Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work presents the synthesis and crystallographical study of indium organometallic compounds series in II and III oxidation states. Br2In(diox)2CH2Br and tetrahedral indium cluster, In4R4 [R = C(SiMe3)3], were adopted as starting materials of this work. We have made two different systematic studies: (a) reaction of Br2In(diox)2CH2Br with dialkylselenides R1SeR2 (R1 = CH3, R2 = CH2Ph; R1 = C2H5, R2 = CH2Ph; R1 = R2 = CH2Ph) and (b) reaction between the tetrahedral indium cluster and different chalcogenide donor ligands, such as PhEEPh (E = S, Se and Te), ArTeTeAr (Ar = CH3C6H4) and PhEBr (E = Se and Te), and haloforms as well, CHX3 (X = Cl, Br and I). The haloforms were applied as mild halogen donors. Br2In(diox)2CH2Br is obtained by the direct reaction between InBr and CH2Br2 in 1,4-dioxane. The Br3InCH2Se(CH3)CH2Ph (1), Br3InCH2Se(C2H5)CH2Ph (2) and Br3InCH2Se(CH2Ph)2 (3) derivatives are obtained by the reaction between Br2In(diox)2CH2Br and their own dialkylselenides. Tetrahedral indium cluster is obtained by the reaction between InBr and C(SiMe3)3·2THF in equivalent amounts. The new organoindium subhalides, R2In2Cl2 (4), R2In2Br2 (5), R2In2I2 (6), and the new indium(III) dimeric compounds as well, [RIn(SPh)2]2 (7), [RIn(SePh)2]2 (8), [RIn(TePh)2]2 (9) and [RIn(ArPh)2]2 (10), [RIn(Br)SePh]2 (11), [RIn(Br)TePh]2 (12), were obtained by the direct reaction of tetrahedral indium cluster and their respective halide or chalcogenide donors. / Este trabalho apresenta a síntese e o estudo cristalográfico de uma série de compostos organometálicos de índio nos estados de oxidação II e III. Os materiais de partida utilizados neste trabalho foram o Br2In(diox)2CH2Br e o cluster tetraédrico de índio, In4R4 [R = C(SiMe3)3]. Realizou-se dois tipos de estudos sistemáticos: (a) reação de Br2In(diox)2CH2Br com dialquilselenetos R1SeR2 (R1 = CH3, R2 = CH2Ph; R1 = C2H5, R2 = CH2Ph; R1 = R2 = CH2Ph) e (b) reação do cluster de índio com diferentes ligantes contendo calcogênios, como PhEEPh (E = S, Se e Te), ArTeTeAr (Ar = CH3C6H4) e PhEBr (E = Se e Te) e com halofórmios, CHX3 (X = Cl, Br e I). Os halofórmios foram utilizados como doadores de halogênio moderados. Br2In(diox)2CH2Br é obtido através da reação entre InBr e CH2Br2 em 1,4-dioxano. Os derivados Br3InCH2Se(CH3)CH2Ph (1), Br3InCH2Se(C2H5)CH2Ph (2) e Br3InCH2Se(CH2Ph)2 (3) são obtidos através da reação entre Br2In(diox)2CH2Br e seus respectivos dialquilselenetos. O cluster tetraédrico de índio é obtido a partir da reação de InBr e C(SiMe3)3·2THF em quantidades equivalentes. Os novos derivados de halogênio, R2In2Cl2 (4), R2In2Br2 (5), R2In2I2 (6), e os novos compostos diméricos de índio(III), [RIn(SPh)2]2 (7), [RIn(SePh)2]2 (8), [RIn(TePh)2]2 (9) e [RIn(ArPh)2]2 (10), [RIn(Br)SePh]2 (11), [RIn(Br)TePh]2 (12), foram obtidos através da reação direta do cluster de índio com seus respectivos doadores de halogênio ou calcogênio.

