Doubly Spiro-Conjugated Chiral Carbocycles Exhibiting SOMO-HOMO Inversion in Persistent Radical Cations.

Persistent chiral organic open-shell systems have captured growing interest due to their potential applications in organic spintronic and optoelectronic devices. Nevertheless, the integration of configurationally stable chirality into an organic open-shell system continues to pose challenges in molecular design. The π-extended skeleton incorporated in spiro-conjugated carbocycles can provide robust chiroptical properties and a significant stabilization of the excited and ionic radical states. However, this approach has been relatively less explored in the design of persistent organic open-shell systems. We report here the (S,S)-, (R,R)-, and meso-isomers of doubly spiro-conjugated carbocycles featuring flat and rigid carbon-bridged para-phenylenevinylene (CPV) of different conjugation lengths connected by two spiro-carbon centers, which we denote D-spiro-CPV for its quasi-dimeric structure. Our synthetic method based on a double lithiation cyclization approach enables facile production of D-spiro-CPV. D-spiro-CPVs exhibit circularly polarized luminescence (CPL) with high fluorescence quantum yields (ΦFL) resulting in a high CPL brightness of 21 M-1 cm-1 and also exhibit high thermal and photostability. The monoradical cation of D-spiro-CPV absorbing near-infrared light is notably persistent, exhibiting a half-life of 570 h under ambient conditions due to doubly spiro-conjugative stabilization. Theoretical and electrochemical studies indicate the radical cation of D-spiro-CPVs presents a non-Aufbau electron filling, exhibiting inversion of the energy level of the singly occupied molecular orbital (SOMO) and the highest (doubly) occupied molecular orbitals with the SOMO level even below the HOMO-1 level (double SHI effect). Our discoveries provide valuable insights into non-Aufbau molecules and the development of configurationally stable, optically active persistent radicals.

Atomically Precise Incorporation of BN-Doped Rubicene into Graphene Nanoribbons.

Substituting heteroatoms and non-benzenoid carbons into nanographene structure offers a unique opportunity for atomic engineering of electronic properties. Here we show the bottom-up synthesis of graphene nanoribbons (GNRs) with embedded fused BN-doped rubicene components on a Au(111) surface using on-surface chemistry. Structural and electronic properties of the BN-GNRs are characterized by scanning tunneling microscopy (STM) and atomic force microscopy (AFM) with CO-terminated tips supported by numerical calculations. The periodic incorporation of BN heteroatoms in the GNR leads to an increase of the electronic band gap as compared to its undoped counterpart. This opens avenues for the rational design of semiconducting GNRs with optoelectronic properties.

Organic/Inorganic Hybrid p-Type Semiconductor Doping Affords Hole Transporting Layer Free Thin-Film Perovskite Solar Cells with High Stability.

A feature of perovskite devices is their suitability in the fabrication of semitransparent solar cells (ST-SCs). Methylammonium lead iodide based perovskite material (MAPbI3 or PV) is a possible material of choice because of its semitransparent nature in thin film form and after considering a balance among average visible light transmittance (AVT), power conversion efficiency (PCE), and device stability. However, there are issues to be addressed in the design of PV ST-SCs, such as the stability of small grain crystals forming in thin films and reducing the number of layers in the device to increase AVT. We report herein that doping PV with a 0.03 wt % hybrid organic p-type semiconductor, fluorinated tetraarylbenzo [1,2- b:4,5- b']dipyrrol-1,5-yl alkanediylsulfonate salt (BDPSO), affords a device with a 280 nm active layer directly fabricated on an indium tin oxide/glass substrate, without fabricating a hole transporting layer. Such a device exhibited a 30% higher PCE of 16.9% than the device made without doping. This device exhibited a stable photocurrent output at the maximum power point (MPP) for >1000 s under air and an operational stability of retaining 93% of the initial PCE after 1000 h continuous light soaking at the MPP. The ST-SC devices made of BDPSO-doped 140 nm and 90 nm thick PV films and a 6 nm thick Au electrode achieved PCEs of 10.3 and 8.0% and whole device semitransparency values of 22 and 30% AVT, respectively. The origins of the observed doping effect of BDPSO are ascribed to the bissulfonate structure that can effectively passivate defects at the interface and grain boundaries and to the HOMO level matching with PV to facilitate charge transfer.

Hydroarylation of 2-Aryloxybut-1-en-3-ynes via Pd/Acid-Catalyzed C-H Bond Activation: A Concise Synthesis of 2,3-Bismethylene-2,3-dihydrobenzofurans.

An intramolecular exo-hydroarylation of 2-aryloxy-1,4-disilylbut-1-en-3-ynes via ortho-C-H bond activation under palladium(0) and acid catalysis was found to give 2,3-bis(silylmethylidene)-2,3-dihydrobenzofurans. The two silyl groups present probably promoted the reaction and played a key role in stabilizing the diene moiety in the product. The products readily led to functionalized condensed cycles by a Diels-Alder reaction.