π-Conjugated phospholes and their incorporation into devices: components with a great deal of potential

Photochromic Barbiturate Pendant-Containing Benzo[b]phosphole Oxides with Co-Assembly Property and Photoinduced Morphological Changes

A series of novel barbiturate pendant-containing benzo[b]phosphole oxides has been demonstrated to exhibit photochromic and co-assembly properties. Both the open form and the photogenerated closed form of the diarylethene-based benzo[b]phosphole oxides have displayed color changes with new appearance of the bathochromic-shifted lowest-energy absorption bands upon addition of the H-bonding ditopic receptor that is complementary to the barbiturate groups, probably resulting in the formation of a supramolecular polymer. The co-assembly mixtures have displayed dissociation and association processes upon heating and cooling, respectively. Moreover, both the unassembled and co-assembled states of the benzo[b]phosphole oxide have exhibited photoinduced coloration, leading to a near-infrared absorption behavior. Multiaddressable states of the co-assembly mixture with multiple colors have been achieved via the combination of photochromism and thermochromism. More interestingly, photoinduced morphological changes from extensive porous network structures to ring-like aggregates have been observed for the co-assembly upon photoirradiation. The present work provides important insight for further developments of the multiaddressable systems and the supramolecular polymers with photo- and thermo-responsive behaviors, paving the way for the future design of photochromic materials with interesting photocontrollable functions.

Topotactic Synthesis of Phosphabenzene-Functionalized Porous Organic Polymers: Efficient Ligands in CO2 Conversion

Progress toward the preparation of porous organic polymers (POPs) with task-specific functionalities has been exceedingly slow-especially where polymers containing low-oxidation phosphorus in the structure are concerned. A two-step topotactic pathway for the preparation of phosphabenzene-based POPs (Phos-POPs) under metal-free conditions is reported, without the use of unstable phosphorus-based monomers. The synthetic route allows additional functionalities to be introduced into the porous polymer framework with ease. As an example, partially fluorinated Phos-POPs (F-Phos-POPs) were obtained with a surface area of up to 591 m²  g^-1 . After coordination with Ru species, a Ru/F-Phos-POPs catalyst exhibited high catalytic efficiency in the formylation of amines (turnover frequency up to 204 h^-1 ) using a CO₂ /H₂ mixture, in comparison with the non-fluorinated analogue (43 h^-1 ) and a Au/TiO₂ heterogeneous catalysts reported previously (<44 h^-1 ). This work describes a practical method for synthesis of porous organic phosphorus-based polymers with applications in transition-metal-based heterogeneous catalysis.

Transition metal-free phosphonocarboxylation of alkenes with carbon dioxide via visible-light photoredox catalysis

Catalytic difunctionalization of alkenes has been an ideal strategy to generate structurally complex molecules with diverse substitution patterns. Although both phosphonyl and carboxyl groups are valuable functional groups, the simultaneous incorporation of them via catalytic difunctionalization of alkenes, ideally from abundant, inexpensive and easy-to-handle raw materials, has not been realized. Herein, we report the phosphonocarboxylation of alkenes with CO2 via visible-light photoredox catalysis. This strategy is sustainable, general and practical, providing facile access to important β-phosphono carboxylic acids, including structurally complex unnatural α-amino acids. Diverse alkenes, including enamides, styrenes, enolsilanes and acrylates, undergo such reactions efficiently under mild reaction conditions. Moreover, this method represents a rare example of redox-neutral difunctionalization of alkenes with H-P(O) compounds, including diaryl- and dialkyl- phosphine oxides and phosphites. Importantly, these transition-metal-free reactions also feature low catalyst loading, high regio- and chemo-selectivities, good functional group tolerance, easy scalability and potential for product derivatization.

Dithieno[3,2-b:2',3'-d]arsole-containing conjugated polymers in organic photovoltaic devices

Arsole-derived conjugated polymers are a relatively new class of materials in the field of organic electronics. Herein, we report the synthesis of two new donor polymers containing fused dithieno[3,2-b:2',3'-d]arsole units and report their application in bulk heterojunction solar cells for the first time. Devices based upon blends with PC₇₁BM display high open circuit voltages around 0.9 V and demonstrate power conversion efficiencies around 4%.

