Silicon Analogues Research Articles

How Does the Central Atom Substitution Impact the Properties of a Criegee Intermediate? Insights from Multireference Calculations.

Complete active space self-consistent field (CASSCF) and multireference configuration interaction (MRCI)-based multireference calculations have been performed to better understand the ground state properties and the photodissociation mechanism of SiH2OO, a silicon analogue of the parent Criegee intermediate, CH2OO. The CASSCF/aug-cc-pV(T+d)Z results suggest that the ground state of SiH2OO is severely multireference in nature. This explains why SiH2OO could not be characterized in recently reported coupled cluster calculations. An important implication of this multireference character is the dramatically enhanced reactivity of SiH2OO, i.e., the calculated barrier for the cyclization of SiH2OO is only 4.4 kcal/mol, which is nearly 10 kcal/mol lower than that reported for the CH2OO case. The MRCI/aug-cc-pV(T+d)Z results on the evolution of the low-lying singlet electronic states along the OO bond suggest that SiH2OO absorbs strongly in the near UV-vis region. These results improve our fundamental understanding of the thermal and photobehavior of XH2OO (X = C, Si, Ge, and Sn) that serve as precursors for dioxiranes, an important class of oxidants for the synthesis of value-added chemicals, and also find their applications in optodevices.

Prediction of the structural and spectral properties and reactivity of the silicon analogs of cyclobutadiene C4-nSinH4 (n=0-4) by density functional theory computations

In recent years, it has been noted that the silicon analogs compounds have more pharmaceutical applications due to their excellent lipophilicity properties. The present study evaluated the structural, spectral properties, and reactivity of the silicon analogs of cyclobutadiene compound. This study was conducted based on the quantum-mechanical computations. All the studied compounds were optimized by B3LYP/6-311++G(d,p) basis set of theory. The IR computations showed no imaginary frequency for all molecules, proved the accuracy of the methods. The results revealed that, the silicon analogs have more benefits in terms of the structural and stability properties in comparison with the carbon analog.

Silicon amino acids

AbstractThe existence and gas phase stability of silicon analogues of three natural amino acids (i.e., silicon glycine, silicon alanine, and silicon valine) belonging to the novel class of compounds termed silicon amino acids (SiAA) are investigated theoretically on the basis of ab initio QCISD/aug‐cc‐pVTZ and MP2/aug‐cc‐pVTZ calculations. All molecules studied (in their gas phase canonical forms) are structurally comparable to their proteinogenic counterparts (i.e., glycine, l‐alanine, and l‐valine) and capable of forming several structural isomers as such. These higher energy isomers are characterized by small relative energies (not exceeding 4 kcal mol−1). The simulated IR spectra of the Si‐Gly, Si‐Ala, and Si‐Val global minima are also presented and discussed.

