A synthesis of a new macromolecular class of vinylene-arylene copolymers with double-decker silsesquioxane in the main chain is presented. Two transition-metal-catalyzed processes, which is silylative-coupling copolycondensation (SCC) and ADMET copolymerization of divinyl-substituted double-decker silsesquioxanes (DDSQ-2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ-silylene-vinylenearylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties.

Si-Bridged chromophores have been proposed as sources for blue-green emission in several technological applications. The origin of this dual emission is to be found in an internal charge transfer reaction. The current work is an attempt to describe the details of these processes in these kinds of substances, and to design a molecular architecture to improve their performance. Nuclear motions essential for intramolecular charge transfer (ICT) can involve processes from twisted internal moieties to dielectric relaxation of the solvent. To address these issues, we studied ICT between adjacent chromophores in a molecular compound containing N-isopropylcarbazole (CBL) and 1,4-divinylbenzene (DVB) linked by a dimethylsilylene bridge. In nonpolar solvents emission arises from the local excited state (LE) of carbazole whereas in solvents of higher polarity dual emission was detected (LE + ICT). The CT character of the additional emission band was concluded from the linear dependence of the fluorescence maxima on solvent polarity. Electron transfer from CBL to DVB resulted in a large excited-state dipole moment (37.3 D) as determined from a solvatochromic plot and DFT calculations. Steady-state and picosecond time-resolved fluorescence experiments in butyronitrile (293-173 K) showed that the ICT excited state arises from the LE state of carbazole. These results were analyzed and found to be in accordance with an adiabatic version of Marcus theory including solvent relaxation.

A new copolymer consisting of N-isopropylcarbazole/dimethylsilylene bridge/divinylbenzene units was synthesized and characterized. Dual fluorescence was observed in this copolymer in polar solvents. The absence of the second band at the lower transition energy of the two emission maxima in nonpolar solvents and the quantitative correlation of the lower-energy emission band maxima with solvent polarity indicate that the lower-energy emission band arises from an intramolecular charge transfer (ICT) state. A series of model compounds was synthesized to investigate the source of the charge transfer. It was found that the Si-bridged dyad with a single N-isopropylcarbazole and a single divinylbenzene was the minimum structure necessary to observe dual luminescence. The lack of dual luminescence in low-temperature glasses indicates that the ICT requires a conformation change in the copolymer. Analogous behavior in the Si-bridged dyad suggests that the ICT in the copolymer is across the silicon bridge. Results from time-resolved luminescence measurements with picosecond and subnanosecond excitation were used to support the thesis that twisted charge-transfer states are the likely source of the observed dual luminescence.

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Meeting the challenge of designing new light-emitting materials, we synthesized the compound N-isopropylcarbazole (CBL)−SiMe 2 −divinylbenzene (DVB), which represents the general idea of building attractive emitters by stitching together simple, well-known block elements. Following this strategy, an extraordinary emission emerges from photoinduced intramolecular processes between silylene-bridged adjacent chromophores, e.g., intramolecular energy and/or electron transfer (PET). The reported compound displays an attractive blue emission that occurs no matter which of the linked chromophores is excited (i.e., regardless of the excitation wavelength in the range 240−360 nm). Excitation of CBL leads directly to intramolecular charge transfer (ICT) state formation within 35 ps, whereas excitation of DVB results in "pumping" the CBL excited state via 300 fs energy transfer. In the latter case, DVB acts as an intramolecular photosensitizer of the ICT precursor. Both mechanisms, proceeding via ultrafast processes, are confirmed by femtosecond transient absorption experiments performed on the investigated bichromophoric compound and its individual Si-containing chromophores in acetonitrile solution. Analysis of the transient absorption bands allowed us to characterize the ICT excited state as a radical ion pair of carbazole radical cation and divinylbenzene radical anion linked by a silylene bridge.