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Combination of borane and diaminoferrocene monomers by Si/B exchange condensation reactions afforded either diazabora-[3]ferrocenophanes or, via stepwise processes, larger macrocycles and a series of linear oligomers. Additional incorporation of p-phenylene moieties in the backbone yielded alternating concatenation. [ABSTRACT FROM AUTHOR]

Substituting CC with the isoelectronic BN units is a promising approach to modify the optoelectronic properties of polycyclic aromatic hydrocarbons. While computational studies have already addressed trends in the electronic structure of the various isosteres, experimental data are still scarce. Here, the excited state spectroscopy and dynamics of 4a,8a-azaboranaphthalene were studied by picosecond time-resolved photoionization in a supersonic jet and analyzed with the aid of XMS-CASPT2 and time-dependent DFT calculations. A resonance-enhanced multiphoton ionization spectrum (REMPI) reveals the S1 origin at v = 33 830 ± 12 cm−1. Several vibrational bands were resolved and assigned by comparison with the computations. A [1+1] photoelectron spectrum via the S1 origin yielded an adiabatic ionization energy of 8.27 eV. Selected vibrational bands were subsequently investigated by pump–probe photoionization. While the origin as well as several low-lying vibronic states exhibit lifetimes in the ns-range, a monoexponential decay is observed at higher excitation energies, ranging from 400 ps at +1710 cm−1 to 13 ps at +3360 cm−1. The deactivation is attributed to an internal conversion of the optically excited S1 state via a barrier that gives access to a conical intersection (CI) to the S0 state. The doping significantly changes the energetic ordering of CIs and lowers the corresponding energy barrier for the associated deactivation pathway, as revealed by nudged elastic band (NEB) calculations. [ABSTRACT FROM AUTHOR]

The incorporation of BN units in organic scaffolds by isoelectronic/isosteric substitution of selected CC couples has emerged as an efficient tool to produce new materials with useful properties and functions. The knowledge about BN‐doped inorganic–organic hybrid polymers, however, is still rather scarce. This is especially true for linear or cyclolinear macromolecules that feature longer inorganic chains. Herein, we introduce 1,2,5‐azadiborolane as a polymer building block for the first time. An attempt to apply it for the synthesis of a cyclolinear poly(iminoborane) resulted after only two B−N coupling events in the formation of a molecular compound comprising a chain of three nitrogen and two boron atoms – as confirmed by single‐crystal X‐ray diffractometry. In combination with a p‐phenylene diamine‐based co‐monomer, we accomplished to incorporate the 1,2,5‐azadiborolane into a hybrid polymer of considerable molecular weight that features a B2N3 chain. We additionally synthesized a small molecular model compound for the polymer and characterized it crystallographically as well. Comparison of the UV‐vis spectra of the monomer, the oligomer, and the polymer revealed systematic red‐shifts of the longest‐wavelength absorption band with increasing number of BN units in the chain. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The first poly(ferrocenylene iminoborane), that is, a polyferrocene-based metallopolymer featuring C＝C-isoelectronic/-isosteric B＝N linking units, and a series of monodisperse ferrocenylene iminoborane oligomers are presented. Our studies provide important insight into the structural and electronic nature of this novel class of hybrid materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of linear oligo(p-phenylene iminoboranes), which are BN-modified congeners of oligo(p-phenylene vinylenes), featuring pendent ferrocene groups have been prepared. Stoichiometric reaction of a bis-silylamine with a bisborane led to selective formation of an unprecedented macrocycle, without the use of a template. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The reaction of a cyclic alkyl(amino)carbene (CAAC)‐stabilized thiazaborolo[5,4‐d]thiazaborole (TzbTzb) with strong Brønsted acids, such as HCl, HOTf (Tf=O2SCF3) and [H(OEt2)2][BArF4] (ArF=3,5‐(CF3)2C6H3), results in the protonation of both TzbTzb nitrogen atoms. In each case X‐ray crystallographic data show coordination of the counteranions (Cl−, OTf−, BArF4−) or solvent molecules (OEt2) to the doubly protonated fused heterocycle via hydrogen‐bonding interactions, the strength of which strongly influences the 1H NMR shift of the NH protons, enabling tuning of both the visible (yellow to red) and fluorescence (green to red) colors of these salts. DFT calculations reveal that the hydrogen bonding of the counteranion or solvent to the protonated nitrogen centers affects the intramolecular TzbTzb‐to‐CAAC charge transfer character involved in the S0→S1 transition, ultimately enabling fine‐tuning of their absorption and emission spectral features. [ABSTRACT FROM AUTHOR]

The Moore (C(super 2)-C(super 7)) cyclization and its regio alternative C(super 2)-C(super 6) cyclization of enyne-ketenes are studied. Results of this experiment are compared to biradical cyclization of enyne-allenes to study similarities.