Takeaki Iwamoto

Angewandte Chemie International EditionVolume 56, Issue 31 p. 8930-8930 Author ProfileFree Access Takeaki Iwamoto First published: 21 March 2017 https://doi.org/10.1002/anie.201702167AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract “My favorite place on earth is Bora Bora in Tahiti. The most important thing I learned from my parents is kindness. ...” This and more about Takeaki Iwamoto can be found on page 8930. Takeaki Iwamoto The author presented on this page has published more than 10 articles in Angewandte Chemie in the last 10 years, most recently: “An Isolable Potassium Salt of a Borasilene–Chloride Adduct”: Y. Suzuki, S. Ishida, S. Sato, H. Isobe, T. Iwamoto, Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201612545; Angew. Chem. 2017, DOI: 10.1002/ange.201612545. Date of birth: November 25, 1970 Position: Professor, Department of Chemistry, Graduate School of Science, Tohoku University E-mail: iwamoto@m.tohoku.ac.jp Homepage: http://www.ssoc.chem.tohoku.ac.jp/en_index.html ORCID: 0000-0002-8556-5785 Education: 1993 BSc, Tohoku University 1998 DSc supervised by Mitsuo Kira, Tohoku University 2006–2007 Visiting Scholar with T. Don Tilley, University of California, Berkeley Awards: 1999 Inoue Research Award for Young Scientists; 2004 The Chemical Society of Japan Award for Young Chemists; 2009 The Young Scientists' Prize, The Commendation for Science and Technology by the Ministry of Education, Culture, Sports, Science and Technology, Japan; 2010 Nozoe Memorial Award for Young Organic Chemists Research: Low-coordinate compounds of main-group elements, especially silicon and germanium Hobbies: Listening to music, walking, traveling My favorite place on earth is Bora Bora in Tahiti. The most important thing I learned from my parents is kindness. If I could have dinner with three famous scientists from history, they would be Stanley F. Kipping, Dmitri I. Mendeleev, and Masataka Ogawa. I chose chemistry as a career because the unexpected structures and behavior of new compounds fascinated me. If I were not a scientist, I would be a software programmer. My most exciting discovery to date has been the unexpected formation of spiropentasiladiene. I lose track of time when I watch science fiction movies or when I repair PCs. My favorite author (fiction) is Ryunosuke Akutagawa. My top three films of all time are Star Wars: Episode IV—A New Hope, Nausicaä of the Valley of the Wind, and Mission: Impossible. My favorite food is lasagne. My favorite piece of music is Quartet for the End of Time (Olivier Messiaen). If I won the lottery, I would travel all over the world with my family and construct a new building for my laboratory. My 5 top papers: References 1“A Stable Bicyclic Compound with Two Si=Si Double Bonds”: T. Iwamoto, M. Tamura, C. Kabuto, M. Kira, Science 2000, 290, 504. (This study taught me the importance of carefully interpreting the obtained results.) 2“A Stable Fused Bicyclic Disilene as a Model for Silicon Surface”: H. Kobayashi, T. Iwamoto, M. Kira, J. Am. Chem. Soc. 2005, 127, 15376. (Mitsuo Kira allowed me to be a corresponding author for the first time.) 3“Fused Tricyclic Disilenes with Highly Strained Si−Si Double Bonds: Addition of a Si−Si Single Bond to a Si−Si Double Bond”: R. Tanaka, T. Iwamoto, M. Kira, Angew. Chem. Int. Ed. 2006, 45, 6371; Angew. Chem. 2006, 118, 6519. (The properties of silicon–silicon double bonds can be controlled by the careful design of the substituents.) 4“A heavy analogue of the smallest bridgehead alkene stabilized by a base”: T. Iwamoto, N. Akasaka, S. Ishida, Nat. Commun. 2014, 5, 5353. (A silicon analogue of bicyclo[1.1.0]but-1(2)-ene, the smallest bridgehead alkene that has not been isolated to date.) 5“A Dialkylsilylene-Pt(0) Complex with a DVTMS Ligand for the Catalytic Hydrosilylation of Functional Olefins”: T. Iimura, N. Akasaka, T. Iwamoto, Organometallics 2016, 35, 4071. (Isolable alkylsilylenes are promising ligands for transition-metal catalysts.) Volume56, Issue31July 24, 2017Pages 8930-8930 ReferencesRelatedInformation

Hydroaminoalkylation of Allylsilanes and a One-Pot Procedure for the Synthesis of 1,5-Benzoazasilepines.

Allylsilanes undergo highly regioselective intermolecular alkene hydroaminoalkylation with secondary amines in the presence of a titanium mono(formamidinate) catalyst. Corresponding reactions of a suitable allyl(2-bromophenyl)silane which exclusively deliver the branched hydroaminoalkylation products combined with a subsequent Buchwald-Hartwig amination result in the development of an elegant one-pot procedure for the synthesis of literature-unknown silicon analogues of 1,5-benzodiazepines, the so-called 1,5-benzoazasilepines.

Synthesis and Olfactory Properties of a 6'-Silasubstituted "Spiro[4.5]-δ-Damascone".

The silicon analogue of the potent spirocyclic δ-damascone odorant 6 was synthesized from allyltrichlorosilane (15) and but-2-en-1-ol (16). The latter was transformed to 3-methylpen-4-enenitrile (11) by Saucy-Marbet reaction with ethoxyethane and subsequent treatment with HONH2 ⋅HCl. The resulting γ,δ-unsaturated nitrile 11 was silylated with 1-allyl-1-chlorosilolane (14), which was prepared from allyltrichlorosilane (15) and the bis-Grignard reagent of 1,4-dichlorobutane. Metathetic ring closure employing the Grubbs I catalyst, followed by DIBAL reduction with non-aqueous work up, Grignard reaction with prop-1-en-1-ylmagnesium bromide, and Attenburrow MnO2 oxidation concluded the synthesis. The target compound was found to be olfactorily related to the spiro[4.5]-δ-damascone lead, but approximately 900 times weaker. In a type of enol Brook rearrangement, it thermally decomposes however to 3,6-dihydro-2H-1,2-oxasilocine (20), which surprisingly is a damascone odorant as well; although, 12 000 times weaker.

Carbene stabilized interconnected bis-germylene and its silicon analogue with small methyl substituents.