The discovery of high-temperature superconductivity in 1986 in copper-oxide materials have opened up new avenues to investigate new families of quantum materials that were previously not known. Understanding the mechanism of superconductivity in high-T[sub]c superconductors has been an important research theme in condensed matter physics, as it is believed to be essential to realize the next generation engineered materials that become superconducting at room temperature. Discovered in 2006, iron based superconductors are a new addition to the family of high-T[sub]c superconductors, these materials exhibit several interesting properties and show some vivid similarities with cuprates and other families of high-temperature superconductors. In this thesis, I will present the spin-polarized scanning tunneling microscopy (SPSTM) study carried out on the parent compound of iron chalcogenide high temperature superconductor Fe[sub](1+y)Te to investigate the bi-collinear antiferromagnetic order. Magnetic tips in this work are prepared using a novel preparation technique by picking up excess iron atoms and clusters of FeTe from the surface of the sample. Next, I will present the SP-STM results obtained in the spin glass phase of Fe[sub](1+y)SeₓTe₁₋ₓ visualizing the interplay between the short ranged bi-directional bi-collinear antiferromagnetic order and superconductivity at the atomic scale. In this thesis, I will also present the scanning tunneling microscopy and spectroscopy (STM/STS) study of the native and engineered defect bound states in the iron-pnictide superconductor LiFeAs. This study addresses the pairing symmetry of the superconducting order parameter and understanding of dip-hump features seen in STM spectra outside the superconducting gap in iron pnictide superconductor LiFeAs.

The thesis entitled "Synthesis of Novel Chalcogenides using Acyloxyphosphonium Intermediates and Doubly Activated Cyclopropanes" is divided into six chapters. Chapter 1: Part 1: Synthesis of thioesters from carboxylic acids and alkyl halides using benzyltriethylammonium tetrathiomolybdate In this chapter, we describe the synthesis of thioesters from carboxylic acids and alkyl halides. Aryl carboxylic acids are first activated using PPh3 and NBS to form the corresponding acyloxy phosphonium intermediates which then on further reaction with reagent, 1generate thioaroylate ions in situ. These thioaroylates on further reaction with various electrophiles such as alkyl halides / dihalides in the same pot gives the corresponding functionalized thioesters. This methodology was then extended to carbohydrate based thioesters as they are important synthetic intermediates in various transformations and also they could be deprotected later to synthetically more valuable thiols. For this study, we took 1,2,3,4tetra-O-acetyl-β-D-glucopyranuronic acid which on treatment with PPh3,NBS, reagent, 1 and I-bromo propane (CHCl3, 28°C, 2h) afforded the corresponding thioester in 55% yield. An intramolecular version of the reaction was then performed on a compound containing both anomeric bromide and carboxylic acid functionality. This was achieved by treating tetra acetyl glucuronic acid, with HBr/AcOH to form α-D-bromo-glucopyranuronic acid which on further treatment with PPh3, NBS and reagent, 1 gave the corresponding bicyclic thiolactone in 55% yield. Chapter 1: Part 2: Synthesis of Thioesters by Simultaneous Activation of Carboxylic Acids and Alcohols using PPh3/NBS In this chapter, we have shown the synthesis of thioester from carboxylic acids and alcohols. Both carboxylic acids and alcohols are first activated using PPh3 and NBS to form the corresponding phosphonium salts. Reagent, 1 then reacts selectively with acyloxyphosphonium intermediates to generate thioaroylate ions in situ which then react either with alkoxy phosphonium salts or the corresponding alkyl bromide to give thioesters in good yield. The same methodology was then used for a one pot conversion of N-Boc serine ester to s-protected cysteine using reagent 1 as the key sulfur transfer reagent. Chapter 2: Part 1: Tetrathiomolybdate mediated Michael addition of thioaroylates generated from acyloxyphosphonium salts In this chapter, we have reported an easy and alternative protocol for the Michael addition of thioacids to various Michael acceptors. Acyloxyphosphonium salts and tetrathiomolybdate reacts to generate thioaroylate ions which then undergo Michael additionto givethe corresponding Michael adducts. This methodology was then extended for the synthesis carbohydrate based thiolactone by an intramolecular Michael addition reaction to show the applicability of the methodology. Chapter 2: Part 2: Regioselective and chemoselective ring opening of aziridines and epoxides using thioaroylate ions In this chapter, we have demonstrated nucleophilic ring opening of Aziridines and epoxides using thioaroylate ions generated from acyloxyphosphonium salts and tetrathiomolybdate as a sulfur transfer reagent. We have also demonstrated chemoselective ring opening of azirdines in the presence of an epoxide and tosylate to show the novelty of our method. Chapter 3: Synthesis