Pentacyclic fused diborepinium ions with carbene- and carbone-mediated deep-blue to red emission

Designing molecules that can undergo late-stage modifications resulting in specific optical properties is useful for developing structure-function trends in materials, which ultimately advance optoelectronic applications. Herein, we report a series of fused diborepinium ions stabilized by carbene and carbone ligands (diamino-N-heterocyclic carbenes, cyclic(alkyl)(amino) carbenes, carbodicarbenes, and carbodiphosphoranes), including a detailed bonding analysis. These are the first structurally confirmed examples of diborepin dications and we detail how distortions in the core of the pentacyclic fused system impact aromaticity, stability, and their light-emitting properties. Using the same fused diborepin scaffold, coordinating ligands were used to dramatically shift the emission profile, which exhibit colors ranging from blue to red (358-643 nm). Notably, these diborepinium ions access expanded regions of the visible spectrum compared to known examples of borepins, with quantum yields up to 60%. Carbones were determined to be superior stabilizing ligands, resulting in improved stability in the solution and solid states. Density functional theory was used to provide insight into the bonding as well as the specific transitions that result in the observed photophysical properties.

Near-IR Emissive B-N Lewis Pair-Functionalized Anthracenes via Selective LUMO Extension in Conjugated Dimer and Polymer

Acenes are attractive as building blocks for low gap organic materials with applications, for example, in organic light emitting diodes, solar cells, bioimaging and diagnostics. Previously, we have shown that modification of dipyridylanthracene via B-N Lewis pair fusion (BDPA) strongly redshifts the emission, while facilitating self-sensitized reactivity toward O2 to reversibly generate the corresponding endoperoxides. Herein, we report on the further expansion of the π-system of BDPA to a vinyl-substituted monomer, vinylene-bridged dimer, and a polymer with an average of 20 chromophores. The extension of π-conjugation results in largely reduced band gaps of 1.8 eV for the dimer and 1.7 eV for the polymer, the latter giving rise to NIR emission with a maximum at 731 nm and an appreciable quantum yield of 7 %. Electrochemical and computational studies reveal efficient delocalization of the lowest unoccupied molecular orbital (LUMO) along the pyridyl-anthracene-pyridyl axis, which results in effective electronic communication between BDPA units, selectively lowers the LUMO, and ultimately narrows the band gap. Time-resolved emission and transient absorption (TA) measurements offer insights into the pertinent photophysical processes. Extension of π-conjugation also slows down the self-sensitized formation of endoperoxides, while significantly accelerating the thermal release of singlet oxygen to regenerate the parent acenes.

Unlocking Biradical Character in Diborepins

Systems that possess open- and closed-shell behavior attract significant attention from researchers due to their inherent redox and charge transport properties. Herein, we report the synthesis of the first diborepin biradicals. They display tunable biradical character based on the steric and electronic profile of the stabilizing ligand and the resulting geometric deviation of the diborepin core from planarity. While there are numerous all-carbon-based biradical systems, boron-based biradical compounds are comparatively rare, particularly ones in which the radical sites are disjointed. Calculations using density functional theory (DFT) and multireference methods demonstrate that the fused diborepin scaffold exhibits high biradical character, up to 95%. Use of a nonsterically demanding diaminocarbene promotes the planarization of the pentacyclic framework, resulting in the synthetic realization of a diborepin containing a dibora-quinoidal core, which possesses a closed-shell ground state and thermally accessible triplet state. The biradicals were structurally authenticated and characterized by both solution and solid-state electron paramagnetic resonance (EPR) spectroscopy. Half-field transitions were observed at low temperatures (about 170 K), confirming the presence of the triplet state. Initial reactivity studies of the biradicals led to the isolation and structural characterization of bis(borepin hydride) and bis(borepin dianion).

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.

Synthesis, structures, and photophysical properties of π-extended arsaborins

In this study, various (hetero)arene-fused arsaborins were synthesized. All the synthesized arsaborins were stable under ambient conditions and allowed for the chemical modification of the lone pair of the arsenic atom. Experimental and computational studies revealed that these compounds possessed planar structures and weak anti-aromatic properties. Fluorescence with large Stokes shifts was observed due to drastic structural relaxation at 298 K, whereas intense phosphorescence due to the heavy-atom effect of arsenic was observed at 77 K. Furthermore, a thiophene-fused derivative demonstrated a temperature-dependent emission color change in the solid state, attributable to the gradual alteration in the ratio of monomer fluorescence, excimer fluorescence, and phosphorescence.

