Peter Hammershøj

Microporous Polycarbazole with High Specific Surface Area for Gas Storage and Separation

Microporous polycarbazole via straightforward carbazole-based oxidative coupling polymerization is reported. The synthesis route exhibits cost-effective advantages, which are essential for scale-up preparation. The Brunauer-Emmett-Teller specific surface area for obtained polymer is up to 2220 m(2) g(-1). Gas (H(2) and CO(2)) adsorption isotherms show that its hydrogen storage can reach to 2.80 wt % (1.0 bar and 77 K) and the uptake capacity for carbon dioxide is up to 21.2 wt % (1.0 bar and 273 K), which show a promising potential for clean energy application and environmental field. Furthermore, the high selectivity toward CO(2) over N(2) and CH(4) makes the obtained polymer possess potential application in gas separation.

Organic Light‐Emitting Diodes from Symmetrical and Unsymmetrical π‐Extended Tetraoxa[8]circulenes

The understanding and development of molecular electronics depends on the discovery and exploitation of new pextended organic materials. One area of interest is the design of small molecules that are suitable as the fluorescent component in blue organic light-emitting diodes (OLEDs). OLEDs based on small organic molecules or conjugated polymers have been explored for applications in full-colour flat-panel displays, since the seminal work by the group at Kodak. Some classes of low-mass blue-emitting materials have been exploited, such as spirobifluorenes, oligofluorenes, siloles and distyrylarylenes, but the introduction of completely new structural motifs remain scarce. To this end, we report the acid-mediated condensation of a 2,3-diACHTUNGTRENNUNGalkyl-1,4-benzoquinone with 1,4-naphthoquinone to produce a series of highly soluble p-extended tetraoxa[8]circulenes (Figure 1) as well as the application of these materials in blue OLEDs. Tetraoxa[8]circulene (4 B) is a planar heteroaromatic compound formed in trace amounts by treating 1,4-benzoquinone with strong acids. The structure of the tetraoxa[8]circulene framework was deduced by means of mass spectrometry of the all-naphthalene tetraoxa[8]circulene (4 N) by Erdtman and Hçgberg, and was later confirmed by single-crystal X-ray crystallography. It became clear that when one side of the 1,4-benzoquinone was substituted, either by using 1,4-naphthoquinone or a 2,3-disubstituted1,4-benzoquinone, the tetraoxa[8]circulene was a major product upon acid treatment. More recently a series of liquid-crystalline tetraoxa[8]circulenes were synthesised by attachment of linear alkyl chains to the tetraoxa[8]circulene framework. That work also introduced a relatively mild method for the cyclisation reaction: treatment of the quinone with BF3·OEt2 in boiling CH2Cl2. The tetraoxa[8]circulene has been suggested as an intercalator for DNA. Rathore and co-workers used this synthetic protocol to prepare new stable radical cation salts based on tetraoxa[8]circulenes. From a synthetic and a materials point of view, the exploration of p-extended tetraoxa[8]circulenes is of interest. As the processing ability of large aromatic materials and polymers relies on solubility in organic solvents, the development of tetraoxa[8]circulenes based on 2,3-dialkyl-1,4-ben[a] Dr. C. B. Nielsen, T. Brock-Nannestad, Dr. T. K. Reenberg, Dr. P. Hammershøj, Dr. J. B. Christensen, Dr. M. Pittelkow Department of Chemistry, University of Copenhagen Universitetsparken 5, 2100 Copenhagen Ø (Denmark) E-mail : pittel@kiku.dk [b] Dr. J. W. Stouwdam Laboratory of Macromolecular and Organic Chemistry Eindhoven University of Technology, P. O. Box 513 5600 MB Eindhoven (The Netherlands) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201002261. Figure 1. Structure of symmetrical and unsymmetrical p-extended tetraACHTUNGTRENNUNGoxa[8]circulenes.

Solution-Based Fabrication of Single-Crystalline Arrays of Organic Nanowires

Organic single-crystalline nanowire arrays, with a length of several hundreds of micrometers and controllable width, are grown on a substrate surface by vertically pulling the substrate out of an organic solution of the molecule of interest. Optical microscopy and atomic force microscopy show that the large-scale arrays are oriented parallel to the pulling direction and are well adhered to the substrate surface. Cross-polarized microscopy, polarized UV-vis absorption, and grazing incidence X-ray diffraction confirm that the arrays have high crystal quality. On the basis of this method, the fabrication of organic devices is realized in one step. The results presented here for three different small molecules show the promising potential of this facile solution-based process for the growth of high-quality organic semiconductors, the fabrication of high-density and high-performance devices, and the fabrication of controlled assemblies of nanoscale circuits for fundamental studies and future applications.

Azatrioxa[8]circulenes: Planar Anti-Aromatic Cyclooctatetraenes

We describe herein the first synthesis of a new class of anti-aromatic planar cyclooctatetraenes: the azatrioxa[8]circulenes. This was achieved by treating a suitably functionalised 3,6-dihydroxycarbazole with 1,4-benzoquinones or a 1,4-naphthoquinone. We fully characterised the azatrioxa[8]circulenes by using optical, electrochemical and computational techniques as well as by single-crystal X-ray crystallography. The results of a computational study (NICS) suggest that the central planar cyclooctatetraene is anti-aromatic when the molecules are in neutral or oxidised states (2+), and that the corresponding dianions are aromatic. We discuss the aromatic/anti-aromatic nature of the planar cyclooctatetraenes and compare them with the isoelectronic tetraoxa[8]circulenes.