A number of novel alkynyl‐functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl‐appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well‐characterized macromolecular species with B−B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size‐exclusion chromatography techniques. [ABSTRACT FROM AUTHOR]

A series of bifuran-bridged bis(triarylboranes) have been synthesized via classical metathesis or catalytic silicon/boron exchange reactions, respectively. The products obtained are strongly luminescent, with quantum yields up to 85%, and reversibly twofold reduced via successive one-electron processes. [ABSTRACT FROM AUTHOR]

Thermoresponsive polymers are frequently involved in the development of materials for various applications. Here, polymers containing poly(2‐ benzhydryl‐2‐oxazine) (pBhOzi) repeating units are described for the first time. The homopolymer pBhOzi and an ABA type amphiphile comprising two flanking hydrophilic A blocks of poly(2‐methyl‐2‐oxazoline) (pMeOx) and the hydrophobic aromatic pBhOzi central B block (pMeOx‐b‐pBhOzi‐b‐pMeOx) are synthesized and the latter is shown to exhibit inverse thermogelling properties at concentrations of 20 wt.% in water. This behavior stands in contrast to a homologue ABA amphiphile consisting of a central poly(2‐benzhydryl‐2‐oxazoline) block (pMeOx‐b‐pBhOx‐b‐pMeOx). No inverse thermogelling is observed with this polymer even at 25 wt.%. For 25 wt.% pMeOx‐b‐pBhOzi‐b‐pMeOx, a surprisingly high storage modulus of ≈22 kPa and high values for the yield and flow points of 480 Pa and 1.3 kPa are obtained. Exceeding the yield point, pronounced shear thinning is observed. Interestingly, only little difference between self‐assemblies of pMeOx‐b‐pBhOzi‐b‐pMeOx and pMeOx‐b‐pBhOx‐b‐pMeOx is observed by dynamic light scattering while transmission electron microscopy images suggest that the micelles of pMeOx‐b‐pBhOzi‐b‐pMeOx interact through their hydrophilic coronas, which is probably decisive for the gel formation. Overall, this study introduces new building blocks for poly(2‐oxazoline) and poly(2‐oxazine)‐based self‐assemblies, but additional studies will be needed to unravel the exact mechanism. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A series of methylene‐bridged bis(triarylboranes) has been synthesized via two complementary routes using metal‐free catalytic Si/B exchange condensation under mild conditions. The title compounds comprise two borane moieties that show effective internal π‐conjugation involving the respective boron centers and the adjacent hetaryl groups. Conjugation between both borane units, however, is disrupted by the aliphatic linker. Cyclic voltammetry revealed minimal electronic communication between the boron centers, as evidenced by two closely spaced reduction processes. The UV‐vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which is attributed to the methylene bridge. A further red‐shift results upon introduction of methyl or SiMe3 groups at the terminal thiophene rings. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article titled "Front Cover: 1,2,5-Azadiborolane as a Building Block for Inorganic-Organic Hybrid Polymers" discusses the synthesis of an oligomer as a model for a BCN hybrid polymer. The reaction of the azadiborolane with a disilylated amine resulted in a single B-N coupling event, while the reaction with silylated diamines led to polymerization. The polymer showed a bathochromic shift in the absorption band, indicating p-electron delocalization. X-ray crystallography studies supported this finding. The article acknowledges the individuals responsible for designing the image and provides more information in the Research Article by H. Helten and co-workers. [Extracted from the article]

Rainer Streubel's significant contribution to the field of low‐valent phosphorous chemistry has had a great impact on the field. This special collection was assembled to honor Prof. Streubel on the occasion of his retirement. The central theme is the beauty of inorganic chemistry. [ABSTRACT FROM AUTHOR]

Epoxides, aziridines, and thiiranes are electrophilic building blocks that are widely used in synthetic organic chemistry and also as electrophilic 'warheads' for irreversible peptidic or peptidomimetic cysteine protease inhibitors. The experimental results concerning variations in the reactivities and the regioselectivities and also the different reasons for the increased inhibition potency of three-membered heterocycles containing an acidic substituent are discussed

Cysteine proteases play pivotal roles in many diseases, making them attractive targets for the development of new drugs. The results show that the large enhancement of the inhibition potencies of aziridines at lower pH values results from a strong catalysis even by weak proton donors.

