Exploratory Synthesis Research Articles

ChemInform Abstract: Superheated Solvent Media for Organometallic (Poly)chalcogenide Cluster Synthesis

Abstract Solvothermal reactions in superheated aqueous and nonaqueous solvent media have led to many new metal-carbonyl chalcogenido clusters. This efficient synthetic technique, usually applied to synthesize solid state materials, is also surprisingly useful in preparing molecular clusters in crystalline form. Thus, many of the often laborious purification and separation procedures which are associated with conventional solution methods can be avoided. This method holds substantial promise for the exploratory synthesis of inorganic/organometallic compounds. In this short account we intend to focus on the contributions of the solventothermal technique to the organometallic polytelluride cluster chemistry.

Practical routes to (SiH3)3P: Applications in group IV semiconductor activation and in group III–V molecular synthesis

The (SiH₃)₃P hydride is introduced as a practical source for n-doping of group IV semiconductors and as a highly-reactive delivery agent of -(SiH₃)₂P functionalities in exploratory synthesis. In contrast to earlier methods, the compound is produced here in high purity quantitative yields via a new single-step method based on reactions of SiH₃Br and (Me₃Sn)₃P, circumventing the need for toxic and unstable starting materials. As an initial demonstration of its utility we synthesized monosubstituted Me₂M-P(SiH₃)₂ (M = Al, Ga, In) derivatives of Me₃M containing the (SiH₃)₂P ligand for the first time, in analogy to the known Me₂M-P(SiMe₃)₂ counterparts. A dimeric structure of Me₂M-P(SiH₃)₂ is proposed on the basis of spectroscopic characterizations and quantum chemical simulations. Next, in the context of materials synthesis, the (SiH₃)₃P compound was used to dope germanium for the first time by building a prototype p(++)Si(100)/i-Ge/n-Ge photodiode structure. The resultant n-type Ge layers contained active carrier concentrations of 3-4 × 10¹⁹ atoms cm⁻³ as determined by spectroscopic ellipsometry and confirmed by SIMS. Strain analysis using high resolution XRD yielded a Si content of 4 × 10²⁰ atoms cm⁻³ in agreement with SIMS and within the range expected for incorporating Si₃P type units into the diamond cubic Ge matrix. Extensive characterizations for structure, morphology and crystallinity indicate that the Si co-dopant plays essentially a passive role and does not compromise the device quality of the host material nor does it fundamentally alter its optical properties.

Exploratory Synthesis: The Fascinating and Diverse Chemistry of Polar Intermetallic Phases†This article is based on J. D. Corbett’s address upon receipt of the 2008 American Chemical Society’s F. Albert Cotton Award in Synthetic Inorganic Chemistry sponsored by the F. Albert Cotton Endowment Fund.

Exploratory synthetic adventures regarding the inorganic chemistry of polar intermetallic phases have proven to be especially productive of novel compositions, new and unprecedented structures, and unusual bonding regimes. Reactions of diverse elements with widely different electronegativities allow the definition of two opposed classes of products: polycationic or polyanionic clusters or networks of metals paired with the corresponding monatomic anions or cations. These can be usefully viewed as intermetallic "salts", redox products of simpler neutral intermetallic systems but with widely different factors governing their stabilities. Thus, combinations of rare-earth metals alone or with late transition metals form a novel variety of polymetal network structures with relatively isolated telluride (or halide) spacer anions. Similarly, extensions of traditional Zintl phases of the alkali or alkaline-earth metals from the later p elements to the earlier triels, Ga-Tl especially, yield many new and elegant polyanionic structures. The substitution or addition of still earlier p or late d metal components produces still electron-poorer and more condensed polar intermetallic phases with increasingly delocalized bonding, higher coordination numbers, and more unusual structures and bonding. These discoveries have also led to new approaches: electronic tuning via band calculations to generate new families of quasicrystals and their crystalline approximants with their characteristic structural regimes and regularities. Gold as a substituent generates particularly novel bonding in arrays of mixed metals or polygold anionic networks.

