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Conjugated macrocycles can exhibit concealed antiaromaticity; that is, despite not being antiaromatic, under specific circumstances, they can display properties typically observed in antiaromatic molecules due to their formal macrocyclic 4n π-electron system. Paracyclophanetetraene (PCT) and its derivatives are prime examples of macrocycles exhibiting this behaviour. In redox reactions and upon photoexcitation, they have been shown to behave like antiaromatic molecules (requiring type I and II concealed antiaromaticity, respectively), with such phenomena showing potential for use in battery electrode materials and other electronic applications. However, further exploration of PCTs has been hindered by the lack of halogenated molecular building blocks that would permit their integration into larger conjugated molecules by cross-coupling reactions. Here, we present two dibrominated PCTs, obtained as a mixture of regioisomers from a three-step synthesis, and demonstrate their functionalisation via Suzuki cross-coupling reactions. Optical, electrochemical, and theoretical studies reveal that aryl substituents can subtly tune the properties and behaviour of PCT, showing that this is a viable strategy in further exploring this promising class of materials.

Numerous articles in the recent literature report molecules that are claimed to be antiaromatic, as they feature a formal 4n π-electron system. The purported antiaromaticity often serves well as an explanation for some of the observed properties, but it neglects the actual local aromaticity of the molecules, which often feature multiple subunits with 4n+2 π-electrons besides the formal 4n π-electron system. This has led to considerable criticism from those who believe that the term antiaromatic should not be used for any molecule with a formal 4n π-electron system but should be reserved for truly antiaromatic molecules. To reconcile the different viewpoints, the term and concept of concealed antiaromaticity is introduced here. The concept accepts that many of the molecules claimed to be antiaromatic are not truly antiaromatic. However, it acknowledges that this does not prevent those molecules from exhibiting behaviour under certain conditions that would normally be expected for antiaromatic molecules, due to the formal, concealed 4n π-electron system that characterizes these molecules. Based on the conditions under which the molecules can behave like antiaromatic molecules, three types of concealed antiaromaticity are distinguished here: concealed antiaromaticity revealable in redox reactions (Type I-CA), upon excitation (Type II-CA), and in intermolecular interactions (Type III-CA). The concept of concealed antiaromaticity will enable the conscious, rational design of molecules that show the desirable properties of antiaromatic molecules while avoiding or diminishing the undesirable properties, namely the low stability of truly antiaromatic molecules. This will yield molecules and materials with highly interesting properties for a broad range of applications, from organic electronics to supramolecular chemistry.

Post-polymerisation functionalisation provides a facile and efficient way for the introduction of functional groups on the backbone of conjugated polymers. Using post-polymerisation functionalisation approaches, the polymer chain length is usually not affected, meaning that the resulting polymers only differ in their attached functional groups or side chains, which makes them particularly interesting for investigating the influence of the different groups on the polymer properties. For such functionalisations, highly efficient and selective reactions are needed to avoid the formation of complex mixtures or permanent defects in the polymer backbone. A variety of suitable synthetic approaches and reactions that fulfil these criteria have been identified and reported. In this review, a thorough overview is given of the post-polymerisation functionalisations reported to date, with the methods grouped based on the type of reaction used: cycloaddition, oxidation/reduction, nucleophilic aromatic substitution, or halogenation and subsequent cross-coupling reaction. Instead of modifications on the aliphatic side chains of the conjugated polymers, we focus on modifications directly on the conjugated backbones, as these have the most pronounced effect on the optical and electronic properties. Some of the discussed materials have been used in applications, ranging from solar cells to bioelectronics. By providing an overview of this versatile and expanding field for the first time, we showcase post-polymerisation functionalisation as an exciting pathway for the creation of new conjugated materials for a range of applications.

Featuring small charge transport scattering, mesoscale size, and easy fabrication, one-dimensional self-assembled micro/nanomaterials (1D-MNMs) based on organic π-conjugated systems can be facilely incorporated into integrated microcircuits. Although tremendous progress has been made in 1D-MNMs based on p- or n-channel organic semiconductors, examples of lD-MNMs based on ambipolar organic semiconductors are scarce. Herein, we achieved a novel 1D-MNM based on 6,13-dicyanopentacene (DCP) with a 1D slipped stacking motif using the physical vapor transport method. The DCP-based 1D-MNM showed outstanding, well-balanced ambipolar charge transport with electron and hole mobilities of up to 0.34 and 0.38 cm2 V−1 s−1, respectively, which are among the best ambipolar transport characteristics of 1D-MNMs. Furthermore, a complementary inverter based on the ambipolar 1D-MNM of DCP was also constructed with a gain of up to 7, indicating potential application in organic logic circuits.

