Room-Temperature Synthesis of Transition Metal Clusters and Main Group Polycations from Ionic Liquids

Main group polycations and transition metal clusters had traditionally been synthesized via high-temperature routes by performing reactions in melts or by CTR, at room-temperature or lower temperature by using so-called superacid solvents, and at room-temperature in benzene–GaX3 media. Considering the major problems associated with higher temperature routes (e.g. long annealing time, risk of product decomposition, and low yield) and taking into account the toxicity of benzene and liquid SO2 in room-temperature or lower temperature synthesis, a soft and sustainable chemical approach has been developed, employing a Lewis-acidic IL [bmim]Cl/AlCl3. This new alternative reaction medium has proven to be an excellent solvent system for the single–step synthesis of main group polycations and transition metal clusters. X-ray diffraction and Raman spectroscopy have been used for the structural characterization of the isolated compounds. Physical properties and quantum chemical calculations of some of the compounds have also been carried out

Organophosphorus Chemistry 2018

Organophosphorus chemistry is an important discipline within organic chemistry. Phosphorus compounds, such as phosphines, trialkyl phosphites, phosphine oxides (chalcogenides), phosphonates, phosphinates and >P(O)H species, etc., may be important starting materials or intermediates in syntheses. Let us mention the Wittig reaction and the related transformations, the Arbuzov- and the Pudovik reactions, the Kabachnik–Fields condensation, the Hirao reaction, the Mitsunobu reaction, etc. Other reactions, e.g., homogeneous catalytic transformations or C-C coupling reactions involve P-ligands in transition metal (Pt, Pd, etc.) complex catalysts. The synthesis of chiral organophosphorus compounds means a continuous challenge. Methods have been elaborated for the resolution of tertiary phosphine oxides and for stereoselective organophosphorus transformations. P-heterocyclic compounds, including aromatic and bridged derivatives, P-functionalized macrocycles, dendrimers and low coordinated P-fragments, are also of interest. An important segment of organophosphorus chemistry is the pool of biologically-active compounds that are searched and used as drugs, or as plant-protecting agents. The natural analogue of P-compounds may also be mentioned. Many new phosphine oxides, phosphinates, phosphonates and phosphoric esters have been described, which may find application on a broad scale. Phase transfer catalysis, ionic liquids and detergents also have connections to phosphorus chemistry. Green chemical aspects of organophosphorus chemistry (e.g., microwave-assisted syntheses, solvent-free accomplishments, optimizations, and atom-efficient syntheses) represent a dynamically developing field. Last, but not least, theoretical approaches and computational chemistry are also a strong sub-discipline within organophosphorus chemistry

Characterization of Electronic and Ionic Transport in Soft and Hard Functional Materials

Control over concurrent transport of multiple carrier types is desired in both soft and hard materials. For both types of materials, I demonstrate ways to characterize and execute governance over both electronic and ionic transport, and apply these concepts in the fabrication of devices with applications in conducting composites, photovoltaics, electrochemical energy storage, and memristors. In soft materials, such as polymers, the topology of the binary polymer mesoscale morphology has major implications on the charge/ion transport. Traditional approaches to co-continuous structures involve either using blends of polymers or diblock copolymers. In polymer blends, the structures are kinetically trapped and thus have poor long term stability. In diblock polymers, such morphologies are not universally accessible to non-random coil polymers. I discuss an approach to binary polymer mesoscale morphologies via the assembly of polymer nanoparticles. In this strategy, polymers are assembled into spherical nanoparticles, which are then assembled into hierarchical mesoscale structures. First, I demonstrate, experimentally and computationally, that the electrical transport in semiconducting/insulating polymer nanoparticle assemblies can be predictably tuned according to power law percolation scaling. Then I show that nanoparticle assemblies can be utilized for tunable concurrent transport of electrons and holes for photovoltaics, and for electronic and ionic charges aimed at applications in electrochemical energy storage. For hard materials, I detail the characterization of mixed electronic and ionic transport in hybrid organic/inorganic lead triiodide perovskites. I used the understanding of mixed electronic and ionic transport in these materials to explain poorly understood phenomena such as photo-instability and current-voltage hysteresis. Then, I show several examples of interfacial materials, and the characterization and implications of their respective work functions, as charge transport materials to control selective charge extraction from perovskites. And finally, I show how interfacial charge transport materials with ionic functionality can be used to change the interfacial chemistry at perovskite/charge transport material interfaces to control both electronic and ionic transport. In this regard, I demonstrate how an adsorbing interface for mobile ions can be used to control current-voltage hysteresis and state-dependent resistance, introducing a novel paradigm of interfacial ion adsorption to fabricate novel perovskite-based memristor devices

