Organophosphorus pi-conjugated materials

Organophotoredox-Catalyzed C-H Functionalizations of Benzophospholes

An organophotoredox-catalyzed oxidative C-H functionalization of benzophospholes has been developed. The C-H alkoxycarbonylation with methyl carbazate occurs in the presence of Rose bengal, whereas Eosin Y enables the dehydrogenative coupling with secondary phosphine oxides and ethers, delivering the C-H phosphinylated and alkylated products. The scope of coupling partners is complementary to that of conventional metal-promoted C-H activation, thus successfully expanding the chemical space of substituted phospholes accessed by C-H functionalization protocols.

Organocatalyzed Photoelectrochemistry for the Generation of Acyl and Phosphoryl Radicals through Hydrogen Atom-Transfer Process

An organocatalyzed photoelectrochemical method for the generation of acyl and phosphoryl radicals from formamides, aldehydes, and phosphine oxides has been developed. This protocol utilizes 9,10-phenanthrenequinone (PQ) as both a molecular catalyst and a hydrogen atom-transfer (HAT) reagent, eliminating the requirement for external metal-based reagents, HAT reagents, and oxidants. The generated acyl radicals can be applied to a range of radical-mediated transformation reactions, including C-H carbamoylation of heteroarenes, intermolecular tandem radical cyclization of CF3-substituted N-arylacrylamides, as well as intramolecular cyclization reactions. The use of acyl radicals in these transformations offers an efficient and sustainable approach to accessing structurally diverse carbonyl compounds.

Ligand-Free Iron-Catalyzed Construction of C-P Bonds via Phosphorylation of Alcohols: Synthesis of Phosphine Oxides and Phosphine Compounds

An efficient method for the construction of C-P(V) and C-P(III) bonds via the iron-catalyzed phosphorylation of alcohols under ligand-free conditions is disclosed. This strategy represents a straightforward process to prepare a series of phosphine oxides and phosphine compounds in good to excellent yields from the readily available alcohols and P-H compounds. A plausible mechanism is also proposed. We anticipate that this mode of transforming simple alcohols would apply in chemical synthesis widely.

Palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts to access atropoisomeric phosphines

A palladium-catalyzed regio- and stereo-selective phosphination of cyclic biarylsulfonium salts (racemic) with HPAr3Ar4 for straightforward synthesis of atropoisomeric phosphines (P,S-ligands) bearing a stereogenic axis or both a stereogenic axis and a P-stereogenic center is reported. The high reactivity and regio- and stereo-selectivity originate from the torsional strain release and palladium catalysis, and the construction of a P-stereogenic center is enabled by an efficient dynamic kinetic resolution. The high performance of the nascent P,S-ligands has been demonstrated in palladium-catalyzed asymmetric allylic substitutions, indicating the great potential of the present methodology.

Thermal and Photoinduced Radical Cascade Annulation using Aryl Isonitriles: An Approach to Quinoline-Derived Benzophosphole Oxides

Herein, we present a radical cascade addition cyclization sequence to access quinoline-based benzophosphole oxides from ortho-alkynylated aromatic phosphine oxides using various aryl isonitriles as radical acceptors and inexpensive tert-butyl-hydroperoxide (TBHP) as a terminal oxidant in the presence of a catalytic amount of silver acetate. Alternatively, the same cascade can be realized through a sustainable photochemical approach utilizing 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as an organic photocatalyst at room temperature. The introduced modular approach shows broad functional group tolerance and offers straightforward access to complex P,N-containing polyheterocyclic arenes. These novel π-extended benzophosphole oxides exhibit interesting photophysical and electrochemical properties such as absorption in the visible region, emission and reversible reduction at low potentials, which makes them promising for potential materials science applications. The photophysical properties can further be tuned by the addition of external Lewis and Brønsted acids.

Palladium-catalyzed (Z)-selective allylation of phosphine oxides with vinylethylene carbonates to construct phosphorus allyl alcohols

Allylphosphine oxide compounds are important building blocks with broad applications in organic synthesis and pharmaceutical science. Herein, we report an unprecedented palladium-catalyzed allylation of phosphine oxides with vinylethylene carbonates, producing various phosphorus allyl alcohols in excellent yields with high Z-selectivity. In addition, gram-scale synthesis and further functional group transformations demonstrate the practical utility of this synthetic method.

Water-Promoted Mild and General Michaelis-Arbuzov Reaction of Triaryl Phosphites and Aryl Iodides by Palladium Catalysis

A Pd-catalyzed relatively general Michaelis-Arbuzov reaction of triaryl phosphites and aryl iodides for preparing useful aryl phosphonates was developed. Interestingly, water can greatly facilitate the reaction through a water-participating phosphonium intermediate rearrangement process, which also makes the reaction conditions rather mild. In comparison with the known methods, this reaction is milder and more general, as it exhibits excellent functional group tolerance, can be applied to various triaryl phosphites and aryl iodides, and can be extended to aryl phosphonites and phosphinites. A gram-scale reaction with a low catalyst loading also revealed its practicality and potential in large-scale preparation.