Aromatic carboxylic anhydrides are ubiquitous building blocks in organic materials chemistry. In particular, dianhydrides and their conversion into imides have received considerable attention in the synthesis of organic semiconductors, pigments, and battery electrode materials. Here we extend the family of aromatic carboxylic anhydrides with a unique new member, a conjugated cyclophane with four anhydride groups. The cyclophane, named squarephaneic tetraanhydride due to its square shape, is obtained in a three-step synthesis; the anhydride groups are located at the corners and allow for efficient functionalisation, as shown by the conversion into imides and carboxylates. The crystal structures of the tetraanhydride and one of the imides demonstrate the high degree of porosity achievable with the new building block. Electrochemical measurements in solution and solid state are also presented. Considering the short synthesis and unique properties, we expect widespread use of the new building block in the development of organic materials.

Reported here is a new high electron affinity acceptor end group for organic semiconductors, 2,1,3‐benzothiadiazole‐4,5,6‐tricarbonitrile (TCNBT). An n‐type organic semiconductor with an indacenodithiophene (IDT) core and TCNBT end groups was synthesized by a sixfold nucleophilic substitution with cyanide on a fluorinated precursor, itself prepared by a direct arylation approach. This one‐step chemical modification significantly impacted the molecular properties: the fluorinated precursor, TFBT IDT, a poor ambipolar semiconductor, was converted into TCNBT IDT, a good n‐type semiconductor. The electron‐deficient end group TCNBT dramatically decreased the energy of the highest occupied and lowest unoccupied molecular orbitals (HOMO/LUMO) compared to the fluorinated analogue and improved the molecular orientation when utilized in n‐type organic field‐effect transistors (OFETs). Solution‐processed OFETs based on TCNBT IDT exhibited a charge‐carrier mobility of up to μ e≈0.15 cm2 V−1 s−1 with excellent ambient stability for 100 hours, highlighting the benefits of the cyanated end group and the synthetic approach., A new strongly electron‐accepting end group, 2,1,3‐benzothiadiazole‐4,5,6‐tricarbonitrile (TCNBT), has been prepared by a one‐step sixfold nucleophilic substitution reaction. Cyanation results in a significant enhancement of the electron affinity in comparison to the fluorinated analogue, and the material demonstrates promising n‐type performance in solution processed organic field‐effect transistors with excellent stability.

π-Conjugated macrocycles are molecules with unique properties that are increasingly exploited for applications and the question of whether they can sustain global aromatic or antiaromatic ring currents is particularly intriguing. However, there are only a small number of experimental studies that investigate how the properties of π-conjugated macrocycles evolve with systematic structural changes. Here, we present such a systematic experimental study of a set of [2.2.2.2]cyclophanetetraenes, all with formally Hückel antiaromatic ground states, and combine it with an in-depth computational analysis. The study reveals the central role of local and global aromaticity for rationalizing the observed optoelectronic properties, ranging from extremely large Stokes shifts of up to 1.6 eV to reversible fourfold reduction, a highly useful feature for charge storage/accumulation applications. A recently developed method for the visualization of chemical shielding tensors (VIST) is applied to provide unique insight into local and global ring currents occurring in different planes along the macrocycle. Conformational changes as a result of the structural variations can further explain some of the observations. The study contributes to the development of structure–property relationships and molecular design guidelines and will help to understand, rationalize, and predict the properties of other π-conjugated macrocycles. It will also assist in the design of macrocycle-based supramolecular elements with defined properties., Insights into how the optoelectronic properties of π-conjugated macrocycles evolve as a result of systematic structural changes are presented, helping to develop structure–property relationships and molecular design guidelines.