Boron-centred soft ligands and their complexes with Na, K, Bi(III) and Pb(II) ions : an approach towards inexpensive luminescent materials

Muhammad I. Boron-centred soft ligands and their complexes with Na, K, Bi(III) and Pb(II) ions : an approach towards inexpensive luminescent materials. Bielefeld: Universität Bielefeld; 2014.The proposed chemistry in this project was aimed for the fundamental exploration of the preparative accessibility and properties of a broad range of boron centred soft ligands and their metal complexes particularly with bismuth(III) ions, investigation of their structures in the solid and solution state followed by preliminary photo-physical measurements and optimization of the emitter quality after a feed-back from such measurements. Consequently three main types of soft ligands were synthesized. (1) Tri-substituted boron-centred soft ligands (Janus scorpionate ligands), (2) di-substituted boron-centred soft ligands (3) heterocyclic precursors as soft ligands. Two novel Janus scorpionate ligands [TrMe]– and [TttMe]– were produced in-situ by the reaction of MBH4 and respective heterocycle (3-mercapto-4-methyl-1,2,4-triazole and 5-mercapto-1-methyltetrazole) and were isolated in the form of alkali metal complexes [MTrMe] (1 & 2) and [MTttMe] (3 & 4) (M = K, Na), respectively. Later on, two mixed complexes such as [NaK(TrMe)2] (5) and [NaK(TttMe)2] (6) were also synthesized with the intention to observe Janus type coordination behaviour and orientation of Na and K towards hard and soft sites of these ligands. These alkali metal complexes exhibit polymeric and sheet-like structures in solid state. K[TrMe] (2), Na[TttMe] (3) and Na[HB(mtdaMe)3] (11)[65] (11 is a reported Janus scorpionate ligand) were reacted with BiX3 (X = Cl–, I–, NO3– and CH3COO–) to afford bismuth complexes [Bi(TrMe)(Cl)(µ-Cl)2]2 (12) and [Bi(TrMe)(Cl)2(µ-Cl)]n (13), [Bi(TttMe)2(CH3COO)] (14), [{HB(mtdaMe)3}2BiCl] (15), [{HB(mtdaMe)3}2Bi(NO3)]n (16) and Na[{HB(mtdaMe)3}2BiI2] (17). The resulting bismuth complexes are monomeric (14, 15 and 17), dimeric (12) and polymeric (13, 16) in nature. Except 17, all of them have distorted geometries with stereochemically active lone pairs on the bismuth atoms. In contrast to Trofimenko’s protocol for 1 – 6, alkali metal complexes [NaBb] (7), [NaBtMe] (8), [NaBttPh] (9) and [KBttMe] (10) of di-substituted boron-centred soft ligands were prepared using THF/toluene solutions. [NaBb] (7), [NaBtMe] (8), [NaBttPh] (9) were reacted with BiX3 (X = Cl–, CH3COO–) to yield bismuth complexes [BiBb2Cl] (18), [BiBbCl(µ Cl)2]2 (19), [BiBtMe3]•CH2Cl2 (20), [BiBtMe3]•CHCl3 (21), [Bi(L2)2]2•THF (22) and [Bi(L2)2]2•2CH3CN (23). Complex 18 exhibits a (B)H...Bi interaction at 2.58 Å which is unprecedented in bismuth chemistry. Complexes 22 and 23 have Bi2+ instead of Bi3+ as central ions which is because of a reduction reaction which occurred during their synthesis. The third category of heterocyclic precursors as soft ligands (3-mercapto-4-methyl-1,2,4-triazole (L1H), 2-mercapto-benzimidazole (L2H), 2-mercapto-4-methylthiazole (L3H) and 2-mercapto-4-phenylthiazole (L4H)) upon reaction with BiCl3 resulted in bismuth complexes [Bi(L1H)4(Cl)2]Cl (24), [Bi(L1H)4Cl2][Bi(L1H)2Cl4] (25), [Bi(L2H)2Cl2(µ-Cl)]2 (26) and [Bi(L4)3] (27). These complexes possess relatively regular coordination geometries when compared with above two types of bismuth complexes 12 – 17 and 18 – 23. Generally the Bi–S bond lengths in 24 – 27 are shorter revealing strong coordination compared to 12 – 23. Finally three mixed-ligand bismuth complexes [{HB(mtdaMe)3}Bi(phen)Cl2] (29), [{HB(mtdaMe)3}Bi(bipy)Cl2] (30) and [BttMeBi(phen)Cl2] (31) were prepared by using boron-centred soft ligands as primary ligands. 