/pdf/aryl-aryl-bond-formation-one-century-after-the-discovery-of-1jdyxlkwix.pdf

Aryl-aryl bond formation one century after the discovery of the Ullmann reaction.

Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

Functionalized acenes and heteroacenes for organic electronics.

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Organic semiconducting oligomers for use in thin film transistors.

The solid-state structures of a series of bithiazole and thiophene oligomers, as well as a series of substituted pentacenes, are rationalized in terms of "pitch and roll" inclinations from an "ideal" cofacial pi-stack. Pitch inclinations translate adjacent molecules relative to one another in the direction of the long molecular axis, whereas roll inclinations translate the molecules along the short molecular axis. Thus, moderately large pitch distortions preserve pi-pi interactions between adjacent molecules, whereas roll translations greater than 2.5 A essentially destroy pi-pi overlap between adjacent molecules. The familiar herringbone packing is characterized by large roll distortions. It is shown that thiophenes tend to exhibit large roll translations, whereas thiazoles have small roll but large pitch translations. Substituted pentacenes tend to have both moderate pitch and roll distances. The relationship of molecular packing to transport properties is discussed.

Solid-State Packing of Conjugated Oligomers: From π-Stacks to the Herringbone Structure

The intercalation of MoS2 with Co and Fe complexes has been accomplished via exfoliation of LixMoS2 by reaction with water, followed by flocculation in the presence of cationic guest species. The resulting self-assembled compounds have been characterized by X-ray absorption spectroscopy, electron diffraction, powder X-ray diffraction, and magnetic measurements. The 2H-type (undistorted) MoS2 undergoes a structural distortion to 1T-type MoS2 during the Li intercalation, which is partially maintained upon exfoliation and flocculation. A structural model of 1T-MoS2 is proposed on the basis of X-ray absorption spectroscopy and electron diffraction, in which the unit cell has P3 symmetry with lattice parameters a = 6.52(5) A, c = 6.14 A. The Mo atoms are shifted approximately 0.5 A from their positions in 2H-MoS2 to form trigonal clusters in 1T-MoS2, with a concomitant change in coordination geometry from trigonal prismatic to distorted octahedral. Layers of Co(OH)2 were intercalated between the distorted and/...

Structural characterization and thermal stability of MoS2 intercalation compounds

Publisher Summary This chapter discusses redistributions catalyzed by transition-metal complexes. Redistribution, or disproportionation, constitutes an important class of reactions in organosilicon chemistry. Redistributions on silicon may be initiated by thermolysis or by catalytic activation at somewhat lower temperatures. In the gas phase, methyl is transferred from Me n SiH 4–n , to CH 3 + almost as readily as hydrogen. Silacyclobutanes with metal substituents may also be polymerized to give novel polymers with pendant metal groups. By using chiral silyl hydrides, it has been demonstrated that the exchanges occur with the retention of configuration at silicon. The complete lack of isomerization of the p -tolyl group during the disproportionation of Ar 3 SiH is noteworthy. Similarly, the vinyl group of trimethylvinylsilane is hydrolyzed by a catalytic amount of Zeise's salt [(C 2 H 4 )PtC1 3 ] - in moist acetone. The redistribution reactions of hydridodisilanes of the type R 3 SiSiR 2 H are more varied than those of the corresponding monosilanes. In redistribution reactions catalyzed by transition-metal complexes, di- or polysiloxanes are expected to share some characteristics of both monosilanes and di- or polysilanes. Thus, the availability of the four-membered metallacycle in the catalytic cycle greatly enhances the rate of disproportionation of tetramethyldisiloxane. Some of these catalytic cycles lead to products that appear to arise from divalent silylenoid species.

Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes

Molecular structure of dicyclopentadienyltetracarbonyldimolybdenum(Mo.tplbond.Mo). Semibridging carbonyls as four-electron donors in complexes with metal-metal multiple bonds

A molecular orbital analysis of the regioselectivity of nucleophilic addition to .eta.3-allyl complexes and the conformation of the .eta.3-allyl ligand in L3(CO)2(.eta.3-C3H5)Mo(II) complexes

M. David Curtis

Papers

Solid-State Packing of Conjugated Oligomers: From π-Stacks to the Herringbone Structure

Structural characterization and thermal stability of MoS2 intercalation compounds

Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes

Molecular structure of dicyclopentadienyltetracarbonyldimolybdenum(Mo.tplbond.Mo). Semibridging carbonyls as four-electron donors in complexes with metal-metal multiple bonds

A molecular orbital analysis of the regioselectivity of nucleophilic addition to .eta.3-allyl complexes and the conformation of the .eta.3-allyl ligand in L3(CO)2(.eta.3-C3H5)Mo(II) complexes