Keeping the Ball Rolling: Fullerene-like Molecular Clusters

The discovery of fullerenes in 1985 opened a new chapter in the chemistry of highly symmetric molecules. Fullerene-like metal clusters, characterized by (multi)shell-like structures, are one rapidly developing class of molecules that share this shape. In addition to creating aesthetically pleasing molecular structures, the ordered arrangement of metal atoms within such frameworks provides the opportunity to develop materials with properties not readily achieved in corresponding mononuclear or lower-nuclearity complexes. In this Account, we survey the great variety of fullerene-like metal-containing clusters with an emphasis on their synthetic and structural chemistry, a first step in the discussion of this fascinating field of cluster chemistry. We group the compounds of interest into three categories based on the atomic composition of the cluster core: those with formal metal-metal bonding, those characterized by ligand participation, and those supported by polyoxometalate building blocks. The number of clusters in the first group, containing metal-metal bonds, is relatively small. However, because of the unique and complex bonding scenarios observed for some of these species, these metalloid clusters present a number of research questions with significant ramifications. Because these cores contain molecular clusters of precious metals at the nanoscale, they offer an opportunity to study chemical properties at size ranges from the molecular to nanoscale and to gain insights into the electronic structures and properties of nanomaterials of similar chemical compositions. Clusters of the second type, whose core structures are facilitated by ligand participation, could aid in the development of functional materials. Of particular interest are the magnetic clusters containing both transition and lanthanide elements. A series of such heterometallic clusters that we prepared demonstrates diverse magnetic properties including antiferromagnetism, ferrimagnetism, and ferromagnetism. Considering the diversity of their composition, their distinct electronic structures, and the disparate coordination behaviors of the different metal elements, these materials suggest abundant opportunities for designing multifunctional materials with varied structures. The third type of clusters that we discuss are based on polyoxometalates, in particular those containing pentagonal units. However, unlike in fullerene chemistry, which does not allow the use of discrete pentagonal building blocks, the metal oxide-based pentagonal units can be used as fundamental building blocks for constructing various Keplerate structures. These structures also have a variety of functions, including intriguing magnetic properties in some cases. Coupled with different linking groups, such pentagonal units can be used for the assembly of a large number of spherical molecules whose properties can be tuned and optimized. Although this Account focuses on the topological aspects of fullerene-like metal clusters, we hope that this topical review will stimulate more efforts in the exploratory synthesis of new fullerene-like clusters. More importantly, we hope that further study of the bonding interactions and properties of these molecules will lead to the development of new functional materials.

Structure and reactivity studies of transition metals ligated by tBuSi3X (X = O, NH, N, S, and CC)

Use of the (t)Bu(3)Si group can sterically protect O, N, S, and acetylide donors, enabling chemistry at low-coordinate transition metal centers. This article provides examples from these laboratories on the utilization of (t)Bu(3)SiO(-), (t)Bu(3)SiNH(-), (t)Bu(3)SiN(2-), (t)Bu(3)SiS(-) and (t)Bu(3)SiCC(-) as ligands in exploratory synthesis and reactivity studies of transition metal complexes.

Self-Efficacy and the Sense of Coherence: Narrative Review and a Conceptual Synthesis

In this study, the authors develop an exploratory synthesis of two major health concepts: Antonovsky's sense of coherence and Bandura's beliefs in one's own efficacy. Reinterpretation of each study in the light of the other can lead to greater conceptual development and expand existing knowledge. The mutual themes are presented with an explanation of their contribution to broader conceptual discussions. The existence of some similarities between the two concepts is suggested. Researchers can obtain valuable and additional arguments through cross-fertilization of ideas across presented studies united by shared assumptions. Further research is recommended among various age groups and social backgrounds in order to verify the possible benefits of such theoretical development. Theoretical and practical implications of such a synthesis are presented.

Report from the third workshop on future directions of solid-state chemistry: The status of solid-state chemistry and its impact in the physical sciences

Report from the third workshop on future directions of solid-state chemistry: The status of solid-state chemistry and its impact in the physical sciences

Exploratory synthesis of peptide–α‐thioester segments spanning the polypeptide sequence of the δ‐opioid receptor, a G protein‐coupled receptor

We have decided to use the delta-opioid receptor (372 residues) as a model system to develop methods for the total chemical synthesis of G protein-coupled receptors. The most important feature of this receptor from a chemical synthesis perspective is the wealth of cysteines spread throughout its sequence, which are required for native chemical ligation. A total of 13 cysteines are located in the the delta-opioid receptor polypetide chain in both loop and putative transmembrane (TM) regions. We envisioned a synthesis of the polypeptide that would make use of peptide-alpha-thioesters ranging from 37 to 63 residues in length. Here, we report data from an exploratory synthesis of such a set of peptide-alpha-thioesters. For all seven peptides, the crude material approximately 30 residues into the synthesis was sufficiently homogeneous to make isolation and purification straightforward. Extension of the peptides to between 40 and 50 residues in length generally produced a significant decrease in the quality of the crude products, although in most cases, we judged that high purity peptides could probably be isolated. By 60 residues, however, the crude peptide product mixtures are probably too heterogeneous to purify to homogeneity by reversed-phase HPLC. In general, delta-opioid receptor peptides with a single predicted TM domain were sufficiently soluble to handle postcleavage and to analyze by reversed-phase HPLC, whereas 1.5 TM domains rendered the peptides too hydrophobic to handle or analyze by standard protocols. Given the challenges of chain assembly, handling, and purification of these peptides, a synthetic strategy that uses approximately 12 or 13 shorter peptide segments of 20-40 residues each is probably a more feasible approach.

