Doping the Backbone of π‐Conjugated Polymers with Tricoordinate Boron: Synthetic Strategies and Emerging Applications

NBN- and BNB-Phenalenyls: the Yin and Yang of Heteroatom-doped π Systems

NBN- and BNB-doped phenalenyls are isoelectronic to phenalenyl anions and cations, respectively. They represent a pair of complementary molecules that have essentially identical structures but opposite properties as electron donors and acceptors. The NBN-phenalenyls 1-4 considered here were prepared from N,N'-dimethyl-1,8-diaminonaphthalene and readily available boron-containing building blocks (i. e., BH3⋅SMe2 (1), p-CF3-C6H4B(OH)2 (2), C6H5B(OH)2 (3), or MesBCl2/iPr2NEt (4)). Treatment of 1 with 4-Me2N-2,6-Me2-C6H2Li gave the corresponding NBN derivative 5. The BNB-phenalenyl 6 was synthesized from 1,8-naphthalenediyl-bridged diborane(6), PhNH2, and MesMgBr. A computational study reveals that the photoemission of 1, 4, and 5 originates from locally excited (LE) states at the NBN-phenalenyl fragments, while that of 2 is dominated by charge transfer (CT) from the NBN-phenalenyl to the p-CF3-C6H4 fragment. Depending on the dihedral angle θ between its Ph and NBN planes, compound 3 emits mainly from a less polar LE (θ >55°) or more polar CT state (θ <55°). In turn, the energetic preference for either state is governed by the polarity of the solvent used. An equimolar aggregate of the NBN- and BNB-phenalenyls 3 and 6 (in THF/H2O) shows a distinct red-shifted emission compared to that of the individual components, which originates from an intermolecular CT state.

Bis-Ortho-Donor-Modification of Boracyclic π-Electron Systems beyond Steric Protection to Produce Thermally Activated Delayed Fluorescence Materials

Polycyclic π-conjugated compounds that contain tricoordinate boron atoms at their periphery represent an attractive class of materials with electron-accepting character. Their molecular design generally requires the introduction of a bulky aryl group onto the boron atom, where it provides predominantly kinetic stabilization. The addition of extra functionality to the aryl group on the boron atom can be expected to further expand the potential utility of this class of materials. Herein, we report the synthesis of a series of boracyclic π-conjugated molecules with firm ortho B⋅⋅⋅N nonbonding interactions by introducing N-containing electron-donors at the ortho-positions of the aryl group on the boron atom. X-ray crystallographic analysis revealed that the combination of a planar boracyclic π-skeleton with only sp2 carbons and a strong electron-donating phenothiazine moiety results in a particularly short B⋅⋅⋅N distance. Theoretical study provided insights into the inherent nature of the B⋅⋅⋅N interaction. Owing to their donor-acceptor (D-A) structures, these molecules exhibit substantially red-shifted fluorescence in solution, albeit that the fluorescence quantum yields (ΦF) are low. In contrast, when incorporated into films, these compounds exhibit thermally activated delayed fluorescence (TADF) with improved ΦF values. Organic light-emitting diodes (OLEDs) fabricated using the ortho-donor-substituted derivatives exhibit orange-red electroluminescence.

Organoboron-thiophene-based polymer electrodes for high-performance lithium-ion batteries

Polymer electrodes are drawing widespread attention to the future generation of lithium-ion battery materials. However, weak electrochemical performance of organic anode materials still exists, such as low capacity, low rate performance, and low cyclability. Herein, we successfully constructed a donor-acceptor thiophene-based polymer (PBT-1) by introducing an organoboron unit. The charge delocalization and lower LUMO energy level due to the unique structure enabled good performance in electrochemical tests with a reversible capacity of 405 mA h g-1 at 0.5 A g-1 and over 10 000 cycles at 1 A g-1. Moreover, electron paramagnetic resonance (EPR) spectra revealed that the unique stable spin system in the PBT-1 backbone during cycling provides a fundamental explanation for the highly stable electrochemical performance. This work offers a reliable reference for the design of organic anode materials and expands the potential application directions of organoboron chemistry.