of bromo esters and bromo thioesters by ring opening of cyclic ethers and thiiranes via acyloxyphosphonium intermediates In this chapter, we report the synthesis of bromo esters and thioesters by the ring opening of epoxides, tetrahydrofuran, and thiiranes with bromide ion to form the corresponding bromo alcohols and thiols followed by the nucleophilic displacement of triphenylphosphine oxide from acyloxyphosphonium salts. At first THF and epoxides were subjected for the ring opening reactions to give the corresponding bromo esters. The methodology was then extended to thiiranes to synthesis bromo thioesters in good to moderate yield. Chapter 4: Synthesis of doubly activated cyclopropranes and their applications to the synthesis of dihydrothiophenes and thiophenes In this chapter we discuss the synthesis and ring opening of doubly activated cyc1opropanes using tetrathiomolybdate and their applications towards the formation of dihydrothiophenes and other bioactive molecules. At first, we synthesized a number of doubly activated cyc1opropanes from dimethyl-α-arylsulfonium bromide,24 a protocol developed by Chow and others. With the doubly activated cyclopropanes in hand, we then attempted the ring opening of cyclopropanes containing a cyano group with tetrathiomolybdate to give the corresponding dihydrothiophene derivatives. Also we have used our methodology for the synthesis of HIV-1 reverse transcriptase inhibitor Chapter 5: Synthesis of unsymmetrical sulfide and disulfide derivatives via ring opening of doubly activated cyclopropanes Here, we describe the synthesis of various monosulfides and mixed disulfides by doubly activated cyclopropane ring opening mediated by tetrathiomolybdate in one pot. Tetrathiomolybdate is known for the reduction of disulfides while diaryl disulfides gives monosulfide, dialkyl disulfides give mixed disulfides with the corresponding doubly activated cyclopropane. Thus diaryl disulfide cleaves readily as the resultant thiolate ion is stable and opens the cyclopropane ring to give a monosulfide. Dibenzyl disulfide on the other hand being less reactive gave a mixed disulfide instead of a monosulfide. We also extended this ring opening reactions for the synthesis of symmetrical disulfides Using tetrathiomolybdate as the key sulfur transfer reagent. Chapter 6: A mild protocol for the nucleophilic ring opening of doubly activated cyclopropanes using selenolates generated in situ Nucleophilic ring opening of doubly activated cyc1opropanes with selenolate ions generated by the reduction of diselenides using NaB14 is discussed in this part of the work. A variety of doubly activated cyc1opropanes have been tested for this reaction giving the corresponding selenium compounds in good yield. This methodology was then extended to other diselenides using nitroester cyclopropane as standard and also to other substituted nitroester cyclopropanes using diphenyl diselenide as standard. This methodology was also then extended to the synthesis of homoselenocysteines by the reduction of nitro group using Sn/HCI for the reduction. (For structural formula pl refer the hard copy)

Les nouveaux matériaux de type chalcogénures (à base de S, Se, Te) font l’objet d’un intérêt croissant, non seulement pour les applications mémoires avancées, photonique et photovoltaïque, mais également autour des matériaux dichalcogénures innovants à base de métaux de transition (MoS₂, WS₂, ..). Les propriétés de ces matériaux, réalisés sous forme d’alliages binaires ou ternaires, avec ou sans dopage, dépendent fortement de leur composition, du profil de composition dans ces couches très fines, ainsi que des conditions de surface et d’interface (préparation, passivation). La maîtrise des propriétés de ces couches fines, déposées par voie chimique (CVD) ou par co-pulvérisation cathodique magnétron, doit s’appuyer sur des nouveaux protocoles de caractérisation aux incertitudes optimisées et compatibles avec un contrôle de fabrication en ligne. Dans cette thèse, nous présentons les performances de protocoles de métrologie spécifiquement développés pour l’analyse de couches minces de chalcogénures. Ces protocoles, qui s’appuient essentiellement sur les techniques non destructives de spectroscopie de photoélectrons (XPS) et de fluorescence X (XRF), ont été optimisés pour la caractérisation surfacique des couches ultrafines, l’analyse quantitative de la composition des matériaux complexes à base de tellure ou de soufre, et la mesure du profil de composition dans des couches et empilements < 50 nm. Dans un premier temps, nous présentons l’étude par XPS quasi in situ des propriétés de surface des matériaux Ge, Sb, Te ainsi que de leurs composés binaires et ternaires. Nous mettons en évidence l’évolution de la surface après remise à l’air puis vieillissement, et nous comparons l’efficacité de stratégies d’encapsulation in situ de couches minces à base de Te et Se. Nous démontrons ensuite les performances de protocoles d’analyses par XRF à dispersion de longueur d’onde (WDXRF) et XPS pour la quantification précise de la composition chimique de composés Ge-Sb-Te (de 1 à 200 nm) et de couches ultrafines de dichalcogénures