Dipole Effect of BN-Doped Tetrathienonaphthalene on Photo-Physical Properties and Lewis Acidity of the D-π-A Derivatives.

Dimesitylboryl-acceptor (A) and diarylamine-donor (D) substituents are introduced at α positions of BN-doped tetrathienonaphthalene in the same and opposite directions of the B-N bond, namely, B-BN-N and N-BN-B, in order to demonstrate how the substitution patterns influence the photophysical properties. The photophysical and electrochemical properties of these D-π-A molecules have been investigated in detail, aided by UV-vis absorption and fluorescence spectroscopy as well as cyclic voltammetry. We find that both B-BN-N and N-BN-B show the typical intramolecular charge transfer emission. N-BN-B exhibits strong fluorescence with a narrower band gap and stronger Lewis acidity than that of B-BN-N. DFT calculations help give a reasonable explanation that subtle differences in the electronic structure of the host skeleton could also influence the substituents and feed back this effect to the entire molecule.

Millisecond Time-scale Photoluminescence of B-N-doped Tetrathienonaphthalene with Borane/Amine Substituents.

BN-doped polycyclic aromatic hydrocarbons (PAHs) have attracted numerous attentions because of their fascinating optical and electronic properties. In this work, a series of electron-donor (amine)- and -acceptor (borane)-functionalized BN-doped polycyclic aromatic hydrocarbons were prepared to study the substituents' effect on the photophysical properties. As a result, the compound with both donor and acceptor, BN, exhibits both local emission (LE) and charge-transfer emission (CT) in polar solvents. Especially, the CT emission with a longer wavelength revealed a lifetime as long as millisecond time scale at room temperature, indicating typical phosphorescence characteristics. Low-temperature photoluminescent (PL) spectroscopy and a theoretical study were conducted to help to interpret this phenomenon, and it turned out to be the lowering of the S1 energy level of BN which makes the intersystem crossing favorable. Furthermore, fluoride anion titration experiments exhibit the application potential of the dual-emission phenomenon of BN for ratiometric sensory materials.

BN-Functionalized Benzotrithiophene-Based Azaborines: Synthesis, Structures, and Anion Binding Properties.

Facile synthesis of BN-functionalized azaborines (4a-4c) was accomplished via Suzuki coupling reactions followed by the electrophilic C-H borylation of benzotrithiophene (BTT). The core structure of BTT enables multiple modifications at the three thiophene rings. Molecular structures of 4a-4c were confirmed by NMR, high-resolution mass spectrometry, and X-ray crystallographic analysis. Their electronic properties were also examined through photophysical and electrochemical measurements as well as density functional theory computations. The red-shifted absorption and emission of these molecules were demonstrated upon fluoride titration in response to anion binding, leading to a remarkable decrease of the oxidation potential in the electrochemical differential pulse voltammetry scans. This work may provide a new pathway to robust redox-active materials for catalytic applications.