A synthetic approach to a two-dimensional grid polymer is proposed and the execution of initial steps is described. Pd-catalyzed coupling of (1,12-dicarba-closo-dodecaboran-1-yl)copper ( 10) with iodobenzene, mdiiodobenzene, and 1,3,5-triiodobenzene yielded the known 1,12-dicarba-closo-dodecaboran-1-ylbenzene (3) and the new m-bis(1,12-dicarba-closo-dodecaboran-1-yl)benzene (4) and 1,3,5-tris(1,12-dicarba-closo-dodecaboran-1yl)benzene (1), respectively. Each arm of the trigonal connector 1 was provided with one or two sticky tentacles by conversion to 1,3,5-tris [12-((3-(ethylthio)propyl)dimethylsilyl)-1,12-dicarba-closo-dodecaboran-1-yl]benzene (7) and 1,3,5-tris [12-(bis(3-(ethylthio)propyl)methylsilyl)-1,12-dicarba-closo-dodecaboran-1-yl]benzene (8). Linear coupling of carboranyl CH terminals through a mercury atom produced very stable dimeric structures from 3 and 4. The carborane 3, its mercury-linked dimer 13, the 1:1 complex of 13 with 2,2′-bipyridyl, and the 2:1 complex of 13 with 2,2′-bipyrimidyl have been structurally characterized by single-crystal X-ray crystallography, but crystals of 1 showed an intriguing disorder and could not be used for molecular structure determination. Grazing incidence IR spectra show that the tentacled species 7 and 8 adsorb firmly on the surface of gold, apparently without a strong preference for a particular orientation. At room temperature, the tritentacled species 7 can be removed readily and the hexatentacled species 8 more slowly by treatment with a THF solution containing fluoride, which severs the tentacles.

Communications able-resource chemicals for utilization as molecular units with optoelectronic properties!']In order to elicit the effect of structure on the electrochemistry and the electropolymerization of the azulenes, a ribonic acid lactone and a D-glucose residue were taken as representative sugar functional groups "R" (Scheme 1) and attached

Radical anions / Dianions / Trianions / One-electron and "Two-electron" transfer processes / Dicyanovinyl substituted heterocyclesThe reductive electron transfer behaviour of 2,5-disubstituted furans with the general formula A is investigated. A comparison with related dicyanovinyl substituted benzene derivatives, a monosubstituted furan, thiophenes and pyrrols is given. Radical anions, dianions and trianions are characterized by cyclic voltammetry and UV/VIS/NIRspectroelectrochemistry. Electronic spectra are reported. The reduction of A to their dianions depends sensitively on the length of the ^-conjugated side chains and can be shifted from a stepwise process with two clearly separated waves to an electron transfer mechanism with a single "two-electron" transfer wave in the cyclic voltammogram. The compounds A with higher conjugated side groups tend to the "merging wave" behaviour. A structural evaluation of these findings is discussed. The furans A and the thiophenes exhibit electrochemichromic behaviour. Applications of A in material science chemistry arc shortly adressed.Das Elektronentransferverhalten von 2,5 disubstituierten Furanen der allgemeinen Formel A wird untersucht. Ein Vergleich mit strukturell vergleichbaren benzoiden Verbindungen, monosubstituiertem Furan, Thiophenen und Pyrroldcrivaten wird durchgeführt. Radikalanionen, Dianionen und in einzelnen Fällen auch Trianionen werden durch Cyclovoltametrie und teilweise auch UV/VIS/NIR-Spektroelektrochemie nachgewiesen und charakterisiert. Der Ablauf der reduktiven Elektronenübertragung für die Umwandlung von A in die entsprechenden Dianionen zeigt im cyclischen Voltamogramm strukturabhängiges Verhalten, das von einem Zweistufenprozeß bis zur einstufigen Zwei-Elektronenübertragung reicht. Der Zusammenhang zwischen diesem Elektronentransferverhalten und der Substratstruktur wird diskutiert. Verbindungen A mit höher konjugierten 192Josef Salbeck, Ulrich Schöberl, Knut M. Rapp and Jörg Daub Seitenketten neigen zu einem Einstufenprozeß bei der Bildung des Dianions. Die zweifachsubstituierten Furane A und Thiophene sind elektrochemichrom. Auf Anwendungen der Verbindungen wird kurz eingegangen.

On the other hand, by increasing the size of the core and the number of paraffinic chains, we have obtained a manifold columnar polymorphism of disc-like diamides; thus, the strong intra-columnar interactions disappear in the nematic phase. Moreover, the orientational order parameter is unusually low and the symmetry properties of the nematic phase have not been yet elucidated.[l] Preceeding communication in this series: P. A. Bross, U. Schoberl, J.[2] In preliminary form reported: Int. Congress Food and Non-Food Applica-Daub, Adv. Muter. 1991, 3, 198. Adv Mater 4 (1992) No. 1 0 VCH Verlugsgesellsthaft mbH, W-6940 Weinhelm, 1992 0935-964R/92/0lOl-0043 $ 3 50+ 2S/U 43

The specificity of ion-pair formation of the radical anions of 2,5-bis(tricyanovinyI)furan (1 ) and 2 5 bis(tricyanoviny1)thiophene (2) has been studied using solvents covering a broad range on the polarity scale and Li', Na+, K + and Cs+ as the counter-ions. The EPR/ENDOR spectra show that 1'-and 2'-can exist as the free radical anions in which the tricyanovinyl groups have a synlanti conformation, but under appropriate conditions 2'can also exist in a synlsyn conformation in an ion-pair with the metal cation. This is rationalised in terms of a selectivity for the formation of ion pairs depending on the size of the alkali-metal cation and of the cavity presented by the proximate pair of cyano groups.In recent years it has been established that a high number of chemical reactions proceed via electron-transfer processes. Obviously a one-electron transfer reaction leads to the formation of a radical ion. As most of the reactions are performed in fluid solution, such charged species are capable of interacting with the solvent and counter-ions. When well defined counter-ions are provided in a solution containing the radical ion, insight into the factors directing such 'guest-host communications' can be gained.When, for example, radical anions are formed by reductive electron transfer from metals, the metal cation formed in the redox process serves as the well defined counter-ion. Depending on solvation, this counter-ion influences the stability and the structure of the negatively charged molecule. The extent of such an influence can be studied readily by EPR spectroscopy.2 This was demonstrated for, inter alia, 1,2-di0nes,~ but-2ene-1,4-diones,, thiophenecarbaldehydes, alkylidene-bridged n-systems and cyano-substituted furans and thiophenes.'In this contribution we investigate the radical anions of 2,5-bis(tricyanovinyl)furan (1) and 2,5-bis(tricyanovinyl)thiophene (2) in various environments and relate these results to those established for the tetracyano derivatives 3'-and 4'-.7 Nc&N NC CN NC CN NC CN NC CN