BN-Phenanthrene- and BN-Pyrene-Based Fluorescent Uridine Analogues

Two unprecedented fluorescent nucleosides that feature BN-doped polycyclic aromatic hydrocarbons are presented. One of them, having a BN-modified phenanthrene moiety incorporated, shows blue fluorescence but suffers from poor stability under aqueous conditions. The other nucleoside comprises an internally BN-doped pyrene as the chromophore. It shows green fluorescence in various solvents and is stable under aqueous and alkaline conditions.

Organoboron-based multiple-resonance emitters: synthesis, structure-property correlations, and prospects

Boron-based multiple-resonance (MR) emitters exhibit the advantages of narrowband emission, high absolute photoluminescence quantum yield, thermally activated delayed fluorescence (TADF), and sufficient stability during the operation of organic light-emitting diodes (OLEDs). Thus, such MR emitters have been widely applied as blue emitters in triplet-triplet-annihilation-driven fluorescent devices used in smartphones and televisions. Moreover, they hold great promise as TADF or terminal emitters in TADF-assisted fluorescence or phosphor-sensitised fluorescent OLEDs. Herein we comprehensively review organoboron-based MR emitters based on their synthetic strategies, clarify structure-photophysical property correlations, and provide design guidelines and future development prospects.

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.

Synthesis, Structure, and Properties of Monodispersed and Highly Luminescent Organoborane Oligomers

Organoborane oligomers with well-defined molecular structures and high luminescence are scarce, among which those with boron not used as bridging atoms are even more so. Here, a series of well-defined ethynyl-linked or butadiynyl-linked conjugated organoborane oligomers with high fluorescence quantum yield and extinction coefficient (i.e., high brightness) were prepared by coupling different building blocks featuring dithienooxadiborepine moieties. Single crystal structures of hexyl modified dithienooxadiborepine (1a-hex) and hexyl-modified butadiynyl-linked conjugated dimer (D2-hex) not only verified the identity of the molecular structures but also revealed that the introduction of the hexyl chains distorted the molecular structures due to steric hindrance. Optical measurements showed that the absorption and emission maxima of the six oligomeric molecules bathochromic shifted with increasing numbers of repeating units. Molecules without hexyl chains emit efficient fluorescence upon photoexcitation, and the fluorescence quantum efficiency of the ethynyl-linked conjugated dimer (D1) is close to unity. Theoretical calculation results using density functional theory methods are consistent with the single crystal data, allowing a better understanding of the spectral properties. Such results indicate that the method is efficient for expanding small organoborane molecules into π-conjugated oligomers, which can be used to modulate to emit different colors with high efficiency.

Highly luminescent antiaromatic diborinines with fused thiophene rings

Tricoordinate boron-incorporated π-conjugated systems are widely investigated as optoelectronic materials because of their unique p-π* orbital interactions and high Lewis acidity. Among them, thiophene-fused diborinines are characterized by moderate antiaromaticity and extended conjugation. In this work, we have developed two new dithienodiborinines with C_2h and C_2v symmetries, which exhibited completely different optical properties. The thiophene-fused diborinines synthesized in this study showed excellent fluorescence properties both in solution and in the solid state, with quantum yields of up to 95%. The high antiaromaticity enhanced the Lewis acidity of the boron centers, as proven by the large association constants with fluoride ion estimated from titration experiments. The high Lewis acidity and the superior luminescence property have enabled their application as fluorescent sensor materials for the detection of ammonia vapor.

Ring Opening Copolymerization of Boron-Containing Anhydride with Epoxides as a Controlled Platform to Functional Polyesters

