σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation

Hlina, Johann; Stella, Filippo; Meshgi, Mohammad Aghazadeh; Marschner, Christoph; Baumgartner, Judith

doi:10.3390/molecules21081079

Cited by 13 publications

(15 citation statements)

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“…From our studies on the σ-bond electron delocalization of oligosilanes and germaoligosilanes [14,15,16,17,18,19,20,21] we have learned that that tris(trimethylsilyl)silyl terminated methyloligosilanes exibit a strong preference for transoid conformations in the solid state and in solution. Increasing the lengths of the main chain results in bathochromic shifts of the low-energy (σ→σ*) transition indicating extension of the delocalized system.…”

Section: Resultsmentioning

confidence: 99%

“…Our group and others have shown that oligosilanes with large end groups exhibit a preference to acquire a transoid conformation as long as the end groups are not too far apart from each other [14,15,16,17,18,19,20]. In a recent study we reported on the influence of the formal replacement of silicon atoms in oligosilanes by germanium atoms on the σ-electron delocalization properties, which was found to be rather negligible [21].…”

Section: Introductionmentioning

confidence: 99%

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Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

2017

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Molecules containing catenated heavy group 14 atoms are known to exhibit the interesting property of σ-bond electron delocalization. While this is well studied for oligo- and polysilanes the current paper addresses the UV-absorption properties of small tin containing oligosilanes in order to evaluate the effects of Sn–Si and Sn–Sn bonds as well as the results of substituent exchange from methyl to phenyl groups. The new stannasilanes were compared to previously investigated oligosilanes of equal chain lengths and substituent pattern. Replacing the central SiMe2 group in a pentasilane by a SnMe2 unit caused a bathochromic shift of the low-energy band (λmax = 260 nm) of 14 nm in the UV spectrum. If, instead of a SnMe2, a SnPh2 unit is incorporated, the bathochromic shift of 33 nm is substantially larger. Keeping the SnMe2 unit and replacing the two central silicon with tin atoms causes shift of the respective band (λ = 286 nm) some 26 nm to the red. A similar approach for hexasilanes where the model oligosilane [(Me3Si)3Si]2(SiMe2)2 (λmax = 253 nm) was modified in a way that the central tetramethyldisilanylene unit was exchanged for a tetraphenyldistannanylene caused a 50 nm bathochromic shift to a low-energy band with λmax = 303 nm.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

2017

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“…A cisoid turn of the main chain leads to broken conjugation between the connected units. [30,31] For the cases of siloles 3 and 5,w ea ssumet hat only trisilanyl units fulfill the conformationald emands of effective conjugation between the silole core and the oligosilanyl unit (cf. siloles 3 and 5 in Figure 13).…”

Section: Discussionmentioning

confidence: 99%

The Combination of Cross‐Hyperconjugation and σ‐Conjugation in 2,5‐Oligosilanyl Substituted Siloles

Pöcheim

Özpınar

Müller

et al. 2020

Chemistry A European J

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Reaction of a 2,5‐dilithiated silole with excess dichlorodimethylsilane gives the respective 2,5‐bis(chlorodimethylsilyl) substituted silole. This compound can be converted to 2,5‐bis(oligosilanyl) substituted siloles by addition of a suitable oligosilanide. In the UV spectra of the thus obtained compounds the lowest energy absorptions are bathochromically shifted compared to the absorptions of the two constituents, namely the 2,5‐disilyl substituted silole and a trisilane. The bathochromic shift is interpreted as being caused by a mixed σ‐conjugation/cross‐hyperconjugation. This assumption is supported by TD‐DFT calculations, which show a significant contribution from Si−Si bonds to the HOMO of the molecule.

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“… 2 − 4 This can allow functionality to be fine-tuned through the orbital interaction between the σ-orbital of silicon and the π-orbital of π-electron systems. 5 , 6 Besides, the highly flexible nature of the Si–Si chain makes the molecule more soluble in common organic solvents and less possible to stack under concentrated conditions, 7 which is beneficial for their practical application and the improvement of emission efficiency in the solid state. Oligosilanyl derivatives have been utilized as novel electronic and optical molecular materials, such as nonlinear optic materials, 8 hole-transporting materials, 9 and emitters in organic light-emitting diodes (OLEDs).…”

Section: Introductionmentioning

confidence: 99%

Oligosilanyl-Bridged Biscarbazoles: Structure, Synthesis, and Spectroscopic Properties

et al. 2020

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Oligosilanyl-bridged systems are expected to give rise to unique optoelectronic properties because of σ–π conjugation between the Si–Si σ orbital and the aryl π orbital. Herein, we synthesized a small series of novel biscarbazoles bridged with permethylated oligosilanyl units (−[Si(CH 3 ) 2 ] n –, n = 1–4) and examined their spectroscopic properties in detail. In the target molecules BCzSi n , n = 2–4, the efficient σ–π conjugation elevated the highest occupied molecular orbital energy level with no influence on the lowest unoccupied molecular orbital. In the solid state, the emission full width at half-maximum (fwhm) of all the compounds narrowed significantly, while the emission efficiency increased and the emission color of carbazole was retained. This research provided a very simple and general way of subtly manipulating the electronic properties of organic materials to construct an emissive color-retaining system for multifunctional applications.

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σ-Bond Electron Delocalization in Oligosilanes as Function of Substitution Pattern, Chain Length, and Spatial Orientation

Cited by 13 publications

References 58 publications

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

Incorporating Methyl and Phenyl Substituted Stannylene Units into Oligosilanes. The Influence on Optical Absorption Properties

The Combination of Cross‐Hyperconjugation and σ‐Conjugation in 2,5‐Oligosilanyl Substituted Siloles

Oligosilanyl-Bridged Biscarbazoles: Structure, Synthesis, and Spectroscopic Properties

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