Ultra-broad near-infrared photoluminescence from crystalline (K-crypt)2Bi2 containing [Bi2]2- dimers

For the first time, we report that a single crystal of (K-crypt)2Bi2 containing [Bi2]2+ displays ultra-broad near-infrared photoluminescence (PL) peaking at around 1190 nm and having a full width at the half maximum of 212 nm, stemming from the inherent electronic transitions of [Bi2]2+.The results not only add to the number of charged Bi species with luminescence, but also deepen the understanding of Bi-related near-infrared emission behavior and lead to the reconsideration of the fundamentally important issue of Bi-related PL mechanisms in some material systems such as bulk glasses, fibers, and conventional optical crystals

Heavy alkaline earth metal amides: Synthetic and structural investigations

During the last decade, heavy alkaline earth organometallic chemistry has emerged from obscurity to becoming a vibrant area of research, owing to a number of synthetic pathways that provide reliable access to these highly reactive target compounds. Nevertheless, synthetic methodologies are all associated with various disadvantages. Thus, the development of improved synthetic routes will have a significant impact on the further development of alkaline earth metal chemistry. Further, analysis of recent work emphasizes difficulties associated with the predictions of the coordination chemistry of these large metals, thus preventing the urgently needed structure/function correlation. As such, the study of ligand and donor effects on the coordination chemistry of these metals provides an avenue for further advancement of alkaline earth organometallics. Part I of this thesis analyzes, in detail, parameters responsible for the coordination chemistry of alkaline earth metal amides, ultimately providing the tools for the development of novel materials for chemical vapor deposition to allow the preparation of advanced precursor materials. Part II evaluates a novel synthetic methodology that provides facile, reliable, inexpensive access to alkaline earth metal amides circumventing many of the known synthetic difficulties associated with the well-established procedures. Importantly, this synthetic methodology represents an environmentally conscious synthetic route, that is amenable towards other ligand systems (i.e. N(R)(SiMe 3 ) (R = SiMe 3 ; 2,4,6-Me 3 C 6 H 2 ; 2,6- i Pr 2 C 6 H 3 ) thus providing unprecedented access to organo alkaline earth metal derivatives. The final part of this work reports on preliminary studies geared to preparing non silylated amides in an attempt to address the commonly observed problem of N-Si bond cleavage in the silylated complexes. This work will ultimately provide attractive precursors for synthetic and solid-state applications

Gas Source Techniques for Molecular Beam Epitaxy of Highly Mismatched Ge Alloys

Ge and its alloys are attractive candidates for a laser compatible with silicon integrated circuits. Dilute germanium carbide (Ge1−xCx) offers a particularly interesting prospect. By using a precursor gas with a Ge4C core, C can be preferentially incorporated in substitutional sites, suppressing interstitial and C cluster defects. We present a method of reproducible and upscalable gas synthesis of tetrakis(germyl)methane, or (H3Ge)4C, followed by the design of a hybrid gas/solid-source molecular beam epitaxy system and subsequent growth of defect-free Ge1−xCx by molecular beam epitaxy (MBE). Secondary ion mass spectroscopy, transmission electron microscopy and contactless electroreflectance confirm the presence of carbon with very high crystal quality resulting in a decrease in the direct bandgap energy. This technique has broad applicability to growth of highly mismatched alloys by MBE

A comparative study of (poly)ether adducts of alkaline earth iodides – an overview including new compounds

New homoligand and mixed-ligand adducts of the heavier alkaline earth metal (Ca, Sr, Ba) halides with oxygen-donor polyether ligands have been isolated and characterized and are compared with previously obtained compounds of the same class in order to give an overview on structures and properties. Homoligand halide adducts, discussed herein, are [CaI(DME)₃]I (1), trans-[SrI₂(DME)₃] (2), trans-[BaI₂(DME)₃] (3), (DME = ethylene glycol dimethyl ether), [CaI(diglyme)₂]I (4), cis-[SrI₂(diglyme)₂] (5), trans-[BaI₂(diglyme)₂] (6),(diglyme = diethylene glycol dimethyl ether, [SrI(triglyme)₂]I (7), and [BaI(triglyme)₂]I (8), (triglyme = triethylene glycol dimethyl ether). Introduction of the mono-coordinating THF ligand (THF = tetrahydrofuran) in the coordination sphere of 1, 2, 3, 4 allows the formation of the new mixed-ligand compounds trans-[CaI₂(DME)₂(THF)] (9), trans-[SrI₂(DME)₂(THF)] (10), trans-[BaI₂(DME)₂(THF)₂] (11), and trans-[CaI₂(diglyme)₂(THF)₂] (12). These compounds were obtained from the metal halide salts in solution with pure or mixtures of ether solvents. While compounds 1–8 appear to be very stable and non-reactive, adducts 9–12 present a comparable reactivity to the well known THF adducts [MI₂(thf)n] (M = Ca, n = 4; Sr, Ba, n = 5)

A Modern Twist to a Classic Synthetic Route: Ph₃Bi-Based Redox Transmetalation Protolysis (RTP) for the Preparation of Barium Metalorganic Species

This paper reports advances in redox transmetalation/protolysis (RTP) utilizing the readily available Ph₃Bi for the synthesis of a series of barium metal-organic species. On the basis of easily available starting materials, an easy one-pot procedure, and workup, we have obtained BaL₂ compounds (L = bis­(trimethyl­silyl)­amide, phenyl­(trimethyl­silyl)­amide, penta­methyl­cyclo­penta­dienide, fluorenide, 2,6-di-isopropylphenolate, and 3,5-diphenyl­pyrazolate) quantitatively by sonication of an excess of barium metal with triphenyl­bismuth and HL in per­deutero­tetra­hydrofuran, as established by NMR measurements. Rates of conversion are affected by both p<i>K</i>_a and bulk of HL. Competition occurs from direct reaction of Ba with HL, thereby enhancing the overall conversion, the effect being pronounced for the less bulky and more acidic ligands. Overall, the method significantly adds to the synthetic armory for barium metal-organic/​organometallic compounds