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  • 1
    Electronic Resource
    Electronic Resource
    Electrical Properties of G4-48azo Dendrimer Containing Azobenzene Functional Groups (2004)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 449-452 (Mar. 2004), p. 913-916 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this study, we attempted to fabricate dendrimer Langmuir-Blodgett (LB) filmsfunctionalized with azobenzene groups in their periphery. It is well known that azoenzene-type compounds undergo an efficient and fully reversible photo-isomerization reaction. We investigated monolayer behavior and its characteristics at air-water interface by LB method. Then the molecular behavior shift of the monolayer by 365[nm] light irradiation was also measured because of the isomerization of azobenzene group in periphery. The electrical properties of G4-48Azo dendrimer were compared with between trans form and cis form using metal/dendrimer LB film/metal (MIM)structure and using STM system
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/08/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.449-452.913.pdf
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  • 2
    Electronic Resource
    Electronic Resource
    Reaktivität von Silan- und Germaniminen Me2E=NR (E=Si, Ge)1) (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1357-1368 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Adduct Formation and Reactivity Of Silane- and Germaneimines Me2E=NR (E=Si, Ge)1)Silane- and Germaneimines Me2E= NR (E=Si, Ge; R=silyl), generated as reactive intermediates by thermal [2+3] cycloreversion from [2+3] cycloadducts of Me2E=C(SiMe3)2 or Me2E=NR with silyl azides RN3, combine with reactants a (e. g. NEtMe2) under addition (formation of adducts 7), with a - b [e. g. RO - H, RHN - H, X - SiMe3 (X=Cl, N3, MeO, Me2N), Cl - GeMe3, Cl - SnMe3] under insertion into the a - b bond (formation 13-16), with a=b (e.g. RN=EMe2, O=CPh2) under [2+2] cycloaddition (e. g. formation of 17, 18), with a=b=c (e.g. R′N=N=N) under [2+3] cycloaddition (formation of 19, 20), and with a=b - c - H (e.g. CH2=CR - CH2 - H, O=CMe - CH2 - H) under ene reaction (formation of 21-24). [2+4] cycloaddition of Me2Si=NR with organic 1,3-dienes (e. g. CH2=CR - CR=CH2, cyclopentadiene) is not observed. By comparison with ethenes Me2E=C(SiMe3)2, imines Me2E=NR have greater tendency for insertion and lesser tendency for cycloaddition; by comparison with silaneimines Me2Si=NR, germaneimines Me2Ge=NR are possibly less Lewis acidic.
    Notes: Silan- und Germanimine Me2E=NR (E=Si, Ge; R=Silyl), erzeugt als Zwischenstufen durch thermische [2+3]-Cycloreversion aus den [2+3]-Cycloaddukten von Me2E=C(SiMe3)2 bzw. Me2E=NR mit Silylaziden RN3, reagieren mit Reaktanden a (z. B. NEtMe2) unter Addition (Bildung von Addukten 7), mit a-b [z. B. RO - H, RHN - H, X - SiMe3 (X=Cl, N3, MeO, Me2N), Cl - GeMe3] unter Insertion in die a - b-Bindung (Bildung von 13-16), mit a=b (z. B. RN=EMe2, O=Cph2) unter [2+2]-Cycloaddition (z. B. Bildung von 17, 18), mit a=b=c (z. B. R′N=N=N) unter [2+3]-Cycloaddition (Bildung von 19, 20) und mit a=b - c - H (z. B. CH2=CR - CH2 - H, O=CMe - CH2 - H) unter En-Reaktion (Bildung von 21-24). [2+4]-Cycloaddition von Me2Si=NR mit organischen 1,3-Dienen (z. B. CH2=CR - CR=CH2, Cyclopentadien) wird nicht beobachtet. Verglichen mit den Ethenen Me2E=C(SiMe3)2 zeigen die Imine Me2E=NSiMe3 eine größere Tendenz zur Insertion und kleinere Tendenz zur Cycloaddition; verglichen mit den Silaniminen Me2Si=NR sind die Germanimine Me2Ge=NR wohl weniger Lewis-sauer
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200814
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  • 3
    Electronic Resource
    Electronic Resource
    Reaktivität des Germaethens Me2Ge=C(SiMe3)2 (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 2980-2994 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactivity of the Germaethene Me2Ge=C(SiMe3)2Germaethene Me2Ge=C(SiMe3)2 (2), generated as a reaction intermediate by thermal elimination of LiX from Me2XGe—CLi(SiMe3)2 or by thermal cycloreversion from the adduct 2 · Ph2CO, combines with reactants a—b (e.g. MeO—H) under insertion into the a—b bond (formation of 4), with a = b—c—H (e.g. CH2=CR—CH2—H; R=H, Me, CMe=CH2) under ene reaction (formation of 19-21), and with [e.g. CH2=CHOMe, O=CPh2 or RN=N=N (R = tBu, tBu3-nMenSi), O=N=N or CH2=CR—CR=CH2 (R=H, Me)] under [2 + 2], [2 + 3], and [2 + 4] cycloaddition (formation of 6, 7 or 9-14 or 17, 18). By comparison with the silaethene Me2Si=C(SiMe3)2 (1), 2 is less Lewis acidic and its double bond is less polar.
