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Special Issue "Advances in Silicon Chemistry"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Organic Synthesis".

Deadline for manuscript submissions: closed (15 July 2016)

Special Issue Editor

Guest Editor
Prof. Dr. Mitsuo Kira

Prof. Emeritus, Tohoku University
Guest Professor of Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, China
Website | E-Mail
Interests: bonding, structure, and reactions of stable silicon and related group-14 element unsaturated compounds including silylenes, disilenes, and Si-heteroatom doubly bonded compounds, transition metal complexes with disilene and silylene ligands, oligosilanes and polysilanes, and silicon-based molecular machines

Special Issue Information

Dear Colleagues,

Today, in addition to tetravalent and hypercoordinate silicon compounds, various silicon unsaturated compounds, such as silylenes, silaethenes, disilenes, disilynes, and silicon-heteroatom doubly bonded compounds, are in our hands as isolable compounds thanks to the recent efforts of many researchers. They have revealed rather unusual features of bonding and structure of these silicon compounds, asking for restructuring of a widely applicable theory of bonding and structure of heavy main group elements including silicon. As single element chemistry, silicon chemistry is going to compare favorably with relatively well-established organic chemistry. To overview which directions studies in this research field are heading, this Special Issue is aimed to provide a forum for every aspect of molecular silicon compounds, including synthesis, properties, and new reactions of various molecular silicon compounds, their theoretical, spectroscopic, optoelectronic, and mechanistic studies, and their application towards the material science.

Prof. Dr. Mitsuo Kira
Guest Editor

Manuscript Submission Information

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Keywords

  • low-coordinate and multiply-bonded silicon compounds
  • silicon compounds with unusual structures
  • hypercoordinate silicon compounds
  • silicon transition-metal complexes
  • bonding and structure
  • reactions and mechanisms
  • silicon-based materials

Related Special Issues

Published Papers (13 papers)

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Editorial

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Open AccessEditorial Strait Gate: Special Issue on Advances in Silicon Chemistry
Molecules 2017, 22(9), 1497; doi:10.3390/molecules22091497
Received: 5 September 2017 / Accepted: 6 September 2017 / Published: 7 September 2017
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Abstract
Manufacturing high-purity element silicon and organic polysilicones are two major silicon industries, supporting the basis of the modern electronic industry and our daily lives [...]
Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)