The cyclic alkyl(amino) carbene (cAAC) [:C{N-C6H3(2,6-IPr2)}(CMe2)2CH2] stabilized MeGeGeMe has been isolated in the molecular form with composition (cAAC)MeGe-GeMe(cAAC) (1) at room temperature. Compound 1 was synthesized from the reduction of MeGeCl3 using three equivalents of KC8 in the presence of one equivalent of cAAC. The corresponding silicon compound (cAAC)MeSi-SiMe(cAAC) (2) was also prepared. Compounds 1 and 2 are the first examples of REER compounds (E = Ge, Si) carrying the smallest organic group. Furthermore the structures of compounds 1 and 2 have been investigated by using theoretical methods. The theoretical analysis of the structure of 1 is in agreement with the formation as an unprecedented carbene stabilized bis-germylene whereas compound 2 can be equally described as carbene stabilized bis-silylene with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene. The compounds were also characterized by X-ray crystallography.

Defect-sensitive performance of silicene sheets under uniaxial tension: mechanical properties, electronic structures and failure behavior

As a silicon analog of graphene, silicene has attracted considerable attention due to its unique physical and chemical properties.

Spin-valley Hall conductivity of doped ferromagnetic silicene under strain

The spin-valley Hall conductivity (SHC-VHC) of two-dimensional material ferromagnetic graphene's silicon analog, silicene, is investigated in the presence of strain within the Kubo formalism in the context of the Kane–Mele Hamiltonian. The Dirac cone approximation has been used to investigate the dynamics of carriers under the strain along the armchair (AC) direction. In particular, we study the effect of external static electric field on these conductivities under the strain. In the presence of the strain, the carriers have a larger effective mass and the transport decreases. Our findings show that SHC changes with respect to the direction of the applied electric field symmetrically while VHC increases independently. Furthermore, the reflection symmetry of the structure has been broken with the electric field and a phase transition occurs to topological insulator for strained ferromagnetic silicene. A critical strain is found in the presence of the electric field around . SHC (VHC) decreases (increases) for strains smaller than this value symmetrically while it increases (decreases) for strains larger than one.

Electronic heat capacity and magnetic susceptibility of ferromagnetic silicene sheet under strain

Abstract The electronic heat capacity (EHC) and magnetic susceptibility (MS) of the two-dimensional material ferromagnetic graphene's silicon analog, silicene, are investigated by the strain-induced and the applied electric field within the Green's function technique and the Kane-Mele Hamiltonian. Dirac cone approximation has been performed to investigate the system under strain along the zigzag (ZZ) direction. The main attention is focused on the effects of external static electric field in the presence of strain on EHC and MS of a ferromagnetic silicene sheet. In the presence of strain, carriers have a larger effective mass and transport decreases. As a result, the temperature dependence of EHC and MS gives a critical strain around 10%. Furthermore, electric field breaks the reflection symmetry of the structure and a transition to the topological insulator for strained ferromagnetic silicene has occurred when the electric field is increased. In this phase, EHC and MS have weird behaviors with temperature.

Electronic Structure and Potential Reactivity of Silaaromatic Molecules.

Silicon-based materials are crucial for conventional electronics. The fascinating properties of the new two-dimensional material silicene, the silicon analogue of graphene (one atom-thick silicon sheets), offer a potential bridge between conventional and molecular electronics. The ground-state configuration of silicene is buckled, which compromises optimal constructive overlap of p orbitals. Because silicene is not planar like graphene, it has a lower intrinsic electron/hole mobility than graphene. This motivates a search for improved, alternative, planar materials. Miniaturization of silicene/graphene hybrid monolayers affords diverse silicon-organic and -inorganic molecules, whose potential as building blocks for molecular electronics is unexplored. Additionally, hybridization of pure silicon rings (or sheets) is a versatile way to control the geometrical and electronic characteristics of the aromatic ring. In this work we systematically investigate, computationally, architectures and electronic structures of a series of hybrid silaaromatic monomers and fused-ring oligomers. This includes the thermochemistry of representative reactions: hydrogenation and oxidation. The effect of various skeletal substituents of interest is elucidated as well. We show that the specific location of carbon and silicon atoms, and their relative populations in the rings are crucial factors controlling the molecular geometry and the quasi-particle gap. Furthermore, we suggest that electron-withdrawing substituents such as CN, F, and CF3 are promising candidates to promote the air-stability of silaaromatics. Finally, on the basis of the analysis of benzene-like silaaromatic molecules, we discuss a set of alternative, prototype ring molecules that feature planarity and delocalized π bonds. These motifs may be useful for designing new extended materials.