29 and 30 feature interestingly (B)H...Bi interactions at 2.76(3) Å for 29 and 2.71(2) Å for 30; these are weaker compared to 2.58 Å found in 18. Lead(II) complexes were also synthesized by the reaction of a tri-, a di-substituted boron-centred soft ligand and eight small heterocyclic soft ligands with Pb(NO3)2. The resulting complexes are [Pb(L1)2(L7H)2Lʹ] 33 (where Lʹ is 1-methyl-2-pyrrolidinone), [PbL22] 34 (where L2 = dihydrobis(thiazolyl)borate(BtMe)), [PbL32(NO3)2] 35, [PbL43(μ-L4)(NO3)2]2 36, [Pb(L5)(L5H)2(NO3)(H2O)]n 37, [PbL64(NO3)2] 38, [Pb(L7)2(L7H)]n 39a, [Pb(L7)2(L7H)(CH3OH)]n 39b, [PbL82]n 40, [PbL92]n 41, [PbL102]n 42. The coordination numbers of these complexes vary from 4 to 8 and the majority of them are polymeric in nature with hemidirected environments around the lead ions. Preliminary photo-physical studies were carried out on a few selected bismuth complexes such as 12, 20, 24, 25 etc. Generally, it has been observed that upon complexation of the Bi(III) ion by heterocyclic thione units, the π-π* absorption band are bathochromically shifted. MC sp transitions were also observable. Some of the complexes are not emissive in solution, however, at 77 K in ethanol glasss show emission bands (e.g 25 exhibit this band at 537 nm). 25 also exhibits thermochromic behaviour, its crystalline sample is orange at room temperature and changes its colour to yellow when cooled with liquid nitrogen. Conclusively this work provided a successful approach to study the versatile coordination behavior (such as κ3-S,S,S, κ2-S,S, κ1-S, κ3-H,S,S, κ4-H,S,S,S; κ2-H,S, κ3-H,H,S, κ3-H,N,S, κ3-N,N,N, κ2-N,N and κ1-N) of tri- and di-substituted boron-centred soft ligands towards Na, K, Bi(III) and Pb(II) ions. Additionally for bismuth complexes, the use of different anions or conjugated neutral systems as co-ligands influenced the stereochemically activity of lone pair resulting interesting bonding situations e.g unprecedented B–H...Bi interactions. These unprecedented interactions in bismuth chemistry can be further explored to investigate bismuth-hydride activation or Bi→B dative bond formation (metalloboranes). Bismuth complexes based on smaller soft heterocyclic ligands were found to be better luminescent compared to those based on tri- and di-substituted boron-centred soft ligands, as the former lead to a stronger binding of the ligand (as revealed from M–S bond lengths) and to an enhanced interaction between metal-centred and ligand-centred molecular orbitals thus enhancing the desired spin-orbit coupling effects. From these preliminary luminescence studies, it can be suggested that if such soft systems are used and the lewis-acidity of the bismuth atom is further increased by some electron withdrawing groups like perfluoro alky/aryl substituents etc., the desire of strong spin-orbit coupling effects as well as the stability of the complexes will be enhanced and this approach will decisively contribute to further improvement of luminescence activity for their potential applications in displays and area light sources

Feature Papers in Compounds

This book represents a collection of contributions in the field of the synthesis and characterization of chemical compounds, natural products, chemical reactivity, and computational chemistry. Among its contents, the reader will find high-quality, peer-reviewed research and review articles that were published in the open access journal Compounds by members of the Editorial Board and the authors invited by the Editorial Office and Editor-in-Chief

