The ferroelectricity in fluorite oxides has gained increasing interest due to its promising properties for multiple applications in semiconductor as well as energy devices. The structural origin of the unexpected ferroelectricity is now believed to be the formation of a non-centrosymmetric orthorhombic phase with the space group of Pca2₁. However, the factors driving the formation of the ferroelectric phase are still under debate. In this study, to understand the effect of annealing temperature, the crystallization process of doped HfO₂ thin films is analyzed using in situ, high-temperature X-ray diffraction. The change in phase fractions in a multiphase system accompanied with the unit cell volume increase during annealing could be directly observed from X-ray diffraction analyses, and the observations give an information toward understanding the effect of annealing temperature on the structure and electrical properties. A strong coupling between the structure and the electrical properties is reconfirmed from this result.

This letter investigates the impact of self-heating on the post-cycling functionality of a scaled hafnium oxide-based ferroelectric field-effect transistor (FeFET). The full recovery of FeFET switching properties and data retention after the cycling endurance failure is reported. This is achieved by damage annealing through localized heating, which is intentionally induced by a large current flow through the drain (source)-body p-n junctions. The results highlight that the local thermal treatments could be exploited to extend the cycling endurance of FeFETs.

<p dir="ltr">The separation of tellurium from cadmium telluride is examined using a unique combination of mild, anhydrous chlorination and complexation of the subsequent tellurium tetrachloride with 3,5-di-<i>tert</i>-butylcatechol. The resulting tellurium complex, Te(dtbc)₂, is isolated in moderate yield and features a 10³ to 10⁴ reduction in cadmium content, as provided by XRF and ICP-MS analysis. Similar results were obtained from zinc telluride. A significant separation between Te, Se, and S was observed after treating a complex mixture of metal chalcogenides with this protocol. These three tunable steps can be applied for future applications of CdTe photovoltaic waste.</p><p dir="ltr">We report the synthesis and characterization of the first series of tellurium and selenium complexes featuring an η⁵-cyclopentadienyl ligand. Reaction of Ph₃TeX (X = Cl, S₂CNEt₂) with MCp^R (M = Li, K; R = H, Me₄, Me₅) results in high yields of [Cp][TePh₃] (<b>1</b>), [Cp^Me4][TePh₃] (<b>2</b>), and [Cp*][TePh₃] (<b>3</b>), respectively. Similarly, reaction of Ph₃SeCl with LiCp and KCp* furnishes [Cp][SePh₃] (<b>4</b>) and [Cp*][SePh₃] (<b>5</b>). Each was characterized by X-ray crystallography, revealing similar η⁵-coordination with little distortion from an idealized half-sandwich geometry, presumably from the remaining lone pair on tellurium and selenium. The Te–centroid distances are relatively long (<b>1</b>: 2.770(3), <b>2</b>: 2.746(1), and <b>3</b>: 2.733(1) Å), suggesting a mostly ionic interaction. Se–centroid distances (<b>4</b>: 2.748(3), <b>5</b>: 2.707(2), 2.730(2) Å) were found to be surprisingly similar despite its smaller atomic radius. Compounds <b>2</b>, <b>3</b>, and <b>5</b> display rapid decomposition at room temperature, extruding a phenylated cyclopentadiene and the and the respective diphenylchalcogenide. The nature of bonding within these complexes was investigated through DFT methods and found to be primarily ionic in nature.</p><p dir="ltr">Synthesis of homoleptic zirconium and hafnium dithiocarbamate via carbon disulfide insertion into zirconium and hafnium amides were investigated for their utility as soluble molecular precursors for chalcogenide perovskites and binary metal sulfides. Treating M(NEtR)₄ (M= Zr, Hf and R= Me, Et) with CS₂ resulted in quantitative yields of homoleptic Group IV dithiocarbamates. Zr(k²-S₂CNMeEt) (<b>1</b>), Zr(k²-S₂CNEt₂)₄ (<b>2</b>), and Hf(k²-S₂CNEt₂)₄(<b>4</b>), a rare example of a crystal of a homoleptic hafnium CS₂ inserted amide species, were characterized. A computational analysis confirmed assignments for IR spectroscopy.<b> </b>To exemplify the utility of the Group IV dithiocarbamates, a solution-phase nanoparticle synthesis was performed to obtain ZrS₃ via the thermal decomposition of Zr(S₂CNMeEt)₄</p><p dir="ltr">Chalcogenide perovskites have garnered interest for applications in semiconductor devices due to their excellent predicted optoelectronic properties and stability. However, high synthesis temperatures have historically made these materials incompatible with the creation of photovoltaic devices. Here, we demonstrate the solution processed synthesis of luminescent BaZrS₃ and BaHfS₃ chalcogenide perovskite films using single-phase molecular precursors at sulfurization temperatures of 575 °C and sulfurization times as short as one hour. These molecular precursor inks were synthesized using known carbon disulfide insertion chemistry to create Group 4 metal dithiocarbamates, and this chemistry was extended to create species, such as barium dithiocarboxylates, that have never been reported before. These findings, with added future research, have the potential to yield fully solution processed thin films of chalcogenide perovskites for various optoelectronic applications.