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.

Titanium-Catalyzed Polymerization of a Lewis Base-Stabilized Phosphinoborane

The reaction of the Lewis base-stabilized phosphinoborane monomer tBuHPBH2 NMe3 (2 a) with catalytic amounts of bis(η5 :η1 -adamantylidenepentafulvene)titanium (1) provides a convenient new route to the polyphosphinoborane [tBuPH-BH2 ]n (3 a). This method offers access to high molar mass materials under mild conditions and with short reaction times (20 °C, 1 h in toluene). It represents an unprecedented example of a transition metal-mediated polymerization of a Lewis base-stabilized Group 13/15 compound. Preliminary studies of the substrate scope and a potential mechanism are reported.

Poly(thiophene iminoborane): A Poly(thiophene vinylene) (PTV) Analogue with a Fully BN-Doped Backbone

An unprecedented poly(thiophene iminoborane)-a boron-nitrogen analogue of the well-established conjugated organic polymer poly(thiophene vinylene)-is presented. The polymer synthesis is achieved by selective Si/B exchange polycondensation of a 2,5-diborylthiophene with a 2,5-diaminothiophene derivative. For the latter, a facile synthetic strategy is devised, which makes this versatile, strongly electron-releasing building block easily accessible. The novel polymer and a series of monodisperse thiophene iminoborane oligomers reveal systematic bathochromic shifts in their absorption with increasing chain length, and thus extended π-conjugation over the BN units along the backbone, which is further supported by TD-DFT calculations.

Poly(arylene iminoborane)s, Analogues of Poly(arylene vinylene) with a BN-Doped Backbone: A Comprehensive Study

Despite the great success of the concept of doping organic compounds with BN units to access new materials with tailored properties, its use in polymer chemistry has only been realized quite recently. Herein, we present a comprehensive study of oligo- and poly(arylene iminoborane)s comprising a backbone of phenylene or thiophene moieties, as well as combinations thereof, linked via B=N units. The novel polymers can be regarded as BN analogues of poly(p-phenylene vinylene) (PPV) or poly(thiophene vinylene) (PTV) or their copolymers. Our modular synthetic approach allowed us to prepare four polymers and 12 monodisperse oligomers with modulated electronic properties. Alternating electron-releasing diaminoarylene and electron-accepting diborylarylene building blocks gave rise to a pronounced donor-acceptor character. Effective π-conjugation over the arylene iminoborane backbone is evidenced by systematic bathochromic shifts of the low-energy UV-vis absorption maximum with increasing chain length, which is furthermore supported by crystallographic and computational investigations. Furthermore, all compounds investigated show emission of visible light in the solid state and aggregation-induced emission (AIE) behavior, due to the presence of partially flexible linear B=N linkages in the backbone.

Structures and Stability of Mixed Main Group Hydrides [PBEH6]n (E = C, Si, Ge; n = 1-4) and Donor-Acceptor Stabilization of Monomeric Chain Isomers

Structures and stability of mixed group 13-14-15 element hydrides PBEH6 (E = C, Si, Ge), their oligomers, and complexes with Lewis acids and Lewis base are computationally studied at the B3LYP-D3/def2-TZVP level of theory. Unsubstituted chain hydrides are unstable and are expected to form cyclic oligomers. Cyclization can be prevented by the donor-acceptor complex formation. For complexes of chain hydrides with Lewis acid in many cases additional reactivity beyond the donor-acceptor complex formation is observed: cyclization and migration of terminal group from the group 13 Lewis acid to the boron or group 14 terminal atoms of the hydride. The most promising compounds for the experimental studies have been identified. Joint stabilization by both W(CO)5 and trimethylamine provides a synergetic effect, allowing stabilization of 13-14-15 chain compounds.

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.

