7r-conjugated system

Structures, Reactions and Functions of d-d and d-7r Conjugated Systems Editors A. Nakamura, N. Ueyama, and K. Yamaguchi... 

Hydrogen-Bonded Assemblies of Dyes and Extended 7r-Conjugated Systems A. Ajayaghosh S. J. George A. P. H. J. Schenning... 

It has also been shown that surface delocalization can adopt a preferential direction if the cyclopropyl group interacts with a 7r-conjugated system. There are basically two directions of surface delocalization as indicated in Scheme 9 for vinylcyclopropane (20) and divinylcyclopropane 47. In homoaromatic molecules, surface delocalization is perpendicular to the 1,3-bond while in homoantiaromatic molecules it is parallel to the 1,3-bond ... 

Systems which contain cr(E-E)-7r conjugated systems (E = Si or Ge) have been the subject of many photochemical investigations. For the most part investigations have focussed on silicon systems, that first identified carbon-silicon double-bonded species as photoproducts . Later studies also indicated that arylsilanes undergo 1,3-sigmatropic shift reactions as well as extrusion processes yielding silylenes . ESR studies have... 

Most polymeric materials, as we usually know them, are insulators. During the past 15-20 years, however, a new class of organic polymers evolved with the ability to conduct electric current. At the present time, it is not completely understood by what mechanism the electric current passes through them. We do know, however, that all conductive polymers are similar in one respect. They all consist of extended 7r-conjugated systems, namely, alternating single and double bonds along the chain. 

The electronic and optical properties of conjugated poljuners briefly described in this chapter are summarized in Table 1.1. It is these properties that are the subject of this book. We investigate semiempirical models of 7r-conjugated systems to address the following issues ... 

The 7i-conjugated polymers can also be chemically induced to undergo redox reactions (e.g. oxidation by I2 and FeCls and reduction by Na), and the electro-chemically oxidized or reduced polymers show electrical conductivity in the 10 to 10 Scm range, presumably due to formed cationic (positive) or anionic (negative) carriers along the 7r-conjugated system. 

The reaction of 33 with a tetrabromo derivative of thiophene with a bicyclo spiranic structure afforded 36 in 86% yield. The two orthogonal 7r-conjugated systems in 36 may function as a self-contained electronic device (see Section 14.2.2.2). 

Ajayaghosh A, George SJ, Schenning APHJ (2005) Hydrogen-Bonded Assemblies of Dyes and Extended 7r-Conjugated Systems. 258 83-118 Albert M, Fensterbank L, Lacote E, Malacria M (2006) Tandem Radical Reactions. 264 1-62 Alberto R (2005) New Organometallic Technetium Complexes for Radiopharmaceutical Imaging. 252 1-44... 

Hydrogen-Bonded Assemblies of Dyes and Extended 7r-Conjugated Systems... 

While steric factors do not directly affect the reactivity of the monomer, they can exert considerable influence on the structure and properties of the polymer. Steric interactions between substituents on adjacent monomers induce a distortion of the 7r-conjugated system, which results in a shortening of effective conjugation and hence in a drop in conductivity. 

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