Research

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Open AccessCommunication Discovery of an Octahedral Silicon Complex as a Potent Antifungal Agent
Molecules 2017, 22(4), 637; doi:10.3390/molecules22040637
Received: 11 February 2017 / Revised: 5 April 2017 / Accepted: 12 April 2017 / Published: 15 April 2017
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Abstract
Octahedral transition metal complexes have been shown to have tremendous applications in chemical biology and medicinal chemistry. Meanwhile, structural transition metals can be replaced by inert octahedral silicon in a proof-of-principle study. We here introduce the first example of octahedral silicon complexes, which
[...] Read more.
Octahedral transition metal complexes have been shown to have tremendous applications in chemical biology and medicinal chemistry. Meanwhile, structural transition metals can be replaced by inert octahedral silicon in a proof-of-principle study. We here introduce the first example of octahedral silicon complexes, which can very well serve as an efficient antimicrobial agent. The typical silicon arenediolate complex 1 {[(phen)2Si(OO)](PF6)2, with phen = 1,10-phenanthroline, OO = 9,10-phenanthrenediolate} exhibited significant inhibition towards the growth of Cryptococcus neoformans with MIC and MFC values of 4.5 and 11.3 μM, respectively. Moreover, it was fungicidal against both proliferative and quiescent Cryptococcus cells. This work may set the stage for the development of novel antifungal drugs based upon hexacoodinate silicon scaffolds. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle A Computational Investigation of the Substituent Effects on Geometric, Electronic, and Optical Properties of Siloles and 1,4-Disilacyclohexa-2,5-dienes
Molecules 2017, 22(3), 370; doi:10.3390/molecules22030370
Received: 17 January 2017 / Revised: 16 February 2017 / Accepted: 20 February 2017 / Published: 28 February 2017
PDF Full-text (3351 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Thirty two differently substituted siloles 1a1p and 1,4-disilacyclohexa-2,5-dienes 2a2p were investigated by quantum chemical calculations using the PBE0 hybrid density functional theory (DFT) method. The substituents included σ-electron donating and withdrawing, as well as π-electron donating and withdrawing groups,
[...] Read more.
Thirty two differently substituted siloles 1a1p and 1,4-disilacyclohexa-2,5-dienes 2a2p were investigated by quantum chemical calculations using the PBE0 hybrid density functional theory (DFT) method. The substituents included σ-electron donating and withdrawing, as well as π-electron donating and withdrawing groups, and their effects when placed at the Si atom(s) or at the C atoms were examined. Focus was placed on geometries, frontier orbital energies and the energies of the first allowed electronic excitations. We analyzed the variation in energies between the orbitals which correspond to HOMO and LUMO for the two parent species, here represented as ΔεHL, motivated by the fact that the first allowed transitions involve excitation between these orbitals. Even though ΔεHL and the excitation energies are lower for siloles than for 1,4-disilacyclohexa-2,5-dienes the latter display significantly larger variations with substitution. The ΔεHL of the siloles vary within 4.57–5.35 eV (ΔΔεHL = 0.78 eV) while for the 1,4-disilacyclohexa-2,5-dienes the range is 5.49–7.15 eV (ΔΔεHL = 1.66 eV). The excitation energy of the first allowed transitions display a moderate variation for siloles (3.60–4.41 eV) whereas the variation for 1,4-disilacyclohexa-2,5-dienes is nearly doubled (4.69–6.21 eV). Cyclobutadisiloles combine the characteristics of siloles and 1,4-disilacyclohexa-2,5-diene by having even lower excitation energies than siloles yet also extensive variation in excitation energies to substitution of 1,4-disilacyclohexa-2,5-dienes (3.47–4.77 eV, variation of 1.30 eV). Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Theoretical Study on the Second Hyperpolarizailities of Oligomeric Systems Composed of Carbon and Silicon π-Structures
Molecules 2016, 21(11), 1540; doi:10.3390/molecules21111540
Received: 13 September 2016 / Revised: 18 October 2016 / Accepted: 9 November 2016 / Published: 15 November 2016
PDF Full-text (1649 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
To explore the prospect of molecules involving silicon-silicon multiple bonds as nonlinear optical molecular systems, the relationship between the structure and the second hyperpolarizabilities γ of the oligomeric systems composed of carbon and silicon π-structures is investigated using the density functional theory method.