Dibenzo[b,e]phosphindolizines synthesized by a ring-closing metathesis of benzo[b]phospholes with two vinyl tethers

Dibenzo[b,e]phosphindolizines 1 were successfully synthesized by a ring-closing metathesis of benzo[b]phosphole chalcogenides 2a-2c with two vinyl tethers (for chalcogen analogs 1a-1c), and by a deselenization reaction (for lone-pair analog 1d). The structures, properties, and bowl inversion derived from a phosphorus atom were fully investigated.

Heavier pnictogens - treasures for optical electronic and reactivity tuning

We highlight recent advances in organopnictogen chemistry contrasting the properties of lighter and heavier pnictogens. Exploring new bonding situations, discovering unprecedented reactivities and producing fascinating opto-electronic materials are some of the most prominent directions of current organopnicogen research. Expanding the chemical toolbox towards the heavier group 15 elements will continue to create new opportunities to tailor molecular properties for small molecule activation/reactivity and materials applications alike. This frontier article illustrates the elemental substitution approach in selected literature examples.

[​4+2] versus [​2+2] Homodimerization in P(V) Derivatives of 2,4-Disubstituted Phospholes

Phosphole P(V) derivatives are interesting building blocks for various applications from ligand synthesis to material sciences. We herein describe the preparation and characterisation of new 2,4-disubstituted oxo-, thiooxo-, and selenooxophospholes. The nature of the substituents on the phosphole ring determines the reactivity of these compounds towards homodimerization reactions. Aryl and trimethylsilyl substituted oxophospholes undergo selective [4+2] dimerization, whereas, for thiooxo- and selenooxophospholes, light-induced, selective [2+2] head-to-head dimerization occurs in the case of aryl substituents. DFT calculations provide some insights on these differences in reactivity.

Phosphahelicenes: From Chiroptical and Photophysical Properties to OLED Applications

Herein, the experimental physicochemical and chiroptical properties of a series of phosphahelicenes are reported, focusing on their UV/Vis absorption, luminescence, electronic circular dichroism, optical rotations, and circularly polarized luminescence. Furthermore, detailed analysis of absorption and ECD spectra performed with the help of quantum-chemical calculations allowed us to highlight general features of these helicenic phosphines. Finally, due to well-suited electrochemical properties and thermal stability, the systems were successfully used as emitters in organic light-emitting diodes.

Doping Sumanene with Both Chalcogens and Phosphorus(V): One-Step Synthesis, Coordination, and Selective Response Toward AgI

Heterasumanenes 4-6 containing chalcogen (S, Se, and Te) and phosphorus atoms have been synthesized in a one-pot reaction from trichalcogenasumanenes 1-3 by replacing one chalcogen atom with a P=S unit. The P=S unit makes 4-6 almost planar and shrinks the HOMO-LUMO gap as compared to 1-3. The bonding between Ag⁺ and S atom on P=S brings about a distinct change to the optical properties of 4-6; 4 in particular shows a selective fluorescence response toward Ag⁺ with LOD of 0.21 μm. Compounds 4-6 form complexes with AgNO₃ to be (4)₂ ⋅AgNO₃ , (5)₂ ⋅AgNO₃ , and (6)₂ ⋅(AgNO₃ )₃ . In complexes, the coordination between Ag⁺ and P=S is observed, which leads to shrinkage of C-P and C-X (X=S, Se, Te) bond lengths. As a result, 4, 5, and 6 are all bowl-shaped in complexes with bowl-depths reaching to 0.66 Å, 0.42 Å, and 0.40 Å, respectively. There are Ag-Te dative bonds between Ag⁺ and Te atom on telluorophene in (6)₂ ⋅(AgNO₃ )₃ .

