Two isomers of a multifunctional π-expanded macrocyclic oligothiophene 8-mer, E,E-1 and Z,Z-1, were synthesized using a McMurry coupling of a dialdehyde composed of four 2,5-thienylene and three ethynylene units under high dilution conditions. On the other hand, cyclo[8](2,5-thienylene-ethynylene) 2 was synthesized by intramolecular Sonogashira cyclization of ethynyl bromide 5. From STM measurements, both E,E-1 and Z,Z-1 formed self-assembled monolayers at the solid-liquid interface to produce porous networks, and from X-ray analyses of E,E-1 and 2, both compounds had a round shape with a honeycomb stacked structure. E,E-1 formed various fibrous polymorphs due to nanophase separation of the macrorings. E,E-1 and Z,Z-1 in solution exhibited photochromism upon irradiation with visible and UV light, respectively, and this photoisomerization was confirmed by using STM. Furthermore, amorphous films of Z,Z-1 and E,E-1 showed photoisomerization, although single crystals, fibers, and square tubes of E,E-1 remained unchanged under similar conditions. E,E-1 with a 12.5-14.7 Å inner cavity incorporated fullerene C60 in the cavity in solution and the solid state to produce a Saturn-like complex, whose structure was determined by X-ray analysis. 2 also formed a Saturn-like complex with C60 in the solid state. These Saturn-like complexes are stabilized by van der Waals interactions between the sulfur atoms of 8-mer and C60. The complexes exhibited charge-transfer interactions in the solid state. Like E,E-1, Saturn-like complex E,E-1⊃C60 formed small cube and fiber structures depending on the solvent used, whereas those of Saturn-like complex 2⊃C60 were limited due to the rigidity of the macroring of 2.

Multifunctional π-expanded macrocyclic oligothiophene 6-mer 1, as well as 9- (2) and 12-mers (3), was synthesized using a McMurry coupling reaction as the key step. The 6-mer 1 was converted to cyclo[6](2,5-thienylene-ethynylene) (4) by using a bromination-dehydrobromination procedure. From X-ray analysis, the crystal structures of nonplanar 1 and round-shaped 2 and 4 were elucidated. STM showed that 4 formed a self-assembled monolayer at the liquid/solid interface to produce a hexagonal porous network. Chemical oxidation of 1, 2, and 4 with 1 and 2 equiv of Fe(ClO4)3 produced 1(•+) and 1(2+), 2(•+) and 2(2+), and 4(•+) and 4(2+), respectively. Although oligothiophene radical cations containing β,β-disubstituted thiophenes usually do not form π-dimers, 4(•+) clearly formed a π-dimer owing to its planar, round shape. As for the dications of 1, 2, and 4, 1(2+), which has 34π-electrons, exhibited a large diatropic ring current effect, whereas 34π dication 4(2+) only showed a medium diatropic ring current effect. In contrast to 1(2+) and 4(2+), 52π dication 2(2+) had biradical cationic character instead of Hückel-type cyclic conjugation. Interestingly, 6-mer 1 showed polymorphism and unusual melting point behavior due to the number of stable conformations in the solid state. Single crystals of 1 melted at 176 °C, whereas an amorphous film of 1 crystallized in the temperature range of 80-83 °C to form a lamellarly stacked microcrystalline film, which melted at 139 °C. The polymorphism of 1 was applied to either fluorescence switching or switching of field effect transistor (FET) activity and electrical conductivity.

5371to occur upon carbidization2q3 in metal crystallites of first-row transition metals. Acknowledgment. We thank the M.P.I. for a grant and the "Centro per lo Studio della Sintesi e della Struttura" for the use of equipment. Supplementary Material Available: A list of atomic coordinates and thermal factors of [NMe3CH2Ph]5[HNi34(C0)38c4] (Table I) and [NEt4]6[Ni35(C0)39C4] (Table 11) (14 pages). Ordering information is given on any current masthead page. The [Ni35(C0)39C4]6 cluster was isolated from the decomposition products obtained by refluxing [NEt4I2[Nis(CO) '21 in CH&' Crystals of [NMe3CH2Ph]5[HNi34(CO)38C4] and [NEt4]6-16) Nakagura, S. J. Phys. SOC. Jpn. 1957, 12,482. (17) Ceriotti, A,; Longoni, G.; Perego, M.; Manassero, M.; Sansoni, M.

The zero-valent nickel complexes, which are generated in situ from nickel(I1) complexes by reduction with zinc, have been found to catalyze the cyclooligomerization of butatrienes, 2,3-dihalo-1,3-butadienes, 1,4-dichloro-2-butyne, and 1,l-dibromoethylene to give the corresponding [4]-and [6]radialenes. The formation of the [4]-and (6lradialenes depends on the reaction conditions, especially on solvent, and each product of the reactions can be prepared selectively. This method provides access to the synthesis of novel derivatives of radialenes of theoretical and synthetic interest. The spectral and chemical data indicate the highly symmetrical structure of radialenes Radialenes (polymethylenecycloalkanes) have received considerable attention from both theorists and experimentalists'-" because of their particular arrangement of r-electrons and because of advances in the understanding of their potentials as electron donor and acceptor for organic metals5 and ferromagnetic organic compounds.6 Of the parent radialenes, [ 3]-2 and [4]radialene3 (1 and 2) were reported two decades ago. However, [5]radialene 0002-7863/88/1510-8494$01.50/0 I , , 0 1988 American Chemical Society Nickel-Catalyzed Radialene ConstructionScheme I11

A radical cation, generated from an extended π-conjugated thiophene 6-mer composed of four ethynylene-thienylene and two vinylene-thienylene units, was observed to form a stable three-dimensional π-dimer containing 70 π-electrons. The π-dimer prepared in solution was investigated by using magnetic circular dichroism (MCD), ESR spectroscopy, and UV–vis–NIR absorption spectroscopy. Probing the individual NIR absorption bands showed that the MCD signals can be assigned to the pseudo Faraday A term, indicating that the absorption bands are comprised of nearly degenerate electronic transitions. X-ray crystallographic analysis revealed that the π-dimer has a three-dimensional face-to-face and continuous π-conjugated donutlike structure. Analysis of the UV–vis–NIR and ESR spectra of the π-dimer in the solid state confirmed that it possesses the dimer structure. The prediction made by using TD-DFT calculations that the dimer would have a 70 π-electron diatropic nature was confirmed by using solid state 1H NMR spectroscopy.