One-Pot Synthesis of Polymers Containing PC Bonds in the Main Chain

Placement of phosphorus in the polymer main chain leads to organophosphorus polymers with potentially unique chemical and physical properties. Herein, it is demonstrated that the Abramov phosphonylation reaction can be extended to the synthesis of such polymers, by reacting di- or tricarbaldehydes with phosphinic acid (PA) in the presence of N,O-bis(trimethylsilyl)acetamide (BSA). This technique affords polymers with main chain PC bonds, wherein phosphorus (V), aromatic rings, and hydroxymethylene moieties are linked by bis(α-hydroxymethylene)phosphinic acid (BHMPA) units. The resulting polymers are water soluble, display resilience against acid- and base-catalyzed hydrolysis, and exhibit superior thermal stability with high char yield in air (≈83%) and nitrogen (≈76%) atmosphere.

Synthesis and Structure-Property Relationships in Regioisomeric Alternating Borane-Terthiophene Polymers

Main-chain boron-containing π-conjugated polymers are attractive for organic electronic, sensing, and imaging applications. Alternating terthiophene-borane polymers were prepared and the effects of regioisomeric attachment of the conjugated linker and variations in the electronic effect of the pendent aryl groups (2,4,6-tri-tert-butylphenyl, Mes*; 2,4,6-tris(trifluoromethyl)phenyl, FMes) examined. Pd₂ dba₃ /P(t-Bu)₃ -catalyzed Stille polymerization of arylbis(2-thienyl)borane and arylbis(3-thienylborane) with 2,5-bis(trimethylstannyl)thiophene at 120 °C gave polymers with appreciable molecular weight but MALDI-TOF MS analyses showed evidence of unusually prominent homocoupling. These defects could be suppressed by using brominated rather than iodinated monomers, more hindered 2,5-bis(tri-n-butylstannyl)thiophene as comonomer, and Pd₂ dba₃ /P(o-tol)₃ as the catalyst at 100 °C. Under these conditions, macrocyclic species with n=3-10 repeating units formed preferentially according to MALDI-TOF MS analyses. Photophysical studies revealed a prominent effect of the regiochemistry and the nature of the pendent aryl groups on the absorption and emission, giving rise to orange, yellow-green, blue-green, and blue emissive materials respectively. The electronic effects were rationalized through DFT calculations on bis(terthiophene) model systems.

Tetra-Coordinated Boron-Functionalized Phenanthroimidazole-Based Zinc Salen as a Photocatalyst for the Cycloaddition of CO2 and Epoxides

A unique B-N coordinated phenanthroimidazole-based zinc salen was synthesized. The zinc salen thus synthesized acts as a photocatalyst for the cycloaddition of carbon dioxide with terminal epoxides under ambient conditions. DFT study of the cycloaddition of carbon dioxide with terminal epoxide indicates the preference of the reaction pathway when photocatalyzed by zinc salen. We anticipate that this strategy will help to design new photocatalysts for CO₂ fixation.

Group 16 conjugated polymers based on furan, thiophene, selenophene, and tellurophene

Five-membered aromatic rings containing Group 16 elements (O, S, Se, and Te), also referred as chalcogenophenes, are ubiquitous building blocks for π-conjugated polymers (CPs). Among these, polythiophenes have been established as a model system to study the interplay between molecular structure, solid-state organization, and electronic performance. The judicious substitution of alternative heteroatoms into polythiophenes is a promising strategy for tuning their properties and improving the performance of derived organic electronic devices, thus leading to the recent abundance of CPs containing furan, selenophene, and tellurophene. In this review, we first discuss the current status of Kumada, Negishi, Murahashi, Suzuki-Miyaura, and direct arylation polymerizations, representing the best routes to access well-defined chalcogenophene-containing homopolymers and copolymers. The self-assembly, optical, solid-state, and electronic properties of these polymers and their influence on device performance are then summarized. In addition, we highlight post-polymerization modifications as effective methods to transform polychalcogenophene backbones or side chains in ways that are unobtainable by direct polymerization. Finally, the major challenges and future outlook in this field are presented.

