Tuning the HOMO–LUMO Gap of Pyrene Effectively via Donor–Acceptor Substitution: Positions 4,5 Versus 9,10

Donor and acceptor substituents were introduced at pyrene’s K-regions in order to engineer its optoelectronic properties. A study of the influence of the substitution pattern on the frontier orbitals as well as on the molecular packing is provided. A comparison with the pure donor and acceptor substituted pyrene derivatives highlights the strong impact of the presented donor–acceptor substitution

Single crystal X-ray structure of (solvent not shown): a) Top view; b) Side view of two molecules of in the crystal

<p><b>Copyright information:</b></p><p>Taken from "Shape-persistent macrocycles with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure"</p><p>http://bjoc.beilstein-journals.org/content/4/1/1</p><p>Beilstein Journal of Organic Chemistry 2008;4():1-1.</p><p>Published online 9 Jan 2008</p><p>PMCID:PMC2238743.</p><p></p

Tetramethoxypyrene-Based Biradical Donors with Tunable Physical and Magnetic Properties

Synthesis of 2,7-disubstituted tetramethoxypyrene-based neutral biradical donors is reported. The biradicals were characterized by EPR, UV–vis, CV, SQUID, and single-crystal X-ray diffraction, and their optical, electrochemical, and structural properties were compared and discussed. The experimental results are well supported by DFT calculations. Systematic tuning of magnetic exchange interactions was achieved by varying the radical moieties

Crystal Engineering of Tolane Bridged Nitronyl Nitroxide Biradicals: Candidates for Quantum Magnets

The tolane bridged nitronyl nitroxide biradicals with hydrogen bond donor and acceptor functional groups were synthesized. The magnetic measurements and the DFT calculations were performed to ascertain the influence of the functional groups on inter- and intramolecular magnetic exchange interactions. While upon functionalizing the tolane bridge the intramolecular exchange interactions remained nearly unchanged, the fine-tuning of intermolecular exchange interactions could be achieved by employing the crystal engineering approach

Making Benzotrithiophene a Stronger Electron Donor

A new member of the benzotrithiophene family, benzo[2,1-<i>b</i>:-3,4-<i>b</i>′:5,6-<i>c</i>″]trithiophene (<b>3a</b>), and its alkyl substituted derivatives (<b>3b</b>–<b>e</b>) were synthesized and characterized. Their photophyscial, electrochemical, crystallographic, and self-assembly properties were described. Thin film structures varied widely with the exact nature of the alkyl substitution pattern, with decreasing self-assembly propensity with increasing alkyl chain length. The high HOMO levels and the coplanarity of these molecules show their potential as organic semiconductors and as donor components in donor–acceptor copolymers

Crystal Engineering of Tolane Bridged Nitronyl Nitroxide Biradicals: Candidates for Quantum Magnets

The tolane bridged nitronyl nitroxide biradicals with hydrogen bond donor and acceptor functional groups were synthesized. The magnetic measurements and the DFT calculations were performed to ascertain the influence of the functional groups on inter- and intramolecular magnetic exchange interactions. While upon functionalizing the tolane bridge the intramolecular exchange interactions remained nearly unchanged, the fine-tuning of intermolecular exchange interactions could be achieved by employing the crystal engineering approach

Planar Biphenyl-Bridged Biradicals as Building Blocks for the Design of Quantum Magnets

We have synthesized and investigated a new biphenyl-4,4′-bis­(nitronyl nitroxide) radical with intermediately strong antiferromagnetic interactions. This organic biradical belongs to a family of materials that can be used as a building block for the design of new quantum magnets. For quantum magnetism, special attention has been paid to coupled <i>S</i> = ¹/₂ dimer compounds, which when placed in a magnetic field, can be used as model systems for interacting boson gases. Short contacts between the oxygen atoms of the nitronyl nitroxide units and the hydrogen atoms of the benzene rings stabilize a surprisingly planar geometry of the biphenyl spacer and are responsible for a small magnetic interdimer coupling. The strength of the antiferromagnetic intradimer coupling constant <i>J</i>/<i>k</i>_B = −14.0 ± 0.9 K, fitting the experimental SQUID-data using an isolated-dimer model. The deviations from the isolated-dimer model are attributed to a small interdimer coupling <i>J</i>′/<i>k</i>_B, on the order of 1 K, consistent with the crystal structure

π‑Conjugated Heterotriangulene Macrocycles by Solution and Surface-supported Synthesis toward Honeycomb Networks

A comparative analysis between a solution and a surface-mediated synthesis of heterotriangulene macrocycles is reported. The results show a preferential formation of the π-conjugated macrocycles on surface due to two-dimensional confinement. The macrocycle prepared on a several hundred milligram scale by solution chemistry was characterized by single-crystal X-ray analysis and was furthermore extended toward next generation honeycomb species. Investigation of the photophysical and electronic properties together with the good thermal stability revealed the potential of <b>MC6</b> as hole-transport material for organic electronics

π‑Conjugated Heterotriangulene Macrocycles by Solution and Surface-supported Synthesis toward Honeycomb Networks

A comparative analysis between a solution and a surface-mediated synthesis of heterotriangulene macrocycles is reported. The results show a preferential formation of the π-conjugated macrocycles on surface due to two-dimensional confinement. The macrocycle prepared on a several hundred milligram scale by solution chemistry was characterized by single-crystal X-ray analysis and was furthermore extended toward next generation honeycomb species. Investigation of the photophysical and electronic properties together with the good thermal stability revealed the potential of <b>MC6</b> as hole-transport material for organic electronics

Tetraaryltetraanthra[2,3]porphyrins: Synthesis, Structure, and Optical Properties

A synthetic route to symmetrical tetra­aryl­tetra­anthra­[2,3]­porphyrins (Ar₄TAPs) was developed. Ar₄TAPs bearing various substituents in <i>meso</i>-phenyls and anthracene residues were prepared from the corresponding pyrrolic precursors. The synthesized porphyrins possess high solubility and exhibit remarkably strong absorption bands in the near-infrared region (790–950 nm). The scope of the method, selection of the peripheral substituents, choice of the metal, and their influence on the optical properties are discussed together with the first X-ray crystallographic data for anthraporphyrin