The Dilute Charged Impurity Effects on Electronic Heat Capacity and Magnetic Susceptibility of Ferromagnetic Silicene Sheet

Starting from the Kane-Mele Hamiltonian, Dirac cone approximation and self-consistent Born approximation (SCBA), the effects of dilute charged impurity doping on electronic heat capacity (EHC) and magnetic susceptibility (MS) of a two-dimensional material ferromagnetic graphene’s silicon analog, silicene, are investigated within the Green’s function approach that allows the accurate assessment of dynamic of carriers. Also, we have studied the behavior of these quantities in the presence of applied external electric field (AEEF). Our results show that the inversion symmetry is broken by impurity doping. According to EHC behaviors, the band gap is decreased with impurity concentration (IC), impurity scattering strenght (ISS), and AEEF. As a remarkable point, a phase transition from ferromagnetic to paramagnetic and antiferromagnetic has been observed. On the other hand, there is a critical impurity concentration for maximum response to the temperature and magnetic field. The effect of AEEF leads to the decrease of band gap and phase transition depends on the direction of AEEF.

Luminescent siliceous materials based on sodium silicate, organic polymers and silicon analogs

A new composite materials of various particle morphology were obtained by silicic acid condensation in the presence of oligomeric polyamine, poly (vinyl amine) or co(1-vinylimidazole - acrylic acid). These organic compounds are the models of biopolymers which participate in synthesis of siliceous structures in living organisms. Hydroxides of silicon analogs (Ge, Ti, Zr and Sn) were also applied as additives in the composite synthesis. The obtained materials show greatly more intensive luminescence comparing with pure silica without essential changes in luminescence spectra and lifetimes. We suppose the increase in emission intensity under the action of organic and inorganic additives is connected with increase of concentration of the luminescence-active defects which present in pure silica. Our results show possibility to obtain bright luminescent siliceous materials with controllable nano- and micro-level morphology by the action of polymeric amines and silicon analogs.

Exotic SiO(2)H(2) Isomers: Theory and Experiment Working in Harmony.

Replacing carbon with silicon can result in dramatic and unanticipated changes in isomeric stability, as the well-studied CO2H2 and the essentially unknown SiO2H2 systems illustrate. Guided by coupled-cluster calculations, three SiO2H2 isomers have been detected and spectroscopically characterized in a molecular beam discharge source using rotational spectroscopy. The cis,trans conformer of dihydroxysilylene HOSiOH, the ground-state isomer, and the high-energy, metastable dioxasilirane c-H2SiO2 are abundantly produced in a dilute SiH4/O2 electrical discharge, enabling precise structural determinations of both by a combination of isotopic measurements and calculated vibrational corrections. The isotopic studies also provide insight into their formation route, suggesting that c-H2SiO2 is formed promptly in the expansion but that cis,trans-HOSiOH is likely formed by secondary reactions following formation of the most stable dissociation pair, SiO + H2O. Although less abundant, the rotational spectrum of trans-silanoic acid, the silicon analogue of formic acid, HSi(O)OH, has also been observed.

Energetic Sila-Nitrocarbamates: Silicon Analogues of Neo-Pentane Derivatives.

Four silanes based on the neo-pentane skeleton Me4-xSi(CH2R)x containing carbamate groups (x = 1-4, R = OC(O)NH2) have been prepared via the corresponding alcohols Me4-xSi(CH2OH)x, starting from the chlorosilanes Me4-xSiClx. Subsequent nitration leads to the corresponding primary nitrocarbamates (R = OC(O)NHNO2), examined for the purpose as potential energetic materials, including the silicon analogue of pentaerythritol tetranitrocarbamate (sila-PETNC) and a siloxane based nitrocarbamate side-product. All compounds were thoroughly characterized by spectroscopic methods including X-ray diffraction. Thermal stabilities and sensitivities toward impact and friction were examined, as well as detonation values by calculating energies of formation using the EXPLO5 V6.02 software.

Density Functional Theory (DFT) Study: Electronic Properties of Silicene under Uniaxial Strain as H<sub>2</sub>S Gas Sensor

First principle calculation is performed to investigate structural and electronic properties of strained silicene (silicon analogue of graphene) when absorbing the hydrogen sulfide molecule gas. Two configuration of silicene-H2S system, center and hollow configuration, is checked under 0% (pure), 5%, and 10% uniaxial engineering strain. We report that the silicene-H2S system in center configuration has larger binding energy compare to the silicene-H2S system in hollow configuration. The results show that H2S is physisorbed on silicene. In this work, we also find the change of band gap energy (~60 meV) is appearing when H2S interacted with silicene in center configuration, whereas the band gap energy of silicene has no change when interacted with H2S in hollow configuration.

