A Boryl‐Substituted Diphosphene: Synthesis,Structure, and Reaction with n‐Butyllithium To Form a Stabilized Adduct by pπ‐pπ Interaction

A boryl‐substituted diphosphene was synthesized through the nucleophilic borylation of PCl₃ with a borylzinc reagent, followed by a reduction with Mg. A combined analysis of the resulting diboryldiphosphene by single‐crystal X‐ray diffraction, DFT calculations, and UV/Vis spectroscopy revealed a σ‐electron‐donating effect for the boryl substituent that was slightly weaker than that of the 2,4,6‐tri‐tert‐butylphenyl (Mes*) ligand. The reaction of this diboryldiphosphene with ⁿBuLi afforded a boryl‐substituted phosphinophosphide that was, in comparison with the thermally unstable Mes*‐substituted diaryldiphosphene, stabilized by a π‐electron‐accepting effect of the boryl substituent.     

Isolation and Characterization of Radical Anions Derived from a Boryl‐Substituted Diphosphene

Radical anions of a diphosphene with two boryl substituents were isolated and characterized by single‐crystal X‐ray diffraction, electron spin resonance (ESR), and UV/Vis absorption spectroscopy as well as DFT calculations. Structural analysis of the radical anions revealed an elongation of the P=P bond and a contraction of the B−P bonds relative to the neutral diphosphene. The UV/Vis spectra of these radical anions showed a strong absorption in the visible region, which was assigned to SOMO‐related transitions on the basis of DFT calculations. The ESR spectra revealed that the hyperfine coupling constant with the phosphorus nuclei is the smallest that has been reported thus far. The results of the DFT calculations furthermore suggest that this should be attributed to a soaking of electron spin to the vacant p orbitals of the boryl substituents.     

Synthesis of γ‐Boryl‐Substituted Homoallylic Alcohols with anti Stereochemistry Based on a Double‐Bond Transposition

The stereoselective synthesis of anti isomers of γ‐boryl‐substituted homoallylic alcohols is disclosed. (E)‐1,2‐Di(boryl)alk‐1‐enes undergo Ru‐catalyzed double‐bond transposition with control of the geometry. The in situ generated (E)‐1,2‐di(boryl)alk‐2‐enes add to aldehydes in a stereospecific manner. The alkenylboron group within the product is amenable to a variety of synthetic derivatizations.     

An Acyclic Arsenium Cation Stabilised by a Single P–As π‐Interaction and a Cyclic Diphosphinophosphonium Salt

Stable acyclic arsenium cations R₂As⁺, isoelectronic analogues of germylenes, are rare in comparison to the corresponding phosphenium cations. The first example of a diphosphaarsenium salt, [{(Dipp)₂P}₂As][Al{OC(CF₃)₃}₄]?1 PhMe, is described. This salt exhibits remarkable stability due to the delocalisation of a lone pair from a planar phosphorus centre into the vacant p‐orbital at arsenic; the bonding in 2 has been probed by DFT calculations. An attempt to synthesise an analogous diphosphaphosphenium salt unexpectedly generated the cyclic phosphonium salt [cyclo‐{(Mes)P}₂P(Mes)₂][BAr^F₄]?CyMe through the cyclisation of a putative phosphine‐substituted diphosphene cation intermediate.     

Stabilization of a Diphosphagermylene through pπ–pπ Interactions with a Trigonal‐Planar Phosphorus Center

N‐Heterocyclic carbenes and their heavier homologues are, in part, stabilized by delocalization of the N lone pairs into the vacant p‐orbital at carbon (or a heavier Group 14 element center). These interactions are usually absent in the corresponding P‐substituted species, owing to the large barrier to planarization of phosphorus. However, judicious selection of the substituents at phosphorus has enabled the synthesis of a diphosphagermylene, [(Dipp)₂P]₂Ge, in which one of the P centers is planar (Dipp=2,6‐diisopropylphenyl). The planar nature of this P center and the correspondingly short P? Ge distance suggest a significant degree of P? Ge multiple bond character that is due to delocalization of the phosphorus lone pair into the vacant p‐orbital at germanium. DFT calculations support this proposition and NBO and AIM analyses are consistent with a Ge? P bond order greater than unity.     

4,10‐Dibromoanthanthrone as a New Building Block for p‐Type,n‐Type,and Ambipolar π‐Conjugated Materials

New p‐type, n‐type, and ambipolar molecules were synthesized from commercially available 4,10‐dibromoanthanthrone dye. Substitution at the 4,10‐ and 6,12‐positions with different electron‐rich and electron‐poor units allowed the modulation of the optoelectronic properties of the molecules. A bis(dicyanovinylene)‐functionalized compound was also prepared with a reduction potential as low as ?50 mV versus Ag⁺ with a crystalline two‐dimensional lamellar packing arrangement. These characteristics are important prerequisites for air‐stable n‐type organic field‐effect transistor applications.     