</p><p dir="ltr">Np(IV) Lewis base adducts were prepared by ligand substitution of NpCl₄(DME)₂. Using acetonitrile and pyridine, NpCl₄(MeCN)₄ (<b>1</b>) and NpCl₄(pyr)₄ (<b>2</b>), were isolated, respectively. All species were fully characterized using spectroscopic and structural analyses.</p>

Due to the voltage driven switching at low voltages combined with nonvolatility of the achieved polarization state, ferroelectric materials have a unique potential for low power nonvolatile electronic devices. The competitivity of such devices is hindered by compatibility issues of well-known ferroelectrics with established semiconductor technology. The discovery of ferroelectricity in hafnium oxide changed this situation. The natural application of nonvolatile devices is as a memory cell. Nonvolatile memory devices also built the basis for other applications like in-memory or neuromorphic computing. Three different basic ferroelectric devices can be constructed: ferroelectric capacitors, ferroelectric field effect transistors and ferroelectric tunneling junctions. In this article first the material science of the ferroelectricity in hafnium oxide will be summarized with a special focus on tailoring the switching characteristics towards different applications.The current status of nonvolatile ferroelectric memories then lays the ground for looking into applications like in-memory computing. Finally, a special focus will be given to showcase how the basic building blocks of spiking neural networks, the neuron and the synapse, can be realized and how they can be combined to realize neuromorphic computing systems. A summary, comparison with other technologies like resistive switching devices and an outlook completes the paper.

Zirconium tetrachloride (ZrF4) is extensively used in the manufacturing of zirconium metal. The concept of producing zirconium tetrafluoride from dissociated zircon and ammonium bifluoride is well established at the South African Nuclear Energy Corporation (Necsa) State Owned Company (SOC) Limited. Zirconium and hafnium are always found in the same minerals. In nuclear application zirconium is used for structural construction and as a cladding material for fuel, because of the low thermal neutron absorption, while hafnium is used as control rod in nuclear reactor, because of the high thermal neutron absorption. The methods of separating hafnium from zirconium prefer the use of ZrCl4 than ZrF4. This is because of the high solubility in both aqueous solutions and organic solvents and low sublimation temperature of ZrCl4, while ZrF4 is almost insoluble in organic solvent and has a high sublimation temperature. Thermodynamic evaluations showed that chlorinating ZrF4 with either CaCl2, KCl, LiCl or NaCl respectively was not favourable, while chlorinating ZrF4 with either BeCl2 or MgCl2 was favourable. But due to cost consideration chlorinating ZrF4 with BeCl2 was not investigated. A thermogravimetric apparatus was used to investigate the isothermal and the non-isothermal kinetics of chlorinating analytical grade ZrF4 with MgCl2. The thermogravimetric apparatus revealed that chlorination of ZrF4 commence at temperature above 350°C. Isothermal kinetics of chlorinating analytical grade ZrF4 with MgCl2 was investigated at temperatures of 400, 450, 480, 500°C. The reaction progressed towards completion prematurely before the isothermal temperatures were reached, due to a low heating rate of 20 °C/minutes was used to heat up the reaction mixture to the desired isothermal temperatures. As a result, the isothermal kinetics could not be determined. Heating rates of 5, 10, 15 and 20 °C/minutes were used to investigate the non-isothermal kinetics. The apparent activation energy of chlorinating ZrF4 with MgCl2 varied significantly when the non-isothermal kinetics was investigated. The variation was due to changes in the reaction mechanism. As a result, rate law of chlorinating ZrF4 with MgCl2 could not be determined due to variation of the apparent activation energy. Crude ZrF4 prepared at Necsa SOC ltd. was chlorinated with MgCl2, a mixture of MgCl2 and KCl, a mixture of MgCl2 and LiCl, and a mixture of MgCl2 and NaCl respectively. Chlorination of the crude ZrF4 was conducted at temperatures