Silicon‐Bridge Effects on Photophysical Properties of Silafluorenes

Abstract

The preparation of 4,5-dimethylsilylene- or 4,5-tetramethyldisilylene-bridged 9-silafluorenes was achieved by lithiation of 2,2',6,6'-tetrabromobiphenyls followed by silylation with dichlorodimethylsilane or 1,2-dichloro-1,1,2,2-tetramethyldisilane, respectively. X-ray analysis of the silylene-bridged silafluorene revealed that the molecular framework was perfectly planar and four Si-C(methyl) sigma bonds were completely orthogonal to the plane. Both the silicon atoms and the benzene rings were significantly deformed from the normal tetrahedral and hexagon shapes, respectively. The silicon bridge at the 4,5-positions was found to induce a red shift of the absorption and fluorescence spectra measured in cyclohexane, compared with 9-silafluorenes. It is remarkable that the disilylene-bridged silafluorene emitted blue light (lambda(em)=450 nm) with a large Stokes shift. The emission maxima of the silicon-bridged silafluorenes in thin films were similar to those measured in cyclohexane solution. DFT calculations suggested that introduction of the silicon bridge led to increases in both the HOMO and LUMO levels compared with 9-silafluorene.

Integrated Palladium‐Catalyzed Arylation of Heavier Group 14 Hydrides

“…Various electronically and structurally diverse aryl iodides were successfully used to produce the corresponding quaternary Group 14 compounds. In particular, a smoother transformation was observed when 4-iodoanisole was used as the first arylating agent, and doubly arylated compounds could be obtained in moderate to good yields by using a second aryl-A C H T U N G T R E N N U N G ating agent (Table 6, entries [1][2][3][4][5][6][7][8][9][10][11][12][15][16][17][18]. The reaction was sensitive to the electronic properties of the first arylating agent.…”

Conjugated Organosilicon Materials for Organic Electronics and Photonics

“…19) despite their moderate efficiency (Φ F ranges from 0.02 for T 2 TS 2 S 2 to 0.22 for PyTS 2 S 2 ). Solely TS3T 2 Et, the oligomer containing eight conjugated aromatic rings, was found to be active as semiconductor in OTFT, vapordeposited films as well as spin-coated films of which exhibiting a hole mobility of μ = 2.6 × 10 [84]. 4,5-Dimethylsilyleneor 4,5-tetramethyldisilylene-bridged 9-silafluorenes Si2F and SiDSF were prepared by lithiation of 2, 2 , 6, 6 -tetrabromobiphenyls followed by silylation with dichlorodimethylsilane or 1,2-dichloro-1,1,2,2-tetramethyldisilane, respectively.…”

Catalytic Asymmetric Bromine‐Lithium Exchange: A New Tool to Build Axial Chirality

“…The organic phases were filtered through a pad of Na 2 SO 4 and solvents removed on a rotatory evaporator. Chromatographic separation on silica gel, with pure pentane, then pentane/ether (9/1), gave a white solid with ee = 80%; yield: 86%; [a] (S)-(6,6'-Dibromobiphenyl-2,2'-diyl)bis(trimethylsilane) (32) [16] Following the general procedure of asymmetric brominelithium exchange using ent-14 as catalyst with as electrophile TMSCl (5 equiv.) in 5 mL of THF.…”