Fluorescent Polymers Conspectus

The development of luminescent materials is critical to humankind. The Nobel Prizes awarded in 2008 and 2010 for research on the development of green fluorescent proteins and super-resolved fluorescence imaging are proof of this (2014). Fluorescent probes, smart polymer machines, fluorescent chemosensors, fluorescence molecular thermometers, fluorescent imaging, drug delivery carriers, and other applications make fluorescent polymers (FPs) exciting materials. Two major branches can be distinguished in the field: (1) macromolecules with fluorophores in their structure and (2) aggregation-induced emission (AIE) FPs. In the first, the polymer (which may be conjugated) contains a fluorophore, conferring photoluminescent properties to the final material, offering tunable structures, robust mechanical properties, and low detection limits in sensing applications when compared to small-molecule or inorganic luminescent materials. In the latter, AIE FPs use a novel mode of fluorescence dependent on the aggregation state. AIE FP intra- and intermolecular interactions confer synergistic effects, improving their properties and performance over small molecules aggregation-induced, emission-based fluorescent materials (AIEgens). Despite their outstanding advantages (over classic polymers) of high emission efficiency, signal amplification, good processability, and multiple functionalization, AIE polymers have received less attention. This review examines some of the most significant advances in the broad field of FPs over the last six years, concluding with a general outlook and discussion of future challenges to promote advancements in these promising materials that can serve as a springboard for future innovation in the field.

A Benzodiphosphaborolediide

The first example of a diphosphaborolediide, the benzo-fused [C₆ H₄ P₂ BPh]^2- (1^2- ), is prepared from ortho-bis(phosphino)benzene (C₆ H₄ {PH₂ }) and dichlorophenylborane, via a sequential lithiation approach. The dilithio-salt can be obtained as an oligomeric THF solvate or discrete TMEDA adduct, both of which are fully characterized, including by X-ray diffraction. Alongside NICS calculations, data strongly suggest some aromaticity within 1^2- , which is further supported by preliminary coordination studies that demonstrate η⁵ -coordination to a zerovalent molybdenum center, as observed crystallographically for the oligomeric [{Mo(CO)₃ (η⁵ -1)}{μ-η¹ -Mo(CO)₃ (TMEDA)}₂ ] ⋅ [μ-Li(THF)][μ-Li(TMEDA)].

Stability and Electronic Structure of Donor-Acceptor Stabilized Group 13/15 Oligomers

Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers [H₂MEH₂]_n (M = B, Al, Ga, E = P, As; n = 4-15) are presented. Donor-acceptor interaction with both Lewis acids and Lewis bases effectively stabilizes chain isomers with respect to spontaneous cyclization and significantly changes their electronic structure.

Modular Synthesis of Pentagonal and Hexagonal Ring-Fused NBN-Phenalenes Leading to an Excited-State Aromatization-Induced Structural Planarization Molecular Library

Although polycyclic aromatic hydrocarbons (PAHs) with a nitrogen-boron-nitrogen (NBN) moiety have recently attracted tremendous interest due to their intriguing electronic and optoelectronic properties, all of the NBN-fused π-systems reported to date are called NBN-dibenzophenalenes and were synthesized by electrophilic aromatic substitution. The synthesis of NBN-phenalenes remains challenging, and transition-metal catalysis has never been utilized to construct NBN-embedded π-scaffolds. Herein, a palladium-catalyzed cyclization/bicyclization strategy was developed for the synthesis of diverse pentagonal and hexagonal ring-fused NBN-phenalenes and half-NBN-phenalenes. All of the NBN-embedded π-scaffolds presented in our paper are fluorescent in both solution and the solid state. Further investigations showed that the five-membered NBN rings exhibit the properties of traditional luminogens, while those with a six-membered NBN ring generally undergo photoinduced structural planarization (PISP) and exhibit different colors and quantum yields of fluorescence with different concentrations in solution. Time-resolved spectroscopy and TD-DFT calculations revealed that excited-state aromatization is the driving force for PISP in hexagonal ring-fused NBN-π systems, leading to the formation of excimers. Notably, the scope of PISP compounds is still quite limited, and PISP has never been observed in NBN-π systems before. These hexagonal ring-fused NBN-π systems constitute a novel PISP molecular library and appear to be a new class of aggregation-induced excimer emission (AIEE) materials. Finally, the AIEE behavior of these six-membered NBN rings was applied to the detection of nitro explosives, achieving excellent sensitivity. In general, this work provides a new viewpoint for synthesizing NBN-fused π-systems and understanding the excited-state motion of luminogens.