à base de métaux de transition (MoS₂, WS₂). L’analyse combinée WDXRF/XPS permet de mesurer l’évolution avec la composition des facteurs de sensibilité relative des composantes Ge3d, Te4d et Sb4d, et par conséquent d’améliorer la précision de mesure par XPS de la composition des matériaux à changement de phase de type GexSbyTez. Nous soulignons également l’influence des effets de matrice sur la capacité de la WDXRF à l’analyse quantitative de l’azote dans des matériaux Ge-Sb-Te. Nous évaluons la possibilité d’un étalonnage de la WDXRF fondé sur des analyses par faisceaux d’ions spécifiques, ce qui permet in fine un suivi en ligne de couches GeSbTeN dans une fenêtre procédé donnée. Enfin, nous présentons deux stratégies de caractérisation non destructive du profil de composition dans des couches minces de chalcogénures. D’une part, nous démontrons que la combinaison des techniques de XRF en géométrie d'incidence rasante (GIXRF) et de réflectométrie X (XRR) permet une mise en évidence non ambiguë de faibles variations dans les procédés de dépôts, voire de phénomènes de diffusion dans des empilements de 10 nm d'épaisseur. L'utilisation de substrats multicouches en lieu et place du silicium permet d’optimiser la distribution en profondeur du champ d'ondes stationnaires, ce qui conduit à une amélioration nette de la sensibilité des stratégies XRR / GIXRF. D’autre part, nous montrons l’adéquation de protocoles fondés sur l’analyse XPS résolue en angle pour la caractérisation du profil de composition dans des couches nanométriques de GeTe et Ge₂Sb₂Te₅, ce qui permet une étude fine des premières étapes de dépôt de ces matériaux. / Chalcogenide materials are compounds based on S, Se, and Te elements from group VI of the periodic table. They are receiving an extensive interest not only for applications in resistive memories (PCRAM and CBRAM), photonics and photovoltaics but also in the development of new 2-D materials (e.g. spintronics applications). Chalcogenide materials are already present in the semiconductor roadmaps and it is already replacing flash memories (e.g. phase change material and ovonic threshold switch in new random access memory). For the next technology nodes, chalcogenide properties can be scaled by tuning the chemical composition or by reducing the film thickness. Nonetheless, it also means that their properties become more tightly influenced by the chemical composition, the surface/interface effects and the depth-profile composition. Hence, dedicated metrology protocols must be developed, first to assist the optimization of chalcogenide materials processes in cleanroom environment, then to allow non-destructive process monitoring with industry-driven uncertainties. In this PhD thesis, we developed metrology protocols based on X-ray techniques, dedicated to thin chalcogenides materials and fully compatible with inline monitoring. First, we used quasi in-situ X-ray Photoelectron Spectroscopy (XPS) to characterize the surface of Ge, Sb, Te thin materials and compounds, and to study the composition-dependent evolution of the surface after air break and ageing. The efficiency of in situ capping strategies to protect Te-based and Se-based thin layered materials from ageing was also investigated. Secondly, we demonstrated the ability of improved metrology strategies based on in-line Wavelength Dispersive X-ray Fluorescence (WDXRF) and XPS to accurately quantify the chemical composition of Ge-Sb-Te compounds (from 1 to 200 nm) and ultrathin 2D transition metal dichalcogenides (MoS₂, WS₂). Combined WDXRF/XPS analysis was used to determine refined values of composition-dependent relative sensitivity factors for Te4d, Sb4d and Ge3d that allow for XPS-based metrology of PCRAM materials with mastered accuracy. We pointed the need for in-depth study of the significant matrix effects that alter the ability of WDXRF to quantify Nitrogen in Ge-Sb-Te materials: ion beam analysis was carefully investigated as possible input for WDXRF calibration, and a WDXRF protocol was established for inline monitoring of N-doped Ge-Sb-Te films in a specific process window. Finally, we investigated two ways to non-destructively characterize the in-depth chemical distribution in thin chalcogenide films: we demonstrated that the combination of XRF in grazing incidence geometry (GIXRF) and X-ray reflectometry (XRR) was able to unambiguously reveal small process differences along with process-induced diffusion in 10 nm-thick stackings. We showed that the use of multilayered substrate instead of silicon allowed fine-tuning of the depth-dependent X-ray standing wave field, resulting in improved sensitivity of XRR/GIXRF strategies. We also developed an angle-resolved XPS protocol for the evaluation of the first deposition steps of GeTe and Ge₂Sb₂Te₅ films, revealing the process-dependent elemental distribution as a function of the film growth. Therefore, in this work we not only elaborated advanced metrology protocols for the development of new chalcogenide films but also metrological solutions for the next technology nodes (28 nm and below), since current in-line metrology tools reach their detection limits.

