Tailored Triarylborane Polymers as Supported Catalysts and Luminescent Materials

Abstract

Two novel luminescent triarylborane polymeric Lewis acids and the corresponding molecular model compounds were prepared, studies on their photophysical properties performed, and applications as supported catalysts in Lewis acid-catalyzed hydrosilylation reactions explored. Variations of the substituents in the ortho-position of a phenylene linker between the Lewis acidic borane and the polystyrene framework lead to steric and electronic fine-tuning while retaining the high Lewis acidity of the boron center. The polymeric Lewis acids serve as effective catalysts in the hydrosilylation of aldehyde, ketone, and imine compounds and because of their distinct solubility characteristics are readily amenable to recycling. In addition, as a result of the twisted biphenyl donor−π-acceptor structure, both the styrene copolymers and model compounds display strong luminescence in solution and the solid state, encompassing prompt fluorescence and in the case of the chlorophenyl-linked derivative also longer-lived room temperature phosphorescence (RTP). Consistent with quantum-chemical calculations, the greater donor strength of the 2,6dimethylphenyl in comparison to the 2-chlorophenyl linker leads to a red-shifted emission, while the chloro substituent leads to a larger gap between singlet and triplet excited states. In the solid state, distinctly different emission properties are observed for the polymers in comparison to the molecular compounds because of the site isolation of the chromophores embedded in the polymer matrix.

Conjugated Boron Porous Polymers Having Strong p−π* Conjugation for Amine Sensing and Absorption

“…Our interest in B-based building blocks stems from the empty p orbital of the B atom, enabling diverse applications in the areas of materials science and organic catalysis. For example, Yamaguchi and co-workers have reported that B containing materials show selective sensing properties toward the fluoride anion. − Liu and co-workers have shown that B–N containing units enhance the electron-accepting and electron-transporting characters of smaller molecules and polymers. , Jakle and co-workers revealed that tuning the chemical structure of B-moieties can improve the mechanical properties and catalytic performance of the polymeric materials. − Although they have been shown to exhibit diverse functionalities, B containing small molecules and polymers generally require blocks having large protecting groups to stabilize the B-centers against water and oxygen, which seriously limits enriching structure design and diversifying functionality of the B containing materials (Chart ). Furthermore, the large steric groups can also create twisted aromatic groups (Ars) at the B-centers that will diminish the electronic communication between the B-centers (Chart ).…”

Clickable Polymerization‐Induced Emission Luminogens Toward Color‐Tunable Modification of Non‐Traditional Intrinsic Luminescent Polymers

“…Luminescent polymers are an important class of functional polymer materials, which generally can be molecularly designed by incorporation of traditional luminogens into polymer chain through strategies such as conjugated 𝜋 system extension and 𝜋-𝜋 stacking. [18][19][20] Compared with those traditional strategies for luminescent polymers, polymerizationinduced emission (PIE) has become an emerging strategy for the molecular design of luminescent polymers without traditional luminogens. [21][22][23][24][25][26] Interestingly, the monomer and repeating unit of polymer are non-emissive; however, the resulting polymer is luminescent, where the smallest or simplest non-emissive moiety is regarded as PIE luminogen (PIEgen).…”

Structural and mechanistic studies of excitation- and temperature-tunable multicolor luminescence of triarylborane

“…These room-temperature phosphorescent functional groups with excellent luminescence properties have greatly stimulated the development of the phosphorescence field, leading to the emergence of many new room-temperature phosphorescent groups. Recently, several studies have shown that unique phosphorescence can be observed for boroorganic materials [42][43][44][45][46][47][48][49][50] especially triarylborane compounds due to unusual electronic structures. For example, Marder's group 47,50 found that triarylboranes without any lone pair of electrons can exhibit excellent RTP properties, e.g., tris (2,6dimethylphenyl)borane showing an ultralong phosphorescence lifetime of 478 ms. Zhao's group 46 reported that Br substituted triarylboranes exhibit RTP of 73 and 52 μs in the solid state.…”

“…More interestingly, Jäkle et al reported that the RTP can also be observed in triarylborane polymers. 45 Some other arylboranes were tested for their phosphorescent properties in solution at low temperatures. 42,43 All results indicate that the unique electronic properties conferred by the boron functional group and the lack of elemental toxicity make it an attractive and very promising area of exploration for organic RTP materials.…”