π-Extended Phosphepines: Redox and Optically Active P-Heterocycles with Nonplanar Framework

In this letter, we present the synthesis of a new family of π-extended dithieno[ b, f]phosphepines. The Pd-catalyzed direct arylation allows the introduction of various substituents, which tune the absorption/emission in the visible range as well as the redox properties. All those modifications were rationalized through DFT calculations. The physical properties of ambipolar phosphepine with diphenylamino substituents inspired us to use it as a semiconductor in p-type organic field-effect transistors (OFETs).

Synthesis, Optical, and Redox Properties of Regioisomeric Benzoheterocycles-Fused Pyrene

A new synthetic route toward the synthesis of benzo[b]phospholes- and benzo[b]siloles-fused pyrenes using a transition metal-catalyzed C-H bond activation is described. The compounds were fully characterized including X-ray diffraction. A combined experimental and theoretical study shows that both the heteroatom and the substitution pattern impact the optical and redox properties.

Oligofluorene with multiple spiro-connections: its and their use in blue and white OLEDs

This work reports the synthesis and characterization of super rigid oligofluorenes. We also demonstrate their applications in blue and white OLEDs.

Lighting with organophosphorus materials: solution-processed blue/cyan light-emitting devices based on phosphaphenalenes

The suitability of phosphaphenalene derivatives for light-emitting diodes and electrofluorochromic devices is herein demonstrated.

The Dawn of Functional Organoarsenic Chemistry

Organoarsenic chemistry was actively studied until the middle of 20th century. Although various properties of organoarsenic compounds have been computationally predicted, for example, frontier orbital levels, aromaticity, and inversion energies, serious concern to the danger of their synthetic processes has restricted experimental studies. Conventional synthetic routes require volatile and toxic arsenic precursors. Recently, nonvolatile intermediate transformation (NIT) methods have been developed to safely access functional organoarsenic compounds. Important intermediates in the NIT methods are cyclooligoarsines, which are prepared from nonvolatile inorganic precursors. In particular, the new approach has realized experimental studies on conjugated arsenic compounds: arsole derivatives. The elucidation of their intrinsic properties has triggered studies on functional organoarsenic chemistry. As a result, various kinds of arsenic-containing π-conjugated molecules and polymers have been reported for the last few years. In this minireview, progress of this recently invigorated field is overviewed.

Tuning the Optoelectronic Properties of Stannoles by the Judicious Choice of the Organic Substituents

Stannoles are organometallic rings in which the heteroatom is involved in a form of conjugation that is called σ*-π* conjugation. Only very little is known about how the substituents on the Sn atom or substituents on the stannole ring determine the optoelectronic properties of these heterocycles. In this work, this question has been studied experimentally and theoretically. Calculations of optimized equilibrium geometries, energy gaps between the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs), and of the absorption spectra of a wide range of compounds were performed. The computational data showed that the substituents on the Sn atom influence the optoelectronic properties to a lower extent than the substituents in the 2 and 5 positions of the ring. These substituents in the 2 and 5 positions of the stannole ring can also have a strong influence on the overall planarity of the structure, in which mesomeric effects can play a substantial role only if the structure is planar. Thus, only structures with a planar backbone are of interest in the context of tuning the optoelectronic properties. These were selected for the experimental studies. On the basis of this information, a series of six novel stannoles was synthesized by the formation of a zirconium intermediate and subsequent transmetalation to obtain the tin compound. The calculated electronic HOMO-LUMO energy gaps varied between 2.94 and 2.68 eV. The measured absorption maxima were located between 415 and 448 nm compared to theoretically calculated values ranging from 447 nm (2.77 eV) to 482 nm (2.57 eV). In addition to these optical measurements, cyclic voltammetry data could be obtained, which show two reversible oxidation processes for three of the six stannoles. With this study, it could be demonstrated how the judicious choice of the substituents can lead to large and predictable bathochromic shifts in the absorption spectra.