This thesis deals with the synthesis and characterization of Ge-Te-Sb (GST) thin films. The films were deposited using a Pulsed Laser Deposition (PLD) method and mainly characterized with XRD, SEM, AFM and TEM. For amorphous and polycrystalline films, un-etched Si(100) was used. The amorphous films showed a similar crystallization behavior as films deposited with sputtering and evaporation techniques. When depositing GST on un-etched Si(100) substrates at elevated substrate temperatures (130-240°C), polycrystalline but highly textured films were obtained. The preferred growth orientation was either GST(111) or GST(0001) depending on if the films were cubic or hexagonal. Epitaxial films were prepared on crystalline substrates. On KCl(100), a mixed growth of hexagonal GST(0001) and cubic GST(100) was observed. The hexagonal phase dominates at low temperatures whereas the cubic phase dominates at high temperatures. The cubic phase is accompanied with a presumed GST(221) orientation when the film thickness exceeds ~70 nm. Epitaxial films were obtained with deposition rates as high as 250 nm/min. On BaF2(111), only (0001) oriented epitaxial hexagonal GST films are found, independent of substrate temperature, frequency or deposition background pressure. At high substrate temperatures there is a loss of Ge and Te which shifts the crystalline phase from Ge2Sb2Te5 towards GeSb2Te4. GST films deposited at room temperature on BaF2(111) were in an amorphous state, but after exposure to an annealing treatment they crystallize in an epitaxial cubic structure. Film deposition on pre-cleaned and buffered ammonium fluoride etched Si(111) show growth of epitaxial hexagonal GST, similar to that of the deposition on BaF2(111). When the Si-substrates were heated directly to the deposition temperature films of high crystal-line quality were obtained. An additional heat treatment of the Si-substrates prior to deposition deteriorated the crystal quality severely. The gained results show that PLD can be used as a method in order to obtain high quality epitaxial Ge-Sb-Te films from a compound target and using high deposition rates.

As the demand for energy increases, competition for a sustainable alternative to non-renewable energy resources has resulted in the growth of the photovoltaic industry. Although most photovoltaic technologies are based on crystalline silicon, thin film technologies have been developed with the expectation of generating a comparably high-performing product with lower processing costs. These materials have demonstrated sufficiently high optoelectronic performance to enable commercialization but concerns such as material scarcity limit terawatt level power production.<div><br></div><div>In the continuous pursuit of earth abundant solar absorber materials appropriate for thin film technologies, enargite Cu3AsS4 has been identified as a promising material due to its ideal direct band gap, stability, and high absorption. Recent efforts have demonstrated this class of copper chalcogenides exhibits band gap tunability and has solution processing capabilities for potentially scalable manufacturing. Furthermore, recent first-principles calculations of enargite Cu3AsS4 have hypothesized this material may have high carrier mobility and defect-tolerant optoelectronic properties, which further support investigation into this material. <br></div><div><br></div><div>In this dissertation, a novel reactive deposition processing route has been developed which has produced dense, single-phase enargite thin films. A champion device efficiency of 0.54% was achieved following a post deposition etching procedure on these films, which demonstrates the density and observable secondary phases were not limiting to initial nanoparticle-based device performances. Together with recent modeling efforts, the non-ideal band alignment with both the back contact and diode junction is concluded to be the primary limiting factor for high efficiency devices. <br></div><div><br></div><div>As this technology contains arsenic, concerns have been raised about its potential carcinogenicity and toxicity. Similar concerns were raised during the development of cadmium telluride technology, but these concerns have been mitigated through careful life cycle analyses and identifying strategies for responsible life cycle management. Therefore, a life cycle analysis and two risk assessments have been completed on Cu3AsS4 systems. Although emissions of arsenic and its contributions to life cycle impacts are expected to be low due to the small quantity required, hot spots have been identified to reduce waste and emissions. Reduction strategies for this material system are found to be applicable to other PV systems and include minimizing molybdenum sputter waste, reusing and recycling balance of system components, and investigating low-energy processing routes on thin substrates. This work serves to establish a basis on which the potential environmental implications of this thin film technology are understood. <br></div><div><br></div><div>This dissertation will serve as a guide toward the technical and environmental development of Cu3AsS4 thin films. Having a life cycle perspective during the systematic development of a technology will enable sustainable engineering. Furthermore, the processing and characterization methods detailed herein are expected to be generally applicable to other copper chalcogenide systems. <br></div>

