9,10-Dihydro-9,10-diboraanthracene (DBA) provides a versatile scaffold for the development of boron-doped organic luminophores. Symmetrically C-halogenated DBAs are obtained through the condensation of 4-bromo-1,2-bis(trimethylsilyl)benzene or 4,5-dichloro-1,2-bis(trimethylsilyl)benzene with BBr3 in hexane. Unsymmetrically C-halogenated DBAs are formed via an electrophilic solvent activation reaction if the synthesis is carried out in o-xylene. Mechanistic insight has been achieved by in situ NMR spectroscopy, which revealed C-halogenated 1,2-bis(dibromoboryl)benzenes to be the key intermediates. Treatment of the primary 9,10-dibromo-DBAs with MesMgBr yields air- and water-stable C-halogenated 9,10-dimesityl-DBAs (2-Br-6,7-Me2-DBA(Mes)2; 2,6-Br2-DBA(Mes)2; 2,3-Cl2-6,7-Me2-DBA(Mes)2; 2,3,6,7-Cl4-DBA(Mes)2). Subsequent Stille-type C-C-coupling reactions give access to corresponding phenyl, 2-thienyl, and p-N,N-diphenylaminophenyl derivatives, which act as highly emissive donor-acceptor dyads or donor-acceptor-donor triads both in solution and in the solid state. 2-Thienyl was chosen as a model substituent to show that already a variation of the number and/or the positional distribution of the donor groups suffices to tune the emission wavelength of the resulting benchtop stable compounds from 469 nm (blue) to 540 nm (green). A further shift of the fluorescence maximum to 594 nm (red) can be achieved by switching from 2-thienyl to p-aminophenyl groups. A comparison of the optoelectronic properties of selected C-substituted DBA(Mes)2 derivatives with those of the isostructural anthracene analogues unveiled the following: (i) The DBA core is a much better electron acceptor. (ii) The emission colors of DBAs fall in the visible range of the spectrum (blue to orange), while anthracenes emit exclusively in the near-ultraviolet to blue wavelength regime. (iii) DBAs show significantly higher solid-state quantum yields.

of p-type or electron-donating materials, which have been well researched and include, but are not limited to, polyacetylenes, organosulfur compounds, paraquinones, tetracyanoquinodimethane, and polypyrrole composites. [ 6 ] While anode (n-type or electron-accepting) materials are far more rare in the fi eld of organic batteries, one particular class of compounds have appeared as potential candidates to develop fully organic and fl exible, lightweight batteries: compounds based on quaternized pyridine moieties, such as viologens (quaternized 4,4′-bipyridiniums). [ 7 ] Viologens are known to exhibit rapid and reversible electron transfers giving them great potential for use in a variety of applications such as, redox mediators, electrochromic devices, and now as electrode materials for organic batteries. Palmore and co-workers have recently reported a polymer anode material with pendant viologens, utilizing the fi rst reduction state of the viologen moieties for charge storage. [ 8 ] In 2011, our research group introduced a new class of viologen, the phosphaviologen, which is a phosphoryl-bridged 4,4′-bipyridine derivative with exceptionally strong electronaccepting properties. [ 9 ] Since the initial synthesis of the phosphaviologen scaffold, we have explored a variety of functionalizations at the nitrogen centers, including both benzyl [ 10 ] and aryl [ 11 ] substituents, to tune both the electronics and chromics of this species. With their enhanced electron-accepting properties (reduction thresholds 500 mV less than methylviologen for both reduction steps), we have chosen to investigate their properties as battery electrode materials.In this paper, we now report our initial contribution to the fi eld by applying our recently developed phosphaviologens P-MV and P-BnV ( Figure 1 ) as electrode materials in a hybrid organic/Li-ion battery setting. These initial studies focus on using the previously synthesized materials to test their viability as electrode materials in proof-of-concept devices via half-cell measurements versus Li-metal. While we do not provide large leaps in terms of overall capacity, our phosphaviologens (PV) utilize both redox steps in the charging/discharging cycles, allowing us to double the electron capacity per molecule compared to that of conventional viologens used as electrode materials. In an attempt to improve performance and stability, we have developed new synthetic methods to access phosphaviologen dimers, along with polymeric species that can be solution-processed as electrode materials in proof-of-concept Lithium-ion batteries are one of the most common forms of energy storage devices used in society today. Due to the inherent limitations of conventional Li-ion batteries, organic materials have surfaced as potentially suitable electrode alternatives with improved performance and sustainability. Viologens and phosphaviologens in particular, are strong electron-accepting materials with excellent kinetic properties, making them suitable candidates for battery applications. In this p...

