Pushing Up the Size Limit of Boron-doped peri-Acenes: Modular Synthesis and Characterizations

Heteroatom-doped peri-acenes (PAs) have recently attracted considerable attention considering their fascinating physical properties and chemical stability. However, the precise sole addition of boron atoms along the zigzag edges of PAs remains challenging, primarily due to the limited synthetic approach. Herein, we present a novel one-pot modular synthetic strategy toward unprecedented boron-doped PAs (B-PAs), including B-[4,2]PA ( 1 a-2 ), B-[4,3]PA ( 1 b-2 ) and B-[7,2]PA ( 1 c-3 ) derivatives, through efficient intramolecular electrophilic borylation. Their chemical structures are unequivocally confirmed with a combination of mass spectrometry, NMR, and single-crystal X-ray diffraction analysis. Notably, 1 b-2 exhibits an almost planar geometry, whereas 1 a-2 displays a distinctive bowl-like distortion. Furthermore, the optoelectronic properties of this series of B-PAs are thoroughly investigated by UV/Vis absorption and fluorescence spectroscopy combined with DFT calculation. Compared with their parent all-carbon analogs, the obtained B-PAs exhibit high stability, wide energy gaps, and high photoluminescence quantum yields of up to 84 %. This study reveals the exceptional ability of boron doping to finely tune the physicochemical properties of PAs, showcasing their potential applications in optoelectronics.     

Pnictogen Interactions with Nitrogen Acceptors

Stabilizing nitrogen pnictogen bond interactions were measured using molecular rotors. Intramolecular C=O⋅⋅⋅N interactions were formed in the bond rotation transition states which lowered the rotational barriers and increased the rates of rotation, as measured by EXSY NMR. The pnictogen interaction energies show a very strong correlation with the positive electrostatic potential on nitrogen, which was consistent with a strong electrostatic component. In contrast, the NBO perturbation and pyramidalization analyses show no correlation, suggesting that the orbital-orbital component is minor. The strongest C=O⋅⋅⋅N pnictogen interactions were comparable to C=O⋅⋅⋅C=O interactions and were stronger than C=O⋅⋅⋅Ph interactions, when measured using the same N-phenylimide rotor system. The ability of the nitrogen pnictogen interactions to stabilize transition states and enhance kinetic processes demonstrates their potential in catalysis and reaction design.     

Palladium-Catalyzed Inverse and Normal Dehydrogenative Aza-Morita–Baylis–Hillman Reactions with γ,δ-Unsaturated Compounds

σ-Lewis base-catalyzed regio- and enantioselective aza-Morita–Baylis–Hillman (MBH) reaction of α,β,γ,δ-unsaturated systems remains a challenge due to the intrinsic covalent activation mode. Here we demonstrate that a Pd⁰ complex can mediate the dehydrogenative reaction of γ,δ-unsaturated compounds to give corresponding electron-poor dienes, which further undergo δ-regioselective umpolung Friedel–Crafts-type addition to imines via auto-tandem Pd⁰-π-Lewis base catalysis. After β-H elimination of in situ formed Pd^II-complexes, unprecedented and chemically inverse aza-MBH-type adducts are finally furnished with fair to outstanding enantioselectivity, and a diversity of functional groups and both ketimine and aldimine acceptors can be well tolerated. Moreover, switchable α-regioselective normal aza-MBH-type reaction also can be realized by tuning catalytic conditions, whereas moderate to good enantioselectivity with low to excellent Z/E-selectivity is attained.     

The Chemistry of the Cyaphide Ion

We review the known chemistry of the cyaphide ion, (C≡P)⁻. This remarkable diatomic anion has been the subject of study since the late nineteenth century, however its isolation and characterization eluded chemists for almost a hundred years. In this mini-review, we explore the pioneering synthetic experiments that first allowed for its isolation, as well as more recent developments demonstrating that cyaphide transfer is viable in well-established salt-metathesis protocols. The physical properties of the cyaphide ion are also explored in depth, allowing us to compare and contrast the chemistry of this ion with that of its lighter congener cyanide (an archetypal strong field ligand and important organic functional group). Recent studies show that the cyaphide ion has the potential to be used as a versatile chemical regent for the synthesis of novel molecules and materials, hinting at many interesting future avenues of investigation.     

Recent Development of SnII,SbIII-based Birefringent Material: Crystal Chemistry and Investigation of Birefringence

The combination of Sn^II or Sb^III with π, non-π-conjugated units has produced birefringent crystals with birefringence ranging from 0.005 to 0.468@1064 nm. It is proven that introducing Sn^II or Sb^III into crystals is a feasible strategy to enlarge the birefringence, which not only promotes the miniaturization of fabricated devices, but also effectively modulates polarized light. Herein, recently discovered Sn^II, Sb^III-based birefringent crystals with birefringence investigated are summarized, including their crystal structure and optical properties, especially birefringence. This review also presents the influence of Sn^II, Sb^III with stereochemically active lone pair on the optical anisotropy. We hope that this work provides a clear perspective on the crystal chemistry of Sn^II, Sb^III-based optical functional crystals and promotes the development of new birefringent crystals with large optical anisotropy.     

π-Complexation and C—H hydrogen bonding in the formation of colored cocrystals

The present study evaluates the potential combination of charge-transfer electron-donor–acceptor π–π complexation and C—H hydrogen bonding to form colored cocrystals. The crystal structures of the red 1:1 cocrystals formed from the isomeric pyridines 4- and 3-{2-[4-(dimethylamino)phenyl]ethynyl}pyridine with 1-[2-(3,5-dinitrophenyl)ethynyl]-2,3,5,6-tetrafluorobenzene, both C₁₄H₄F₄N₂O₄·C₁₅H₁₄N₂, are reported. Intermolecular interaction energy calculations confirm that π-stacking interactions dominate the intermolecular interactions within each crystal structure. The close contacts revealed by Hirshfeld surface calculations are predominantly C—H interactions with N, O, and F atoms.