In this combined experimental and theoretical study, a computational protocol is reported to predict the excited states in D‐π‐A compounds containing the B(
F
Xyl)
2
(
F
Xyl = 2,6‐bis(trifluoromethyl)phenyl) acceptor group for the design of new thermally activated delayed fluorescence (TADF) emitters. To this end, the effect of different donor and π‐bridge moieties on the energy gaps between local and charge‐transfer singlet and triplet states is examined. To prove this computationally aided design concept, the D‐π‐B(
F
Xyl)
2
compounds
1
–
5
were synthesized and fully characterized. The photophysical properties of these compounds in various solvents, polymeric film, and in a frozen matrix were investigated in detail and show excellent agreement with the computationally obtained data. Furthermore, a simple structure–property relationship is presented on the basis of the molecular fragment orbitals of the donor and the π‐bridge, which minimize the relevant singlet–triplet gaps to achieve efficient TADF emitters.
Using 4‐phenylpyridine or 2‐phenylpyridine in place of biphenyl, two electron‐poor phenylpyridyl‐fused boroles, [TipPBB1]4 and TipPBB2 were prepared. [TipPBB1]4 adopts a unique coordination mode and forms a tetramer with a cavity in both the solid state and solution. The boron center of TipPBB2 is 4‐coordinate in the solid state but the system dissociates in solution, leading to 3‐coordinate borole species. Compared to its borafluorene analogues, the electron‐accepting ability of TipPBB2 is largely enhanced by the pyridyl group. TipPBB2 exhibits dual fluorescence in solution due to an equilibrium between free TipPBB2 and a weak intermolecular coordination adduct with a second molecule. This equilibrium was further investigated by low‐temperature NMR spectroscopy and photophysical studies. Theoretical studies indicate that the highest occupied molecular orbital (HOMO) of TipPBB2 localizes at the Tip group, in contrast to its borafluorene derivatives, wherein the HOMOs are localized on the borafluorene cores.
Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional molecules represents an extremely useful process in organic synthesis. Herein, we describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio-and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcohols. Control experiments demonstrated that the key to this high reactivity and selectivity is the addition of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex molecules. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be especially useful in a lead optimization program.
Bis(1-(4-tolyl)-carboran-2-yl)-(4-tolyl)-borane [(1-(4-MeC 6 H 4 )-closo-1,2-C 2 B 10 H 10 -2-) 2 (4-MeC 6 H 4 )B] (1), a new bis(ocarboranyl)-(R)-borane was synthesised by lithiation of the ocarboranyl precursor and subsequent salt metathesis reaction with (4-tolyl)BBr 2 . Cyclic voltammetry experiments on 1 show multiple distinct reduction events with a one-electron first reduction. In a selective reduction experiment the corre-sponding paramagnetic radical anion 1 * À was isolated and characterized. Single-crystal structure analyses allow an indepth comparison of 1, 1 * À , their calculated geometries, and the S 1 excited state of 1. Photophysical studies of 1 show a charge transfer (CT) emission with low quantum yield in solution but a strong increase in the solid state. TD-DFT calculations were used to identify transition-relevant orbitals.
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