The synthesis of two novel n-type molecular organic semiconductors based on a fluorinated indacenodithiophene core in combination with an electron withdrawing N-cyanoimine group is reported, and the influence of the regiochemistry of the solubilizing sidechain is investigated. The N-cyanoimine is confirmed to be a strongly electron accepting group, which in combination with the core fluorination resulted in high electron affinities for both materials. Single crystal analysis demonstrated that whilst both materials arrange in ordered slipped stacks with close π–π stacking distances (∼3.40 Å), significant differences in electron transfer integrals for the two regioisomers were observed, relating to differences in relative molecular displacement along the π-stacking direction. Organic thin-film transistors fabricated via blade-coating displayed electron mobility up to 0.13 cm2 V−1 s−1 for the isomer with the larger transfer integral.

Excited-state symmetry breaking is investigated in a series of symmetric 9,10-dicyanoanthracenes linked to electron-donating groups on the 2 and 6 positions via different spacers, allowing for a tuning of the length of the donor–acceptor branches. The excited-state properties of these compounds are compared with their dipolar single-branch analogues. The changes in electronic structure upon their optical excitation are monitored by transient electronic spectroscopy in the visible and near-infrared regions as well as by transient vibrational spectroscopy in the mid-infrared. Our results reveal that, with the shortest branches, electronic excitation remains distributed almost symmetrically over the molecule even in polar environments. Upon increasing the donor–acceptor distance, excitation becomes unevenly distributed and, with the longest one, it fully localises on one branch in polar solvents. The influence of the branch length on the propensity of quadrupolar dyes to undergo excited-state symmetry breaking is rationalised in terms of the balance between interbranch coupling and solvation energy., Excited-state symmetry breaking in quadrupolar molecules depends on the balance between inter-branch coupling and polar solvation energy.

Background: Poly(p-phenylene vinylene)s (PPVs) and [2.2.2.2]paracyclophanetetraene (PCT) are both composed of alternating π-conjugated para-phenylene and vinylene units. However, while the former constitute a class of π-conjugated polymers that has been used in organic electronics for decades, the latter is a macrocycle that only recently revealed its potential for applications such as organic battery electrodes. The cyclic structure endows PCT with unusual properties, and further tuning of these may be required for specific applications. Methods: In this article, we adopt an approach often used for tuning the properties of PPVs, the introduction of alkoxy (or alkylthio) substituents at the phenylene units, for tuning the optoelectronic properties of PCT. The resulting methoxy- and methylthio-substituted PCTs, obtained by Wittig cyclisation reactions, are studied by UV-vis absorption, photoluminescence, and cyclic voltammetry measurements, and investigated computationally using the visualisation of chemical shielding tensors (VIST) method. Results: The measurements show that substitution leads to slight changes in terms of absorption/emission energies and redox potentials while having a pronounced effect on the photoluminescence intensity. The computations show the effect of the substituents on the ring currents and chemical shielding and on the associated local and global (anti)aromaticity of the macrocycles, highlighting the interplay of local and global aromaticity in various electronic states. Conclusions: The study offers interesting insights into the tuneability of the properties of this versatile class of π-conjugated macrocycles.

Anthracene derivatives have been used for a wide range of applications and many different synthetic methods for their preparation have been developed. However, despite continued synthetic efforts, introducing substituents in some positions has remained difficult. Here we present a method for the synthesis of 2,3,6,7-substituted anthracene derivatives, one of the most challenging anthracene substitution patterns to obtain. The method is exemplified by the preparation of 2,3,6,7-anthracenetetracarbonitrile and employs a newly developed, stable protected 1,2,4,5-benzenetetracarbaldehyde as the precursor. The precursor can be obtained in two scalable synthetic steps from 2,5-dibromoterephthalaldehyde and is converted into the anthracene derivative by a double intermolecular Wittig reaction under very mild conditions followed by a deprotection and intramolecular double ring-closing condensation reaction. Further modification of the precursor is expected to enable the introduction of additional substituents in other positions and may even enable the synthesis of fully substituted anthracene derivatives by the presented approach.