[...] Read more.
To explore the prospect of molecules involving silicon-silicon multiple bonds as nonlinear optical molecular systems, the relationship between the structure and the second hyperpolarizabilities γ of the oligomeric systems composed of carbon and silicon π-structures is investigated using the density functional theory method. It is found that these compounds indicate intramolecular charge transfer (ICT) from the silicon units to the carbon units together with nonzero diradical characters. The γ values of these compounds are shown to be 2–13 times as large as those of the carbon analogs. Although asymmetric carbon and silicon π-systems exhibit comparable enhancement to the corresponding symmetric systems, donor-π-donor structures exhibit remarkable enhancement of γ despite of their both-end short silicon π-chain moieties (donor units). Further analysis using the odd electron and γ densities clarifies that the intermediate diradical character also contributes to the enhancement of γ. These results predict that even short π-conjugated silicone moieties can cause remarkable enhancement of γ by introducing them into π-conjugated hydrocarbon structures. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Reactions of an Isolable Dialkylsilylene with Aroyl Chlorides. A New Route to Aroylsilanes
Molecules 2016, 21(10), 1376; doi:10.3390/molecules21101376
Received: 14 September 2016 / Revised: 3 October 2016 / Accepted: 8 October 2016 / Published: 15 October 2016
Cited by 2 | PDF Full-text (3796 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The reactions of isolable dialkylsilylene 1 with aromatic acyl chlorides afforded aroylsilanes 3a3c exclusively. Aroylsilanes 3a3c were characterized by 1H-, 13C-, and 29Si-NMR spectroscopy, high-resolution mass spectrometry (HRMS), and single-crystal molecular structure analysis. The reaction mechanisms
[...] Read more.
The reactions of isolable dialkylsilylene 1 with aromatic acyl chlorides afforded aroylsilanes 3a3c exclusively. Aroylsilanes 3a3c were characterized by 1H-, 13C-, and 29Si-NMR spectroscopy, high-resolution mass spectrometry (HRMS), and single-crystal molecular structure analysis. The reaction mechanisms are discussed in comparison with related reaction of 1 with chloroalkanes and chlorosilanes. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessCommunication Synthesis of Thioethers by InI3-Catalyzed Substitution of Siloxy Group Using Thiosilanes
Molecules 2016, 21(10), 1330; doi:10.3390/molecules21101330
Received: 6 September 2016 / Accepted: 3 October 2016 / Published: 6 October 2016
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Abstract
The substitution of a siloxy group using thiosilanes smoothly occurred in the presence of InI3 catalyst to yield the corresponding thioethers. InI3 was a specifically effective catalyst in this reaction system, while other typical Lewis acids such as BF3⋅OEt
[...] Read more.
The substitution of a siloxy group using thiosilanes smoothly occurred in the presence of InI3 catalyst to yield the corresponding thioethers. InI3 was a specifically effective catalyst in this reaction system, while other typical Lewis acids such as BF3⋅OEt2, AlCl3, and TiCl4 were ineffective. Various silyl ethers such as primary alkyl, secondary alkyl, tertiary alkyl, allylic, benzylic, and propargylic types were applicable. In addition, bulky OSitBuMe2 and OSiiPr3 groups, other than the OSiMe3 group, were successfully substituted. The substitution reaction of enantiopure secondary benzylic silyl ether yielded the corresponding racemic thioether product, which suggested that the reaction of tertiary alkyl, secondary alkyl, benzylic, and propargylic silyl ethers would proceed via a SN1 mechanism. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessCommunication Synthesis of a 1-Aryl-2,2-chlorosilyl(phospha)silene Coordinated by an N-Heterocyclic Carbene
Molecules 2016, 21(10), 1309; doi:10.3390/molecules21101309
Received: 30 August 2016 / Revised: 22 September 2016 / Accepted: 24 September 2016 / Published: 30 September 2016
Cited by 4 | PDF Full-text (2144 KB) | HTML Full-text | XML Full-text
Abstract
Phosphasilenes, P=Si doubly bonded compounds, have received considerable attention due to their unique physical and chemical properties. We report on the synthesis and structure of a chlorophosphasilene coordinated by an N-heterocyclic carbene (NHC), which has the potential of functionalization at the Si–Cl
[...] Read more.