Dithiophosphinylation of Allenyl Acetates: Access to 1,2-Bis(diphenylphosphino)ethane-Type Bidentate Ligands

1,2-Bis(diphenylphosphino)ethanes (DPPEs) are versatile and immensely important ligands in transition metal catalysts. Here we report the dithiophosphinylation of readily available allenyl acetates to give DPPEs in high yields and regioselectivity. This protocol features a broad substrate scope and mild conditions, avoiding the use of transition metals and air-sensitive sources of phosphorus. Mechanism studies indicate that the reaction was accomplished via an SN2'-type addition-elimination followed by a 1,4-addition step.

Pd-catalysed C-H alkynylation of benzophospholes

A palladium-catalysed C2-H alkynylation of benzophospholes with alkynyl bromides has been developed to afford the corresponding phosphole-alkyne conjugations in good to high yields. The C-C triple bond as well as terminal alkyne C-H bond in the obtained products is a good synthetic handle for further manipulations, thus giving the versatile π-conjugated benzophosphole derivatives. The optoelectronic properties of the newly synthesized conjugated benzophospholes are also described.

Phosphonylacylation of Alkenes Enabled by Visible-Light-Induced N-Heterocyclic Carbene Catalysis

Herein, we report the phosphonylacylation of alkenes via visible-light-induced N-heterocyclic carbene (NHC) catalysis to afford a series of γ-ketophosphonates in moderate to good yields. This protocol features mild conditions, free of photocatalyst, and good compatibility of functional groups. The excited Breslow enolate intermediate was proposed to undergo single-electron transfer with oxime phosphonate to generate the corresponding ketyl radical and phosphonyl radical.

Illuminating the Path to Enhanced Bioimaging by Phosphole-based Fluorophores

As the research of biological systems becomes increasingly complex, there is a growing demand for fluorophores with a diverse range of wavelengths. In this study, we introduce phosphole-based fluorophores that surpass existing options like dansyl chloride. The reactive S-Cl bond in chlorosulfonylimino-5-phenylphosphole derivatives allows rapid and direct coupling to peptides making the fluorophores easily introducible to peptides. This coupling process occurs under mild conditions, demonstrated for [F7 ,P34 ]-NPY and its shorter analogues. Peptides linked with our fluorophores exhibit similar receptor activation to the control peptide, while maintaining high stability and low toxicity, making them ideal biolabeling reagents. In fluorescence microscopy experiments, they can be easily visualized even at low concentrations, without suffering from the typical issue of bleaching. These phosphole-based fluorophores represent a significant leap forward in the field. Their versatility, ease of modification, superior performance, and applicability in biological labeling make them a promising choice for researchers seeking advanced tools to unravel the details of complex biological systems.

Zn-Catalyzed Dehydroxylative Phosphorylation of Allylic Alcohols with P(III)-Nucleophiles

A novel and efficient protocol for the synthesis of diarylallyl-functionalized phosphonates, phosphinates, and phosphine oxides through the zinc-catalyzed dehydroxylative phosphorylation of allylic alcohols with P(III)-nucleophiles via a Michaelis-Arbuzov-type rearrangement is reported. A broad range of allylic alcohols and P(III)-nucleophiles (P(OR)3, ArP(OR)2, and Ar2P(OR)) are well tolerated in this reaction, and the expected dehydroxylative phosphorylation products could be synthesized with good to excellent yields under the optimal reaction conditions. The reaction can be easily scaled up at a gram-synthesis level. Furthermore, through the step-by-step control experiments, kinetic study experiments, and 31P NMR tracking experiments, we acquired insights into the reaction and proposed the possible mechanism for this transformation.

Cyclic Hydrocarbon Frameworks Containing Two Bismuth Atoms: Towards 9,10-Dibismaanthracene

When bismuth atoms are incorporated into cyclic organic systems, this commonly goes along with strained or distorted molecular geometries, which can be exploited to modulate the physical and chemical properties of these compounds. In six-membered heterocycles, bismuth atoms are often accompanied by oxygen, sulfur or nitrogen as a second hetero-element. In this work, we present the first examples of six-membered rings, in which two CH units are replaced by BiX moieties (X=Cl, Br, I), resulting in dihydro-anthracene analogs. Their behavior in chemically reversible reduction reactions is explored, aiming at the generation of dibisma-anthracene (bismanthrene). Heterometallic compounds (Bi/Fe, Bi/Mn) are introduced as potential bismanthrene surrogates, as supported by bismanthrene-transfer to selenium. Analytical techniques used to investigate the reported compounds include NMR spectroscopy, high-resolution mass spectrometry, single-crystal X-ray diffraction analyses, and DFT calculations.

