1,1,4,4-Tetra-tert-butyl-1,4-dichloro-2,2,3,3-tetra­phenyl­tetra­silane

The title compound, C40H56Cl2Si4, was synthesized by the coupling of 1,1-di-tert-butyl-1,2-dichloro-2,2-diphenyl­disilane with lithium. The asymmetric unit contains one half-mol­ecule, which is completed by an inversion centre. In the mol­ecule, the tetra­silane skeleton adopts a perfect anti conformation and the Si—Si bonds [2.4355 (5) and 2.4328 (7) Å] are longer than the standard Si—Si bond length (2.34 Å). The Si—Si—Si angle [116.09 (2)°] is larger than the tetra­hedral bond angle (109.5°). These long bond lengths and the wide angle are favorable for reducing the steric hindrance among the tert-butyl and the phenyl groups. The dihedral angle between the phenyl rings in the asymmetric unit is 37.36 (8)°

1,1,3,3-Tetra-tert-butyl-2,2-diisopropyl-4,4-diphenylcyclotetrasilane

The molecule in the structure of the title compound, C34H60Si4, lies on a twofold rotation axis that passes through the two Si atoms, resulting in a planar cyclotetrasilane ring. The dihedral angle between the cyclotetrasilane ring and the phenyl ring is 68.20 (5)°. The Si—Si bonds [2.4404 (8) and 2.4576 (8) Å] are longer than a standard Si—Si bond (2.34 Å) and the C—Si—C bond angle [97.07 (14)°] of the phenyl-substituted Si atom is smaller than the tetrahedral bond angle (109.5°). These long bonds and small bond angle are favorable for reducing the steric hindrance among the bulky substituents

Cooperation of σ–π and σ*–π* Conjugation in the UV/Vis and Fluorescence Spectra of 9,10-Disilylanthracene

In 1996, we reported that silyl groups of 9,10-disilylanthracenes significantly affect the UV/Vis and fluorescence spectra. Although the results indicate that the silyl groups have strong electronic effects on anthracene, the details of the mechanisms responsible for this have not yet been clarified. This article describes the analysis of the UV/Vis and fluorescence spectra of 9,10-bis(diisopropylsilyl)anthracene by theoretical calculations. This study reveals that π conjugation of anthracene is extended by cooperation of σ–π and σ*–π* conjugation between the silyl groups and anthracene. This effect increases the transition moment of the π–π* transition of anthracene. As a result, the molecular extinction coefficient of the 1La band and the fluorescence quantum yield are increased

anti-2,2,3,3,6,6,7,7,10,10,11,11,14,14,15,15-Hexadecamethyl-2,3,6,7,10,11,14,15-octasilapentacyclo[10.4.2.24,9.05,8.013,16]icosa-1(17),4,8,12(18),13(16),19-hexaene

The title compound, C28H52Si8, was synthesized by condensation of two molecules of 1,2,3,4-tetrakis(chlorodimethylsilyl)benzene with lithium. The 3,4-disila-1,2-benzocyclobutene rings in the centrosymmetric molecule are bridged by 1,1,2,2-tetramethyldisilanylene chains with an anti conformation. The benzene rings are deformed by fusion with a 3,4-disilacyclobutene ring resulting in a slight boat conformation. Two Si—C bonds are bent to reduce the steric repulsion between the methyl groups on the two Si atoms and the methyl groups on another two Si atoms