Rational Design, Exploratory Synthesis and Lanthanide Emission Efficiency Comparison of Lanthanide(III)-cored Complexes Based on Naphthalene Acid Ligands for Efficient Energy Transfer Pathways

E-mail: hwanm@kki mail.hannamakrc..Received August 7, 2006Key Words : Naphthalene acid, Lanthanide complexes, Near-infrared emission, Energy transfer processThe development of luminescent lanthanide complexeshas been attracted considerable attention because of a widevariety of applications, such as planar waveguide ampli-fiers,

Spedding Award Lecture. Exploratory Synthesis of Reduced Rare‐Earth‐Metal Halides, Chalcogenides, Intermetallics. New Compounds, Structures, and Properties

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Synthesis, Structure, and Magnetic Properties of Cs2-xRbxCu3P4O14 (0.0 ≤ x ≤ 0.8): A New Series of Copper(II) Phosphates Containing Periodic Arrays of Staggered Square-Planar CuO4 Trimers

In our continued exploratory synthesis of compounds containing transition-metal oxide magnetic nanostructures, a new copper(II) phosphate phase, Cs2Cu3P4O14 (1), was isolated employing the mixed CsCl/2CsI molten flux. The X-ray single-crystal structural analysis shows that the Cs2Cu3P4O(14) phase crystallizes in a monoclinic space group with a = 7.920(2) A, b = 10.795(2) A, c = 7.796(2) A, beta = 103.90(3) degrees , and V = 646.9(2) A(3); P2(1)/c (No. 14); Z = 2. The structure has been refined by the full-matrix least-squares method to a final solution with R1 = 0.0248, wR2 = 0.0553, and GOF = 1.02. The three-dimensional Cu-O-P framework exhibits pseudo-one-dimensional channels where the Cs+ cations reside. The framework consists of trimeric CuO4 square-planar units stacked in a staggered configuration. These CuO4 trimers are interlinked by the P2O7 units via vertex-sharing O atoms. The stacked CuO4 units are slanted with respect to the Cu...Cu...Cu vector, resulting in additional Cu-O long bonds, 2.71(1) A, and a possibly shortened Cu...Cu distance, 3.38(3) A. 1 shows limited cation substitution with smaller alkali-metal cations; in fact, only a relatively small concentration of Cs+ can be substituted by Rb+ to form Cs(2-x)RbxCu3P4O14 (0.0 </= x </= 0.8). The temperature-dependent magnetic susceptibility studies of 1 and its Rb-substituted analogues (x = 0, 0.33, 0.50, and 0.80) reveal a weak ferromagnetic transition at Tc = approximately 14 K, which evidently is independent of the variation of x. In this paper, we report the synthesis, structure, and properties of the title compounds, as well as its brief comparison with the previously discovered Li2Cu3Si4O12 phase, which exhibits fused square-planar CuO4 trimers.

Exploratory synthesis of reduced rare-earth-metal halides, chalcogenides, intermetallics: New compounds, structures, and properties

A new direction in reduced rare-earth-metal (R) compounds opened up when tantalum (and niobium) were adapted to use as virtually faultless containers for these reactions, as these gave immediate access to many new metal-rich phases and structures. Examples are summarized for the new binary dihalides (e.g., Pr, Nd, Dy, Ho, Tm), metallic diodides (Sc, La, Ce, Gd), and metal–metal bonded chains (Sc, Y, Gd, Lu) that were so discovered. Furthermore, a large array of condensed metal cluster, chain, and sheet halides arise when a stoichiometric amount of a diverse variety of nonmetal or metal atoms is included to serve as an interstitial, the earliest examples originating with traces of common impurities. A change in anion charge type to telluride affords a whole new regime of condensed metal-rich cluster compounds and structures, including such remarkable examples as (Sc, Gd, Dy) 2Te, Lu 11Te 4, Lu 8Te, and Sc 6PdTe 2. Also, a number of novel Zintl phases, interstitial derivatives of the type R 5Ge 3Z, quasicrystals, and their approximants are generated in other intermetallic systems. Generalities in structures and bonding are described along the way.

