DFT Study of Mechanism and Stereochemistry of Nickel-Catalyzed <i>trans</i>-Arylative Desymmetrizing Cyclization of Alkyne-Tethered Malononitriles

Present here is a density functional theory (DFT) study of the mechanism and origin of enantioselectivity of Ni-catalyzed desymmetric cyclization of alkyne-tethered malononitriles and aryl boronic acids. The reaction starts from transmetalation and arylnickel addition, followed by trans to cis isomerization to give cis-alkenyl nickel species. The stereodetermining step is the CN insertion, which prefers a transition state with the bystander CN group staying away from the ligand to reduce steric repulsion, and gives the final (R)-product

Synthesis, Properties, and Semiconducting Characteristics of BF₂ Complexes of β,β-Bisphenanthrene-Fused Azadipyrromethenes

Three novel π-extended BF₂ complexes of β,β-bisphenanthrene-fused azadipyrromethenes containing nine fused rings have been synthesized on the basis of a tandem Suzuki coupling reaction on readily available 2,6-dibromoazaBODIPYs followed by an intramolecular oxidative aromatic coupling mediated by iron­(III) chloride. These resultant BF₂ complexes exhibit strong absorption (extinction coefficients up to 2.4 × 10⁵ M^–1 cm^–1) and emission in the near-infrared (NIR) range (790–816 nm) with excellent photo and thermal stabilities. The hole mobility of the thin-film field-effect transistors of these dyes fabricated by a solution process reaches up to 0.018 cm² V^–1 s^–1

Highly Efficient NIR-II Photothermal Conversion Based on an Organic Conjugated Polymer

Development of special organic materials that are able to absorb light energy in the second near-infrared window (NIR-II) is significantly important for treating deep-tissue-buried diseases or supplying power to implantable electronic devices. Herein, a narrow bandgap donor–acceptor (D-A) conjugated polymer with thiophene-fused benzodifurandione-based oligo­(p-phenylenevinylene) (TBDOPV) as acceptor part and 2,2′-bithiophene (DT) as donor part was developed and exploited as a photothermal conversion material with high extinction coefficient and robust photostability in the NIR-II window. According to transient absorption analysis results, the photothermal conversion ability of this polymer is attributed to the fast internal conversion (IC) process. The high photothermal conversion efficiency makes this polymer a promising NIR-II adsorbing antenna to remotely actuate thermo-dependent devices, e.g., high-performance photothermal–electrical and photothermal–mechanical converters

Highly Efficient NIR-II Photothermal Conversion Based on an Organic Conjugated Polymer

Development of special organic materials that are able to absorb light energy in the second near-infrared window (NIR-II) is significantly important for treating deep-tissue-buried diseases or supplying power to implantable electronic devices. Herein, a narrow bandgap donor–acceptor (D-A) conjugated polymer with thiophene-fused benzodifurandione-based oligo­(p-phenylenevinylene) (TBDOPV) as acceptor part and 2,2′-bithiophene (DT) as donor part was developed and exploited as a photothermal conversion material with high extinction coefficient and robust photostability in the NIR-II window. According to transient absorption analysis results, the photothermal conversion ability of this polymer is attributed to the fast internal conversion (IC) process. The high photothermal conversion efficiency makes this polymer a promising NIR-II adsorbing antenna to remotely actuate thermo-dependent devices, e.g., high-performance photothermal–electrical and photothermal–mechanical converters

Donor End-Capped Hexafluorinated Oligomers for Organic Solar Cells with 9.3% Efficiency by Engineering the Position of π‑Bridge and Sequence of Two-Step Annealing

A pair of isomeric hexafluorinated oligomers (<b>Th6FSe</b> and <b>Se6FTh</b>), which are with the same aromatic compositions (difluorobenzothiadiazoles central core, IDT units, and donor end-capped groups), but differ in the π-bridge position (selenophene and thiophene), were designed and successfully synthesized. The potential of the resulted oligomers as donor materials for BHJ-OSCs was systematically investigated through optical absorption, AFM, TEM, GIXD, charge mobility measurement, and photovoltaic device fabrication. It was found that the π-bridge sequences in the resulted oligomers play a subtle but key role in device performances. Moreover, as a result of increase of crystalline content and desired phase separation after rapid SVA or combined TA and SVA treatment, the device performance of the resultant devices undergo significant enhancement. Notably, the <b>Se6FTh</b> devices showed a best PCE of ca. 9.3% with SVA+TA treatment, which is the highest PCE of BHJ-OSCs based on donor end-capped oligomers. These primary study demonstrated that the sequence of π-bridge and annealing treatments play critical roles for improving ordered and crystalline morphology and enhanced PCE, and hence can provide an useful strategy toward highly efficient oligomers for BHJ-OSCs

Fine-Tuning of Crystal Packing and Charge Transport Properties of BDOPV Derivatives through Fluorine Substitution

Molecular packing in organic single crystals greatly influences their charge transport properties but can hardly be predicted and designed because of the complex intermolecular interactions. In this work, we have realized systematic fine-tuning of the single-crystal molecular packing of five benzodifurandione-based oligo­(<i>p</i>-phenylenevinylene) (BDOPV)-based small molecules through incorporation of electronegative fluorine atoms on the BDOPV backbone. While these molecules all exhibit similar column stacking configurations in their single crystals, the intermolecular displacements and distances can be substantially modified by tuning of the amounts and/or the positions of the substituent fluorine atoms. Density functional theory calculations showed that the subtle differences in charge distribution or electrostatic potential induced by different fluorine substitutions play an important role in regulating the molecular packing of the BDOPV compounds. Consequently, the electronic couplings for electron transfer can vary from 71 meV in a slipped stack to 201 meV in a nearly cofacial antiparallel stack, leading to an increase in the electron mobility of the BDOPV derivatives from 2.6 to 12.6 cm² V^–1 s^–1. The electron mobility of the five molecules did not show a good correlation with the LUMO levels, indicating that the distinct difference in charge transport properties is a result of the molecular packing. Our work not only provides a series of high-electron-mobility organic semiconductors but also demonstrates that fluorination is an effective approach for fine-tuning of single-crystal packing modes beyond simply lowering the molecular energy levels

Fine-Tuning of Crystal Packing and Charge Transport Properties of BDOPV Derivatives through Fluorine Substitution

Molecular packing in organic single crystals greatly influences their charge transport properties but can hardly be predicted and designed because of the complex intermolecular interactions. In this work, we have realized systematic fine-tuning of the single-crystal molecular packing of five benzodifurandione-based oligo­(<i>p</i>-phenylenevinylene) (BDOPV)-based small molecules through incorporation of electronegative fluorine atoms on the BDOPV backbone. While these molecules all exhibit similar column stacking configurations in their single crystals, the intermolecular displacements and distances can be substantially modified by tuning of the amounts and/or the positions of the substituent fluorine atoms. Density functional theory calculations showed that the subtle differences in charge distribution or electrostatic potential induced by different fluorine substitutions play an important role in regulating the molecular packing of the BDOPV compounds. Consequently, the electronic couplings for electron transfer can vary from 71 meV in a slipped stack to 201 meV in a nearly cofacial antiparallel stack, leading to an increase in the electron mobility of the BDOPV derivatives from 2.6 to 12.6 cm² V^–1 s^–1. The electron mobility of the five molecules did not show a good correlation with the LUMO levels, indicating that the distinct difference in charge transport properties is a result of the molecular packing. Our work not only provides a series of high-electron-mobility organic semiconductors but also demonstrates that fluorination is an effective approach for fine-tuning of single-crystal packing modes beyond simply lowering the molecular energy levels