While polysulfones constitute a class of well‐established, highly valuable applied materials, knowledge about polymers based on the related sulfoximine group is very limited. We have employed functionalized diaryl sulfoximines and a p‐phenylene bisborane as building blocks for unprecedented BN‐ and BO‐doped alternating inorganic–organic hybrid copolymers. While the former were accessed by a facile silicon/boron exchange protocol, the synthesis of polymers with main‐chain B–O linkages was achieved by salt elimination. [ABSTRACT FROM AUTHOR]

The doping of π‐conjugated organic compounds with trivalent boron atoms produces materials with intriguing properties and functions that result from the interaction of the π‐electron system with the vacant p orbital on boron. This offers unique opportunities in various applications such as organic (opto)electronics, biomedical imaging, and sensors for physiologically relevant anions or amines, as demonstrated by numerous examples on the molecular scale. Recently, the B‐doping strategy has been expanded to polymer chemistry with a view to benefit from the best of both worlds. Herein, recent advances in the synthesis of π‐conjugated polymers doped with tricoordinate boron in the backbone are reviewed. Selected applications are described where these functional materials have already been successfully implemented. Doped with pi: Doping of conjugated polymers with trivalent boron leads to functional materials with unique properties and new possibilities in applications such as organic (opto)electronics, nonlinear optics, and optical sensors. Rapid progress is enabled by recent synthetic advances such as hydroboration polymerization, Sn/B and (catalytic) Si/B exchange polycondensation, as well as catalytic C−C coupling processes of robust organoboranes. [ABSTRACT FROM AUTHOR]

The potential of our metal-free B-C coupling method using catalytic Si/B exchange condensation is demonstrated by the synthesis of a series of monodisperse (het)arylborane oligomers with four (het)arene moieties and three boron centers (i.e., 'trimers'). Photophysical and electrochemical investigations evidenced effective p-conjugation over the (het)arene rings and the boron centers. [ABSTRACT FROM AUTHOR]

This article discusses the development of inorganic-organic hybrid polymers with a BN-doped backbone using a modular synthetic approach. The researchers combined different building blocks to create p-conjugated polymers and monodisperse oligomers with tailored properties, such as solid-state and aggregation-induced emission at specific wavelengths. The article provides a polymer sequence and background color illustration to demonstrate the incorporation of different building blocks. For more information, readers can refer to the research article by H. Helten et al. [Extracted from the article]

Direct functionalization and Pd-catalyzed cross-coupling of difuryl(supermesityl)borane (1) led to highly emissive organoborane compounds 3 and 4. Photophysical and TD-DFT studies reveal an increase of the HOMO levels with higher hetarene content and stabilization of the HOMO and LUMO levels through B-doping, leading to very robust, air-stable electron-accepting materials. [ABSTRACT FROM AUTHOR]

Abstract: The application of our newly developed B–C coupling method by catalytic Si/B exchange is demonstrated for the synthesis of a series of triarylboranes (1), monodisperse thienyl‐ and furylborane dimers (2) and trimers (9), extended oligomers (3) and polymers (3′), as well as mixed (oligo)thienyl‐/furylboranes. The structures of 1 aaTip, 1 bbTip, and 2 bbbMes*, determined by X‐ray crystallography, reveal largely coplanar hetarene rings and BR3 environments, which are most pronounced in the furylborane species. Photophysical investigations, supported by TD‐DFT calculations, revealed pronounced π‐electron delocalization over the hetarene backbones including the boron centers. With an extended series of derivatives of varying chain lengths available, we were able to determine the effective conjugation lengths (ECL) of poly(thienylborane)s and poly(furylborane)s, which have been reached with the highest‐molecular‐weight derivatives of our study. Through variation of the furan‐to‐thiophene ratio, the photophysical properties of these materials are effectively modulated. Significantly, higher furan contents lead to considerably increased fluorescence intensities. Compounds 1 aaTip, 1 bbTip, and 3 aTip showed the ability to bind fluoride anions. The binding process is signaled by a distinct change in their optical absorption characteristics, thus rendering these materials attractive targets for sensory applications. [ABSTRACT FROM AUTHOR]

Abstract: The reaction of n‐C8H17B[N(Me)SiMe3]2 (1) with n‐C8H17BCl2 (2 a) yielded, instead of a linear poly(iminoborane), the aminoborane n‐C8H17B(Cl)N(Me)SiMe3 (4) and after cyclotrimerization the borazine cyclo‐(n‐C8H17BNMe)3 (6). Side reactions that result in borazine formation were effectively suppressed if 1,3‐bis(trimethylsilyl)‐1,3,2‐diazaborolidines 7 were employed as co‐monomers in combination with dichloro‐ or dibromoboranes 2 or 8, respectively. Silicon/boron exchange polycondensation led to oligo(iminoborane)s 11 a,b,ac,d. Alternative synthetic routes to such species involve Sn/B exchange of 1,3‐bis(trimethylstannyl)‐2‐n‐octyl‐1,3,2‐diazaborolidine (16) and n‐C8H17BBr2 (8 a), and the initiated polycondensation of the dormant monomer 14 in the presence of a Brønsted acid (HCl, HOTf, or HNTf2; Tf=trifluoromethylsulfonyl). Although an attempt to obtain an oligo‐/poly(iminoborane) with phenyl side groups yielded only insoluble material, the incorporation of aryl groups was proven for a derivative with both phenyl and n‐octyl boron substituents (11 ac), as well as for a derivative with 4‐n‐butylphenyl side groups (11 d). The highest‐molecular‐weight sample obtained was 11 ac. Featuring about 18 catenated BN units, on average, this is the closest approach to a poly(iminoborane) known. [ABSTRACT FROM AUTHOR]

