Synthesis and optical properties of σ-π Conjugated organic-inorganic hybrid gels

Organic-inorganic hybrid gels containing Si-vinylene units have been synthesized by a hydrosilylation reaction of tri- or tetra-ethynyl aryl compounds, 1,3,5-triethynylbenzene (TEB), 3,3,5,5-tetraethynylbiphenyl (TEBP), or tetrakis(4-ethynylphenyl)methane (TEPM), and bisdimethylsilyl compounds, 1,1,3,3-tetramethyldisiloxane (TMDS) or 1,4-bisdimetylsilylbenzene (BDMSB), in toluene. Network structure of the resulting gels was quantitatively characterized by a scanning microscopic light scattering. The reactions yielded the gels having homogeneous network structure of 1.5-2.9 nm mesh size under the monomer concentrations that were relatively higher than the critical gelation concentration. The gels obtained from TEB showed broad absorption in the range from 340 to 370 nm, and emission in the range from 440 to 490 nm. The TEB-BDMSB gels showed remarkable red shift of the emission in comparison with that of the corresponding reaction solutions derived from the network formed by σ-π conjugation. The TEPM-TMDS, BDMSB gels exited by 280 nm showed not only the emission peak at around 360 nm derived from TEPM, but the broad peak at around 420 nm, which should be derived from interaction between phenyl groups of TEPM in the gels.