New Low-Dimensional Iron(II) Phosphates Exhibiting Field-Dependent Magnetization Steps

AbstractA new family of transition-metal-containing phosphates ANa3M7(PO4)6, where A = K, Rb, Cs and M = Mn, Fe, Co, was synthesized via high-temperature (650-800 °C), solid state reactions. Sizable single crystals up to 1 cm (ca. 160 mg) were grown for structure and property characterization. The extended structure comprises of alternating corner- and edge-sharing triangular chains of FeOn (n = 5,6) polyhedra involving four crystallographically distinct Fe(II) cations. The triangular chains propagate along the a and b directions to form slabs, which are interlinked by P5+ and a fifth Fe2+ cation to form the three-dimensional lattice. The magnetic susceptibility studies suggest that some of these fascinating compounds exhibit a ferromagnetic transition at temperatures between 10K and 15K. The field-dependent studies on the oriented single crystal of RbNa3M7(PO4)6 show the occurrence of magnetization steps at 2 -5K. In this report, we will first discuss some prior research developments relevant to the study of geometrically frustrated magnetic (GFM) interactions, followed by the results of our exploratory synthesis in the pseuo-quaternary iron(II) phosphate system and finally some initial investigations of temperature- and field-dependent magnetic properties.

Exploratory Synthesis in Molten Salts: Role of Flux Basicity in the Stabilization of the Complex Thiogermanates Cs4Pb4Ge5S16, K2PbGe2S6, and K4Sn3Ge3S14.

AbstractFor Abstract see ChemInform Abstract in Full Text.

From Schism to Continuum? The Problematic Relationship Between Expert and Lay Knowledge—An Exploratory Conceptual Synthesis of Two Qualitative Studies

Ideas about lay and expert knowledge increasingly underscore debates within qualitative health research. In this article, the authors develop an exploratory synthesis of two qualitative studies in which they critique the lay-expert divide, suggesting instead a spectrum of knowledge(s) about health and scientific issues. In the original studies, the researchers examined food risks and alternative medicine, and they shared an interest in the lay-expert knowledge relationship. Reinterpreting each study in the light of the other led to greater conceptual development. Three mutual themes emerged and are presented with discussion of their contribution to wider theoretical debates. This worked example indicates that researchers can achieve valuable additional conceptual development through the cross-fertilization of ideas across qualitative studies united not by common health topics but by shared conceptual concerns.

Synthesis, crystal structure and magnetic properties of a new lithium cobalt metaphosphate, LiCo(PO 3) 3

A new lithium cobalt metaphosphate, LiCo(PO 3) 3, is reported for the first time, which was discovered during the exploratory synthesis in Li–Co–P–O system by solid state reaction. The structure has been refined by powder X-ray Rietveld refinement method ( P2 12 12 1, a = 8.5398(2) Å, b = 8.6326(2) Å and c = 8.3520(2) Å, Z = 4, R p = 13.6%, R wp = 19.4%, R exp = 17.7%, S = 1.11, χ 2 = 1.23). It is isostructural with LiM(PO 3) 3 (M = Fe, Cu). It contains (PO 3) 1− chains with the Co atoms localized in the octahedral sites, bridging four neighboring chains. The magnetic susceptibility measurement showed a typical paramagnetic behavior of high spin of Co 2+, following the Curie–Weiss law in the temperature range of 5–300 K. Unlike the olivine type lithium cobalt phosphate, LiCoPO 4, cyclic voltammetry of LiCo(PO 3) 3 assembled in the coin-type cell showed no electrochemical activity in the voltage region of 1–5 V versus Li/Li +.

Ligand‐Bridged Oligomeric and Supramolecular Arrays of the Hexanuclear Rhenium Selenide Clusters—Exploratory Synthesis, Structural Characterization, and Property Investigation

AbstractFor Abstract see ChemInform Abstract in Full Text.

An expanded set of functional groups in bis(dithiolene)tungsten(IV,VI) complexes related to the active sites of tungstoenzymes, Including WIV-SR and WVI-O(SR).

