Perfluorophenyl–Phenyl Interactions in the Crystallization and Topochemical Polymerization of Triacetylene Monomers

A series of symmetrically and unsymmetrically substituted octa‐2,4,6‐triyne‐1,8‐diol derivatives with benzoyl, 4‐dodecyloxybenzoyl, as well as perfluorobenzoyl substituents were prepared and investigated with respect to their crystal structures and topochemical polymerizability. Single‐crystal structures for several of these triacetylene monomers have been obtained and proved that the perfluorophenyl–phenyl interactions played a decisive role in the molecular packing. As a consequence of the geometric requirements imposed by the perfluorophenyl–phenyl interactions, packing parameters appropriate for a topochemical triacetylene polymerization in the sense of either a 1,6‐ or a 1,4‐polyaddition along different crystallographic axes were observed in two cases, and UV irradiation led to successful polymerization. Raman as well as solid‐state ¹³C NMR spectra of the obtained polymers revealed that the polymerization had predominantly proceeded in the form of a 1,4‐polyaddition.     

Thermal Rearrangements of Monoterpenes and Monoterpenoids

The thermal conversions of monoterpenes and monoterpenoids are an interesting field of research with respect to mechanistic, kinetic, and theoretical issues. Since the beginning of the 20th century, these reactions have attracted the interest of many research groups, and even today there are sufficient problems and questions to deal with. This review covers the thermal isomerization chemistry of pinanes, pinenes, carenes, and thujenes over the past 70 years. Categorization of these compounds into groups, each of them being represented by a small parent molecule (cyclobutane, vinylcyclobutane, vinylcyclopropane), allows systematization of multitude of publications.     

Angular Benzoperylenetetracarboxylic Bisimides

Benzoperylene derivatives with two angularly attached dicarboxylic imide rings, which were prepared by the Diels–Alder‐Reaction, exhibit strong fluorescence and their free peri positions allow either control of the UV/Vis spectra through their substituents or form anchor positions for the attachment of functional units. The angular chromophore 3 may be used both for fluorescent labeling such as for primary amines or enzymes or as building blocks for more complex assemblies where they may act as energy donors for FRET or electron acceptors in PET such as for photovoltaic solar cells.     

Iridium‐Catalyzed Allylic Substitutions with Cyclometalated Phosphoramidite Complexes Bearing a Dibenzocyclooctatetraene Ligand: Preparation of (π‐Allyl)Ir Complexes and Computational and NMR Spectroscopic Studies

(π‐Allyl)Ir complexes derived from dibenzocyclooctatetraene and phosphoramidites by cyclometalation are effective catalysts for allylic substitution reactions of linear monosubstituted allylic carbonates. These catalysts provide exceptionally high degrees of regioselectivity and allow the reactions to be run under aerobic conditions. A series of (π‐allyl)Ir complexes were prepared and characterized by X‐ray crystal structure analyses. An allylic amination with aniline displayed different resting states depending on the presence of a strong base. DFT calculations were carried out on the mechanistic aspects of these reactions. The results suggest that for the (π‐allyl)Ir complexes, the formation and reactions with nucleophiles proceed with comparable rates.     

Luminescent N-isopropylacrylamide–surfmer copolymer hydrogels prepared upon electrostatic self-assembly of 1-pyrenesulfonate

The preparation of luminescent hydrogels based on the electrostatic self-assembly of 1-pyrenesulfonate (PyS) anions in a positively charged N-isopropylacrylamide (NiPAAm)/surfmer copolymer gel is described. The hydrogels were prepared from a micellar aqueous solution of 11-acryloyloxyundecyltrimethylammonium bromide and NiPAAm upon ⁶⁰Co-gamma irradiation. For assembly of PyS, the gel was shrunken at 50 °C and re-swollen at 20 °C in an aqueous solution of sodium 1-pyrenesulfonate. Re-swelling was accompanied by electrostatic assembly of PyS anions within the gel. Subsequently, the excess non-bound PyS ions were removed by repeatedly swelling and shrinking the gel in pure water at 20 °C and 50 °C, respectively. Incorporation of PyS ions in the hydrogel was studied using UV/Vis spectroscopy and energy dispersive x-ray (EDX) measurements. The amount of electrostatically adsorbed PyS was found to be proportional to the amount of copolymerized surfmer. EDX studies indicated that 20% of the bromide counterions were replaced for PyS. The PyS counterions could be released again if the functionalized hydrogel was immersed in acidified water. At a pH of 1, an almost complete release of PyS was found after 250 h. The preparation method can be used to introduce a variety of functional properties in thermoresponsive charged copolymer gels.     

Synthesis and reactivity of some diselenasila cycles containing an annelated dicarba‐closo‐dodecaborane(12) unit

The use of 1,2‐diselenolato‐1,2‐dicarba‐closo‐dodecaborane(12) dianions [1,2‐(1,2‐C₂B₁₀H₁₀)Se₂]^2? prepared in situ as the dilithium salt may lead to irreproducible results. This is shown by the straightforward synthesis of silanes using the purified and isolated dianions, in contrast with previous less successful attempts. Thus, the reactions of the dianions with dichlorosilanes afford the five‐membered diselenasila cycles containing the SiMe₂ or the SiPh₂ units, and with 1,2‐dichloro‐tetramethyldisilane the six‐membered cycle containing the Si₂Me₄ unit. The latter was studied by X‐ray diffraction, and all products were characterized by multinuclear magnetic resonance (¹H, ¹³C, ²⁹Si, ⁷⁷Se NMR) in solution. Novel isotope effects were detected in ¹³C and ⁷⁷Se NMR spectra. Exchange reactions of the five‐ and six‐membered diselanasila cycles with chlorosilanes were studied. Copyright © 2009 John Wiley & Sons, Ltd.