    Notes: Das Germaethen Me2Ge=C(SiMe3)2 (2), erzeugt als Reaktionszwischenstufe durch thermische LiX-Eliminierung aus Me2XGe=CLi(SiMe3)2 (2 · LiX) oder durch thermische Cycloreversion aus dem Addukt 2 · Ph2CO, reagiert mit Reaktanden a= (z. B. MeO=H) unter Insertion in die a-b-Bindung (Bildung von 4), mit a—b—c—H (z. B. CH2=CR=CH2=H; R = H, Me, CMe=CH2) unter En-Reaktion (Bildung von 19-21) und mit [z. B. CH2=CHOMe, O=CPh2 oder RN=N=N (R=tBu, tBu3-nMenSi), O=N=N oder CH2=CR—CR=CH2 (R = H, Me)] unter [2 + 2]-, [2 + 3]- sowie [2 + 4]-Cycloaddition (Bildung von 6, 7 bzw. 9-14 bzw. 17, 18). Verglichen mit dem Silaethen Me2Si=C(SiMe3)2 (1), ist 2 weniger Lewis-sauer und seine Doppelbindung unpolarer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861191009
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  • 4
    Electronic Resource
    Electronic Resource
    Erzeugung und Nachweis des Germaethens Me2Ge=C(SiMe3)2 (1986)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 119 (1986), S. 2966-2979 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Generation and Evidence of the Germaethene Me2Ge=C(SiMe3)2Bromogermyldisilylmethanes (Me3Si)2(Me2XGe)CBr (3-13) are formed as a result of the reaction of (Me3Si)2(Me2PhGe)CBr (14) with bromine (X = Br) and also through the reaction of (Me3Si)2(Me2BrGe)CBr (3) with AgX (X = F, Ph2POn) or MX (M = H, Li, Na; X = OR, SR, R). Lithium organyls RLi convert 3-11 (X = Hal, OR, SR, Ph2POn) at low temperatures by Br/Li exchange into protolysable, thermolabile compounds (Me3Si)2(Me2XGe)CLi, and by X/R exchange into (Me3Si)2(Me2RGe)CBr. Thermal decomposition of (Me3Si)2(Me2XGe)CLi in diethyl ether at -110 to 100°C leads under LiX elimination to 1,3-digermacyclobutane [Me2Ge=C(SiMe3)2]2 (24). The reactive intermediate is the germaethene Me2Ge = C(SiMe3)2 (2), the intermediate existence of which has been established through chemical means by trapping 2 with 2,3-dimethyl-1,3-butadiene (formation of a [2 + 4] cycloadduct as well as an ene-reaction product).
    Notes: Bromgermyldisilylmethane (Me3Si)2(Me2XGe)CBr (3-13) entstehen durch Reaktion von (Me3Si)2(Me2PhGe)CBr (14) mit Brom (X = Br) sowie durch Reaktion von (Me2Si)2(Me2BrGe)CBr (3) mit AgX (X = F, Ph2POn) oder MX (M = H, Li, Na; X = OR, SR, R). Lithiumorganyle RLi verwandeln 3-11 (X = Hal, OR, SR, Ph2POn) bei tiefen Temperaturen unter Br/Li-Austausch in protolysierbare, thermolabile Verbindungen (Me3Si)2(Me2XGe)CLi und unter X/R-Austausch in (Me3Si)2(Me2RGe)CBr. Der thermische Zerfall von (Me3Si)2(Me2XGe)CLi führt in Diethylether bei -110 bis 100°C unter LiX-Eliminierung zum 1,3-Digermacyclobutan [Me2Ge=C(SiMe3)2]2 (24). Reaktives Zwischenprodukt ist das Germaethen Me2Ge = C(SiMe3)2 (2), dessen intermediäre Existenz auf chemischem Wege durch Abfangen von 2 mit 2,3-Dimethyl-1,3 butadien wahrscheinlich gemacht werden konnte (Bildung eines [2 + 4]-Cycloaddukts sowie eines En-Reaktionsprodukts.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19861191008
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  • 5
    Electronic Resource
    Electronic Resource
    Speicherung von Silan- und Germaniminen Me2E=NR (E=Si, Ge) in Form von Sila- und Germadihydrotetrazolen1) (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1213-1221 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Storage of Silan- and Germanimines Me2E=NR(=Si, Ge) by Way of Sila- or Germadihydrotetrazoles1)Silan- and germanimines Me2E=NR (1, 2) [generated by thermolysis of sila- and germadihydrotriazoles 3, 4; E=Si, Ge; R=SiMentBu3-n, SiPh3, EMe2N(SiMe3)2] react with azidoalkanes or -silanes R′N3 [R′=tBu, SiMentBu3-n, SiPh3, SiMe2N(SiMe3)2] by [2 + 3] cycloaddition to form sila- or germatetrazoles 5, 6 (in addition, insertion products of Me2E=NR in the R′N bond of the azides and others are formed in some cases). The sila- or germadihydrotetrazoles decompose at raised temperatures in a first-order reaction, reversing their formation by [2 + 3] cycloreversion into azides R′N3 or RN3 and imines Me2E=NR or Me2E=NR′ (rate constants: Table 1). Consequently, azides operate as stores for silan- and germanimines. The unsaturated systems are formed only as short-lived intermediates. Their stabilization, as a rule, takes place by dimerization and/or insertion of the imines into the RN or R′N bond of the azides, formed as well by thermolysis of dihydrotetrazoles.