Atomically thin 2D layered semiconductor materials such as Transition Metal Di-Chalcogenides (TMDCs) have great potential for use as flexible, ultra-thin photovoltaic materials in solar cells due to their favorable photon absorption and electronic transport properties. In this dissertation, the electronic properties, such as band structure and bandgap, and optical absorption properties of a TMDC known as Tungsten Disulfide (WS2) were obtained from Density Functional Theory (DFT) calculations to design conventional and unconventional solar cells. Using these properties, a 1 μm thick heterojunction solar cell based on monolayer and bulk WS2 together with amorphous silicon (a-Si) was modeled using numerical calculations and simulations. The maximum efficiency of this cell is 23.3% with Voc = 0.84 V and Jsc = 33.5 mA/cm2 under the AM1.5G terrestrial solar spectrum. Next, a similar but even thinner solar cell with a thickness of 200 nm, together with a light trapping structure and an anti-reflection coating layer, was modeled under the AM0 space solar spectrum; similar device performance efficiencies around 21-23% were obtained. The performance of these solar cell models is comparable to many commercial cells in both terrestrial and space photovoltaics. As conventional photovoltaics approach the Shockley-Queisser limit, the need for unconventional materials and approaches has become more apparent. Hybrid alloys of TMDCs exhibit tunable direct bandgaps and significant dipole moments. Dark state protection induced by dipole-dipole interactions forms new bright and dark states in the conduction band that reduce radiative recombination and enhance photon-to-electron conversion, leading to significantly higher photocurrents. In our work, current enhancement of up to 35% has been demonstrated by modeling dark state protection in a solar cell composed of Tungsten Diselenide (WSe2) and Tungsten Sulfo-Selenide (WSeS), with the potential to exceed the Shockley-Queisser limit under ideal conditions.

Ionic liquids (ILs) are nowadays a large and widely explored class of ionic compounds that melt below 100 °C. Due to their attractive properties, ILs are now of growing interests in a variety of inorganic materials preparation. However, most studies have put much focus on the description of new synthetic strategies. The chemical reactivity of ILs in the reactions is often neglected. In this dissertation, a series of metal chalcogenides were synthesized using the decompositions of ILs. The role or chemical reactivity of ILs in the reactions was demonstrated in detail. The hierarchical desert-rose-like SrTiO3 particles have been successfully prepared based on an ethylene glycol (EG) mediated one-pot IL-assisted solvothermal synthetic route. The used basic ionic liquid tetrabutylammonium hydroxide (TBAH) serves as an alkaline source and can also replace EG as the sole solvent to synthesize polyhedral SrTiO3, showing “all-in-one” solvent and reactant. A series of metal sulfides, such as Sb2S3, Bi2S3, PbS, CuS, Ag2S, ZnS, and CdS have been obtained from a choline chloride/thioacetamide based deep eutectic solvent (DES, an IL analog solvent) by a simple and general synthetic method. The reaction mainly proceeds in two steps: i) the dispersion of metal salts in the DES and the formation of a metal-DES complex, and ii) the decomposition of the metal-DES complex and formation of the final products. In addition, the chemical reactivity of phosphonium based ILs with selenium and tellurium at above 220 °C was systematically investigated by a series of dissolution experiments, tracking the solute selenium and tellurium species by nuclear magnetic resonance (NMR). NMR results clearly indicate some common decomposition mechanisms for quaternary phosphonium ILs at a relatively high temperature in the presence of selenium or tellurium. The decomposition of the quaternary phosphonium cations should proceed by an elimination of one alkyl substituent via an SN2 reaction, forming the respective trialkylphosphane selenides or tellurides in the presence of selenium or tellurium, which is then responsible for the genuine dissolution of selenium or tellurium. However, in the case of tellurium, the dissolution behavior is much more complicated compared to that of selenium. The coupling of P and Te which indicates a P–Te bond formation is only observed in the NMR spectra when a sufficient amount of tellurium (e.g. Te : IL = 1 : 1) is provided. The existence of a parallel-competitive IL decomposition route besides the SN2 reaction is regarded as the side reaction for the dissolution of tellurium. This may at least partially explain the relatively lower solubility of tellurium in phosphonium based ILs compared to that of selenium.