Enhanced optical nonlinearity based on silicon ring

ABSTRACTThe time-dependent density functional cubic response calculations show that silicon analogues of polycyclic aromatic hydrocarbons have much larger non-resonant second-order optical hyperpolarisabilities (γ) than corresponding hydrocarbons. An analysis of fuzzy atom bond order quantitatively reveals that these silicon analogues have a very similar π-electron delocalisation to corresponding hydrocarbons. The enhanced optical nonlinearity of these silicon analogues is attributed to the higher (hyper)polarisabilities of the silicon atom and a significant decrease in transition energies of silicon analogues compared with corresponding hydrocarbons. The silicon analogues of polycyclic aromatic hydrocarbons would be good candidates as infrared nonlinear optical materials due to their enhanced non-resonant nonlinear optical polarisabilities in the infrared range.

Influence of rare earth cation size on the crystal structure in rare earth silicates, Na2RESiO4(OH) (RE = Sc, Yb) and NaRESiO4 (RE = La, Yb)

Crystals of Na2ScSiO4(OH) and Na2YbSiO4(OH) were synthesized at low temperatures using a sodium hydroxide based hydroflux, while crystals of NaLaSiO4 and NaYbSiO4 were grown at high temperatures using a sodium fluoride/sodium chloride eutectic flux. Both structure types were crystallized under reaction conditions that, when used for medium sized rare earths (RE = Pr, Nd, Sm – Tm) yield the Na5RE4X[SiO4]4 structure type, where X is OH in the hydroflux conditions and F in the eutectic flux conditions. Herein, we report the synthesis, structure, size effect, and magnetic properties of these compositions and introduce the new structure type of Na2RESiO4(OH), which crystallizes in the orthorhombic space group Pca21, of NaLaSiO4, which crystallizes in the orthorhombic space group Pna21, and of NaYbSiO4, which crystallizes in the orthorhombic space group Pnma, where both NaRESiO4 compounds have one silicon structural analog.

Coplanar Oligo(p-phenylenedisilenylene)s as Si═Si Analogues of Oligo(p-phenylenevinylene)s: Evidence for Extended π-Conjugation through the Carbon and Silicon π-Frameworks.

A series of oligo(p-phenylenedisilenylene)s (Si-OPVs 1-4), silicon analogues of oligo(p-phenylenevinylene)s, up to the tetramer have been synthesized and isolated by the introduction of a newly developed protecting group [(HexO)MEind] for improving their solubility. The experimental and theoretical studies of the Si-OPVs 1-4 demonstrate the fully extended π-conjugation of the Si-OPV main chains. Single crystal X-ray analyses of the monomer 1 and the dimer 2 revealed the highly coplanar Si-OPV backbones facilitating the effective extension of the π-conjugation, which has further been validated by the significant increases in the absorption maxima from 465 nm for the monomer 1 to 610 nm for the tetramer 4. The absorption maxima exhibit an excellent fit to Meier's equation, leading to the estimation of an effective conjugation length (ECL) of 9 repeat units (nECL = 9) and the absorption maximum of 635 nm for the infinite chain (λ∞ = 635 nm). In sharp contrast to other nonemissive disilenes, the Si-OPVs 2-4 show an intense fluorescence from 613 to 668 nm at room temperature with the quantum yields up to 0.48. All the data presented here provide the first evidence for the efficient extended π-conjugation between the Si═Si double bonds and the carbon π-electron systems over the entire Si-OPV skeleton. This study reveals the possibility for developing the conjugated disilene π-systems, in which the Si═Si double bonds would be promising building blocks, significantly optimizing the intrinsic photophysical and electrochemical properties of the carbon-based π-conjugated materials.

ChemInform Abstract: Synthesis of Furans and Pyrroles via Migratory and Double Migratory Cycloisomerization Reactions of Homopropargylic Aldehydes and Imines.

A novel gold-catalyzed divergent synthesis of furans and pyrroles employing readily available homopropargylic aldehydes and imines has been developed. The regiochemical outcome of this reaction is dependent on the substituent on the terminal alkyne of substrate. Thus, substrates possessing alkyl and aryl substituent at the alkyne moiety produce 2,3,5-substituted furans and pyrroles via a migratory cycloisomerization reaction. Whereas, their silicon analogues are capable of undergoing a double migratory process leading to 2,3,4-substituted heterocycles.