Phosphasilenes, P=Si doubly bonded compounds, have received considerable attention due to their unique physical and chemical properties. We report on the synthesis and structure of a chlorophosphasilene coordinated by an N-heterocyclic carbene (NHC), which has the potential of functionalization at the Si–Cl moiety. Treatment of a silylphosphine, ArPH–SiCl2RSi (Ar = bulky aryl group, RSi = Si(SiMe3)3) with two equivalents of Im-Me4 (1,3,4,5-tetramethylimidazol-2-ylidene) afforded the corresponding NHC-coordinated phosphasilene, ArP=SiClRSi(Im-Me4) as a stable compound. Bonding properties of the P=Si bond coordinated to an NHC will be discussed on the basis of theoretical calculations. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessCommunication Effects of Substitution on Solid-State Fluorescence in 9-Aryl-9-methyl-9H-9-silafluorenes
Molecules 2016, 21(9), 1173; doi:10.3390/molecules21091173
Received: 15 July 2016 / Revised: 30 August 2016 / Accepted: 31 August 2016 / Published: 3 September 2016
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Abstract
Aromatic groups were incorporated into 9H-9-silafluorene units at the 9-position (mono-9H-silafluorenes) and 9,9′-positions (di-9H-9-silafluorenes). The aryl substituents showed weak conjugation to the 9H-9-silafluorene for 9-aryl substituted ones 17 and a 9,9′-phenylene substituted one
[...] Read more.
Aromatic groups were incorporated into 9H-9-silafluorene units at the 9-position (mono-9H-silafluorenes) and 9,9′-positions (di-9H-9-silafluorenes). The aryl substituents showed weak conjugation to the 9H-9-silafluorene for 9-aryl substituted ones 17 and a 9,9′-phenylene substituted one (compound 8) and they exhibited similar absorption and emission spectra. The 9H-9-silafluorene 10 containing a 5,5′-(2,2′-bithiophenyl) group showed a significantly red-shifted absorption and fluorescence maxima in the solid-state. Single-crystal X-ray diffraction studies found J-type aggregated structures formed by intermolecular CH–π interactions (ca. 2.6–2.7 Å). Density functional theory (DFT), time-dependent DFT (TD-DFT), and configuration interaction single (CIS) calculations were conducted to explain the observed optical properties. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Facile Access to Stable Silylium Ions Stabilized by N-Heterocyclic Imines
Molecules 2016, 21(9), 1155; doi:10.3390/molecules21091155
Received: 26 July 2016 / Revised: 23 August 2016 / Accepted: 25 August 2016 / Published: 30 August 2016
Cited by 5 | PDF Full-text (2665 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Novel silylium ions with N-heterocyclic imines were successfully synthesized. The reaction of trimethylsilyl imidazolin-2-imine Me3SiNIPr (NIPr = bis(2,6-diisopropylphenyl)-imidazolin-2-imino) with B(C6F5)3 leads to dimeric imino-substituted silylium ions through a methyl group abstraction on the silicon atom.
[...] Read more.
Novel silylium ions with N-heterocyclic imines were successfully synthesized. The reaction of trimethylsilyl imidazolin-2-imine Me3SiNIPr (NIPr = bis(2,6-diisopropylphenyl)-imidazolin-2-imino) with B(C6F5)3 leads to dimeric imino-substituted silylium ions through a methyl group abstraction on the silicon atom. Meanwhile, the intermolecular imino-coordinated silylium ion is formed by using the less sterically crowded imine Me3SiNItBu (NItBu = bis(tert-butyl)-imidazolin-2-imino). Furthermore, the treatment of dimethylchlorosilane Me2(Cl)SiNIPr with AgOTf affords the contact ion pair Me2(OTf)SiNIPr by substitution of the chloride. A novel complex with the formula [Me2(DMAP)SiNIPr][OTf] was prepared by coordination with 4-dimethylamino-pyridine (DMAP). In the solid state, the DMAP adduct [Me2(DMAP)SiNIPr][OTf] contains a distinct [Me2(DMAP)SiNIPr]+ moiety. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation
Molecules 2016, 21(8), 1079; doi:10.3390/molecules21081079
Received: 21 July 2016 / Revised: 3 August 2016 / Accepted: 4 August 2016 / Published: 18 August 2016
Cited by 2 | PDF Full-text (8225 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis), it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes
[...] Read more.
Polysilanes are known to exhibit the interesting property of σ-bond electron delocalization. By employing optical spectroscopy (UV-vis), it is possible to judge the degree of delocalization and also differentiate parts of the molecules which are conjugated or not. The current study compares oligosilanes of similar chain length but different substitution pattern. The size of the substituents determines the spatial orientation of the main chain and also controls the conformational flexibility. The chemical nature of the substituents affects the orbital energies of the molecules and thus the positions of the absorption bands. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Intramolecular Chain Hydrosilylation of Alkynylphenylsilanes Using a Silyl Cation as a Chain Carrier