A Direct Synthesis of Highly Substituted π‐Rich Aromatic Heterocycles from Oxetanes

The ubiquitous use of π‐rich five‐membered heterocycles has driven the development of new methods for their synthesis for more than a century. Here, we disclose a general and reliable reaction manifold for the construction of highly substituted heterocycles through a facile Lewis‐acid‐catalyzed oxetane rearrangement. Notably, this methodology employs a keto‐oxetane motif as a 1,4‐dicarbonyl surrogate, which can be synthesized using robust alkylation or alkenylation reactions, and thus obviates the need to access 1,4‐dicarbonyl compounds via umpoled starting materials. We harnessed this reactivity to generate a broad range of substituted furans and pyrroles, and extended this methodology to produce benzo‐fused versions thereof.     

An Isolable Diphosphene Radical Cation Stabilized by Three‐Center Three‐Electron π‐Bonding with Chromium: End‐On versus Side‐On Coordination

Two salts ( 2 and 4 ) containing the radical cations of complexed diphosphenes have been isolated and characterized by electron paramagnetic resonance (EPR) spectroscopy, IR spectroscopy, and single‐crystal X‐ray diffraction. The P?P bond is coordinated to the Cr center either in an end‐on (in 2 ) or a side‐on (in 4 ) fashion. The spin density of the radical is delocalized over the Cr atom and the two P atoms in 2 whereas the unpaired electron is mainly localized on the Cr atom in 4 . This work provides the first example of a complexed diphosphene radical ( 2 ) featuring novel three‐center three‐electron (3c‐3e) π‐bonding in the Cr‐P‐P unit, and the first example of a 17 e Cr radical with a side‐on π‐bonded ligand ( 4 ).     

Synthesis, π‐Face‐Selective Aggregation,and π‐Face Chiral Recognition of Configurationally Stable C3‐Symmetric Propeller‐Chiral Molecules with a π‐Core

The C₃‐symmetric propeller‐chiral compounds (P,P,P)‐ 1 and (M,M,M)‐ 1 with planar π‐cores perpendicular to the C₃‐axis were synthesized in optically pure states. (P,P,P)‐ 1 possesses two distinguishable propeller‐chiral π‐faces with rims of different heights named the (P/L)‐face and (P/H)‐face. Each face is configurationally stable because of the rigid structure of the helicenes contained in the π‐core. (P,P,P)‐ 1 formed dimeric aggregates in organic solutions as indicated by the results of ¹H NMR, CD, and UV/Vis spectroscopy and vapor pressure osmometry analyses. The (P/L)/(P/L) interactions were observed in the solid state by single‐crystal X‐ray analysis, and they were also predominant over the (P/H)/(P/H) and (P/L)/(P/H) interactions in solution, as indicated by the results of ¹H and 2D NMR spectroscopy analyses. The dimerization constant was obtained for a racemic mixture, which showed that the heterochiral (P,P,P)‐ 1 /(M,M,M)‐ 1 interactions were much weaker than the homochiral (P,P,P)‐ 1 /(P,P,P)‐ 1 interactions. The results indicated that the propeller‐chiral (P/L)‐face interacts with the (P/L)‐face more strongly than with the (P/H)‐face, (M/L)‐face, and (M/H)‐face. The study showed the π‐face‐selective aggregation and π‐face chiral recognition of the configurationally stable propeller‐chiral molecules.     

p–π Conjugated Polymers Based on Stable Triarylborane with n‐Type Behavior in Optoelectronic Devices

p–π conjugation with embedded heteroatoms offers unique opportunities to tune the electronic structure of conjugated polymers. An approach is presented to form highly electron‐deficient p–π conjugated polymers based on triarylboranes, demonstrate their n‐type behavior, and explore device applications. By combining alternating [2,4,6‐tris(trifluoromethyl)phenyl]di(thien‐2‐yl)borane (FBDT) and electron‐deficient isoindigo (IID)/pyridine‐flanked diketopyrrolopyrrole (DPPPy) units, we achieve low‐lying lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) energy levels, high electron mobilities, and broad absorptions in the visible region. All‐polymer solar cells with these polymers as electron acceptors exhibit encouraging photovoltaic performance with power conversion efficiencies of up to 2.83 %. These results unambiguously prove the n‐type behavior and demonstrate the photovoltaic applications of p–π conjugated polymers based on triarylborane.     

β‐Octamethoxy‐Substituted 22π and 26π Stretched Porphycenes: Synthesis,Characterization, Photodynamics,and Nonlinear Optical Studies

Three meso‐expanded tetrapyrrolic aromatic macrocycles, including 22π and 26π acetylene–cumulene bridged stretched octamethoxyporphycenes and octamethoxy[22]porphyrin‐(2.2.2.2), are reported, for the first time, by modification of previously reported synthetic methods. This strategy led to an enhancement in the overall yield of their corresponding octaethyl analogues. The methoxy‐substituted expanded porphycenes display slightly blueshifted absorption relative to their ethyl analogues, along with very weak fluorescence, probably due to efficient intramolecular charge transfer (ICT). Additionally, the two‐photon absorption (TPA) cross sections of these macrocycles were evaluated; these are strongly related to core expansion of the porphyrin aromaticity through increased meso‐bridging carbon atoms as well as conformational flexibility and substitution effects at the macrocyclic periphery. In particular, the octamethoxy stretched porphycenes display strong TPA compared with the octaethyl analogues due to the dominant ICT character of methoxy groups with a maximum TPA cross section of 830 GM at 1700 nm observed for 26π‐octamethoxyacetylene–cumuleneporphycene.