of 400, 450 and 500°C respectively. The aim of chlorinating the crude ZrF4 was to investigating the effect of the chlorinating on the purity of the produced ZrCl4. A batch reactor was used in this study. The reactor was divided into two sections, namely the reaction zone and the condensation zone. The diameter of the condensation zone was larger than that of the reaction zone. Reactants were placed into the reaction zone and the products were collected at the reaction zone and the condensation zone. Samples were collected from these products and analysed using for X-Ray Diffraction analysis (XRD) and Inductive Coupled Plasma Optical Emissions Spectroscopy (ICP-OES). XRD was used to identify the compounds that were present in the products and ICP-OES was used to determine the concentration of the elements that were present in the products. The analysis of the results obtained showed that the highest recovery of zirconium in the products collected from the condensation zone, the sublimed products, was achieved by chlorinating ZrF4 with MgCl2 at 500°C. About 80% was recovered. About 96% of the concentration of the impurities in the sublimed products was reduced when ZrF4 was chlorinated with a mixture of MgCl2 and LiCl at 450°C. About 36% of hafnium in the sublimed products was reduced when ZrF4 was chlorinated with a mixture of MgCl2 and NaCl at 400°C. / Chemical Engineering / M.Tech. (Chemical Engineering)

Les macrolactones sont des squelettes structuraux importants dans de nombreuses sphères de l’industrie chimique, en particulier dans les marchés pharmaceutiques et cosmétiques. Toutefois, la stratégie traditionnelle pour la préparation de macrolactones demeure incommode en requérant notamment l’ajout (super)stœchiométrique d’agents activateurs. Conséquemment, des quantités stœchiométriques de sous-produits sont générées; ils sont souvent toxiques, dommageables pour l’environnement et nécessitent des méthodes de purification fastidieuses afin de les éliminer. La présente thèse décrit le développement d’une macrolactonisation efficace catalysée au hafnium directement à partir de précurseurs portant un acide carboxylique et un alcool primaire, ne générant que de l’eau comme sous-produit et ne nécessitant pas de techniques d’addition lente et/ou azéotropique. Le protocole a également été adapté à la synthèse directe de macrodiolides à partir de mélanges équimolaires de diols et de diacides carboxyliques et à la synthèse de dimères tête-à-queue de seco acides. Des muscs macrocycliques ainsi que des macrolactones pertinentes à la chimie médicinale ont pu être synthétisés avec l’approche développée. Un protocole pour l’estérification directe catalysée au hafnium entre des acides carboxyliques et des alcools primaires a aussi été développé. Différentes méthodes pour la macrolactonisation catalytique directe entre des alcools secondaires et des acides carboxyliques ont été étudiées. En outre, la stratégie de séparation de phase en macrocyclisation en débit continu a été appliquée lors de la synthèse totale formelle de la macrolactone ivorenolide A. Les étapes-clés de la synthèse incluent une macrocyclisation par le couplage d’alcynes de Glaser-Hay et une réaction de métathèse d’alcènes Z-sélective. / Macrolactones are important structural motifs in numerous chemical industries particularly in the pharmaceutical and cosmetic markets. However, the traditional strategy for the preparation of macrolactones remains cumbersome, often requiring stoichiometric or excess amounts of activating reagents. Consequently, stoichiometric quantities of by-products are generated. They are often toxic, environmentally damaging, and/or require tedious purification methods to remove them. The following thesis describes the development of an efficient hafnium-catalyzed direct macrolactonization between carboxylic acid and primary alcohol functionalities, generating only water as a by-product and without the need for slow addition or azeotropic techniques. The protocol was also adapted for the direct synthesis of macrodiolides from equimolar mixtures of diols and dicarboxylic acids and for the selective head-to-tail dimerization of seco-acids. Macrocyclic musks and macrolactones relevant to medicinal chemistry were synthesized using the developed approach. A hafnium-catalyzed esterification protocol between carboxylic acids and primary alcohols was also developed. Different methods for the direct catalytic macrolactonization from secondary alcohols and carboxylic acids were studied. Furthermore, the phase separation strategy for macrocyclization in continuous flow was applied in the formal total synthesis of the macrolactone ivorenolide A. The key steps of the synthesis include the Glaser-Hay alkyne coupling macrocyclization and a Z-selective olefin metathesis reaction.