Towards tetrasubstituted furans through rearrangement and cyclodimerization of acetylenic ketones

Cyclodimerization of readily accessible acetylenic ketones facilitated by a phosphane-borane complex under basic conditions is achieved. This methodology allows one-pot synthesis of phosphorus-involved tetrasubstituted furans via the construction of a C-P bond and a furan ring within a single procedure. A plausible reaction mechanism is proposed.

Highly Diastereo- and Enantioselective Synthesis of Chiral Cyclohexylphosphines by Cu-Catalyzed Phosphination-Aldol Cyclization of Ketone-Enamides

A highly diastereo- and enantioselective phosphinative cyclization of ketone-enamides with secondary diarylphosphines enabled by copper catalysis is reported, providing a range of chiral tertiary cyclohexylphosphines bearing three contiguous stereogenic centers in high yields. This asymmetric phosphination-aldol cyclization protocol can also be extended to desymmetrization of dione-enamides to create four contiguous stereogenic centers in a highly selective manner.

A Nickel Anchored Covalent Organic Framework as Unimolecular Metallaphotocatalyst for Visible Light Driver C-P Bond Coupling Reaction

The urgent need to develop a sustainable and environmentally friendly method for synthesizing organophosphine compounds is underscored by their extensive applications in organic synthesis, coordination chemistry, medicinal chemistry, and photoelectric materials. Metalated covalent organic frameworks (MCOFs), which seamlessly integrate the inherent photo properties of COF with the catalytic capabilities of metal ions, offer an optimal material for efficient transformation of organics sustainably. In this study, we introduce a simple COF with nickel anchorages (Bpy-COF-NiCl2 ) as a unimolecular metallaphotocatalytic system for effective C-P bond formation. This heterogeneous photocatalyst exhibits superior catalytic performance, achieving yields of up to 95 %, and demonstrates broad substrate tolerance and functional group reactivity. Notably, the metallaphotocatalytic system has demonstrated the capability to process aryl bromides to produce the desired product, a feat not previously reported. Finally, the production and reusability test at the gram scale attests to its superior practicality for designing future organic cross-coupling reactions.

Phospha-cyanines in Their Ideal Polymethine State: Synthesis and Structure-Property Relationships

We report the synthesis and full characterization of a family of phosphorus-containing polymethine cyanines (phospha-cyanines). The compounds are easily prepared in two steps, starting from readily available phosphanes. The impact of the P-substituents and the counterions on the structural and optical properties is investigated through a joint experimental/theoretical approach. Based on the study of the single-crystal X-ray diffraction structures, all phospha-cyanines present a bond length alternation close to zero, independently of the substituents and counterions, which indicates an ideal polymethine state. All these compounds display the typical cyanine-like UV-vis absorption with an intense and sharp transition with a vibronic shoulder despite possessing a reverse electronic configuration compared to "classical" cyanines. Time-dependent density-functional theory calculations allowed us to fully rationalize the optical properties (absorption/emission wavelengths, luminescence quantum yields). Interestingly, due to the tetrahedral shape of the P atom, the optical properties are independent of the counterion, which is in marked contrast with N-analogues, which enables predictive engineering of the phospha-cyanines regardless of the medium in which they are used.

Azaphosphinines and their derivatives

Six-membered heterocycles containing one phosphorus and one nitrogen atom, known as azaphosphinines, have existed in the shadows of their single heteroatom-containing analogues for almost 150 years. Despite this, recent chemistry has seen a rapid increase in publications concerning this uncommon scaffold. Azaphosphinines exist in one of six isomers-there are three possible orientations of the pnictogen atoms and in each of these, the phosphorus is in one of two valences (PIIIvs. PV). This review aims to outline and inform on the synthesis and applications of all six isomers. PV-oxo azaphosphinines are of particular interest to this review as many of the discussed heterocycles either form as the pentavalent species directly or oxidize to this over time. In very recent years the published applications of azaphosphinines have blossomed into subjects spanning several fields of chemistry such as asymmetric catalysis, supramolecular association, cellular imaging, and medicinal chemistry.

Theoretical Insight into the Effect of Phosphorus Oxygenation on Nonradiative Decays: Comparative Analysis of P-Bridged Stilbene Analogs

Incorporation of the phosphorus element into a π-conjugated skeleton offers valuable prospects for adjusting the electronic structure of the resulting functional π-electron systems. Trivalent phosphorus has the potential to decrease the LUMO level through σ*-π* interaction, which is further enhanced by its oxygenation to the pentavalent P center. This study shows that utilizing our computational analysis to examine excited-state dynamics based on radiative/nonradiative rate constants and fluorescence quantum yield (ΦF) is effective for analyzing the photophysical properties of P-containing organic dyes. We theoretically investigate how the trivalent phosphanyl group and pentavalent phosphine oxide moieties affect radiative and nonradiative decay processes. We evaluate four variations of P-bridged stilbene analogs. Our analysis reveals that the primary decay pathway for photoexcited bis-phosphanyl-bridged stilbene is the intersystem crossing (ISC) to the triplet state and nonradiative. The oxidation of the phosphine moiety, however, suppresses the ISC due to the relative destabilization of the triplet states. The calculated rate constants match an increase in experimental ΦF from 0.07 to 0.98, as simulated from 0.23 to 0.94. The reduced HOMO-LUMO gap supports a red shift in the fluorescence spectra relative to the phosphine analog. The thiophene-fused variant with the nonoxidized trivalent P center exhibits intense emission with a high ΦF, 0.95. Our prediction indicates that the ISC transfer is obstructed owing to the relatively destabilized triplet state induced by the thiophene substitution. Conversely, the thiophene-fused analog with the phosphine oxide moieties triggers a high-rate internal conversion mediated by conical intersection, leading to a decreased ΦF.