This Thesis describes the synthesis, reactivity, coordination properties, and catalytic activity of novel electronically dissymmetric bisphosphines structurally related to 1,1'-bis(diphenylphosphino)ferrocene (dppf). First, a methylene spaced congener containing a primary phosphine group, which is stable in the air, Ph2PfcCH2PH2 (fc = ferrocene-1,1'-diyl), was prepared. While studying its reactivity, an unprecedented stable primary phosphine oxide, Ph2PfcCH2P(O)H2, was isolated. The primary phosphine, the corresponding phosphine oxide, dppf and the known bis-tertiary phosphine Ph2PfcCH2PPh2 were studied as ligands in Ru(II) complexes. The catalytic activity of the defined complexes was compared in two ruthenium-catalyzed reactions: cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dimethylfuran and isomerization of estragole to anethole. Second, the remarkable stability of the prepared primary phosphine oxide called for a detailed investigation of this poorly described class of compounds. As a result, stable primary phosphine chalcogenides lacking steric protection FcCH2P(Y)H2 (Fc = ferrocenyl; Y = O, S, Se) were isolated for the first time. These compounds were studied as ligands in reactions with hard and soft Lewis acids (Zn(II) and Ru(II)), and the reactivity of the P-H hydrogens was...

As the UN summit in September 2015 addressed with the Sustainable Development Goals (SDG), our planet faces great challenges.[1] Not only since then has the role of synthetic materials chemistry been discussed in this context.[2–16] This not only concerns the development of new materials with outstanding properties such as catalysts, materials for energy conversion, and cost-efficient energy converting and storage materials, but also a reduction of the energy consumption of established functional material syntheses. Therefore, new approaches addressing the three main categories to promote the potential for energy and resource efficiency have been proposed: lowering the temperature of the synthetic processes, improving the yield and purity of the materials, and reducing the amount of waste materials. In this context a number of low-temperature processes have been established, in which mainly solvents, i.e. amines and alcohols, are used in combination with previously synthesised precursors as the solubility of the starting materials limits their usability and most elements are not soluble in these solvents. Novel solvents like ionic liquids (ILs) showcase growing interest as they are considered particularly resource-efficient.[17,18] ILs are defined as liquids that are comprised entirely of ions, with melting points below 100 °C. Continuing on from the reported work in this field, this thesis focuses on investigating the ability of ILs in the syntheses for known chalcogenides at lower temperatures and the synthesis of new materials. The main focus lies on conversions with high atom economy, especially by starting from the elements and completely recycling the IL afterwards, and mechanistic studies elucidating the intermediate dissolved species. Furthermore, as imidazolium based ILs, and their derived LEWIS-acidic ILs [BMIm]Cl/nAlCl3 mixtures, have proven to be good crystallisation media in inorganic syntheses, and the class of mostly room-temperature liquid ILs (RTILs) based on phosphonium cations [P66614]Cl showcased the ability to dissolve red phosphorous, Pred, and the heavier chalcogens S, Se, and Te, this work mainly focuses on these two IL systems. This was also chosen as an in-depth understanding of the activation and resource-efficient synthesis of these chalcogenides has still not been established. As they are RTILs, they also made the characterisation of the reactive and dissolved species by liquid state NMR, Raman, UV/Vis spectroscopy and electrochemical characterisation possible. This expands the knowledge of which main group elements and ore-like starting materials can be used in ionothermal synthesis. As a starting point the thermoelectrically interesting materials class of tellurides is addressed. The under normal conditions hard to dissolve element tellurium readily dissolves in phosphonium ILs with the cations [P66614]+ and [P4444]+. In ILs with carboxylate anions a deep purple hue of the IL already occurred by dissolving tellurium at temperatures of 60 °C. Investigations on the solutions in the acetate ILs revealed the formation of tellurium anions (Ten)2– with chain lengths up to at least n = 5, which are in a dynamic equilibrium with each other. Since external influences could be excluded and no evidence of an IL reaction was found, disproportionation of the tellurium is the only possible dissolution mechanism. However, the spectroscopic detection of tellurium cations in these solutions is difficult, but the coexistence of tellurium cations, such as (Te4)2+ and (Te6)4+, and tellurium anions could be proven by cyclic voltammetry and electrodeposition experiments. DFT calculations indicate that electrostatic interactions with the ions of the ILs are sufficient in stabilizing both types of tellurium ions in solution.