Aromatic organic compounds can be used as electrode materials in rechargeable batteries and are expected to advance the development of both anode and cathode materials for sodium‐ion batteries (SIBs). However, most aromatic organic compounds assessed as anode materials in SIBs to date exhibit significant degradation issues under fast‐charge/discharge conditions and unsatisfying long‐term cycling performance. Now, a molecular design concept is presented for improving the stability of organic compounds for battery electrodes. The molecular design of the investigated compound, [2.2.2.2]paracyclophane‐1,9,17,25‐tetraene (PCT), can stabilize the neutral state by local aromaticity and the doubly reduced state by global aromaticity, resulting in an anode material with extraordinarily stable cycling performance and outstanding performance under fast‐charge/discharge conditions, demonstrating an exciting new path for the development of electrode materials for SIBs and other types of batteries., Aromatic stabilization of both states: A molecular design concept for highly stable organic battery electrode materials is presented using the conjugated macrocycle [2.2.2.2]paracyclophane‐1,9,17,25‐tetraene (PCT). The compound can stabilize both the neutral and reduced state by aromaticity, enabling batteries with extraordinarily stable cycling performance and outstanding performance under fast‐charge/discharge conditions.

Aromaticity is a central concept in chemistry, pervading areas from biochemistry to materials science. Recently, synthetic chemists started to exploit more intricate phenomena such as the interplay of local and global (anti)aromaticity as well as aromaticity in non-planar systems and three dimensions. These phenomena pose new challenges in terms of our fundamental understanding and the practical visualisation of aromaticity, its local variations and anisotropy. To overcome these challenges, a method for the visualisation of chemical shielding tensors (VIST) is developed here. The VIST method is based on nucleus-independent chemical shifts but, in contrast to other methods, allows for a 3D visualisation with quantitative information about the local variations and anisotropy of the chemical shielding. The VIST method is exemplified in benzene to show its main properties, in phenanthrene to highlight various degrees of local aromaticity, and in cyclobuta[l]phenanthrene to illustrate the interplay between local aromaticity and antiaromaticity in its singlet ground state and Baird aromaticity in its triplet excited state.Subsequently, the interplay of local and global aromaticity is investigated in two non-planar macrocycles, paracyclophanetetraene and [8]cycloparaphenylene, exemplifying the unique benefits of the VIST method for studying (anti)aromaticity in molecules with competing $\pi$-conjugated systems aligned in different planes.Finally, a stacked norcorrole dimer is studied, showing clear evidence of through-space aromaticity. In summary, we believe that the VIST method will be a highly valuable addition to the computational toolbox of chemists studying (anti)aromaticity or considering it in their molecular design.

Various polyimides and polyamides have recently been prepared via hydrothermal synthesis in nothing but H2O under high‐pressure and high‐temperature conditions. However, none of the prepared polymers feature a truly conjugated polymer backbone. Here, we report on an expansion of the synthetic scope of this straightforward and inherently environmentally friendly polymerization technique to the generation of conjugated polymers. Selected representatives of two different polymer classes, pyrrone polymers and polybenzimidazoles, were generated hydrothermally. We present a mechanistic discussion of the polymer formation process as well as an electrochemical characterization of the most promising product., In hot water: The scope of hydrothermal polymerization has been expanded. Pyrrone polymers and polybenzimidazoles can now be generated in high‐temperature water by a straightforward one‐step synthesis.

Aromatic organic compounds can be used as electrode materials in rechargeable batteries and are expected to advance the development of both anode and cathode materials for sodium-ion batteries (SIBs). However, most aromatic organic compounds assessed as anode materials in SIBs to date exhibit significant degradation issues under fast-charge/discharge conditions and unsatisfying long-term cycling performance. Now, a molecular design concept is presented for improving the stability of organic compounds for battery electrodes. The molecular design of the investigated compound, [2.2.2.2]paracyclophane-1,9,17,25-tetraene (PCT), can stabilize the neutral state by local aromaticity and the doubly reduced state by global aromaticity, resulting in an anode material with extraordinarily stable cycling performance and outstanding performance under fast-charge/discharge conditions, demonstrating an exciting new path for the development of electrode materials for SIBs and other types of batteries.

The synthesis of a novel fluorinated n‐type small molecule based on an indacenodithiophene core is reported. Fluorination is found to have a significant impact on the physical properties, including a surprisingly dramatic improvement in solubility, in addition to effectively stabilizing the lowest‐unoccupied molecular orbital energy (−4.24 eV). Single‐crystal analysis and density functional theory calculations indicate the improved solubility can be attributed to backbone torsion resulting from the positioning of the fluorine group in close proximity to the strongly electron‐withdrawing dicyanomethylene group. Organic thin‐film transistors made via blade coating display high electron mobility (up to 0.49 cm2 V−1 s−1) along with good retention of performance in ambient conditions.