Sustainable Photo- and Electrochemical Transformation of White Phosphorous (P4 ) into P1 Organo-Compounds

Elemental white phosphorous (P4 ) is a crucial feedstock for the entire phosphorus-derived chemical industry, serving as a common precursor for the ultimate preparation of high-grade monophosphorus (P1 ) fine chemicals. However, the corresponding manufacturing processes generally suffer from a deep reliance on hazardous reagents, inputs of immense energy, emissions of toxic pollutants, and the generation of substantial waste, which have negative impacts on the environment. In this context, sustainability and safety concerns provide a consistent impetus for the urgent overall improvement of phosphorus cycles. In this Concept, we present an overview of the most recent growth in photo- and electrochemical synthesis of P1 organo-compounds from P4 , with special emphasis on sustainable features. The key aspects of innovations regarding activation mode and mechanism have been comprehensively analyzed. A preliminary look at the possible future direction of development is also provided.

Photo-induced imino functionalizations of alkenes via intermolecular charge transfer

A catalyst-free photosensitized strategy has been developed for regioselective imino functionalizations of alkenes via the formation of an EDA complex. This photo-induced protocol facilitates the construction of structurally diverse β-imino sulfones and vinyl sulfones in moderate to high yields. Mechanistic studies reveal that the reaction is initiated with an intermolecular charge transfer between oximes and sulfinates, followed by fragmentation to generate a persistent iminyl radical and transient sulfonyl radical. This catalyst-free protocol also features excellent regioselectivity, broad functional group tolerance and mild reaction conditions. The late stage functionalization of natural product derived compounds and total synthesis of some bioactive molecules have been demonstrated to highlight the utility of this protocol. Meanwhile, the compatibility of different donors has proved the generality of this strategy.

Syntheses and Structures of 5-Membered Heterocycles Featuring 1,2-Diphospha-1,3-Butadiene and Its Radical Anion

LGa(P2 OC)cAAC 2 features a 1,2-diphospha-1,3-butadiene unit with a delocalized π-type HOMO and a π*-type LUMO according to DFT calculations. [LGa(P2 OC)cAAC][K(DB-18-c-6)] 3[K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene radical anion 3⋅- was isolated from the reaction of 2 with KC8 and dibenzo-18-crown-6. 3 reacted with [Fc][B(C6 F5 )4 ] (Fc=ferrocenium) to 2 and with TEMPO to [L-H Ga(P2 OC)cAAC][K(DB-18-c-6)] 4[K(DB-18-c-6] containing the 1,2-diphospha-1,3-butadiene anion 4- . The solid state structures of 2, 3K(DB-18-c-6], and 4[K(DB-18-c-6] were determined by single crystal X-ray diffraction (sc-XRD).

Furan ring opening reaction for the synthesis of 2,5-dicarbonyl-3-ene-phosphates

Furan ring opening reactions are essential in organic synthesis, enabling the incorporation of diverse functional groups and the construction of complex molecular structures. A highly efficient and practical method for synthesizing 2,5-dicarbonyl-3-ene-phosphates from readily available biomass furan and dialkyl phosphonates is reported. The reaction, catalyzed by FeCl3, demonstrated wide substrate scope and high synthetic efficiency. Gram-scale synthesis was achieved, and a one-pot reaction provided a quick access route to the desired compounds. Additionally, a successful Diels-Alder reaction highlighted the versatility of the methodology.

A π-conjugated covalent organic framework enables interlocked nickel/photoredox catalysis for light-harvesting cross-coupling reactions

Covalent organic frameworks (COFs) are an outstanding platform for heterogeneous photocatalysis. Herein, we synthesized a pyrene-based two-dimensional C[double bond, length as m-dash]C linked π-conjugated COF via Knoevenagel condensation and anchored Ni(ii)-centers through bipyridine moieties. Instead of traditional dual metallaphotoredox catalysis, the mono-metal decorated Ni@Bpy-sp2c-COF interlocked the catalysis mediated by light and the transition metal. Under light irradiation, enhanced energy and electron transfer in the COF backbone, as delineated by the photoluminescence, electrochemical, and control experiments, expedited the excitation of Ni centers to efficiently catalyze diverse photocatalytic C-X (X = B, C, N, O, P, S) cross-coupling reactions with efficiencies orders of magnitude higher than the homogeneous controls. The COF catalyst tolerated a diverse range of coupling partners with various steric and electronic properties, delivering the products with up to 99% yields. Some reactions were performed on a gram scale and were applied to diversify pharmaceuticals and complex molecules to demonstrate the synthetic utility.