Boron-functionalized polymers are used in opto-electronics, biology, and medicine. Methods to produce boron-functionalized and degradable polyesters remain exceedingly rare but relevant where (bio)dissipation is required, for example, in self-assembled nanostructures, dynamic polymer networks, and bio-imaging. Here, a boronic ester-phthalic anhydride and various epoxides (cyclohexene oxide, vinyl-cyclohexene oxide, propene oxide, allyl glycidyl ether) undergo controlled ring-opening copolymerization (ROCOP), catalyzed by organometallic complexes [Zn(II)Mg(II) or Al(III)K(I)] or a phosphazene organobase. The polymerizations are well controlled allowing for the modulation of the polyester structures (e.g., by epoxide selection, AB, or ABA blocks), molar masses (9.4 < M_n < 40 kg/mol), and uptake of boron functionalities (esters, acids, "ates", boroxines, and fluorescent groups) in the polymer. The boronic ester-functionalized polymers are amorphous, with high glass transition temperatures (81 < T_g < 224 °C) and good thermal stability (285 < T_d < 322 °C). The boronic ester-polyesters are deprotected to yield boronic acid- and borate-polyesters; the ionic polymers are water soluble and degradable under alkaline conditions. Using a hydrophilic macro-initiator in alternating epoxide/anhydride ROCOP, and lactone ring opening polymerization, produces amphiphilic AB and ABC copolyesters. Alternatively, the boron-functionalities are subjected to Pd(II)-catalyzed cross-couplings to install fluorescent groups (BODIPY). The utility of this new monomer as a platform to construct specialized polyesters materials is exemplified here in the synthesis of fluorescent spherical nanoparticles that self-assemble in water (D_h = 40 nm). The selective copolymerization, variable structural composition, and adjustable boron loading represent a versatile technology for future explorations of degradable, well-defined, and functional polymers.

Efficient side-chain engineering of thieno-imidazole salt-based molecule to boost the optoelectronic attributes of organic solar cells: A DFT approach

This study focused on modeling and density functional theory (DFT) analysis of reference (AI1) and designed structures (AI11-AI15), based on the thieno-imidazole core, in order to create profitable candidates for solar cells. All the optoelectronic properties of the molecular geometries were computed using DFT and time dependent-DFT approaches. The influence of terminal acceptors on the bandgaps, absorption, hole and electron mobilities, charge transfer capabilities, fill factor, dipole moment, etc. Of the recently designed structures (AI11-AI15), as well as reference (AI1), were evaluated. Optoelectronics and chemical parameters of newly architecture geometries were shown to be superior to the cited molecule. The FMOs and DOS graphs also demonstrated that the linked acceptors remarkably improved the dispersion of charge density in the geometries under study, particularly in AI11 and AI14. Calculated values of binding energy and chemical potential confirmed the thermal stability of the molecules. All the derived geometries surpassed the AI1 (Reference) molecule in terms of maximum absorbance ranging from 492 to 532 nm (in chlorobenzene solvent) and a narrower bandgap ranging from 1.76 to 1.99eV. AI15 had the lowest exciton dissociation energy of 0.22eV as well as lowest electrons and hole dissociation energies, while AI11 and AI14 showed highest VOC, fill factor, power conversion efficiency (PCE), IP and EA (owing to presence of strong electron pulling cyano (CN) moieties at their acceptor portions and extended conjugation) than all the examined molecules, implying that they could be used to build elite solar cells with enhanced photovoltaic attributes.

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.

Fusion of Aza- and Oxadiborepins with Furans in a Reversible Ring-Opening Process Furnishes Versatile Building Blocks for Extended π-Conjugated Materials

A modular synthesis of both difurooxa- and difuroazadiborepins from a common precursor is demonstrated. Starting from 2,2'-bifuran, after protection of the positions 5 and 5' with bulky silyl groups, formation of the novel polycycles proceeds through opening of the furan rings to a dialkyne and subsequent re-cyclization in the borylation step. The resulting bifuran-fused diborepins show pronounced stability, highly planar tricyclic structures, and intense blue light emission. Deprotection and transformation into dibrominated building blocks that can be incorporated into π-extended materials can be performed in one step. Detailed DFT calculations provide information about the aromaticity of the constituent rings of this polycycle.

Electrophilic activation of difunctional aminoboranes: B-N coupling versus intramolecular Cl/Me exchange

Treatment of an N-silyl-B-chloro-aminoborane with substoichio-metric quantities of Me₃SiOTf afforded B-N coupling, whereas activation with 5 mol% of Ag[Al{OC(CF₃)₃}₄] led to Cl/Me exchange between the boron and the silicon center. Combined experimental and computational studies of the latter process support a chain reaction that is initiated by nucleation-limited chloride abstraction.