    Notes: Silan- bzw. Germanimine Me2E=NR (1,2) [erzeugt durch Thermolyse von Sila- und Germadihydrotriazolen 3,4; E=Si, Ge; R=SiMentBU3-n, SiPh3, EMe2N(SiMe3)2] reagieren mit Azidoalkanen und -silanen R′N3 [R′=tBu, SiMentBu3-n, SiPh3, SiMe2N(SiMe3)2] unter [2 + 3]-Cycloaddition, d. h. Bildung von Sila- bzw. Germadihydrotetrazolen 5,6 (in einigen Fällen entstehen darüber hinaus Insertionsprodukte von Me2E=NR u. a. in die R′N-Bindung der Azide). Die Sila- bzw. Germadihydrotetrazole zersetzen sich ihrerseits bei erhöhter Temperatur nach 1. Reaktionsordnung in Umkehrung ihrer Bildung unter [2 + 3]- Cycloreversion in Azide R′N3 bzw. RN3 und Imine Me2E=NR bzw. Me2E=NR′ (Geschwindigkeitskonstanten: Tab. 1). Somit wirken Azide als Speicher für Silan- und Germanimine. Die ungesättigten Systeme entstehen nur als kurzlebige Zwischenprodukte. Ihre Stabilisierung erfolgt in der Regel durch Dimerisierung und/oder Insertion der Imine in die RN- bzw. R′N-Bindung der thermisch aus den Dihydrotetrazolen ebenfalls gebildeten Azide.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200717
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  • 6
    Electronic Resource
    Electronic Resource
    Erzeugung von Silan- und Germaniminen Me2E=NR (E=Si, Ge) aus Sila- und Germadihydrotriazolen1) (1987)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 120 (1987), S. 1203-1212 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Silan- and Germanimines Me2E=NR(E = Si, Ge) from Sila and Germadihydrotriazoles1)Sila- or germaethene Me2E=C(SiMe3)2 [E=Si, Ge; generated by reaction of BuLi with Me2EBr-CBr(SiMe3)2 in Et2O] quantitatively react with azidoalkanes or -silanes RN3 [R=tBu, p-Tol. tBunMe3-nSi, Ph3Si, (Me3Si)2NMe2E, Me2SiN3] at-78°C by [2 + 3] cycloaddition to form sila- or germadihydrotriazoles 3 and 4, respectively. The latter decompose partly below (E=Si, R=silyl), partly at or above room temperature (E=Si, R=alkyl; E=Ge) in a first-order reaction by isomerization into diazomethane derivatives as well as by [2 + 3] cycloreversion into (Me3Si)2C=N=N and silan- or germanimines Me2E=NR (rate constants: Table 1). The unsaturated compounds Me2E=NR are formed as short-lived intermediates. Their stabilization, as a rule, takes place by dimerization and in exceptional cases, by reaction with the silan- or germanimine sources (R=SiMe3) or by intramolecular migration processes [R=EMe2N(SiMe3)2, SiPh3].
    Notes: Sila- bzw. Germaethen Me2E=C(SiMe3)2 [E=Si, Ge; erzeugt durch Reaktion von BuLi mit Me2EBr-CBr(SiMe3)2 in Et2O] reagieren mit Azidoalkanen und -silanen RN3 [R=tBu, p-Tol, tBunMe3-nSi, Ph3Si, (Me3Si)2NMe2E, Me2SiN3] bei-78°C quantitativ unter [2 + 3]-Cycloaddition, d.h. unter Bildung von Sila- bzw. Germadihydrotriazolen 3 bzw. 4. Letztere zersetzen sich teils unterhalb (E=Si, R=Silyl), teils bei oder oberhalb Raumtemperatur (E=Si, R=Alkyl; E=Ge) nach 1. Reaktionsordnung unter Isomerisierung in Diazomethan-Derivate sowie unter [2 + 3]-Cycloreversion in (Me3C=N=N und Silan- bzw. Germanimine Me2E=NR (Geschwindigkeitskonstanten: Tab. 1). Die ungesättigten Verbindungen Me2E=NR entstehen als kurzlebige Zwischenprodukte. Ihre Stabilisierung erfolgt in der Regel durch Dimerisierung, in Ausnahmefällen durch Reaktion mit den Silan- bzw. Germaniminquellen (R=SiMe3) oder durch intramolekulare Umlagerungsprozesse [R=EMe2N(SiMe3)2, SiPh3].
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19871200716
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