Search

Four substituted nonacenes were prepared and characterized by UV-vis and EPR spectroscopy and X-ray crystallography. The compounds are the most stable and soluble nonacenes to date - due to six strategically placed triisopropylsilyl(TIPS)-ethynyl groups. They are stable for several weeks in the solid state. In dilute solution their half-life is 5-9 h. Crystal structure analyses of two nonacenes prove their structures. A nonacene derivative was tested in a solution-processed transistor and exhibits ambipolar charge transport (μ e =0.007 cm 2 /Vs; μ h =0.023 cm 2 /Vs)., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Tetraiodotetraazapentacene I 4 TAP, the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS-ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air-stable monoanion and relatively air-stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non-halogenated TAP and Br 4 TAP. I 4 TAP is an n-channel material in thin-film transistors with average electron mobilities exceeding 1 cm 2 (Vs) -1 ., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

We disclose a successive π-expansion of pyracylene towards boat-shaped polycyclic scaffolds. The unique structural features of the resulting compounds were revealed by X-ray crystallographic analysis. Depending on the extent of π-expansion the compounds display intense bathochromically shifted absorption bands in their UV/Vis spectra and are prone to several redox events as documented by cyclic voltammetry. The experimental observations are in line with the computational studies based on density functional theory, suggesting progressive narrowing of the HOMO-LUMO gap and distinct evolution of the electronic structure and aromaticity., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Herein, we report a series of azobenzene-substituted triptycenes. In their design, these switching units were placed in close proximity, but electronically separated by a sp 3 center. The azobenzene switches were prepared by Baeyer-Mills coupling as key step. The isomerization behavior was investigated by 1 H NMR spectroscopy, UV/Vis spectroscopy, and HPLC. It was shown that all azobenzene moieties are efficiently switchable. Despite the geometric decoupling of the chromophores, computational studies revealed excitonic coupling effects between the individual azobenzene units depending on the connectivity pattern due to the different transition dipole moments of the π→π* excitations. Transition probabilities for those excitations are slightly altered, which is also revealed in their absorption spectra. These insights provide new design parameters for combining multiple photoswitches in one molecule, which have high potential as energy or information storage systems, or, among others, in molecular machines and supramolecular chemistry., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Sixfold TIPS-ethynylation combined with fourfold bromination of the armchair edges furnishes a long-lived, soluble heptacene; π-extension via Stille coupling accesses a persistent tetrabenzononacene. Both types of acenes were stabilized best by double TIPS-ethynylation on every other benzene ring. Tetrabromoheptacene is an ambipolar transistor material (up to 0.036 cm 2  V -1  s -1 n-channel), which was corroborated by generation of its monoanion and monocation., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A family of fully bridged triphenylamines with embedded 5- and 7-membered rings is presented. The compounds are potent electron donors capable to undergo donor/acceptor interactions with strong cyano-based acceptors both in the solid state and solution. These interactions were evaluated by IR and UV/vis spectroscopy as well as X-ray crystallography. The vinylene-bridged compound was oxidized to the corresponding 1,2-diketone which readily underwent acid-catalyzed condensation with selected 1,2-phenylenediamines. The resulting π-extended quinoxaline derivatives represent valuable building blocks for the development of functional chromophores upon appropriate functionalization., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The transition-metal-catalyzed cyclization of bissilylethynylated N,N'-dihydrotetraazapentacene (TIPS-TAP-H 2 ) into bissilylated cyclopenta[fg,qr]pentacenes is reported. Depending on the catalyst either none, one or two silyl groups migrate and change their positions in the formed five-membered rings. The optoelectronic properties are quite similar, whereas the packing motifs differ dramatically. Control experiments and quantum chemical calculations were performed to investigate the mechanism of the reaction and the selectivity of the silyl shift., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The correlation of mechanical properties of polymer materials with those of their molecular constituents is the foundation for their holistic comprehension and eventually for improved material designs and syntheses. Over the last decade, optical force probes (OFPs) were developed, shedding light on various unique mechanical behaviors of materials. The properties of polymers are diverse, ranging from soft hydrogels to ultra-tough composites, from purely elastic rubbers to viscous colloidal solutions, and from transparent glasses to super black dyed coatings. Only very recently, researchers started to develop tailored OFP solutions that account for such material requirements in energy (both light and force), in time, and in their spatially detectable resolution. We here highlight notable recent examples and identify future challenges in this emergent field., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Herein, we describe a gold-catalyzed cascade cyclization of Boc-protected benzylamines bearing two tethered alkyne moieties in a domino reaction initiated by a 6-endo-dig cyclization. The reaction was screened intensively, and the scope was explored, resulting in nine new Boc-protected dihydrobenzo[c]phenanthridines with yields of up to 98 %; even a π-extension and two bidirectional approaches were successful. Furthermore, thermal cleavage of the Boc group and subsequent oxidation gave substituted benzo[c]phenanthridines in up to quantitative yields. Two bidirectional approaches under the optimized conditions were successful, and the resulting π-extended molecules were tested as organic semiconductors in organic thin-film transistors., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Photoactivatable compounds for example photoswitches or photolabile protecting groups (PPGs, photocages) for spatiotemporal light control, play a crucial role in different areas of research. For each application, parameters such as the absorption spectrum, solubility in the respective media and/or photochemical quantum yields for several competing processes need to be optimized. The design of new photochemical tools therefore remains an important task. In this study, we exploited the concept of excited-state-aromaticity, first described by N. Colin Baird in 1971, to investigate a new class of photocages, based on cyclic, ground-state-antiaromatic systems. Several thio- and nitrogen-functionalized compounds were synthesized, photochemically characterized and further optimized, supported by quantum chemical calculations. After choosing the optimal scaffold, which shows an excellent uncaging quantum yield of 28 %, we achieved a bathochromic shift of over 100 nm, resulting in a robust, well accessible, visible light absorbing, compact new photocage with a clean photoreaction and a high quantum product (ϵ⋅Φ) of 893 M -1  cm -1 at 405 nm., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)