developments in the SCO field this objective could be achieved in the near future.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18234号 / 工博第3826号 / 新制||工||1586(附属図書館) / 31092 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 北川 進, 教授 松田 建児, 教授 濵地 格 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Ce travail de thèse porte sur l’étude de la dynamique femtoseconde de photo-commutation de matériaux moléculaires bistables, à l’aide d’expériences pompe-sonde basées sur les spectroscopies optiques et rayons X. Une partie des expériences a été réalisée sur synchrotron et X-FEL (X-ray Free Electron Laser). La première partie de la thèse, qui est consacrée à l’étude de systèmes à transition de spin non-octaédriques, a révélé différents chemins de transformations sur la surface de potentiel, associés à différents mécanismes de changement d’état électronique et modulant la cohérence de la dynamique structurale pilotant le processus. La seconde partie porte sur l’étude d’analogues du bleu de Prusse (CoFe) où les expériences ultra-rapides ont permis de d’étudier les dynamiques de transformation autour des sites de fer et de cobalt. / This thesis focuses on the study of the femtosecond photoswitching dynamic in the bistable molecular materials, using the pump-probe experiments which are based on the optical and x-ray spectroscopies.  Part of these experiments was performed at synchrotron and X-FEL (X-ray Free Electron Laser). The first part of the thesis, which is devoted to the study of non-octahedral spin transition systems, revealed different pathways of transformation on the potential surface. The second part focuses on the study of the Prussian Blue Analogues (CoFe), where the ultra-fast experiments allowed to follow the dynamics around the two metal ions.

Lobtention dun bon contraste en imagerie médicale est un pré-requis à un examen de qualité. Limagerie médicale basée sur la résonance nucléaire magnétique utilise diverses substances magnétiques comme agent de contraste. Le développement dagents de contraste à la fois plus performants et plus économiques sappuie fortement sur létude fondamentale des propriétés magnétiques de divers matériaux potentiellement utilisables. Dans ce travail, deux voies ont été poursuivies. La première partie est consacrée à des matériaux à transition de spin, qui pourraient être utilisés comme agents de contraste en résonance magnétique, pour autant que leur température de transition soit voisine de celle du corps humain. En effet, ces matériaux ont la particularité de posséder deux états magnétiques différents et, sous linfluence dune perturbation telle que la pression ou la température, peuvent passer dun état à lautre, à savoir létat paramagnétique ou diamagnétique. Les complexes de fer(II) étudiés sont basés sur des ligands tri-pyrazolyl borate et méthane. Une autre voie suivie pour améliorer le diagnostic médical est le développement et lutilisation de nanoparticules magnétiques fonctionnelles pour la détection et/ou le traitement des cellules cancéreuses. Dans la deuxième partie de ce travail, les propriétés magnétiques de nanoparticules ferriques préparées par deux méthodes différentes sont investiguées. La spectroscopie Mössbauer est largement utilisée dans cette thèse et les résultats obtenus par cette technique constituent la contribution principale de lauteur au travail. Cette technique, basée sur la fluorescence résonnante sans recul des rayons gamma, permet létude des interactions hyperfines de matériaux solides contenant du fer. Appliquée aux matériaux à transition de spin et aux nanoparticules, deux champs dapplication bien distincts, la spectroscopie Mössbauer fournit des informations structurelles et magnétiques. Elle complémente admirablement dautres techniques macroscopiques et microscopiques, comme la magnétométrie, la microscopie électronique et la diffraction des rayons X. Les autres techniques qui ont été utilisées par lauteur sont la magnétométrie et la relaxation des muons. Cest la première fois, que cette dernière technique est introduite dans léventail des techniques exploitées à lUniversité de Liège.

Quantum chemistry has nowadays become a powerful and efficient tool that can be successfully used for studies of biosystems. It is therefore possibleto model the enzyme active-site and the reactions undergoing into it, as well as obtaining quite accurate energetic profiles. Important conclusions can be drawn from such profiles about the  plausibility of different putative mechanisms. Density Functional Theory is used in the present thesis for investigation of the catalytic mechanism of dioxygenase metallo-enzymes and synthetic model complexes. Three enzymes were studied – Homoprotocatechuate 2,3-dioxygenase isolated from Brevibacterium fuscum (Bf 2,3-HPCD), Manganese-Dependent Homoprotocatechuate 2,3-Dioxygenase (MndD) and Homogentisate Dioxygenase (HGD). Models consisting of 55 to 208 atoms have been built from X-ray crystal structures and used in the calculations. The computed energies were put in energy curves and were used for estimation of the feasibility of the suggested reaction mechanisms. A non-heme [(L4Me4)Fe(III)]+3 complex that mimics the reactivity of intradiol dioxygenases, and a heme [T(o-Cl)PPFe] complex catalyzing the stepwise oxidation of cyclohexane to adipic acid, were also studied. For the enzymes and the non-heme biomimetic complex the reaction was found to follow a mechanism that was previously suggested for extradiol and intradiol dioxygenases – ordered substrates binding and formation of peroxo species, which further undergoes homolytic O-O bond cleavage. Different reaction steps appear to be rate limiting in the particular cases: proton transfer from the substrate to the peroxide in Bf 2,3-HPCD, the formation of the peroxo bridge in HGD and the biomimetic complex, and notably, spin transition in MndD. The catalytic oxidation of cyclohexane to adipic acid in the presence of molecular oxygen as oxidant was studied, a reaction of great importance for the chemical industry. Reaction mechanism is suggested, involving several consecutive oxidative steps. The highest calculated enthalpy of activation is 17.8 kcal/mol for the second oxidative step. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: In progress, Paper 5: In progress