Group 14 metalloles are an interesting class of Si-, Ge-, or Sn-based annulated p-conjugated molecules.[1] The silole ring system contains a s* orbital on the silicon atom, which effectively interacts with the p* orbital of the butadiene unit, producing a low-lying LUMO. Although a variety of sophisticated silole derivatives have been prepared, the preparation of these well-designed compounds depends heavily on classical Si À C bond-formation methods by using highly reactive organometallic reagents (Scheme 1a). [2,3] This procedure is not always simple, nor is it safe to implement, from the perspective of its applications.Recently, a transition-metal-catalyzed process has been developed to overcome these problems. The groups of Murakami [4] and Shimizu [5] independently reported the pioneering construction of a silole moiety in the presence of a metal catalyst. These protocols were limited by high reaction temperatures and multistep procedures for the preparation of the starting materials. Thus, the development of mild and general methods for the preparation of silole derivatives has remained an important goal. During development of organosilicon compounds containing an aromatic ring, we identified a new methodology based on transition-metal-catalyzed arylation of hydrosilanes with aryl halides.[6] Herein, we report a novel method for constructing the skeletons of Group 14 metalloles from the corresponding dihydrosilanes or dihydrogermanes using Pd-catalyzed E À C (E= Si, Ge) bond formation (Scheme 1b). The effects of the substituents on the physical properties of these materials will be discussed in detail.We examined the cyclic double intramolecular arylation of a 2,2'-diiodobiaryl with a secondary silane in the presence of the base (iPr) 2 EtN, using [Pd(PA C H T U N G T R E N N U N G (tBu) 3 ) 2 ] as the catalyst. [7,8] The results are shown in Scheme 2. The reaction proceeded smoothly to produce the desired dibenzosiloles or -germoles as colorless solids in good to high yields (1-16). The reaction described herein provides a unique method for the preparation of Group 14 metalloles containing a reactive functional group on the aromatic rings, some of which (13-16) are difficult to synthesize when using conventional synthetic methods. 2,2'-Diiodobithiophene gave an inferior yield for product 17; the reduced product was favored. Unfortunately, the intramolecular cyclization of 1-NpPhSiH 2 (Np = naphthyl) or (tBu) 2 SiH 2 with 2,2'-diiodobiphenyl did not occur at all under the present conditions due to the steric crowding of the secondary silanes.The photophysical properties of compounds 1-17 were determined by UV-visible and fluorescence spectroscopies, collected in dichloromethane or in the corresponding crystalline state. These results are summarized in Table 1. The UVvisible absorption spectra showed that the position of the
Fully oxidized poly(1-(N,N-dimethylamino)pyrrole)s (PDMAPy n+ ), which are synthesized through doping with anions with the same number of polymer units as the original pyrrole, have been proposed as candidates for molecular flat-band magnets from the theoretical calculations of Aoki and coworkers (Phys. Rev. B: Condens. Matter Mater. Phys., 2003, 68, 140403; Phys. Rev. B: Condens. Matter Mater. Phys., 2010, 82, 235127). Here we describe the synthesis of neutral forms of oligo(1-(N,N-dimethylamino)pyrrole)s (ODMAPys) from the dimer (2) to the dodecamer (12). The crystal structures of 2-6 (i.e., up to the hexamer)were determined by single crystal X-ray analysis. The chemical and electrochemical formation of their oxidized forms is also reported. Electrochemical measurements of the ODMAPys indicated that oligomers 4, 6, and 8 underwent 2e À oxidation, whereas 10 and 12 showed quasi-reversible 4e À oxidation. The oxidized forms maintained considerable chemical stability; 4 2+ , 6 2+ , 8 2+ , 10 4+ , and 12 4+ were isolated as SbCl 6 À salts.The neutral forms were colorless (l max = 240-270 nm), whereas the oxidized forms exhibited strong blue color with l max = 670-950 nm. EPR spectroscopy indicated that the dications 4 2+ , 6 2+ , and 8 2+ in the solid salts were intrinsically diamagnetic, but the tetracation of 10 4+ was paramagnetic at 4.4 K, which was supported by magnetic measurements. These physical properties of the ODMAPys are different from those common to polypyrroles, but consistent with their predicted unique electronic structures. Results and discussion Synthesis, characterization, and structure of ODMAPyThe analysis in the present study requires several pure oligomers with different numbers of pyrrole units linked at the 2,5-positions
Versatile Synthesis of Blue Luminescent Siloles and Germoles and Hydrogen--Bond-Assisted Color Alteration. -A variety of dibenzosiloles and -germoles as well as dithiophenosilole (VII) are prepared, better tolerating the functional groups as the methods applied so far. Fluorescence and phosphorescence properties of the products are investigated. -(YABUSAKI, Y.; OHSHIMA, N.; KONDO, H.; KUSAMOTO, T.; YAMANOI*, Y.; NISHIHARA, H.; Chem. Eur.
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