A review of the structural architecture of tellurium oxycompounds

Relative to its extremely low abundance in the Earth's crust, tellurium is the most mineralogically diverse chemical element, with over 160 mineral species known that contain essential Te, many of them with unique crystal structures. We review the crystal structures of 703 tellurium oxysalts for which good refinements exist, including 55 that are known to occur as minerals. The dataset is restricted to compounds where oxygen is the only ligand that is strongly bound to Te, but most of the Periodic Table is represented in the compounds that are reviewed. The dataset contains 375 structures that contain only Te cations and 302 with only Te, with 26 of the compounds containing Te in both valence states. Te was almost exclusively in rather regular octahedral coordination by oxygen ligands, with only two instances each of 4- and 5-coordination. Conversely, the lone-pair cation Te displayed irregular coordination, with a broad range of coordination numbers and bond distances. A threshold was applied for Te-O links of ~2.45 Å or 0.3 valence units with some flexibility, as a criterion to define strongly bound Te-O polymers and larger structural units. Using this criterion, Te cations display one-sided 3-, 4- or 5-coordination by oxygen (with rare examples of coordination numbers 2 and 6). For both valence states of Te, examples are known of TeO complexes which are monomeric (m = 1; neso), noncyclic finite oligomers (soro), rings (cyclo), infinite chains (ino), layers (phyllo) and frameworks (tecto tellurates). There is a clear analogy to the polymerization classes that are known for silicate anions, but the behaviour of Te is much richer than that of Si for several reasons: (1) the existence of two cationic valence states for Te; (2) the occurrence of multiple coordination numbers; (3) the possibility of edge-sharing by TeO polyhedra; (4) the possibility for oxygen ligands to be 3-coordinated by Te; and (5) the occurrence of TeO polymers that are cationic, as well as neutral or anionic. While most compounds contain only one or two symmetrically distinct types of Te atom, Pauling's Fifth Rule is frequently violated, and stoichiometrically simple compounds such as CaTeO can have polymorphs with up to 18 distinct Te sites. There is a tendency for local symmetry features such as the threefold axis of a TeO octahedron or the acentric symmetry of a TeO polyhedron to be inherited by the host structure; the latter in particular can lead to useful physical properties such as nonlinear optical behaviour. We develop for the first time a hierarchical taxonomy of Te-oxysalt structures, based upon (1) valence state of Te; (2) polymerization state of TeO complexes; (3) polymerization state of larger strongly-bound structural units that include non-Te cations. Structures are readily located and compared within this classification

Filling Single-Walled Carbon Nanotubes with Highly Reactive Chemicals

Since the discovery of single-walled carbon nanotubes (SWCNTs) in 1993, there has been a deep fascination with the 1D (one dimensional) nanometre sized cavity that they possess. Having the ability to confine all manner of materials in such a small space had never been possible before, and the surge of new allotropes and chemicals that have either been grown or encapsulated in this nano-test tube has been staggering. Salts and elements have formed the bulk of the confined materials, but chemistry has also been achieved within the cavity, and the reduction of metal oxides has proven straightforward. Consistency in filling SWCNTs in high yields has been difficult to achieve and finding a routine technique that can ascertain a filling yield have been stumbling blocks for the research area. No standard definition of the filling yield has even been agreed upon. These issues have held the field back from becoming a more popular and viable method for enhancing the properties of SWCNTs. To combat some of these issues, this thesis uses consistent and simple practices to determine the filling yield and aims to make consistently high purity materials which can be used for novel purposes. Elemental phosphorus, arsenic and antimony have all been confined within a range of SWCNTs and have been fully characterised to determine their properties. Tetrahedral phosphorus and arsenic molecules have been stabilised by this method in quantities higher than achieved using other techniques. These can be produced either from melt reactions or vapour phase fillings which confirms that these elements fill the voids of the SWCNT in the form of tetrahedral molecules. The confined phosphorus and arsenic tetrahedra have been shown form two new allotropes namely the zigzag ladders and single zigzag chains. These are expected to form either from thermal excitation or when exposed to an electron beam during high resolution transmission electron microscopy (HRTEM). The structure produced is dependent on the diameter of nanotube and has shown consistent results with what is predicted by DFT calculations. There seems to be some dynamic behaviour at play between the conversion of the allotropes due to the small activation energy calculated for transitioning between the structures. SWCNTs have also been filled with aluminium iodide, a strong Lewis acid, in order to induce charge transfer effects. A reliable method of producing high purity samples was developed and Raman spectroscopy has shown that these materials show chargetransfer in the correct direction. Unfortunately, despite the enhanced properties of the SWCNTs, the samples were found to be no more effectively functionalised than their empty counterparts