Stereospecific access to the unprecedented P–B–P bridged [3]ferrocenophane Fe(C5H4PtBu)2BMes is presented. In contrast to acyclic ferrocenylphosphanes, we find evidence for a shift of spin-density from Fe to P upon pyramidal inversion of the P centers in the mono-cation; the latter has a lifetime of τ = 0.31(4) s. [ABSTRACT FROM AUTHOR]

Copyright of Nachrichten aus der Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Substitution of selected CC units in π-conjugated organic frameworks by their isoelectronic and isosteric BN units (BN/CC isosterism) has proven to be a successful concept for the development of BN-doped polycyclic aromatic hydrocarbons (PAHs) with intriguing properties and functions. The first examples have just demonstrated the applicability of this approach to polymer chemistry. Herein, we present the synthesis and comprehensive characterization of the first poly(p-phenylene iminoborane). This novel inorganic-organic hybrid polymer can be regarded as a BN analogue of the well-known poly(p-phenylene vinylene) (PPV). Photophysical investigations on the polymer and a series of model oligomers provide clear evidence of some π-conjugation across the B=N bonds and extension of the conjugation path with increasing chain length. TD-DFT calculations provide deeper insight into the electronic structure of the new materials. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The significance of inorganic main-group polymers is demonstrated most clearly by the commercial relevance of polysiloxanes (silicones). Organoboron-based materials such as π-conjugated organoborane polymers and BN-doped polycyclic aromatic hydrocarbons are currently attracting considerable attention. Surprisingly, poly(iminoborane)s (PIBs; [BRNR′] n), that is, the parent unsaturated BN polymers, which are formally isoelectronic to polyacetylene, have not been convincingly characterized thus far. Herein, we present the synthesis and comprehensive characterization of a linear oligo(iminoborane), which comprises a chain of 12-14 BN units on average. With our synthetic approach, unwanted side reactions that result in borazine formation are effectively suppressed. Supporting DFT and TD-DFT calculations provide deeper insight into the microstructure and the electronic structure of the oligomer. [ABSTRACT FROM AUTHOR]

The replacement of C=C units by their isoelectronic and isosteric B=N units (BN/CC isosterism) in π-conjugated organic compounds, as a strategy to produce novel organic-inorganic hybrid materials, has recently been successfully transferred to π-conjugated polymers. This Concept provides an overview of the recent advances in this quickly evolving field, with a focus on synthesis, photophysical and electrochemical properties of the new polymers and related oligomers, as well as possible future applications in organic electronics and optoelectronics. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Despite the great potential of both π-conjugated organoboron polymers and BN-doped polycyclic aromatic hydrocarbons in organic optoelectronics, our knowledge of conjugated polymers with B−N bonds in their main chain is currently scarce. Herein, the first examples of a new class of organic-inorganic hybrid polymers are presented, which consist of alternating NBN and para-phenylene units. Polycondensation with B−N bond formation provides facile access to soluble materials under mild conditions. The photophysical data for the polymer and molecular model systems of different chain lengths reveal a low extent of π-conjugation across the NBN units, which is supported by DFT calculations. The applicability of the new polymers as macromolecular polyligands is demonstrated by a cross-linking reaction with ZrIV. [ABSTRACT FROM AUTHOR]

Komplexe aus Gruppe ‐ 4 ‐ Metallocenen in der Oxidationsstufe +3 und Amidoboranen oder Phosphidoboranen sind effiziente Präkatalysatoren für die Dehydrokupplung/Dehydrierung von Aminboranen wie Me2NH⋅BH3 (siehe Schema). Solche TiIII ‐ Amidoborankomplexe werden in [Cp2Ti] ‐ katalysierten Aminboran ‐ Dehydrokupplungsreaktionen gebildet, für die ursprünglich diamagnetische MII ‐ und MIV ‐ Spezies als Präkatalysatoren und Intermediate postuliert wurden. [ABSTRACT FROM AUTHOR]