A simple and representative procedure for the synthesis of N,N'-diarylated phosphaviologens directly from both electron-rich and electron-poor diaryliodonium salts and 2,7-diazadibenzophosphole oxide is reported. The latter are electron-deficient congeners of the widely utilized N,N'-disubstituted 4,4'-bipyridinium cations, also known as viologens, that proved to be inaccessible by the classical two-step route. The single-step preparation method for phosphaviologens described herein could be extended to genuine viologens but reached its limit when sterically demanding diaryliodonium salts were used. The studied phosphaviologens feature a significantly lowered reduction threshold as compared to all other (phospha)viologens known to date due to the combination of an extended π-system with an electron deficient phosphole core. In addition, a considerably smaller HOMO-LUMO gap was observed due to efficient π-delocalization across the phosphaviologen core, as well as the N-aryl substituents, which was corroborated by quantum chemical calculations. Detailed characterizations of the singly reduced radical species by EPR spectroscopy and DFT calculations verified delocalization of the radical over the extended π-system. Finally, to gain deeper insight into the suitability of the new compounds as electroactive and electrochromic materials, multicolored proof-of-concept electrochomic devices were manufactured.

1,2-Bis(trimethylsilyl)benzene is the key starting material for the synthesis of efficient benzyne precursors and certain luminescent p-conjugated materials. We now report that it can be conveniently prepared in tetrahydrofuran from 1,2-dibromobenzene, chlorotrimethylsilane, and either Rieke-magnesium (Mg R ) or magnesium turnings in the presence of 1,2-dibromoethane as an entrainer (Mg e ). The most important advantages of these new protocols over the currently best-established procedure (1,2-dichlorobenzene, chlorotrimethylsilane, magnesium turnings, hexamethylphosphoramide) lie in the milder reaction conditions (Mg R : 08C, 2 h; Mg e : room temperature, 30 min vs. 100 8C, 2 days) and in the fact that the cancerogenic solvent hexa-A C H T U N G T R E N N U N G methylphosphoramide is avoided. Moreover, the improved protocols are also applicable for the highyield synthesis of 1,2,4,5-tetrakis(trimethylsilyl)benzene, 4-fluoro-1,2-bis(trimethylsilyl)benzene, 4-chloro-1,2-bis(trimethylsilyl)benzene, and 4,5-dichloro-1,2-bis(trimethylsilyl)benzene.

Air- and water-stable, π-conjugated [−donor–acceptor−] n oligomers containing thiophene fragments as donors and 9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene (DBA(Mes)2) as acceptor units were prepared through Stille-type C–C-coupling protocols. The reaction between 2,6-dibromo-DBA(Mes)2 (1), 2,7-dibromo-DBA(Mes)2 (2), 2-bromo-6,7-dimethyl-DBA(Mes)2 (3), and 2,5-bis(trimethylstannyl)thiophene (7) furnished monodisperse, short-chain model systems 8 0 (2 × DBA(Mes)2, 1 × 2,5-thienylene) and 8 1 (3 × DBA(Mes)2, 2 × 2,5-thienylene) after GPC separation. In the absence of 3, the oligomerization of 1/2 with 7 provided analogous longer chain macromolecules 9 (MALDI–MS reveals up to 7 repeating units; GPC indicates also significantly longer chains). UV/vis absorption spectroscopy suggests that the obtained chain lengths of 9 are already sufficient to reach the maximum effective conjugation length (the lower limit of the HOMO–LUMO band gap corresponds to 2.3 eV). 9 gives rise to a dark orange fluorescence, both in C6H6 solution (ϕf = 47%) and as thin film (ϕf = 13%).

1,2-Bis(trimethylsilyl)benzenes are key starting materials for the synthesis of benzyne precursors, Lewis acid catalysts, and certain luminophores. We have developed efficient, high-yield routes to functionalized 4-R-1,2-bis(trimethylsilyl)benzenes, starting from either 1,2-bis(trimethylsilyl)acetylene/5-bromopyran-2-one (2) or 1,2-bis(trimethylsilyl)benzene (1)/bis(pinacolato)diborane. In the first reaction, 5 (R = Br) is obtained through a cobalt-catalyzed Diels-Alder cycloaddition. The second reaction proceeds via iridium-mediated C-H activation and provides 8 (R = Bpin). Besides its use as a Suzuki reagent, compound 8 can be converted into 5 with CuBr(2) in i-PrOH/MeOH/H(2)O. Lithium-bromine exchange on 5, followed by the addition of Me(3)SnCl, gives 10 (R = SnMe(3)), which we have applied for Stille coupling reactions. A Pd-catalyzed C-C coupling reaction between 5 and 8 leads to the corresponding tetrasilylbiphenyl derivative. The bromo derivative 5 cleanly undergoes Suzuki reactions with electron-rich as well as electron-poor phenylboronic acids.

The synthesis and properties of a new polycyclic aromatic hydrocarbon containing eight annulated rings and based on the anthanthrene core is described. An unexpected, nucleophile-dependent Michael addition to a dibenzanthanthrene-1,7-dione is found, giving a product with three triisopropylsilylacetylene units and a remarkable solid-state structure (as determined by X-ray crystallography).

Changes in color are one of the most obvious and easily followed responses that can be induced by an external stimulus. π-Conjugated organophosphorus compounds are on the rise to challenge established systems by opening up new and simple pathways to diversely modified optoelectronic properties--the main challenge for the development of new chromic materials. Relevant stimuli highlighted in this Frontier article include electronic current (electrochromism), light (photochromism), solvent polarity (solvatochromism), aggregation formation (aggregation induced emission, AIE), mechanical force (mechanochromism), temperature (thermochromism), organic solvent vapor (vapochromism), and pH (halochromism).