Four-layer folding framework: design, GAP synthesis, and aggregation-induced emission

The design and synthesis of a type of [1 + 4 + 2] four-layer framework have been conducted by taking advantage of Suzuki-Miyaura cross-coupling and group-assisted purification (GAP) chemistry. The optimized coupling of double-layer diboronic esters with 1-bromo-naphth-2-yl phosphine oxides resulted in a series of multilayer folding targets, showing a broad scope of substrates and moderate to excellent yields. The final products were purified using group-assisted purification chemistry/technology, achieved simply by washing crude products with 95% EtOH without the use of chromatography and recrystallization. The structures were fully characterized and assigned by performing X-ray crystallographic analysis. UV-vis absorption, photoluminescence (PL), and aggregation-induced emission (AIE) were studied for the resulting multilayer folding products.

Radical Phosphorylation of Aliphatic C-H Bonds via Iron Photocatalysis

The synthesis of tertiary phosphines(III) has been a long-standing challenge in synthetic chemistry because of inevitable issues including harsh conditions, sensitive organometallic reagents, and prefunctionalized substrates in traditional synthesis. Herein, we report a strategically novel C(sp3)-H bond phosphorylation that enables the assembly of structurally diverse tertiary phosphines(III) from industrial phosphine(III) sources under mild photocatalytic conditions. The merger of ligand-to-metal charge transfer (LMCT) of FeCl3 with the hydrogen atom-transfer (HAT) process is the key for the generation of alkyl radicals from hydrocarbons. Strikingly, this catalytic system can be successfully applied for the polymerization of electron-deficient alkenes.

Palladium-Catalyzed Heck Cyclization with P(O)H Compounds to Construct Phosphinonyl-Azaindoline and -Azaoxindole Derivatives

We report herein a concise method for the construction of phosphinonyl-azaindoline and -azaoxindole derivatives via a palladium-catalyzed cascade cyclization with P(O)H compounds. Various H-phosphonates, H-phosphinates, and aromatic secondary phosphine oxides are all tolerated under the reaction conditions. Furthermore, the phosphinonyl-azaindoline isomer families such as 7-, 5-, and 4-azaindolines could be synthesized in moderate to good yields.

Parallel synthesis of donor-acceptor π-conjugated polymers by post-element transformation of organotitanium polymer

The donor-acceptor type π-conjugated polymers having heterole units were prepared by the reaction of a regioregular organometallic polymer having both reactive titanacyclopentadiene and electron-donor thiophene-2,5-diyl units in the main chain with electrophiles such as diphenyltin dichloride, dichlorophenylphosphine, and diiodophenylarsine. For example, a polymer having electron-accepting phosphole unit was obtained in 54% yield whose number-average molecular weight (Mn) and molecular weight distribution (Mw/Mn) were estimated as 3,000 and 1.9, respectively. The obtained polymer exhibits a high highest occupied molecular orbital (HOMO) and low lowest unoccupied molecular orbital (LUMO) energy levels (-5.13 eV and -3.25 eV, respectively) due to the electron-donating thiophene and electron-accepting phosphole units. Reflecting upon the alternating structure of thiophene and phosphole, the polymer exhibits a band gap energy level (Eg) of 1.78 eV which is narrower than that of a derivative of poly(thiophene) (Eg = 2.25 eV).

Metal-free highly chemo-selective bisphosphorylation and deoxyphosphorylation of carboxylic acids

Carboxylic acids are readily available in both the natural and synthetic world. Their direct utilization for preparing organophosphorus compounds would greatly benefit the development of organophosphorus chemistry. In this manuscript, we describe a novel and practical phosphorylating reaction under transition metal-free reaction conditions that can selectively convert carboxylic acids into the P-C-O-P motif-containing compounds through bisphosphorylation, and the benzyl phosphorus compounds through deoxyphosphorylation. This strategy provides a new route for carboxylic acid conversion as the alkyl source, enabling highly efficient and practical synthesis of the corresponding value-added organophosphorus compounds with high chemo-selectivity and wide substrate scope, including the late modification of complex APIs (active pharmaceutical ingredients). Moreover, this reaction also indicates a new strategy for converting carboxylic acids into alkenes by coupling this work and the subsequent WHE reaction with ketones and aldehydes. We anticipate that this new mode of transforming carboxylic acids will find wide application in chemical synthesis.