The active sites of tungstoenzymes have the formulations W(IV,V)L(S(2)pd)(2) and W(VI)LL'(S(2)pd)(2), in which two pyranopterindithiolene cofactor ligands (S(2)pd) are chelated to a tungsten atom. Ligands L and/or L' are not fully defined in any wild-type enzyme. The feasibility of various coordination fragments (functional groups) in potential bis(dithiolene)tungsten site analogues has been examined in previous work by exploratory synthesis. This investigation expands the range of accessible functional groups. The synthetic scheme originates with [W(CO)(2)(S(2)C(2)Me(2))(2)], whose carbonyl groups are labile to substitution. Complexes [W(IV,VI)LL'(S(2)C(2)Me(2))(2)](1-) are described in terms of their functional groups W(IV,VI)LL'. Reaction of the dicarbonyl with formate in acetonitrile/THF affords W(IV)(CO)(eta(1)-HCO(2)) (4) and in Me(2)SO W(VI)O(eta(1)-HCO(2)) (7) by an oxo transfer reaction. Carboxylates yield six-coordinate W(IV)(eta(2)-O(2)CR) (1-3, R = Ph, Me, Bu(t)) with C(2)(v) symmetry. Reaction of 3 (R = Bu(t)) with Me(3)SiSR (R = C(6)H(2)-2,4,6-Pr(i)(3)) gives W(IV)(SR) (5), which undergoes oxo and sulfido atom transfer to form W(VI)O(SR) (8) and W(VI)S(SR) (9), respectively. Attempts to prepare corresponding selenolate complexes, pertinent to the active site of formate dehydrogenase, were unsuccessful, including reactions of W(VI)OCl (10) with RSe(-). Structure proofs of 2-10 were obtained by X-ray structure determinations. Some 26 functional group types in bis(dithiolene)W(IV,V,VI) molecules have now been achieved by synthesis. It remains to be seen which are incorporated in an enzyme site. A number of them (e.g., 5) are directly analogous to molybdoenzyme sites, and may possess corresponding reactivity with biological substrates, as do W(IV)(OR)/W(VI)O(OR) (prepared earlier) in the reduction of N- and S-oxides by atom transfer.

Nanostructured magnetic cuprate cluster: synthesis, structure, UV-Vis spectroscopy, and magnetic properties of a new copper(II) arsenate NaCuAsO4 containing discrete [Cu4O16]24- clusters.

Crystals of copper(II) arsenate NaCuAsO(4) were grown by conventional high-temperature, solid-state methods in molten-salt media. The compounds were characterized by single crystal X-ray diffraction, UV-vis spectroscopy, and magnetic susceptibility measurements. NaCuAsO(4) crystallizes in a monoclinic lattice with a = 6.002 (1) A, b = 10.853 (2) A, c = 10.373 (2) A, beta = 91.50 (3) degrees, and V = 675.4(2) A(3); P2(1)/c (No. 14); Z = 8. The newly isolated sodium copper(II) arsenate reveals a pseudo-one-dimensional channel structure where the sodium cations reside. The extended framework contains nanostructured [Cu(4)O(16)](24-) magnetic clusters that are interlinked by closed-shell, nonmagnetic AsO(4)(3-) oxy anions via sharing vertex oxygen atoms of the CuO(5) and AsO(4) polyhedral units. Each [Cu(4)O(16)](24-) cluster consists of four CuO(5) square pyramidal units in a chair configuration centered by a center of inversion. The two crystallographically independent Cu(2+) cations adopt the [4 + 1] CuO(5) Jahn-Teller distortion giving rise to an intense d-d transition in UV-vis absorption spectra. The magnetic susceptibility measurements reveal that the title compound is antiferromagnetic. At high temperatures, the data follows a pure Curie law, suggesting noninteracting spins, but with a rapid suppression of the effective spin below T = 70 K. At low temperature, the susceptibility collapses, indicating spin gap formation as the magnetic-cluster material settles into the lowest energy magnetic singlet state. The current work in the exploratory synthesis of oxy compounds containing nanostructured transition-metal-oxide magnetic clusters leads to new materials for experimental and theoretical developments of magnetic models.

Exploratory Synthesis and Luminescence Study of the First π-Conjugated Tin-Based Alternating Copolymers for Blue Light-Emitting Diodes at the Very Low Operating Voltage

Tin-based alternating copolymers with a uniform π-conjugated segment were synthesized using the Heck reaction between distyrylstannane monomer and various difunctionalized monomers. The UV−vis absorption maximum peaks of the resulting polymers in chloroform solution and in thin films appeared in the wavelength range of 347−394 nm. Upon photoexcitation with light of wavelength 350 nm, their photoluminescence spectra exhibited an emissive maximum peak around 470−502 nm, corresponding to blue light emission. Multilayered light-emitting diodes with ITO/PEDOT (50 nm)/polymer (80 nm)/Ca (50 nm)/Al (200 nm) composition were fabricated. These LED devices exhibited an emissive maximum peak in the range of 464−472 nm. All of the materials exhibited a very low turn-on voltage of less than 4 V. From cyclic voltammetric studies and optical data, the LUMO level is estimated to be 3.20 eV for SnPhFPV and 2.90 eV for SnPhPVK, and the ionization potentials (HOMO level) were estimated to be 5.90 eV for SnPhFPV and 5.60 eV ...