L'objectif de ce travail est d'apporter un éclairage nouveau à la compréhension des mécanismes physico-chimiques qui contrôlent la croissance des trois oxydes d'Aluminium, de Zirconium, de Hafnium. Ces matériaux sont considérés comme les meilleurs candidats pour remplacer la silice en tant qu'oxyde de grille dans le futur composant MOS. La précision et la fiabilité de la méthode DFT associé à la fonctionnelle B3LYP, ont été testées à l'aide des résultats expérimentaux et des méthodes ab initio les plus précis telles que CCSD(T) et CISD(T), en utilisant différents ensembles des fonctions de bases. Nos résultats montrent que et la méthode hybride DFT peut prédire de façon précise les propriétés statistiques et dynamiques de la famille d'organométalliques (AlxCyHzOt) et des systèmes moléculaires à base de métaux de transition (Zr/HfxClyOzHt). Les premières études systématiques des surfaces d'énergie potentielle de TMA ont été présentes et les caractéristiques des rotors constitués des groups méthyles ont été rapportées avec une grande précision. Les mécanismes réactionnels, à plusieurs étapes, entre les molécules précurseurs de trois oxydes et les molécules d'eau résiduelle phase gazeuse ont été étudies en détail. Les mouvements internes fortement anharmoniques, des espèces moléculaires présentes touts au long du processus d'hydrolyse ont été déterminés. Les effets qualitatifs sur les cinétiques des réactions ont été discutés. La forte exothermicité de la réaction TMA/H2O a été démontrée, alors que la réaction avec les tétrachlorures de Zirconium et Hafnium ont montré un caractère plutôt endothermique. Nous avons aussi étudié les mécanismes réactionnels de la vapeur d'eau avec d'espèces moléculaires chimisorbés en surface. Les réactions interviennent dans les cycles initiales d'ALD sur en substrat de Si(001)-2x1 légèrement oxydé. Les mécanismes que nous proposons sont qualitativement proches des mécanismes d'hydrolyse discutés dans la phase gaz euse : confirmation de la forte réactivité exothermique avec les hydroxyméthyliques d'Aluminium, endothermicité des réactions avec hydroxychlorures de Zirconium et Hafnium. Les composés avec le Zirconium et le Hafnium ont des comportements similaires. Enfin, les effets de coopérativité, à la fois au niveau des molécules de vapeur d'eau, qu'au niveau des complexes en surface, sur les réactions ont été mis en évidence et discutés. Ils montrent des comportements tout à fait intéressants dans le cas des hydroxychlorures des Zirconium et Hafnium. Par contre, ces effets sont de moindre importance dans les cas de l'oxyde d'aluminium, qui est actuellement considéré comme le matériau le plus compatible avec la croissance par ALD

Zirconium tetrachloride (ZrF4) is extensively used in the manufacturing of zirconium metal. The concept of producing zirconium tetrafluoride from dissociated zircon and ammonium bifluoride is well established at the South African Nuclear Energy Corporation (Necsa) State Owned Company (SOC) Limited. Zirconium and hafnium are always found in the same minerals. In nuclear application zirconium is used for structural construction and as a cladding material for fuel, because of the low thermal neutron absorption, while hafnium is used as control rod in nuclear reactor, because of the high thermal neutron absorption. The methods of separating hafnium from zirconium prefer the use of ZrCl4 than ZrF4. This is because of the high solubility in both aqueous solutions and organic solvents and low sublimation temperature of ZrCl4, while ZrF4 is almost insoluble in organic solvent and has a high sublimation temperature. Thermodynamic evaluations showed that chlorinating ZrF4 with either CaCl2, KCl, LiCl or NaCl respectively was not favourable, while chlorinating ZrF4 with either BeCl2 or MgCl2 was favourable. But due to cost consideration chlorinating ZrF4 with BeCl2 was not investigated. A thermogravimetric apparatus was used to investigate the isothermal and the non-isothermal kinetics of chlorinating analytical grade ZrF4 with MgCl2. The thermogravimetric apparatus revealed that chlorination of ZrF4 commence at temperature above 350°C. Isothermal kinetics of chlorinating analytical grade ZrF4 with MgCl2 was investigated at temperatures of 400, 450, 480, 500°C. The reaction progressed towards completion prematurely before the isothermal temperatures were reached, due to a low heating rate of 20 °C/minutes was used to heat up the reaction mixture to the desired isothermal temperatures. As a result, the isothermal kinetics could not be determined. Heating rates of 5, 10, 15 and 20 °C/minutes were used to investigate the non-isothermal kinetics. The apparent activation energy of chlorinating ZrF4 with