Anionic Polymerization of Para-Diethynylbenzene: Synthesis of a Strictly Linear Polymer

Anionic homo- and copolymerization of p-diethynylbenzene in the presence of n-BuLi in polar solvents was carried out. The use of hexamethylphosphortriamide (HMPA) makes it possible to synthesize a completely linear soluble polymer that does not have branching and phenylene fragments. A copolymer of p-diethynylbenzene with diphenyldiacetylene was synthesized. Homo- and copolymers of p-diethynylbenzene have high thermo- and thermo-oxidative stability. By the interaction of side reactive ethynylphenylene groups with various reagents, it is proposed to synthesize clusters along the conducting chain of poly-p-diethynylbenzene. Due to presenting C≡CH side groups, boron, copper, and cobalt derivatives were synthesized. It is shown that not all theoretically possible stereoisomers can be formed as a result of the polymerization. The application of p-diethynylbenzene polymers for the modification of industrial samples of epoxy novolac resin, oligoester acrylates, and carbon fibers has been demonstrated.

Solution Phase Reactivity of Dibenzo[c,e][1,2]azaborinine: Activation and Insertion into Si-E Single Bonds (E=H, OSi(CH3 )3 , F, Cl) by a BN-Aryne

The boron‐nitrogen analogue of ortho‐benzyne, 1,2‐azaborinine, is a reactive intermediate that features a formal boron‐nitrogen triple bond. We here show by combining experimental and computational techniques that the Lewis acidity of the boron center of dibenzo[c,e][1,2]azaborinine allows interaction with the silicon containing single bonds Si−E through the silicon bonding partner E (E=F, Cl, OR, H). The binding to boron activates the Si−E bonds for subsequent insertion reaction. This shows that the BN‐aryne is a ferocious species that even can activate and insert into the very strong Si−F bond.

Linear Extension of Anthracene via B←N Lewis Pair Formation: Effects on Optoelectronic Properties and Singlet O2 Sensitization

The functionalization of polycyclic aromatic hydrocarbons (PAHs) via B←N Lewis pair formation offers an opportunity to judiciously fine-tune the structural features and optoelectronic properties, to suit the demands of applications in organic electronic devices, bioimaging, and as sensitizers for singlet oxygen generation. We demonstrate that the N-directed electrophilic borylation of 2,6-di(pyrid-2-yl)anthracene offers access to linearly extended acene derivatives Py-BR (R=Et, Ph, C₆ F₅ ). In comparison to indeno-fused 9,10-diphenylanthracene, the formal "BN for CC" replacement in Py-BR selectively lowers the LUMO, resulting in a much reduced HOMO-LUMO gap. An even more extended conjugated system with seven six-membered rings in a row (Qu-BEt) is obtained by borylation of 2,6-di(quinolin-8-yl)anthracene. Fluorinated Py-BPf shows particularly advantageous properties, including relatively lower-lying HOMO and LUMO levels, strong yellow-green fluorescence, and effective singlet oxygen sensitization, while resisting self-sensitized conversion to its endoperoxide.

Redox-Active Heteroatom-Functionalized Polyacetylenes

The discovery of metallic conductivity in polyacetylene [-HC=CH-]_n upon doping represents a landmark achievement. However, the insolubility of polyacetylene and a dearth of methods for its chemical modification have limited its widespread use. Here, we employ a ring-opening metathesis polymerization (ROMP) protocol to prepare functionalized polyacetylenes (fPAs) bearing: (1) electron-deficient boryl (-BR₂ ) and phosphoryl (-P(O)R₂ ) side chains; (2) electron-donating amino (-NR₂ ) groups, and (3) ring-fused 1,2,3-triazolium units via strain-promoted Click chemistry. These functional groups render most of the fPAs soluble and can lead to intense light absorption across the visible to near-IR region. Also, the presence of redox-active boryl and amino groups leads to opposing near-IR optical responses upon (electro)chemical reduction or oxidation. Some of the resulting fPAs show greatly enhanced air stability when compared to known polyacetylenes. Lastly, these fPAs can be cross-linked to yield network materials with the full retention of optical properties.

NaRbB3 O4 F3 : A New Fluorooxoborate with a Short UV Cutoff Edge Enriching the Structural Chemistry of Borate

The combination of RbB₃ O₄ F₂ and NaF generates a new member of fluorooxoborates, NaRbB₃ O₄ F₃ , with a wide transparency range from the IR to DUV region. NaRbB₃ O₄ F₃ shows a three-dimensional (3D) structure composed of 1D [B₃ O₄ F₃ ]_∞ chains, [NaO₃ F₃ ] and [RbO₅ F₅ ] polyhedra. The structural evolution from NaRbB₃ O₄ F₃ to RbB₃ O₄ F₂ , as well as the structural comparison between NaRbB₃ O₄ F₃ and its identical stoichiometry compound, Li₂ B₃ O₄ F₃ were discussed in detail. The IR spectrum verifies its structural validity. The spectral measurement shows that the reflectance has no obvious change in the range of 175-300 nm, and its cutoff edge is below 175 nm. In addition, theoretical calculations are carried out to understand its electronic structure and optical properties.

