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23 results on '"Bejan, Iulia"'

3. Transfer of a disilenyl moiety to aromatic substrates and lateral functional group transformation in aryl disilenes

Author

Jeck, Jonathan, Nied, Dominik, Breher, Frank, Scheschkewitz, David, Bejan, Iulia, and White, Andrew J.P.

Subjects
Lithium compounds -- Electric properties, Silicon compounds -- Electric properties, Titanium compounds -- Electric properties, Chemistry
Abstract

The reaction of 1 equiv of the disilenide [Tip.sub.2]Si[double bond]Si(Tip)Li (Tip = 2,4,6-[super i][Pr.sub.3][C.sub.6][H.sub.2]) with para-substituted phenyl iodides, 4-X-PhI, has transferred the [Tip.sub.2]Si[double bond]Si(Tip) moiety with elimination of lithium iodide to produce the laterally functionalized disilenes [Tip.sub.2]Si[double bond]Si(Tip)(4-X-Ph) [X = H, F, Cl, Br, I). The UV-vis absorptions of the functionalized disilenes have shown a linear correlation with electronic Hammett parameters.

Published
2010

5. Transfer of Si=Si double bonds on organic substrates: Stable conjugated systems vs. rearrangement reactions

Author

Bejan, Iulia Cornelia

Subjects
Umlagerung, ddc:540, Doppelbindung, Silicium, Konjugiertes System
Abstract

In dieser Arbeit wurde die Synthese und Charakterisierung von Systemen mit mehreren phenylen- oder vinylen-konjugierten Si=Si- bzw. C=Si-Doppelbindungen angestrebt. An diesen Verbindungen wurde die Art der Wechselwirkung sowie der Grad der Konjugation zwischen siliciumhaltigen Doppelbindungen und aromatischen Verknüpfungseinheiten untersucht. Auf diese Weise wurde die Grundlage für die Darstellung von Polymeren auf Basis dieser Bauelemente bereitet, um die aktuellen Entwicklungen von P=C- und P=P- Doppelbindungssystemen hin zu schwereren Analoga von Polyphenylenvinylen Copolymeren nachvollziehen zu können., In this thesis was shown that disilenide, i. e. disila analogue to vinyl anion, constitute an excellent reagent for the synthesis of new compounds with conjugated Si=Si double bonds. On the first model system for the silicon analogues of poly(phenylene-vinylene)s (PPVs) was established the conjugation of the two Si=Si moieties over the phenylene bridge. New compounds bearing cyclic and bicyclic structures were synthesised by the reaction of disilenid with unsaturated electrophiles. In a midterm time frame the availability of compounds with more than one Si=Si units will offer an alternative access to siliconpolymers. Moreover, the unique dual reactivity of disilenid provides new synthesic routes for the difficult access to the polycyclic ringsystems incorporating silicon atoms.

Published
2010

16. How Stress Factors Affect Electroless Affect Electroless: Many factors can impact internal stress, but tests show bath age and deposition rate are the biggest influencers.

Author

BEJAN, IULIA

Subjects
DEPOSITIONS, NICKEL-plating, STRESS measurement (Mechanics), COATING processes, THICKNESS measurement
Abstract

The article focuses on the role of bath age and deposition rate which impact on the internal stress in electroless nickel coatings in certain applications. Topics discussed include deflection method to measure stress in a coating, thickness of coating depending on factors such as volume, heat distribution and bath age, and effect of phosphorus incorporation.

Published
2018

18. (Oligo)aromatic species with one or two conjugated Si[double bond, length as m-dash]Si bonds: near-IR emission of anthracenyl-bridged tetrasiladiene.

Author

Obeid NM, Klemmer L, Maus D, Zimmer M, Jeck J, Bejan I, White AJP, Huch V, Jung G, and Scheschkewitz D

Abstract

A series of aryl disilenes Tip 2 Si[double bond, length as m-dash]Si(Tip)Ar (2a-c) and para-arylene bridged tetrasiladienes, Tip 2 Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip 2 (3a-d) are synthesized by the transfer of the Tip 2 Si[double bond, length as m-dash]SiTip unit to aryl halides and dihalides by nucleophilic disilenides Tip 2 Si[double bond, length as m-dash]SiTipLi (Tip = 2,4,6-iPr 3 C 6 H 2 , Ar = aryl substituent, LU = para-arylene linking unit). The scope of the nucleophilic Si[double bond, length as m-dash]Si transfer reaction is demonstrated to also include substrates of considerable steric bulk such as mesityl or duryl halides Ar-X (Ar = Mes = 2,4,6-Me 3 C 6 H 2 ; Ar = Dur = 2,3,5,6-Me 4 C 6 H, X = Br or I). Bridged tetrasiladienes Tip 2 Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip 2 with more extended linking units surprisingly exhibit fluorescence at room temperature, albeit weak. DFT calculations suggest that partial charge transfer character of the excited state is a possible explanation.

Published
2017
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19. σ-π conjugated organosilicon hybrid polymers from copolymerization of a tetrasiladiene and 1,4-diethynylbenzene.

Author

Majumdar M, Bejan I, Huch V, White AJ, Whittell GR, Schäfer A, Manners I, and Scheschkewitz D

Abstract

A catalyst- and by-product-free protocol for the synthesis of σ-π conjugated organosilicon polymers is reported. The regiospecific [2+2] cycloaddition of C≡C triple bonds to Si=Si double bonds allowed the preparation of air-stable ethynyl-terminated extended monomers from 1,4-bis(ethynyl)benzene and the para-phenylene bridged tetrasiladiene, Tip2 Si=SiTip-pC6H4-SiTip=SiTip2 (Tip = 2,4,6-iPr3C6H2). The polymer obtained from the extended monomer and further tetrasiladiene exhibits pronounced σ-π conjugation, as was evident from the red-shift in the absorption spectrum compared to model systems. We show that the thermal stability of the employed bis(alkyne) co-monomer is translated into this polymer., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2014
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