Soluble Copper(I) - C halcogenone s : Synthesis, Characterization and Catalytic Applications

The focus on copper chalcogenide chemistry is experiencing continuous growth and interest over last few decades owing to their novel properties and significant applications in materials chemistry. The property of copper chalcogenides is mainly controlled by ch alcogen sources. For example, the recent works have also witnessed the active role of decade old ligand system imidazolin - 2 - chalcogenones for this endeavor. Notably, imidazolin - 2 - chalcogenon ligands have potential to serve as a ligand with copper in medici ne. Some other potential applications of these imidazolin - 2 - chalcogenone ligand supported copper included their use as precursor for nanomaterial synthesis and co - ligand in catalysis. However, these recent efforts have not answered the critical questions s uch as, do “homoleptic two coordinated” key intermediates exist in the catalytic process? How essential is “more π accepting imidazoline - 2 - selone” to isolate the homoleptic two coordinated coinage metal derivatives? In order to address these challenges , th is thesis deals with the t hree main aspects of Imidazolin - 2 - chalcogenones (ImC), su c h as (1) synthesis o f soluble copper(I) chalcogenone , (2) catalytic efficiencies of ImC ‒ Cu complexes , and comparison of catalytic activity of ImC‒Cu with NHC ‒ Cu (Chart A) . Indeed, twenty one new structurally interesting copper(I) chalcogenones have been isolated and characterized by CHN analysis, FT - IR, multinuclear NMR, TGA, UV - vis, and single crystal X - ray diffraction techniques. These new molecules are found to be very active catalysts in ‘cabon - boron ’ , ‘cabon - nitrogen’ and ‘carbon - silicon’ bond formation reactions

Exploring Nanoscale Optoelectronic Properties of Kesterite- and Perovskite-based Devices

Emerging photovoltaic materials such as kesterite and perovskite for optoelectronic devices have inevitable defects that affect the device performance. Therefore, examining the optoelectronic properties of defects is crucial to improve the device performance. Scanning probe microscopy (SPM) is one of the essential techniques to investigate various properties of materials at nanoscale with high resolution. This thesis focuses on characterising kesterite and perovskite using SPM technique to elucidate nanoscale charge transport properties. This primary objective of the first part of this thesis is to understand the effect of compositional variation of kesterite on optoelectronic properties at nanoscale by controlling tin content during the precursor process. This work demonstrated the highest A-type [ZnCu + VCu] defect and altered distribution of sulfur with high near-surface accumulation at an optimised compositional ratio. This synergetic outcome facilitated carrier separation across grain boundaries (GBs). Moreover, the open-circuit voltage deficit was significantly reduced at an optimum compositional ratio owing to improving charge transport through GBs, thereby exhibiting an improved power conversion efficiency. Furthermore, this thesis examines the effect of passivation strategies in halide perovskite for indoor applications using phenethylammonium iodide (PEAI) and lead(II) chloride (PbCl2). A homogenous charge separation across a surface of perovskite was observed when an adequate amount of PEAI was deposited on the perovskite surface. In addition, incorporation of PbCl2 facilitated effective charge transport through GBs. Both strategies facilitated carrier transport towards the surface of perovskite with less ion migration and reduced non-radiative recombination, thereby improving the performance of indoor perovskite solar cells. Finally, another aspect of this thesis is to investigate the optoelectronic properties of two-dimensional perovskite single crystal (butylammonium lead bromide, BA2PbBr4) and elucidate their effect of these optoelectronic properties on the performance of photodetectors (PDs). Accumulation of charge carriers increased at edges with increasing the edge height. Furthermore, the existence of multiple sub-bandgap states in BA2PbBr4, and increasing electron transitions from sub-bandgap states with higher edge height were observed with increasing edge height. This work suggests that edge-height dependence of charge-carrier behaviour in BA2PbBr4 can be utilised in broadband PDs