MgCl2 varied significantly when the non-isothermal kinetics was investigated. The variation was due to changes in the reaction mechanism. As a result, rate law of chlorinating ZrF4 with MgCl2 could not be determined due to variation of the apparent activation energy. Crude ZrF4 prepared at Necsa SOC ltd. was chlorinated with MgCl2, a mixture of MgCl2 and KCl, a mixture of MgCl2 and LiCl, and a mixture of MgCl2 and NaCl respectively. Chlorination of the crude ZrF4 was conducted at temperatures of 400, 450 and 500°C respectively. The aim of chlorinating the crude ZrF4 was to investigating the effect of the chlorinating on the purity of the produced ZrCl4. A batch reactor was used in this study. The reactor was divided into two sections, namely the reaction zone and the condensation zone. The diameter of the condensation zone was larger than that of the reaction zone. Reactants were placed into the reaction zone and the products were collected at the reaction zone and the condensation zone. Samples were collected from these products and analysed using for X-Ray Diffraction analysis (XRD) and Inductive Coupled Plasma Optical Emissions Spectroscopy (ICP-OES). XRD was used to identify the compounds that were present in the products and ICP-OES was used to determine the concentration of the elements that were present in the products. The analysis of the results obtained showed that the highest recovery of zirconium in the products collected from the condensation zone, the sublimed products, was achieved by chlorinating ZrF4 with MgCl2 at 500°C. About 80% was recovered. About 96% of the concentration of the impurities in the sublimed products was reduced when ZrF4 was chlorinated with a mixture of MgCl2 and LiCl at 450°C. About 36% of hafnium in the sublimed products was reduced when ZrF4 was chlorinated with a mixture of MgCl2 and NaCl at 400°C. / Chemical Engineering / M.Tech. (Chemical Engineering)

The knowledge of diffusion parameters provides important understanding of many physical and mechanical properties of materials. In most of the applications silicides are grown by a diffusion controlled process mainly in thin film condition. Because of this reason, most of the studies till date are available in thin film condition. Although more than one phase is present in all these systems, mainly disilicides were found at the interface. In this thesis bulk interdiffusion studies are conducted by coupling pure refractory metals (group IVB, VB and VIB elements) with single crystal Si. Several phase layers grow between binary refractory metal and Si systems. The layer thicknesses of the phases are measured from the microstructures. Composition profiles were measured in electron probe microanalyzer. Different diffusion parameters are estimated such as parabolic growth constants, integrated diffusion coefficients, activation energy for diffusion and ratio of tracer diffusivities of the components are estimated. Growth mechanisms of the phases are discussed with the help of diffusion parameters. The atomic mechanism of the diffusion is discussed considering crystal structure of the phases along with possible defects present. Solid diffusion couple experiments are conducted to analyse the growth mechanism of the phases and the diffusion mechanism of the components in the Ti-Si system. The calculation of the parabolic growth constant and of the integrated diffusion coefficients substantiates that the analysis is intrinsically prone to erroneous conclusions if it is based just on the parabolic growth constants determined for a multiphase interdiffusion zone. The location of the marker plane is detected based on the uniform grain morphology in the TiSi2 phase, which indicates that this phase grows mainly because of Si diffusion. The growth mechanism of the phases and morphological evolution in the interdiffusion zone are explained with the help of imaginary diffusion couples. The activation enthalpies for the integrated diffusion coefficient of TiSi2 and the Si tracer diffusion are calculated as 190±9 and 170±12 kJ/mol, respectively. The crystal structure, details on the nearest neighbours of the elements and the relative mobilities of the components indicate that the vacancies are mainly present on the Si sublattice. Diffusion controlled growth of the phases in the Hf-Si and Zr-Si are studied by bulk diffusion couple technique. Only two phases grow in the interdiffusion zone, although several phases are present in both the systems. The location of the Kirkendall marker plane detected based on the grain morphology indicates that the disilicides grow by the diffusion of Si. Diffusion of the metal species in these phases is negligible. This indicates that vacancies