A thermolytic route to a polysilyne

We report a safe and convenient method to prepare a new class of network polysilane, or polysilyne ([RSi]_n). Simple thermolysis of a readily accessible linear poly(phenylsilane), [PhSiH]_n, affords polysilyne [PhSi]_n with concomitant evolution of monosilanes. This new polymer shows a hyperbranched structure with unique features not observed in known polysilynes prepared via hazardous Wurtz coupling routes. Despite these differences, our soluble, yellow polysilyne exhibits some important properties associated with the traditional random network structure: it absorbs up to 400 nm in the UV spectrum, yet is stable to photolysis under inert atmosphere. This efficient new synthetic route opens the door to exciting applications for these hyperbranched polymers in materials and device technologies.

Electrode and dielectric layer interface device engineering study using furan flanked diketopyrrolopyrrole-dithienothiophene polymer based organic transistors

We successfully demonstrated a detailed and systematic enhancement of organic field effect transistors (OFETs) performance using dithienothiophene (DTT) and furan-flanked diketopyrrolopyrrole based donor-acceptor conjugated polymer semiconductor namely PDPPF-DTT as an active semiconductor. The self-assembled monolayers (SAMs) treatments at interface junctions of the semiconductor-dielectric and at the semiconductor-metal electrodes has been implemented using bottom gate bottom contact device geometry. Due to SAM treatment at the interface using tailored approach, the significant reduction of threshold voltage (Vth) from - 15.42 to + 5.74 V has been observed. In addition to tuning effect of Vth, simultaneously charge carrier mobility (µFET) has been also enhanced the from 9.94 × 10-4 cm2/Vs to 0.18 cm2/Vs. In order to calculate the trap density in each OFET device, the hysteresis in transfer characteristics has been studied in detail for bare and SAM treated devices. Higher trap density in Penta-fluoro-benzene-thiol (PFBT) treated OFET devices enhances the gate field, which in turn controls the charge carrier density in the channel, and hence gives lower Vth = + 5.74 V. Also, PFBT treatment enhances the trapped interface electrons, which helps to enhance the mobility in this OFET architecture. The overall effect has led to possibility of reduction in the Vth with simultaneous enhancements of µFET in OFETs, following systematic device engineering methodology.

Silicon and oxygen synergistic effects for the discovery of new high-performance nonfullerene acceptors

In organic electronics, an aromatic fused ring is a basic unit that provides π-electrons to construct semiconductors and governs the device performance. The main challenge in developing new π-skeletons for tuning the material properties is the limitation of the available chemical approach. Herein, we successfully synthesize two pentacyclic siloxy-bridged π-conjugated isomers to investigate the synergistic effects of Si and O atoms on the geometric and electronic influence of π-units in organic electronics. Notably, the synthesis routes for both isomers possess several advantages over the previous approaches for delivering conventional aromatic fused-rings, such as environmentally benign tin-free synthesis and few synthetic steps. To explore their potential application as photovoltaic materials, two isomeric acceptor-donor-acceptor type acceptors based on these two isomers were developed, showing a decent device efficiency of 10%, which indicates the great potential of this SiO-bridged ladder-type unit for the development of new high-performance semiconductor materials.

Persistent Borafluorene Radicals

N‐Heterocyclic carbene (NHC)‐ and cyclic (alkyl)(amino)carbene (CAAC)‐stabilized borafluorene radicals have been isolated and characterized by elemental analysis, single‐crystal X‐ray diffraction, UV/Vis absorption, cyclic voltammetry (CV), electron paramagnetic resonance (EPR) spectroscopy, and theoretical studies. Both the CAAC–borafluorene radical (2) and the NHC–borafluorene radical (4) have a considerable amount of spin density localized on the boron atoms (0.322 for 2 and 0.369 for 4). In compound 2, the unpaired electron is also partly delocalized over the CAAC ligand ^carbeneC and N atoms. However, the unpaired electron in compound 4 mainly resides throughout the borafluorene π‐system, with significantly less delocalization over the NHC ligand. These results highlight the Lewis base dependent electrostructural tuning of materials‐relevant radicals. Notably, this is the first report of crystalline borafluorene radicals, and these species exhibit remarkable solid‐state and solution stability.