Diazadioxa(8)circulenes: Planar Antiaromatic Cyclooctatetraenes

In this paper we describe a new class of antiaromatic planar cyclooctatetraenes: the diazadioxa[8]circulenes. The synthesis was achieved by means of a new acid-mediated oxidative dimerization of 3,6-dihydroxycarbazoles to yield the diazadioxa[8]circulenes in high yields. The synthetic protocol appears to be general, and is a one-pot transformation in which two C-C bonds and two C-O bonds are formed with the loss of two molecules of water. We also present a detailed characterization of the optical and electrochemical properties of this new class of stable planar cyclooctatetraenes. The properties of the diazadioxa[8]circulenes are compared with the properties of isoelectronic tetraoxa[8]circulenes and azatrioxa[8]circulenes. We discuss the antiaromatic nature of the planar central cyclooctatetraene moiety. The antiaromatic nature of the planar cyclooctatetraenes was studied by using computational methods (NICS calculations), and these calculations reveal that the central eight-membered ring has antiaromatic character.

Counterions Control Whether Self-Assembly Leads to Formation of Stable and Well-Defined Unilamellar Nanotubes or Nanoribbons and Nanorods

Self-assembly of the amphiphilic π-conjugated carbenium ion ATOTA-1(+) in aqueous solution selectively leads to discrete and highly stable nanotubes or nanoribbons and nanorods, depending on the nature of the counterion (Cl(-) vs. PF6(-), respectively). The nanotubes formed by the Cl(-) salt illustrate an exceptional example of a structural well-defined (29±2 nm in outer diameter) unilamellar tubular morphology featuring π-conjugated functionality and high stability and flexibility, in aqueous solution.

A Triptycene‐Based Approach to Solubilising Carbon Nanotubes and C60

We describe herein the synthesis of a triptycene-based surfactant designed with the ability to solubilise single-walled carbon nanotubes (SWNTs) and C(60) in water through non-covalent interactions. Furthermore, an amphiphilic naphthalene-based surfactant with the same ability to solubilise SWNTs and C(60) has also been prepared. The compounds synthesised were designed with either two ionic or non-ionic tails to ensure a large number of supramolecular interactions with the solvent, thereby promoting strong solubilisation. The surfactants produced stable suspensions in which the SWNTs are dispersed and the surfactant/SWNT complexes formed are stable for more than one year. UV/Vis/NIR absorption spectroscopy, TEM and AFM were employed to probe the solubilisation properties of the dispersion of surfactants and SWNTs in water.

X-Ray Crystal Structure of a Highly Functionalized Thiophene as a New Backbone Amide Linker for Solid-phase Peptide Synthesis. Relationship between Crystal Structure and Reactivity

The development of new linkers (handles) for solid-phase synthesis provides new chemical opportunities for peptide synthesis. To understand the chemical properties of a recently developed backbone amide linker from a structural perspective, the crystal structure of S-((5-formyl-3,4-ethylenedioxy)thiophene-2-yl)-3-thiopropionic acid (T-BAL2) was studied. Specifically, we wished to address whether this highly substituted thiophene retained planarity in the aromatic ring as well as between the aromatic ring and the aldehyde carbonyl. Furthermore, we sought an explanation for the relatively low reactivity in reductive aminations of the thienylaldehyde with amines in solution and on solid phase. Based on the crystal structure of T-BAL2, the thienyl-C (aldehyde) and C–O (aldehyde) bond lengths were applied as measures for the electron-deficiency (electrophilicity) of the aldehyde and compared to similar bond lengths found in previously reported formylated homo- and hetero-aromatic systems, which show significantly higher reactivity towards imine formation. The bond lengths found in the present structure are in accordance with normal C–C single bond and C–O double bond lengths. The high similarity in aldehyde bond lengths in the present system and in the reported systems indicates similar electron distribution in these systems. The lower reactivity of the present system may therefore not be attributed to electronic factors.

Tuning and Tracking of Coherent Shear Waves in Molecular Films

We have determined the time-dependent displacement fields in molecular sub-micrometer thin films as response to femtosecond and picosecond laser pulse heating by time-resolved X-ray diffraction. This method allows a direct absolute determination of the molecular displacements induced by electron–phonon interactions, which are crucial for, for example, charge transport in organic electronic devices. We demonstrate that two different modes of coherent shear motion can be photoexcited in a thin film of organic molecules by careful tuning of the laser penetration depth relative to the thickness of the film. The measured response of the organic film to impulse heating is explained by a thermoelastic model and reveals the spatially resolved displacement in the film. Thereby, information about the profile of the energy deposition in the film as well as about the mechanical interaction with the substrate material is obtained.

Bis[S-6-(2,2:6′,2′′-terpyridin-4′-yloxy)hexyl thioacetate]manganese(II) bis(hexafluorophosphate)

The structure of a manganese(II) complex of terpyridine functionalized with acetylsulfanyl-terminated hexyloxy chains, [Mn(C(23)H(25)N(3)O(2)S)(2)](PF(6))(2), is described. This type of complex is of interest in the study of single-molecule transport properties in open-shell systems. The manganese coordination environment is distorted octahedral but, importantly, with no larger deviations from the idealized geometry than those observed for other metal-terpyridine complexes. The Mn-N bond lengths range from 2.192 (2) to 2.272 (3) A. The title compound crystallizes with the cation and anions all on general positions, with the hexafluorophosphate anions exhibiting orientational disorder. When compared with other bis-terpyridine complexes, this structure demonstrates that manganese(II) is no more prone to undergo low-symmetry distortions than systems with ligand field stabilization energy contributions.