Verschiedene Polyimide und Polyamide wurden in letzter Zeit durch hydrothermale Synthese in nichts als H2O unter Hochdruck- und Hochtemperaturbedingungen hergestellt. Keines dieser Polymere weist jedoch ein konjugiertes Polymerrückgrat auf. Hiermit berichten wir über eine Erweiterung des synthetischen Anwendungsbereichs dieser einfachen und von Natur aus umweltfreundlichen Polymerisationstechnik auf die Herstellung von konjugierten Polymeren. Ausgewählte Vertreter von zwei verschiedenen Polymerklassen, Pyrronpolymere und Polybenzimidazole, wurden hydrothermal synthetisiert. Neben einer mechanistischen Diskussion der Polymerbildung wird auch eine elektrochemische Charakterisierung des vielversprechendsten Produktes präsentiert. published

Hochkondensierte, vollständig konjugierte aromatische Verbindungen sind interessante Kandidaten zur Anwendung in organischer Elektronik. Mit steigender Kristallinität verbessern sich ihre elektronischen Eigenschaften. Hier wird gezeigt, dass die Kristallisation von drei Archetypen solcher Moleküle – Pentacentetron, Indigo und Perinon – hydrothermal erreicht werden kann. Dieser Befund ist angesichts der Strukturen dieser Verbindungen höchst erstaunlich. Darüber hinaus wird gezeigt, dass Perinon ausgehend von Naphthalinbisanhydrid und o-Phenylendiamin in ausschließlich hochtemperiertem Wasser und ohne Zusatz von Cosolventien oder Katalysatoren hergestellt werden kann. Weiterhin kann die Transformation durch den Einsatz von Mikrowellen-Strahlung drastisch beschleunigt werden. Dies ist der erste Bericht über die hydrothermale Herstellung von zwei kondensierten Heterocyclen. published

The preparation of 9,10‐dicyanoanthracene triflates is reported. Taking advantage of the high reactivity of these precursors in Suzuki coupling reactions, sterically hindered substituents were introduced. The impact of the substituents on the crystallographic and photophysical properties was investigated. The results highlight the usefulness of the new triflate derivatives and the substituents for the development of 9,10‐dicyanoanthracene‐based materials.

A set of substituted 9,10-dicyanoanthracenes (DCA) has been synthesized, their photophysical and electrochemical properties in liquid solution have been characterized and supplemented by high level ab initio quantum chemical calculations. Three different methoxy-group-containing substituents have been linked to the DCA core in a symmetric and asymmetric fashion to produce six different species with strong quadrupole and dipole moments, respectively. The major difference between the symmetrically and asymmetrically substituted species are the enhanced two-photon absorption intensities of the former. In most of the cases studied, the molecules show reasonably large optical transition probabilities. The fluorescence brightness of these substances makes them interesting objects for two-photon absorption applications. Additionally, all molecules can be both easily reduced and oxidized electrochemically and are therefore suitable for optoelectronic applications.

Modification of functional groups attached to conjugated polymer backbones can drastically alter the material properties. Oxidation of electron-donating thioalkyl substituents to electron-withdrawing sulfoxides or sulfones is a particularly effective modification. However, so far, this reaction has not been studied for the modification of conjugated polymers used in organic electronics. Crucial questions regarding selectivity and reaction time waited to be addressed. Here, we show that the reaction is highly selective and complete within just a few minutes when using dimethyldioxirane (DMDO) for the oxidation of thioalkyl substituents attached to the well investigated conjugated polymers poly(9-(1-octylnonyl)carbazole-alt-4,7-dithienylbenzothiadiazole) (PCDTBT) and poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT). The selectivity was confirmed by comparison with polymers obtained from pre-oxidized monomers and by control experiments using related polymers without thioalkyl substituents. Using DMDO, the oxidation yields acetone as the only side-product, which reduces the work-up to mere evaporation of solvents and excessive reagent. Our results show that this oxidation is an exciting method for the preparation of electron-deficient conjugated polymers. It may even allow the preparation of electron acceptors for solar cells directly from the electron donors.