Four-Coordinate Organoboron Platforms for Efficient Red Phosphorescent Organic Light-Emitting Diodes

So far both three- and four-coordinate organoboron compounds have been widely applied in organic light-emitting diode (OLED) materials. However, the use of four-coordinate organoboron compounds as host materials is rarely reported. In this work, two new four-coordinate organoboron compounds, namely 8-(4-(9H-carbazol-9-yl)phenyl)-6,6-difluoro-6H-6λ⁴ ,7λ⁴ -benzo[4',5']imidazo[1',2':3,4][1,3,2]diazaborolo[1,5-a]pyridine (B1PCz) and 8-(3-(9H-carbazol-9-yl)phenyl)-6,6-difluoro-6H-6λ⁴ ,7λ⁴ -benzo[4',5']imidazo[1',2':3,4][1,3,2]diazaborolo[1,5-a]pyridine (B1MCz), were successfully designed, synthesized, and fully characterized. The red OLEDs using B1PCz and B1MCz as host materials achieved relatively high device performance with a maximum external quantum efficiency of 14.8 % and 11.8 %, respectively. These results will expand the scope of organoboron compounds for OLED materials and reveal the great potential of four-coordinate organoboron materials.

A mechanistic study of the activation of small molecules (H2 and C2H2) by group 14 analogues of selenophene

In this study, the reactivity influenced by group 14 elements (E = C, Si, Ge, Sn, and Pb), which are used as substituents in heterocyclic five-membered rings, was theoretically examined by using density functional theory (B3PW91/def2-SVP).

Poly(3,4-ethylenedioxyselenophene): effect of solvent and electrolyte on electrodeposition, optoelectronic and electrochromic properties

In this article, we report the effect of electropolymerization conditions such as solvent and supporting electrolyte on the redox, optoelectronic and electrochromic properties of PEDOS. Monomer EDOS was synthesized by new and simple route and its electropolymerization was investigated by employing six different combinations of solvent–electrolyte namely TBAClO₄/MeCN, TBAPF₆/MeCN, TBABF₄/MeCN, TBAClO₄/PC, TBAPF₆/PC and TBABF₄/PC. Further, the electrochemical, spectroelectrochemistry, morphology and electrochromic properties of resultant PEDOS films were systematically studied. A pronounced effect of both solvent and supporting electrolyte on the electropolymerization, redox, optoelectronic and electrochromic properties on PEDOS film is noted. Among all solvent–electrolyte systems, MeCN and TBAClO₄ were found to be the most suitable medium for electropolymerization of EDOS. Further, PEDOS films prepared in PC showed red shifted absorption maxima, narrow absorption peaks in UV-vis-NIR spectra, slightly more smooth morphologies, and high optical contrasts ratio and coloration efficiency in comparison to MeCN. PEDOS films prepared in TBABF₄/PC exhibited longer λ_max (670 nm), smooth morphology, and the highest optical contrasts ratio (44.6%) and coloration efficiency (141.8 cm² C⁻¹) compared to the other solvent–electrolyte medium.

In this article, we report the effect of electropolymerization conditions such as solvent and supporting electrolyte on the redox, optoelectronic and electrochromic properties of PEDOS.

Direct comparison of dithienosilole and dithienogermole as π-conjugated linkers in photosensitizers for dye-sensitized solar cells

Dithienosilole (DTS) and dithienogermole (DTG) are useful building units of π-conjugated organic materials. In the present work, donor-π-acceptor (D-π-A) dyes with bis(dihexyloxyphenyl)aminophenyl, DTS or DTG, and pyridine or cyanoacrylic acid as the donor (D), the π-conjugated linker (π), and the acceptor (A) units, respectively, were prepared and their optical properties were investigated. The D-π-A dyes exhibited strong absorption in the visible region, indicating efficient intramolecular donor-acceptor interaction. The addition of trifluoroacetic acid to solutions of pyridine-containing dyes led to red-shifts of the absorption bands as a result of pyridinium salt formation. Similar red-shifts were observed for cyanoacrylic acid dyes, which were due to the enhanced formation of neutral dyes relative to the separated ion pairs. The D-π-A dyes, however, showed similar absorption spectra when attached to the TiO2 surface, indicating that the dye-TiO2 electronic interaction was rather weak. In contrast to the finding that these dyes exhibited similar optical properties regardless of the π-linker (i.e., DTS or DTG), dye-sensitized solar cells (DSSCs) based on DTG-containing dyes exhibited superior performance compared to those based on DTS-containing dyes. Electrochemical impedance spectroscopy measurements supported the higher performance of the DSSCs with DTG-containing dyes.