Molecules 2016, 21(8), 999; doi:10.3390/molecules21080999
Received: 9 July 2016 / Revised: 25 July 2016 / Accepted: 27 July 2016 / Published: 1 August 2016
Cited by 2 | PDF Full-text (921 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Diorganyl[2-(trimethylsilylethynyl)phenyl]silanes 1ac and methyl-substituted phenylsilanes 1d and 1e were treated with a small amount of trityl tetrakis(pentafluorophenyl)borate (TPFPB) as an initiator in benzene to afford the corresponding benzosiloles (2ae) in moderate to good yields. However, no reaction
[...] Read more.
Diorganyl[2-(trimethylsilylethynyl)phenyl]silanes 1ac and methyl-substituted phenylsilanes 1d and 1e were treated with a small amount of trityl tetrakis(pentafluorophenyl)borate (TPFPB) as an initiator in benzene to afford the corresponding benzosiloles (2ae) in moderate to good yields. However, no reaction was observed for the reaction using [2-(1-hexynyl)phenyl]diisopropylsilane lf. The methyl substituent was tolerated under the reaction conditions and increased the yield of the corresponding benzosilole depending on the substitution position. From the result using 1f, the current reaction was found to require the trimethylsilyl group, which can stabilize intermediary alkenyl carbocations by the β-silyl effect. The current reaction can be considered an intramolecular chain hydrosilylation of alkynylarylsilanes involving silyl cations as chain carriers. Therefore, the silyl cations generated by hydride abstraction from hydrosilanes 1 with the trityl cation causes intramolecular electrophilic addition to the C-C triple bond to form ethenyl cations, which abstract a hydride from 1 to afford benzosiloles 2 with the regeneration of the silyl cations. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Isolation of a Cyclic (Alkyl)(amino)germylene
Molecules 2016, 21(8), 990; doi:10.3390/molecules21080990
Received: 7 July 2016 / Revised: 25 July 2016 / Accepted: 26 July 2016 / Published: 29 July 2016
Cited by 7 | PDF Full-text (2904 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A 1,4-addition of a dichlorogermylene dioxane complex with α,β-unsaturated imine 1 gave a dichlorogermane derivative 2 bearing a GeC3N five-membered ring skeleton. By reducing 2 with KC8, cyclic (alkyl)(amino)germylene 3 was synthesized and fully characterized. Germylene 3 readily reacted
[...] Read more.
A 1,4-addition of a dichlorogermylene dioxane complex with α,β-unsaturated imine 1 gave a dichlorogermane derivative 2 bearing a GeC3N five-membered ring skeleton. By reducing 2 with KC8, cyclic (alkyl)(amino)germylene 3 was synthesized and fully characterized. Germylene 3 readily reacted with TEMPO, N2O and S8, producing the 1:2 adduct 4, the oxo-bridged dimer 5 and the sulfido-bridged dimer 6, respectively. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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Open AccessArticle Synthesis of a Conjugated D-A Polymer with Bi(disilanobithiophene) as a New Donor Component
Molecules 2016, 21(6), 789; doi:10.3390/molecules21060789
Received: 30 April 2016 / Revised: 7 June 2016 / Accepted: 13 June 2016 / Published: 17 June 2016
Cited by 2 | PDF Full-text (1528 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A new conjugated donor-acceptor (D-A) polymer pDSBT2-BT containing bi(disilano-bisthiophene) and benzothiadiazole as donor and acceptor units, respectively, was prepared. The polymer showed a broad UV-vis absorption band at λmax = 599 nm in chlorobenzene. The absorption band was shifted to λmax
[...] Read more.
A new conjugated donor-acceptor (D-A) polymer pDSBT2-BT containing bi(disilano-bisthiophene) and benzothiadiazole as donor and acceptor units, respectively, was prepared. The polymer showed a broad UV-vis absorption band at λmax = 599 nm in chlorobenzene. The absorption band was shifted to λmax = 629 nm when the polymer was measured as a film, indicating enhanced interchain interactions of the polymer. Bulk hetero-junction polymer solar cells (BHJ-PSCs) were fabricated using pDSBT2-BT and PC71BM as host and guest materials, respectively. Optimization of cell fabrication conditions provided a maximal power conversion efficiency of 3.3% and the following cell parameters: Voc = 0.86 V, Jsc = 7.56 mA/cm2, and FF = 0.51. Although the efficiency still leaves much to be desired, these data underscore the potential of pDSBT2-BT as a high-voltage polymer solar cell material. Full article
(This article belongs to the Special Issue Advances in Silicon Chemistry)
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