Thiophene-fused boracycles as photoactive analogues of diboraanthracenes

The construction of thiophene-fused analogues of diboraanthracenes with different aryl substituents through boron-mercury exchange followed by the nucleophilic replacement of the chlorines of dichlorodiboradithiophene 2 with Grignard reagents is reported. These diboradithiophenes exhibited unusual photophysical and electrochemical properties. They all undergo photoisomerisation, which can be traced using photophysical and ¹H NMR spectroscopy studies.

Electron-Deficient Heteroacenes that Contain Two Boron Atoms: Near-Infrared Fluorescence Based on a Push-Pull Effect*

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm^-1 in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

A Crystalline B4N2 Dewar Benzene as a Building Block for Conjugated B,N-Chains

Dewar benzene, one of the isolable valence isomers of C₆H₆, has been extensively studied since its first synthesis in 1962. By contrast, the chemistry of inorganic congeners of Dewar benzene, which can be formally gained by replacing the skeletal carbon atoms with heteroatoms, has been less developed despite their peculiar structural and electronic features. Among them, the extant B,N-Dewar benzenes are limited to the B₃N₃ system. Herein, we report the development of the first example of an isolable B₄N₂ Dewar benzene, 3. As predicted by DFT calculations, a judicious selection of the substituents allows synthesizing 3. Single-crystal X-ray analysis, NMR, and computational studies confirmed that 3 possesses a high-lying B(sp³)-B(sp³) σ-bond at the bridgehead position. Reactions with ethylene and phenylacetylene proceeded smoothly under mild conditions, affording the fused B₄C₄N₂ ring systems (4 and 5). Structural characterization as well as DFT calculations revealed that compounds 4 and 5 involve a rigid and conjugated (BN)₄ tetraene scaffold. Formation of 4 and 5 demonstrates that 3 may serve as a building block for the construction of conjugated B,N-chains.

Dithiophene-Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics

Access to dithiophene-fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one-electron reduction processes. The weak aromatic character of the novel 1,2,7-azadiborepin ring is demonstrated with in-depth theoretical investigations using nucleus-independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations.

π-Conjugated Materials Derived From Boron-Chalcogenophene Combination. A Brief Description of Synthetic Routes and Optoelectronic Applications

Functional materials composed of Boron-chalcogenophene conjugates have emerged as promising ensemble featuring commendable optoelectronic properties. This review describes the categories, synthetic routes and optoelectronic applications of a range of boron-chalcogenophene conjugates. Conjugation and linking of different types of tri- and tetra-coordinated boron moieties with chalcogenophenes have remained an important strategy for constructing a range of functional materials. Synthetic protocols have been devised to efficiently prepare such chemically robust conjugates, often exhibiting a myriad of photophysical properties, redox capabilities and also solid-state behaviors. Tin-boron and silicon-boron exchange protocols have been efficiently adapted to access these boron-chalcogenophenes. Few other commonly used methods namely, hydroboration of alkynes as well as electrophilic borylations are also mentioned. The chemical and electronic properties of such boron-chalcogenophene conjugates are directly influenced by the strong Lewis acid character of trivalent boranes which can further alter the intra- and inter- molecular Lewis acid-base interactions. Apart from the synthetic protocols, recent advances in the application of these boron-chalcogenophene conjugates towards analyte sensing, organic electronics, molecular switches and several other aspects will be discussed in this review.

BNB-doped phenalenyls - aromaticity switch upon one-electron reduction

Fully aromatic, luminescent, and highly robust BNB-doped phenalenyls have been prepared, which are isoelectronic to the phenalenyl cation. B-Fluoromesityl-substitution leads to fluorescence in an extremely narrow range and significant increase in the reduction potential. Detailed theoretical investigations revealed an intramolecular aromaticity switch upon one-electron reduction.