Poly(p-phenylene vinylene)s (PPVs) have been studied for decades, but research on this interesting class of conjugated polymers is far from being completed. New applications like in bioimaging keep emerging and even simple structural variations are still waiting to be explored. Surprisingly, not even dithioalkyl-substituted PPVs (S-PPVs) have been reported in the peer-reviewed literature, although the corresponding dialkoxy-substituted PPVs (O-PPVs) like MEH-PPV or MDMO-PPV are most frequently used and although thioalkyl substituents can improve the material properties significantly. We herein report the development of a highly efficient, scalable two-step synthesis of Gilch monomers for S-PPVs starting from low-cost 1,4-diiodobenzene. A low-temperature polymerization protocol has been developed for these monomers, affording high-molecular weight S-PPVs in excellent yields. The thermal, electrochemical, and photophysical properties of S-PPVs are reported to highlight the potential of these polymers. Furthermore, treatment with dimethyldioxirane is demonstrated to result in rapid conversion into sulfone-substituted PPVs (SO2-PPVs), introducing a route to high-molecular weight SO2-PPVs with exceptional stability and solid-state photoluminescence quantum yields of up to 0.46.

A generally applicable direct synthesis of cyanoarenes from quinones is presented. Particular emphasis is placed on the preparation of precursors and target molecules relevant for organic materials, including halogenated cyanoarenes and larger cyanated acenes. The reaction and work-up protocols are adjusted for the challenges presented by the different substrates and products. Screening results of the initial reaction optimization are given to further facilitate adaptation to other synthetic problems. The universality of the reaction is finally highlighted by successful substitution of para-quinones by an ortho-quinone as the starting material.

Reliable reactions for the synthesis of two interesting anthracenetetrones have been identified and optimized. Both syntheses start from dihydroxy-9,10-anthraquinones and were selected for maximized efficiency and minimized work load. Work-up of all reactions can be achieved without column chromatography, which facilitates further scale-up. So far, both target compounds are considerably underexplored despite their promising molecular structure for use in devices and in organic synthesis, especially as building blocks for π-conjugated compounds. The crystal structure of 1,4,5,8-anthracentetrone is reported.

Highly fused, fully conjugated aromatic compounds are interesting candidates for organic electronics. With higher crystallinity their electronic properties improve. It is shown here that the crystallization of three archetypes of such molecules-pentacenetetrone, indigo, and perinone-can be achieved hydrothermally. Given their molecular structure, this is a truly startling finding. In addition, it is demonstrated that perinone can also be synthesized in solely high-temperature water from the starting compounds naphthalene bisanhydride and o-phenylene diamine without the need for co-solvents or catalysts. The transformation can be drastically accelerated by the application of microwave irradiation. This is the first report on the hydrothermal generation of two fused heterocycles. published

A series of 1,2,3-triazole linked donor–acceptor chromophores are prepared by Click Chemistry from ene–yne starting materials. The effects of three distinct chemical variations are investigated: enhancing the acceptor strength through oxidation of the sulphur atom, alteration of the double bond configuration, and variation of the triazole substitution pattern. A detailed photophysical characterization shows that these alterations have a negligible effect on the absorption while dramatically altering the emission wavelengths. In addition, strong solvatochromism is found leading to significant red shifts in the case of polar solvents. The experimental findings are rationalized and related to the electronic structure properties of the chromophores by time-dependent density functional theory as well as the ab initio algebraic diagrammatic construction method for the polarization propagator in connection with a new formalism allowing to model the influence of solvation onto long-lived excited states and their emission energies. These calculations highlight the varying degree of intramolecular charge transfer character present for the different molecules and show that the amount of charge transfer is strongly modulated by the conducted chemical modifications, by the solvation of the chromophores, and by the structural relaxation in the excited state. It is, furthermore, shown that enhanced charge separation, as induced by chemical modification or solvation, reduces the singlet–triplet gaps and that two of the investigated molecules possess sufficiently low gaps to be considered as candidates for thermally activated delayed fluorescence.

2,5-Di­azido-1,4-phenyl­ene di­acetate and dibutyrate are the first structurally characterized representatives with a trans-di­azido­phenyl­ene entity. Both mol­ecules possess inversion symmetry; however, the compounds crystallize in different crystal systems (triclinic versus monoclinic)., The asymmetric units of the title compounds, C10H8N6O4, (I), and C14H16N6O4, (II), each contain half of the respective mol­ecule which is completed by inversion symmetry. The two molecules differ in the ester moiety (acetate versus butyrate) and the crystal symmetry is different, i.e. triclinic for (I) and monoclinic for (II). The di­azido­phenyl­ene moieties are essentially planar [maximum deviation of 0.0216 (7) Å for (I) and 0.0330 (14) Å for (II)], and the ester functionalities are almost perpendicular to these planes, making dihedral angles of 79.93 (3)° for (I) and 79.42 (6)° for (II). In the crystals of both (I) and (II), there are no significant inter­molecular inter­actions present.