are present mainly on the Si sublattice. The activation energies for integrated diffusion coefficients in the HfSi2 and ZrSi2 are estimated as 394 ± 37 and 346 ± 34 kJ/mol, respectively. The same is calculated for the HfSi phase as 485±42 kJ/mol. The activation energies for Si tracer diffusion in the HfSi2 and ZrSi2 phases are estimated as 430 ± 36 and 348 ± 34 kJ/mol, respectively. We conducted interdiffusion studies to understand the atomic mechanism of the diffusing species and the growth mechanism of the phases. Integrated diffusion coefficients and the ratio of tracer diffusion coefficients were estimated for these analyses. The activation energies for the integrated diffusion coefficients were calculated as 550 ± 70 and 410 ± 39 kJ/mol in the TaSi2 and the Ta5Si3 phases, respectively. In the TaSi2 phase, Ta has a slightly lower but comparable diffusion rate with respect to Si, although no TaTa bonds are present in the crystal. In the Ta5Si3 phase, Si has higher diffusion rate, which is rather unusual, if we consider the atoms in the nearest-neighbor positions for both the elements. The ratio of Si to Ta tracer diffusion coefficients is found to be lower in the Si-rich phase, TaSi2, compared to the Si-lean phase, Ta5Si3, which is also unusual. This indicates the type of structural defects present. An analysis on the growth mechanism of the phases indicates that duplex morphology and the Kirkendall marker plane should only be present in the TaSi2 phase. This is not present in the Ta5Si3 phase because of the very high growth rate of the TaSi2 phase, which consumes most of the Ta5Si3 phase layer. The problems in the calculation method used previously by others in this system are also explained. Experiments are conducted in the W-Si system to understand the diffusion mechanism of the species. The activation energies for integrated diffusion are found to be 152±7 and 301±40 kJ/mol in the WSi2 and W5Si3 phases, respectively. In both the phases, Si has a much higher diffusion rate compared to W. The result found in the WSi2 phase is not surprising, if we consider the nearest neighbors in the crystal. However, it is rather unusual to find that Si has higher diffusion rate in the W5Si3 phase, indicating the presence of high concentration of Si antisites in this phase. In the group IVB, VB and VIB M-Si systems are considered to show an interesting pattern in diffusion of components with the change in atomic number in a particular group. MSi2 and M5Si3 are considered for this discussion. Except in the Ta-Si system, activation energy for integrated diffusion of MSi2 is always lower than M5Si3. Interestingly, in both the phases, the relative mobilities measured by the ratio of tracer D* diffusion coefficients, S i decreases with the increase in atomic number in both the DM* groups. Both the phases have similar crystal structures in a particular group in which these parameters are calculated. In both the phases Si has higher diffusion rate compared to M. Absence of any M-M bonds in MSi2 and increase in the diffusivities of M with the increase in atomic number substantiates the increasing concentration of M anti-sites and higher interactions of M with vacancies. Only one or two Si-Si bonds are present in M5Si3, however, the higher diffusion rate of Si indicates the presence of vacancies mainly D* on its sublattice. On the other hand, increase in S i with increasing atomic number in DM* Both the groups substantiates increasing interactions of M and vacancies.

Pas de résumé en français / The goal of this research was the synthesis and spectroscopic, structural andphysical-chemical characterization of cyclic 6- and 7-membered hydroxamicacids, a tetrahydroxamic calix[4]arene-based tetrapodal receptor, and their metalcomplexes with trivalent and tetravalent metal cations. They were characterizedby several techniques such as 1H and 13C NMR, IR, and mass spectroscopies,single crystal X-ray analysis, and potentiometry. Cyclic hydroxamic acids arefound in a few mix siderophores but their coordination properties were stillunknown. The structural features of metal complexes formed with Fe(III),Ga(III), Ce(IV), Zr(IV), Hf(IV), U(IV) and U(VI) have been investigated both inthe solid state and in solution. The synthesis and complexation studies of anoriginal calix[4]arene-based tetrapodal receptor is described. Reactionparameters for all key steps in the synthetic route have been optimized. Thesingle X-ray crystal analysis of benzyl-protected receptor was obtained.Complexation studies with zirconium(IV) and hafnium(IV) evidenced theformation of two metal two ligand complexes rather than 1:1 species, whichwere shown to interact in solution with a third alkali cation