Recent developments in stimuli-responsive luminescent polymers composed of boron compounds

This review summarizes recent developments in stimuli-responsive luminescent polymers with boron chromophores, including three- and four-coordinated compounds. Sensing mechanisms based on the features of boron and polymer structures are described.

Effect of the conjugation pathway on the electronic structures of p–π* conjugated polymers with fused borepin units

Borepin, an aromatic ring system with tricoordinate boron, was incorporated into p–π* conjugated polymers. The polymers exhibited characteristic optical responses upon the addition of cyanide anions in solution.

Bifuran-bridged bisboranes: highly luminescent B-doped oligohetarenes

Boron-doping of oligohetarenes – via classical metathesis or silicon/boron exchange routes – led to strongly luminescent and twofold reversibly reducible oligomers.

Removal of Cadmium (II), Chromium (III), and Lead (II) Heavy Metal Ions from Water by Graft Copolymerization of Acrylonitrile onto Date Palm Fiber Using H2O2/Fe++ as an Initiator

The study is aimed at assessing how the date palm wood fibers (DPWF) can be used for the removal of heavy metals from water. The study involved examination of the radical polymerization and graft polymerization parameters such as reaction period, reaction time, monomer volume, amount of the catalyst, and concentration of initiator to obtain the maximum yield of graft polymerization. Fiber and copolymer were characterized using SEM and FT-IR spectroscopy to ensure the completion of polymerization. Hydroxylamine hydrochloride was used for treating the grafted copolymers for the preparation of polyamidoxime chelating resin, which was then examined for removing the heavy metal ions. Different resin dosages, contact time, and initial concentrations were used, and the batch technique experiment was utilized. The study also applied the Langmuir and Freundlich isotherm model, and Langmuir was found to be better. The absorption ability was found to be better for polyamidoxime resin for metal ions of cadmium (II), chromium (III), and lead (II).

Panchromatic Organoboron Molecules with Tunable Absorption Spectra

Panchromatic molecules, e. g. organic small molecules with wide absorption spectra, are very desirable for solar energy-related applications. Here, we report the development of a series of organoboron compounds composed of an organoboron core unit, two π-bridging units and two electron-withdrawing end-capping units. All seven molecules have the HOMO localized on the core unit and the LUMO delocalized on the whole conjugated backbone. They exhibit wide absorption spectra consisting of two strong absorption bands with the full width at half maximum of ca. 280 nm. These panchromatic compounds can be used as electron acceptors in organic solar cells. We elucidate the relationship between the chemical structures and opto-electronic properties of these organoboron panchromatic compounds. Increasing the electron-withdrawing capability of the core units results in a downshifted HOMO level as well as blueshifted long-wavelength absorption band with increased extinction coefficient. Extending the π-bridging units causes an increased HOMO level and blueshifted long-wavelength absorption band with increased extinction coefficients. Weakening the electron-withdrawing capability of the end-capping units leads to an upshifted LUMO level and blueshifted long-wavelength absorption peak with decreased extinction coefficient. This work provides insight into the absorption spectrum manipulation of panchromatic molecules and would pave the way for the development of solar energy-related applications.

Visualization of the Borazine Core of B3N3-Doped Nanographene by STM

Electronic interface properties and the initial growth of hexa-peri-hexabenzocoronene with a borazine core (BN-HBC) on Au(111) have been studied by using X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM). A weak, but non-negligible, interaction between BN-HBC and Au(111) was found at the interface. Both hexa-peri-hexabenzocoronene (HBC) and BN-HBC molecules form well-defined monolayers. The different contrast in STM images of HBC and BN-HBC at different tunneling voltages with submolecular resolution can be ascribed to differences in the local density of states (LDOS). At positive and negative tunneling voltages, STM images reproduce the distribution of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) as determined by density functional theory (DFT) calculations very well.

Tetraiododiborane(4) (B2 I4 ) is a Polymer Based on sp3 Boron in the Solid State

Herein we present the first solid‐state structures of tetraiododiborane(4) (B₂I₄), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B₂F₄, B₂Cl₄, and B₂Br₄. Single‐crystal X‐ray diffraction, solid‐state NMR, and IR measurements indicate that B₂I₄ in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid‐state structures, and these are compared with the experimental spectra.