[19] In contrast, the acetate ILs show insufficient conversion in reactions of coin metals (Cu, Ag, Au) with tellurium to the corresponding tellurides, especially at low temperatures, however the chloride ILs successfully synthesise Cu2–xTe, CuTe, AuTe2 and Ag2Te. As the synthesis of the tellurides in neat ILs at temperatures down to 60 °C was only sufficient for the system Ag-Te, with a full conversion of the elements to Ag2Te, this was chosen as a model system for further investigations. Even at room temperature, a quantitative yield was achieved by using either 2 mol% of [P66614]Cl in dichloromethane or a planetary ball mill. The unexpected finding that phosphane-free [P66614]Cl also allows the quantitative synthesis of Ag2Te at 60°C implies an additional activation mechanism independent from the phosphane, which is yet unknown.[20] Subsequently, the manifoldly-used lighter chalcogen sulphur is tested for the synthesis of sulphides. Direct synthesis of binary sulphides of B, Bi, Ge, Mo, Cu, Au, Sn, In, Ti, V, Fe, Co, Ga, Ni, Al, Zn, and Sb in [P66614]Cl was tested at 100 °C, i.e. below the melting point of sulphur. Under these conditions, substantial sulphide formation occurred only for nickel (Ni3S4, Ni3S2, NiS) and copper (Cu2S, CuS). Sb showed no formation of crystalline sulphide, but after addition of EtOH, an orange material precipitated which was identified as amorphous metastibnite.[21] As generating these elements from their ores is highly energy consuming, direct dissolution experiments of the crystalline stibnite in [P66614][OAc] and Cl– were investigated and resulted in yellow solutions, from which the amorphous form can be precipitated upon exposure to EtOH air without any sign of decomposition of the IL. In particular, follow-up investigations were conducted on the solubility of Sb2S3 for follow-up chemistry in the LEWIS-acidic IL [BMIm]Cl · 4.7 AlCl3 at 160 °C which resulted in the formation of the novel chloride-terminated [Sb13S16Cl2]5+ quadruple-heterocubane cation-containing compound [Sb13S16Cl2][AlCl4]5.[21] Addition of CuCl in a slightly modified reaction resulted in the formation of the layered semiconductor Cu(Sb2S3)[AlCl4]. From this the AlCl3 can be leached by treatment with 0.1 molar hydrochloric acid, yielding a compound with the presumed composition Cu(Sb2S3)Cl.[22] As ILs showed to be able to activate elements that are insoluble in common solvents, and the formation of Sb2S3 from reactions mixtures of the elements raised the question of whether only the sulphur forms a mobile species or if antimony could additionally activated, the synthesis of binary antimony compounds directly from elements was explored as they are highly discussed as replacements for silicon-based semiconductors. Therefore the 12 elements Ti–Cu, Al, Ga, In, and Te, which are known to form binary compounds with Sb, were reacted with Sb in [P66614]Cl under inert conditions in a simple closed glass flask with vigorous stirring for 16 h at 200 °C. This resulted in the formation of NiSb, InSb, Cu2Sb and Sb2Te3. The applied reaction temperature is several hundred degrees below the temperatures required for solvent-free conversions. Compared to reactions based on diffusions in the solid state, reaction times are much shorter. The IL is not consumed and can be recycled. Since the reaction with Cu showed almost complete conversion, the influences of reaction time, temperature and medium were further investigated. In a diffusion experiment, Cu2Sb formed on the copper, which indicates that antimony forms mobile species in these ILs. These systematic studies hence deliver a contribution to how ILs can help in the synthesis of new materials and how they can make a difference in the synthesis of inorganic materials as well in the context of “GREEN CHEMISTRY”. This can help in developing a more educated choice/toolbox of IL systems for reducing energy costs by reducing the temperature from high temperature inorganic syntheses to syntheses near room-temperature by using the elements as starting materials, with a high atom economy for the synthesis of known and new materials.