Three-Component Coupling Reactions Involving Arynes, Phosphites, and Aldehydes toward 3-Mono-Substituted Benzoxaphosphole 1-Oxides

A mild, efficient, and transition-metal-free three-component coupling reaction involving arynes, phosphites, and aldehydes was established to afford 3-mono-substituted benzoxaphosphole 1-oxides. A range of 3-mono-substituted benzoxaphosphole 1-oxides was obtained from both aryl- and aliphatic-substituted aldehydes in moderate to good yields. Moreover, the synthetic utility of the reaction was demonstrated by a Gram-scale reaction and the transformation of the products into various P-containing bicycles.

Hydrogen-Bonded π Complexes between Phosphaethyne and Hydrogen Chloride

The highly labile complexes between phosphaethyne (HCP) and hydrogen chloride (HCl) with 1:1 and 1:2 stoichiometries have been generated in Ar and N₂ matrices at 10 K through laser photolysis of the molecular precursors 1-chlorophosphaethene (CH₂PCl) and dichloromethylphosphine (CH₃PCl₂), respectively. The IR spectrum of the 1:1 complex suggests the preference of a single "T-shaped" structure in which HCl acts as the hydrogen donor that interacts with the electron-rich C≡P triple bond. In contrast, three isomeric structures for the 1:2 complex bearing a core structure of the "T-shaped" 1:1 complex are present in the matrix. The spectroscopic identification of these rare HCP π-electron complexes is supported by D-isotope labeling and the quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level of theory.

Photoexcitation-Induced Assembly: A Bottom-Up Physical Strategy for Driving Molecular Motion and Phase Evolution

ConspectusIn the field of molecular assembly, photodriven self-assembly is a smart and crucial strategy to regulate the molecular orderliness, multiscale structure, and optoelectronic properties. Traditionally, photodriven self-assembly is based on photochemical processes, through molecular structural change induced by photoreactions. Despite great progress in the photochemical self-assembly, there still exists disadvantages (e.g., the photoconversion rate never reaches 100% with the possible side reactions). Therefore, the photoinduced nanostructure and morphology are often difficult to predict due to insufficient phase transition or defects. In contrast, the physical processes based on photoexcitation are straightforward and can fully utilize photons to avoid the drawbacks of photochemistry. The photoexcitation strategy excludes the change of molecular structure, only utilizing the molecular conformational change from the ground state to excited state. Then, the excited state conformation is employed to drive molecular movement and aggregation, further promoting the synergistic assembly or phase transition of the entire material system. The regulation and exploration of molecular assembly upon photoexcitation can open up a new paradigm to deal with the "bottom-up" behavior and develop unprecedented optoelectronic functional materials.This Account starts with a brief introduction to the problems faced by photocontrolled self-assembly and presents the photoexcitation-induced assembly (PEIA) strategy. Then, we focus on exploring PEIA strategy based on persulfurated arenes as the prototype. The molecular conformational transition of persulfurated arenes from the ground state to the excited state is conducive to the formation of intermolecular interactions, successively driving molecular motion, aggregation, and assembly. Next, we describe our progress in exploring PEIA of persulfurated arenes at the molecular level and then demonstrate that the PEIA of persulfurated arenes can synergistically drive molecular motion and phase transition in various block copolymer systems. Moreover, we provide the potential applications of PEIA in dynamic visual imaging, information encryption, and surface property regulation. Finally, an outlook on further development of PEIA is prospected.

Selective oxidation of benzylic alcohols via synergistic bisphosphonium and cobalt catalysis

A synergistic photocatalytic system using a bisphosphonium catalyst and a cobalt catalyst has been developed, enabling the selective oxidation of benzylic alcohols under oxidant-free and environmentally benign conditions. High efficiencies have been obtained for a variety of alcohol substrates, and exclusive selectivity for aldehyde products has been achieved across the board. Furthermore, this photocatalytic system proved to be efficient when performed under continuous-flow conditions, even using a simple and easily assembled continuous-flow setup.

Nickel-Catalyzed Sodium Hypophosphite-Participated Direct Hydrophosphonylation of Alkyne toward H-Phosphinates

The traditional methods for the synthesis of phosphinate esters use phosphorus trichloride (PCl₃) as the phosphorous source, resulting in procedures that are often highly polluting and energy intensive. The search for an alternative approach that is both mild and environmentally friendly is a challenging, yet highly rewarding task in modern chemistry. Herein, we use an inorganic phosphorous-containing species, NaH₂PO₂, to serve as the source of phosphorous that participates directly in the nickel-catalyzed selective alkyne hydrophosphonylation reaction. The transformation was achieved in a multicomponent fashion and at room temperature, and most importantly, the H-phosphinate product generated is an advanced intermediate which can be readily converted into diverse phosphinate derivatives, including those bearing new P-C, P-S, P-N, P-Se, and P-O bonds, thus providing a complimentary method to classic phosphinate ester synthesis techniques.

