Radical synthesis of trialkyl, triaryl, trisilyl and tristannyl phosphines from P₄

A reaction scheme has been devised according to 3 RX + 3 Ti(III) + 0.25 P₄ → PR₃ + 3 XTi(IV), wherein RX = PhBr, CyBr, Me₃SiI or Ph₃SnCl, with contrasting results in the case of more hindered RX. The scheme accomplishes the direct radical functionalization of white phosphorus without the intermediacy of PCl₃

Probing Surface Defects of InP Quantum Dots Using Phosphorus Kα and Kβ X-ray Emission Spectroscopy

Synthetic efforts to prepare indium phosphide (InP) quantum dots (QDs) have historically generated emissive materials with lower than unity quantum yields. This property has been attributed to structural and electronic defects associated with the InP core as well as the chemistry of the shell materials used to overcoat and passivate the InP surface. Consequently, the uniformity of the core–shell interface plays a critical role. Using X-ray emission spectroscopy (XES) performed with a recently developed benchtop spectrometer, we studied the evolution of oxidized phosphorus species arising across a series of common, but chemically distinct, synthetic methods for InP QD particle growth and subsequent ZnE (E = S or Se) shell deposition. XES afforded us the ability to measure the speciation of phosphorus reliably, quantitatively, and more efficiently (with respect to both the quantity of material required and the speed of the measurement) than with traditional techniques, i.e., X-ray photoelectron spectroscopy and magic angle spinning solid state nuclear magnetic resonance spectroscopy. Our findings indicate that even with deliberate care to prevent phosphorus oxidation during InP core synthesis, typical shelling approaches unintentionally introduce oxidative defects at the core–shell interface, limiting the attainable photoluminescence quantum yields

A Compact Dispersive Refocusing Rowland Circle X-ray Emission Spectrometer for Laboratory, Synchrotron, and XFEL Applications

X-ray emission spectroscopy is emerging as an important complement to x-ray absorption fine structure spectroscopy, providing a characterization of the occupied electronic density of states local to the species of interest. Here, we present details of the design and performance of a compact x-ray emission spectrometer that uses a dispersive refocusing Rowland (DRR) circle geometry to achieve excellent performance for the 2 - 2.5 keV energy range. The DRR approach allows high energy resolution even for unfocused x-ray sources. This property enables high count rates in laboratory studies, comparable to those of insertion-device beamlines at third-generation synchrotrons, despite use of only a low-powered, conventional x-ray tube. The spectrometer, whose overall scale is set by use of a 10-cm diameter Rowland circle and a new small-pixel CMOS x-ray camera, is easily portable to synchrotron or x-ray free electron beamlines. Photometrics from measurements at the Advanced Light Source show somewhat higher overall instrumental efficiency than prior systems based on less tightly curved analyzer optics. In addition, the compact size of this instrument lends itself to future multiplexing to gain large factors in net collection efficiency, or its implementation in controlled gas gloveboxes either in the lab or in an endstation.Comment: Submitted, Review of Scientific Instrument

Organic building blocks at inorganic nanomaterial interfaces

This tutorial review presents our perspective on designing organic molecules for the functionalization of inorganic nanomaterial surfaces, through the model of an “anchor-functionality” paradigm. This “anchor-functionality” paradigm is a streamlined design strategy developed from a comprehensive range of materials (e.g., lead halide perovskites, II–VI semiconductors, III–V semiconductors, metal oxides, diamonds, carbon dots, silicon, etc.) and applications (e.g., light-emitting diodes, photovoltaics, lasers, photonic cavities, photocatalysis, fluorescence imaging, photo dynamic therapy, drug delivery, etc.). The structure of this organic interface modifier comprises two key components: anchor groups binding to inorganic surfaces and functional groups that optimize their performance in specific applications. To help readers better understand and utilize this approach, the roles of different anchor groups and different functional groups are discussed and explained through their interactions with inorganic materials and external environments

Nb-mediated synthesis of P-rich molecules

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2010.Vita. Page 224 blank. Cataloged from PDF version of thesis.Includes bibliographical references.The use of a sterically demanding enolate ligand -OC[2Ad]Mes supported by niobium has allowed for the synthesis of (Mes[2Ad]CO) 3Nb=PP7Nb(OC [2Ad]Mes)3 through P4 coupling by a low-valent niobium intermediate. This asymmetric phosphorus-rich cluster harbors a niobium phosphinidene unit bound to a niobium-supported P7 cluster. The phosphinidene terminus was found to react with a range of ketones to give phosphaalkene complexes R2C=PP7Nb(OC[2Ad]Mes) 3. These phosphaalkenes are unstable towards intramolecular rearrangement to give R2CP8Nb(OC[ 2Ad]Mes)3 in which the carbene unit has been internalized into the P8 cage. This rearrangement was studied through both Eyring and Hammett analyses. Structrually the new R2CPsNb(OC[2Ad]Mes)3 are viewed as coordinated-diphosphenes and it was found that the diphosphene unit could be liberated and trapped by reaction with pyridine-N-oxide in the presence of excess 1,3-cyclohexadiene, generating niobium oxo and R2CP8(C 6H8). Searching for new platforms to investigate niobium-phosphorus chemistry led to the synthesis of [Na(THF) 3][P3Nb(ODipp) 3], an anionic cyclo-P3 complex that is accessible in two steps from commercially available reagents. It was discovered that [Na(THF) 3] [P3Nb(ODipp) 3] could function as a source of P3 3-, which has allowed for the synthesis of the tetraatomic molecule AsP 3 as a pure substance for the first time. AsP 3 has been studied by gas-phase electron diffraction, photoelectron spectroscopy, solid-state NMR spectroscopy, raman spectroscopy, as well as high resolution mass spectrometry, and a variety of quantum chemical calculations. Further, a wide array of AsP3 reaction chemistry has been probed including the synthesis and structural characterization of two metal complexes with a coordinated, intact AsP3 ligand. Motivated to explore the chemistry of [Na(THF)3][P3Nb(ODipp) 3] further, a series of investigations were carried out to generate substituted triphosphirene ligands complexed to niobium. In particular Ph3SnP3Nb(ODipp) 3 was prepared and was found to react cleanly and efficiently with pyridine-N-oxide in the presence of an excess of 1,3-cyclohexadiene to generate the niobium oxo complex and Ph3SnP3(C6H8), the product of a Diels-Alder reaction between the liberated triphosphirene and 1,3-cyclohexadiene. This unusual phosphorus-rich molecule was exploited in a number of transformations. One reaction of particular interest was the synthesis of P3Rh(PPh 3)3 from Ph3SnP3(C6Hg) and Wilkinson's catalyst (ClRh(PPh3)3) with loss of 1,3-cyclohexadiene and ClSnPh3- This transformation is an illustrative example of the ability of Ph3SnP 3(C6H8) to act as a P3 transfer agent.Brandi M. Cossairt.Ph.D