Stable Borepinium and Borafluorenium Heterocycles: A Reversible Thermochromic "Switch" Based on Boron-Oxygen Interactions

The first examples of N-heterocyclic carbene (NHC) and cyclic(alkyl)(amino) carbene (CAAC) stabilized borepinium and borafluorenium heterocycles are reported herein. The optical properties of the heterocyclic borenium cations were tuned by varying the Lewis base and by changing the number of atoms in the ring. More importantly, functionalizing the cationic boron ring system in the NHC-borafluorenium cation affords a temperature-sensitive molecule with reversible colorimetric "turn off/turn on" properties in solution. Notably, this is the first report of thermochromism in these cationic species. This property, which is mediated by an intermolecular boron-oxygen bond equilibrium, was examined in detail by X-ray crystallography, variable temperature-UV/Vis absorption spectroscopy (VT-UV/Vis), and density functional theory (DFT).

Aromatic-fused diketophosphanyl-core organic functional materials: phosphorus mimics of imides or beyond?

Recently, missing pieces of organophosphorus compounds, i.e., aromatic-fused diketophosphanyl compounds, have attracted much attention as promising scaffolds of building blocks for functional organic materials. In this review, the brief historical background, synthetic methods, structures, and optoelectronic aspects of aromatic-fused diketophosphanyls are overviewed.

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%.

Effects of Structural Variation in Conjugated Side Chains on the Photophysics of Conjugated Polymers in Nanoparticles

Conjugated polymers (CPs) are widely used for a variety of applications as a result of their high quantum yields, strong extinction coefficients, and good stability to a variety of experimental conditions. In many cases, the use of conjugated polymer nanoparticles (CPNs) provides additional practical advantages. The ability to understand how the structure of the CP affects its photophysical properties has the potential to significantly accelerate research in this area. In this work we examine 3 CPs, including two novel polymer architectures, and evaluate how the structures of the conjugated side chains affect the photophysical properties of the free polymer chains as well as the properties of aggregated CPNs. Both the linker identity and the terminal aromatic rings of the side chains were found to affect the photophysical properties of the CPs, with the terminal groups leading to the most substantial changes in photophysical properties in all of the polymeric forms (well-solubilized in organic solvent and aggregated in nanoparticles).

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.

Metal-free dehydropolymerisation of phosphine-boranes using cyclic (alkyl)(amino)carbenes as hydrogen acceptors

The divalent carbene carbon centre in cyclic (alkyl)(amino)carbenes (CAACs) is known to exhibit transition-metal-like insertion into E-H σ-bonds (E = H, N, Si, B, P, C, O) with formation of new, strong C-E and C-H bonds. Although subsequent transformations of the products represent an attractive strategy for metal-free synthesis, few examples have been reported. Herein we describe the dehydrogenation of phosphine-boranes, RR'PH·BH3, using a CAAC, which behaves as a stoichiometric hydrogen acceptor to release monomeric phosphinoboranes, [RR'PBH2], under mild conditions. The latter species are transient intermediates that either polymerise to the corresponding polyphosphinoboranes, [RR'PBH2]n (R = Ph; R' = H, Ph or Et), or are trapped in the form of CAAC-phosphinoborane adducts, CAAC·H2BPRR' (R = R' = tBu; R = R' = Mes). In contrast to previously established methods such as transition metal-catalysed dehydrocoupling, which only yield P-monosubstituted polymers, [RHPBH2]n, the CAAC-mediated route also provides access to P-disubstituted polymers, [RR'PBH2]n (R = Ph; R' = Ph or Et).