Catalyst-free thiophosphorylation of in situ formed ortho-quinone methides

A metal-, chloride reagent and base-free thiophosphorylation reaction of in situ formed ortho-quinone methide (o-QM) to synthesize functionalized thiophosphates has been developed. The reaction is an atom-economical process, producing water as the sole byproduct. (EtO)₂P(O)SH functions as both a Brønsted acid and nucleophilic thiolate to produce the o-QM intermediate and the thiophosphate product, respectively. The aza o-QMs were also successfully thiophosphorylated in the presence of catalytic TsOH to form sulfonamido thiophosphates.

Boundaries of the Hyperconjugation from π-Extended Six-Membered Phosphorus Heterocycles

In the context of materials science, six-membered phosphorus heterocycles are intriguing building blocks due to their tunable properties through phosphorus post-functionalization and their unique hyperconjugative effects arising from the phosphorus substituents that contribute to further tuning the optoelectronic properties of the system. Seeking for the discovery of improved materials, the latter features have triggered an astonishing evolution of molecular architectures based on phosphorus heterocycles. Theoretical calculations showed that the hyperconjugation causes a reduction in the S₀-S₁ gap, which strongly depends on the nature of both the P-substituent and the π-conjugated core, but where are the limits? Outlining the hyperconjugative effects of six-membered phosphorus heterocycles would allow scientists to know how to design next-generation organophosphorus systems with enhanced properties. Herein, we discovered that, in cationic six-membered phosphorus heterocycles, an increase in the hyperconjugation does not affect the S₀-S₁ gap anymore; i.e., quaternizing the phosphorus atoms leads to properties that go beyond those provoked by hyperconjugative effects. DFT calculations revealed that the latter is particularly marked in phosphaspiro derivatives. Our detailed investigations spotlight the potential of π-extended systems based on six-membered phosphorus spiroheterocycles for accessing properties beyond those achieved to date through hyperconjugative effects, thus laying the groundwork for new research possibilities toward improved organophosphorus systems.

One-Step Synthesis of Benzophosphole Derivatives from Arylalkynes by Phosphenium-Dication-Mediated Sequential C-P/C-C Bond Forming Reaction

A metal-free, phosphenium-dication-mediated sequential C-P and C-C bond forming reaction has been developed. This protocol can provide concise access to the (di)benzophosphole derivatives in one synthetic operation from the readily available and simple arylalkynes and phosphinic acids. Application to the multiple cyclization reaction and the fully intermolecular three-component-coupling-type reaction are also described.

Preparation of Vinylphosphonates from Ketones Promoted by Tf2O

An efficient triflic anhydride promoted phosphorylation of ketone was disclosed, and vinylphosphorus compounds were prepared under solvent- and metal-free conditions. Both aryl and alkyl ketones could perform smoothly to give vinyl phosphonates in high to excellent yields. In addition, the reaction was easy to carry out and easy to scale up. Mechanistic studies suggested that this transformation might involve nucleophilic vinylic substitution or a nucleophilic addition-elimination mechanism.

Nickel-Catalyzed Radical Ring-Opening Phosphorylation of Cycloalkyl Hydroperoxides Leading to Distal Acylphosphine Oxides

A facile and efficient nickel-catalyzed C-C bond cleavage/phosphorylation of various cycloalkyl hydroperoxides was developed. This radical ring-opening strategy provided practical access to structurally diverse distal ketophosphine oxides in one pot through concurrent C═O/C-P bond formation with high atom economy under mild room temperature and base-free conditions.

Chiral phosphoric acid-catalyzed enantioselective phosphinylation of 3,4-dihydroisoquinolines with diarylphosphine oxides

Chiral phosphorous-containing compounds are playing a more and more significant role in several different research fields. Here, we show a chiral phosphoric acid-catalyzed enantioselective phosphinylation of 3,4-dihydroisoquinolines with diarylphosphine oxides for the efficient and practical construction of a family of chiral α-amino diarylphosphine oxides with a diverse range of functional groups. The phosphine products are suitable for transforming to several kinds of chiral (thio)ureas, which might be employed as chiral ligands or catalysts with potential applications in asymmetric catalysis. Control and NMR tracking experiments show that the reaction proceeds via the tert-butyl 1-(tert-butoxy)-3,4-dihydroiso-quinoline-2(1H)-carboxylate intermediate, followed by C-P bond formation. Furthermore, computational studies elucidated that the hydrogen bonding strength between the phosphonate and isoquinolinium determines the stereoselectivity of the phosphinylation reaction.

Synthesis, Structures, and Properties of π-Extended Phosphindolizine Derivatives

Dibenzo[b,g]phosphindolizine oxide and three types of benzo[e]naphthophosphindolizine oxides have been synthesized by the ring-closing metathesis of benzo[b]phosphole oxide and naphthophosphole oxides with two olefin tethers. Their molecular structures and properties were revealed by X-ray crystallographic analysis, UV-vis spectroscopy, and electrochemical analysis. The number and position of the benzene rings were found to alter the structural geometry and the HOMO/LUMO energy levels, and their effects were investigated by theoretical calculations. Among the phosphindolizine oxide derivatives investigated, only benzo[e]naphtho[2,3-b]phosphindolizine oxide with the naphthalene ring fused at 2,3-positions showed weak yellow fluorescence with a large Stokes shift.