Regioselective functionalization at the 7-position of 1,2,3-triphenylbenzo[b]phosphole oxide via P[double bond, length as m-dash]O-directed lithiation

Various 7-substituted benzo[b]phosphole derivatives were prepared by P[double bond, length as m-dash]O-directed lithiation of 1,2,3-triphenylbenzo[b]phosphole P-oxide and subsequent iodination and cross-coupling reactions. The electron-donating groups introduced at the 7-position produced dramatic solvatofluorochromism owing to the strong charge-transfer character of the excited state of the entire π-system.

Microbial nanowires - Electron transport and the role of synthetic analogues

Electron transfer is central to cellular life, from photosynthesis to respiration. In the case of anaerobic respiration, some microbes have extracellular appendages that can be utilised to transport electrons over great distances. Two model organisms heavily studied in this arena are Shewanella oneidensis and Geobacter sulfurreducens. There is some debate over how, in particular, the Geobacter sulfurreducens nanowires (formed from pilin nanofilaments) are capable of achieving the impressive feats of natural conductivity that they display. In this article, we outline the mechanisms of electron transfer through delocalised electron transport, quantum tunnelling, and hopping as they pertain to biomaterials. These are described along with existing examples of the different types of conductivity observed in natural systems such as DNA and proteins in order to provide context for understanding the complexities involved in studying the electron transport properties of these unique nanowires. We then introduce some synthetic analogues, made using peptides, which may assist in resolving this debate. Microbial nanowires and the synthetic analogues thereof are of particular interest, not just for biogeochemistry, but also for the exciting potential bioelectronic and clinical applications as covered in the final section of the review.

STATEMENT OF SIGNIFICANCE

Some microbes have extracellular appendages that transport electrons over vast distances in order to respire, such as the dissimilatory metal-reducing bacteria Geobacter sulfurreducens. There is significant debate over how G. sulfurreducens nanowires are capable of achieving the impressive feats of natural conductivity that they display: This mechanism is a fundamental scientific challenge, with important environmental and technological implications. Through outlining the techniques and outcomes of investigations into the mechanisms of such protein-based nanofibrils, we provide a platform for the general study of the electronic properties of biomaterials. The implications are broad-reaching, with fundamental investigations into electron transfer processes in natural and biomimetic materials underway. From these studies, applications in the medical, energy, and IT industries can be developed utilising bioelectronics.

(Oligo)aromatic species with one or two conjugated Si[double bond, length as m-dash]Si bonds: near-IR emission of anthracenyl-bridged tetrasiladiene

A series of aryl disilenes Tip₂Si[double bond, length as m-dash]Si(Tip)Ar (2a-c) and para-arylene bridged tetrasiladienes, Tip₂Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip₂ (3a-d) are synthesized by the transfer of the Tip₂Si[double bond, length as m-dash]SiTip unit to aryl halides and dihalides by nucleophilic disilenides Tip₂Si[double bond, length as m-dash]SiTipLi (Tip = 2,4,6-iPr₃C₆H₂, Ar = aryl substituent, LU = para-arylene linking unit). The scope of the nucleophilic Si[double bond, length as m-dash]Si transfer reaction is demonstrated to also include substrates of considerable steric bulk such as mesityl or duryl halides Ar-X (Ar = Mes = 2,4,6-Me₃C₆H₂; Ar = Dur = 2,3,5,6-Me₄C₆H, X = Br or I). Bridged tetrasiladienes Tip₂Si[double bond, length as m-dash]Si(Tip)-LU-Si(Tip)[double bond, length as m-dash]SiTip₂ with more extended linking units surprisingly exhibit fluorescence at room temperature, albeit weak. DFT calculations suggest that partial charge transfer character of the excited state is a possible explanation.

Synthesis and Photophysical Properties of λ5-Phosphinines as a Tunable Fluorophore

A practical synthesis of a variety of λ⁵-phosphinines, which show distinct fluorescence both in solution and solid state, is described. Both C4-selective electrophilic substitutions and the following conversions realized an easy preparation of a wide range of derivatives having several substituents for electronic modification, which provides the potential for fine-tuning of the photophysical properties.