Emission Spectra of σ−π-Conjugated Organosilicon Copolymers Consisting of Alternating Dimethylsilylene and Aromatic Units

Abstract

Emission measurements were performed on a series of σ-π conjugated organosilicon copolymers, -[(SiMe2)mA]n-(m ) 1, 2, 3, 4, and 6), with alternating dimethylsilylene and π-conjugated units (A ) phenylene, diphenylene, and anthranylene) in various solvents. The copolymers with m g 2 exhibit a broad emission ascribable to an intramolecular charge transfer (CT) excited state resulting from the charge transfer between the dimethylsilylene and aromatic units. The solvatochromism of the emission spectra was observed for the organosilicon copolymers, where the emission maximum shifted to longer wavelength in polar solvents. The influence of the dimethylsilylene chain-length and the π-conjugated unit on the CT emission was investigated. The molecular orbital calculations on a model compound suggest that the vibronically structured emission is attributed to the π-character of the aromatic unit, and the structureless broad emission is ascribed to the σ-character of the Si-Si bond in the excited states. The emission lifetime and the quantum yield also show the dimethylsilylene chain-length dependence.

Electron Delocalization in Cross‐Conjugated p‐Phenylenevinylidene Oligomers

“…Linear p-conjugated systems, of which polyacetylene, poly(p-phenylenevinylene)s, and polythiophenes are well-known examples, have by far received the most attention. However, alternative modes of conjugation, [2,3] such as s conjugation found in polysilanes, [4] s ± p conjugation in oligo(cyclohexylidene)s [5,6] and silylene-arylene polymers, [7,8] and homoconjugation in diphenylpropanes, diphenylsilanes, [9,10] and 7,7-diarylnorbornanes, [11] can also form the basis of interesting electronic features.…”

Synthesis and Photophysical Properties of Fluorene or Carbazole-Based Alternating Copolymers Containing Si and Ethynylene Units in the Main Chain

“…1 H and 13 C NMR spectra of the copolymers were recorded at room temperature on a JEOL-JNM-LA300 spectrometer in pulse Fourier transform mode. The sample solution was made in CDCl 3 as a solvent, and the resonance of CDCl 3 (7.24 ppm) was used as an internal reference.…”

“…The result indicates that the reaction of the copolymers with low molecular weights could not form the infinite network structure and yielded the branching copolymers. The degree of the branching, reaction conversion of the ethynly groups in the copolymers, was determined by 13 C NMR spectroscopy. The results cleared that 1/2 to 2/3 part of the ethynyl groups in the copolymers reacted with DMSB.…”

Organic electroluminescent devices using organosilicon polymers containing phenylene or diethynylanthracene units

“…[8][9][10][11][12] However, there have been only a few reports thus far regarding the optical emission of this type of polymer. Fang et al have recently studied the emission spectra of a series of s-p-conjugated organosilicon polymers with an alternating arrangement of oligosilanylene units and p-electron system, [13][14][15][16][17] demonstrating that the emission changes from the type from a s-conjugation unit such as silanylene to the that from a p-conjugation unit response to increasing the chain length of the oligosilanylene units, as well as in response to reducing the extension of the pelectron system. 17 The emission lifetime and the quantum yield also depend on the dimethylsilanylene chain length.…”

“…Fang et al have recently studied the emission spectra of a series of s-p-conjugated organosilicon polymers with an alternating arrangement of oligosilanylene units and p-electron system, [13][14][15][16][17] demonstrating that the emission changes from the type from a s-conjugation unit such as silanylene to the that from a p-conjugation unit response to increasing the chain length of the oligosilanylene units, as well as in response to reducing the extension of the pelectron system. 17 The emission lifetime and the quantum yield also depend on the dimethylsilanylene chain length. Fang et al have also reported that the emission from the polymers having p-electron systems such as phenylene or biphenylene are solvatochromic, and the maxima are red-shifted in polar solvents, which can be explained by the CT (charge transfer)-type excited states between oligosilanylene and the aromatic units.…”