Novel substituted bis[(trimethylsilyl)ethynyl]benzenes have been prepared as versatile building blocks for organic functional materials. The resulting effects of replacing sulfur by selenium and tellurium on photophysical and electrochemical properties have been examined. Polymerization via microwave-assisted Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) and subsequent post-polymerization modification by oxidation reveals the utility of the developed building blocks.

An improved procedure for large-scale and also commercially viable preparation of dimethyldioxirane (DMDO), a common and widely used oxidation agent in organic synthesis, was developed using a conventional laboratory plant. All reaction parameters were optimized, and the stability of a freshly prepared solution of DMDO in acetone was monitored over an extended period of time to ensure long-term use after preparation, transport, and storage. This discontinuous approach, suitable for batch processing, is of interest basically to research laboratories but also to suppliers in the research and fine chemicals market.

The title cyclobutane derivative, C36H40S4, formed serendipitously through a photochemically initiated [2 + 2] cycloaddition. The asymmetric unit contains half a molecule with the 2-(ethylsulfanyl)phenyl substituents in acisconfiguration, the other half of the molecule being generated by the application of a twofold rotation operation. The substituents in both halves of the molecules are in atransarrangement relative to each other. The cyclobutane ring shows angular and torsional strains, with C—C—C bond angles of 89.80 (8) and 88.40 (8)°, and an average absolute torsion angle of 14.28 (10)°. The angle of pucker in the ring is 20.27 (12)°. The Ccb—Ccb—Cbangles between the cyclobutane (cb) ring atoms and the attached benzene (b) ring atoms are widened and range from 115.19 (10) to 121.66 (10)°. A weak intramolecular C—H...S hydrogen-bonding interaction between one of the cyclobutane ring H atoms and the S atom may help to establish the molecular conformation. No specific intermolecular interactions are found.

A novel synthesis of cyanoarenes from quinones by using PCl 3 as the reagent for reductive aromatization of cyanohydrin intermediates is reported. In situ IR spectroscopic measurements were conducted to monitor the reactions and to develop a convenient one-pot protocol. 1,4-Dicyanobenzene and 9,10-dicyanoanthracene were prepared by the new procedure.

An advanced design concept for organic electronic devices relying on functional polymers is presented. The concept aims at realizing a gradual transition from an electron-donating to an electron-accepting material in a specific post-polymerization modification step. Hence, this approach facilitates a straight forward fabrication compared to conventional multi-layer architectures. The synthesis via microwave-assisted Cu(I)-catalyzed azide–alkyne cycloaddition of the reactive polymers based on sulfur, selenium and tellurium as active sites is presented; full characterization of model compounds and polymers is provided. Additionally, a reliable procedure for post-polymerization oxidation applying dimethyldioxirane is developed. Photophysical and electrochemical characteristics of the novel polymers reveal the feasibility but also the challenges of the continuous junction concept.

1,2,3-Triazole-functionalized ene–yne compounds, synthesized by thiophene (selenophene) ring fragmentation followed by azide–alkyne cycloaddition, were investigated as a basis for nonlinear optical (NLO) materials capable of second harmonic generation (SHG). The structure–property relationship was mapped by systematic variation of the molecular scaffold, viz., elongation of the alkyl groups, isomerizations of both the double bond as well as the triazole moiety, sulfur oxidations, and a sulfur–selenium exchange. Nine novel molecular compounds were synthesized, of which eight are solids at room temperature. The latter were characterized by single-crystal X-ray diffraction (XRD). Five crystal structures lacked of inversion symmetry, a prerequisite for NLO activity. The corresponding materials were examined regarding SHG, UV–vis absorption, and powder XRD. By substituting S for Se, we were able to increase the SH intensity by a factor of 20. On the basis of the results, we propose a strategy to further improve the SHG efficiency of this class of materials.

Systematic investigations towards a novel class of quadratic NLO materials, based on the application of 1,2,3-triazole moieties, are outlined to afford organic crystals displaying SHG nonlinearities of more than 9 times the value of KDP.