Three-Component Synthesis of Dioxaphosphorane-Fused Diphosphacycles Exhibiting Unique Dynamic Fluorescence "On/Off" Properties

Rigidly planar polycyclic phosphacycles featuring an internal dioxaphosphorane are promising photofunctional materials. However, the lack of efficient synthetic methods resulted in limited structural diversities which significantly hampered extensive study. Herein, we report a straightforward three-component synthesis of novel dioxaphosphorane-fused diphosphacycles with distinctive photophysical properties. Control experiments and theory calculations were performed to account for a plausible reaction mechanism. We also systematically investigated the structure-property relationships of these unprecedented platforms by combining experiments (X-ray analysis, optical and redox properties) and theoretical computations. Based on their unique structure and properties, a novel fluorescent switch for pH sensing was revealed by a dynamic ring-opening/ring-closing process.

Synthesis and Photophysical Properties of Heavier Pnictogen Complexes

Recent success in the synthesis of π-conjugated heavier pnictogen (As, Sb, and Bi) compounds and their transition metal complexes has led to the current surge in interest that led to significant development in the field of photophysical and optoelectronic properties of heavier pnictogens and their transition metal complexes. The presence of heavier pnictogens (As, Sb and Bi) in the molecular skeleton promotes inter-system crossing (ISC) and reverse inter-system crossing (RISC), because of the heavy atom effect, via altering the intermolecular interactions and orbital energy levels. As a result, π-conjugated heavier pnictogen compounds such as arsines, dibenzoarsepins, arsinoquinoline, heterofluorene, benzo[b]heterole (heterole=arsole, bismole, and stibole) show unique optoelectronic properties such as narrow bandgap, low-energy absorption, and long-wavelength emission than lighter pnictogen-based compounds. This review focuses on recent advances in the synthesis and photophysical properties of heavier pnictogen compounds. The synthesis and photophysical properties of heavier pnictogens are discussed and elaborated.

Molecular Persistent Room-Temperature Phosphorescence from Tetraarylaminoboranes

Herein, we report the synthesis, molecular structure, and optical features of tetrarylaminoboranes 1 (Mes₂B-N(Ph)(C₁₀H₇)) and 2 (Mes₂B-N(Ph)(C₁₄H₉)). In the solution state, 1 shows aggregation-induced emission enhancement and color switching, while 2 displays emission color switching and aggregation-caused quenching. At 77 K, frozen solutions of 1 show delayed fluorescence (DF) and phosphorescence, whereas 2 display only DF. Pristine solids of 1 and 2 showed delayed fluorescence under ambient conditions; however, crystals of both compounds show no phosphorescence under similar conditions. Polymethyl methacrylate thin films of 1 (1 wt % doping concentration) exhibit persistent room-temperature phosphorescence (pRTP) lasting for ∼0.5 s. In contrast, 2 does not show phosphorescence under similar conditions. Systematic photophysical studies and theoretical (DFT and TD-DFT) calculations are performed on these molecules to rationalize their intriguing optical characteristics.

Synthesis of Crystalline Phosphine-Graphdiyne with Self-Adaptive p-π Conjugation

"Dynamic" behavior materials with high surface activity and the ability of chemical bond conversion are the frontier materials in the field of renewable energy. The outstanding feature of these materials is that they have adaptive electronic properties that external stimuli can adjust. An original discovery in a new crystalline two-dimensional phosphine-graphdiyne (P-GDY) material is described here. Although the p-π conjugation of most trivalent phosphorus π-systems is insignificant because of the pyramidal configuration, the lone pair electrons of phosphorus atoms participate strongly in the delocalization under the influence of the interlayer van der Waals forces in P-GDY. Due to the dynamically reversible nature of noncovalent interactions (p-π conjugation), P-GDY exhibits a specific adaptive behavior and realizes the responsive reversible transport of a lithium ion by regulating p-π interactions. Our findings would provide the potential to develop a new family of responsive materials with tunable structures.

Transition-Metal-Free Dehydropolymerization of Phosphine-Boranes at Ambient Temperature

Stoichiometric reaction of phosphine-borane adducts RR'PH⋅BH₃ (R=Ph, R'=H, Ph, Et, and R=R'=^t Bu) with the strong acid HNTf₂ (Tf=SO₂ CF₃ ) leads to H₂ elimination and the formation of the triflimido derivatives, RR'PH⋅BH₂ (NTf₂ ). Subsequent deprotonation by using bases, such as diisopropylethylamine or the carbene IPr (IPr=N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), led to the formation of P-mono- or -disubstituted polyphosphinoboranes [RR'P-BH₂ ]_n . Evidence for the intermediacy of transient phosphinoborane monomers, RR'PBH₂ , was provided by trapping reactions.