Diboramacrocycles are a new form of borole dimers, participating in various addition reactions as “masked” boroles. The reaction of a less crowded diboramacrocycle with organic azides affords unprecedented complex heteropropellanes.

A series of bifuran-bridged bis(triarylboranes) have been synthesized via classical metathesis or catalytic silicon/boron exchange reactions, respectively. The products obtained are strongly luminescent, with quantum yields up to 85%, and...

Doping of π-conjugated polymers or molecular compounds with trivalent boron atoms has recently emerged as a viable strategy to produce new materials with intriguing properties and functions. The combination of boron with furan moieties has been only scarcely explored so far, although the resulting furan-based materials have several notable features, including favorable optoelectronic properties and improved sustainability. Herein, we investigate the doping of α-polyfurans with a varying number of boron atoms. A series of poly­(oligofuran boranes) and oligofuran-bridged bisboranes have been prepared via microwave-assisted Stille-type catalytic cross-coupling protocols. In the solid-state structures of the molecular compounds, the furan and the borane moieties exhibit a strictly coplanar arrangement; the derivative with a pentafuran bridge forms a dimeric structure in the solid state. All new compounds show considerable absorption and emission features in the visible range that arise from π–π* transitions in the oligofurylborane backbone. They are highly luminescent with quantum yields between 89 and 97% for the bisboranes and up to 87% for the difuran-bridged polymer PB2F. Their emission colors can be effectively tuned in the visible range from blue to orange via the length of the oligofuran linker. Spectroelectrochemical investigations on the difuran-bridged bisborane BB2F and polymer PB2F revealed fully reversible stepwise reductions to the respective radical anion (polaron), with absorption features in the near-infrared (NIR) region, and subsequently to a dianion (dipolaron). Overall, the doping of α-oligofurans with boron leads to a decrease of the frontier orbital energies, a reduction of the electronic band gap, and the formation of very robust and oxidatively stable materials.

The reaction of a cyclic alkyl(amino)carbene (CAAC)stabilized thiazaborolo [5,4-d]thiazaborole (TzbTzb) with strong Brønsted acids, such as HCl, HOTf (Tf = O 2 SCF 3 ) and [H(OEt 2 ) 2 ][BAr F 4 ] (Ar F = 3,5-(CF 3 ) 2 C 6 H 3 ), results in the protonation of both TzbTzb nitrogen atoms. In each case X-ray crystallographic data show coordination of the counteranions (Cl À , OTf À , BAr F 4 À ) or solvent molecules (OEt 2 ) to the doubly protonated fused heterocycle via hydrogen-bonding interactions, the strength of which strongly influences the 1 H NMR shift of the NH protons, enabling tuning of both the visible (yellow to red) and fluorescence (green to red) colors of these salts. DFT calculations reveal that the hydrogen bonding of the counteranion or solvent to the protonated nitrogen centers affects the intramolecular TzbTzb-to-CAAC charge transfer character involved in the S 0 !S 1 transition, ultimately enabling fine-tuning of their absorption and emission spectral features.