Oligothiophenes, most important

Another process which has to be considered is the conformation change from the nonrelaxed nonplanar to the planar excited state, which could be connected with a fast increase of absorption. The most important radiationless decay process in oligothiophenes is ISC. Therefore, a fast channel of ISC was suggested, which is effective before the lowest vibronic state of Si is occupied. The fast decay of the AD(f) kinetics is caused by an effective formation of triplets. 

Pentacene is the material most used for preparation of p-type OTFTs based on small molecules, with oligothiophenes and their derivatives being the nest most important. The highest reported mobility is up to 6 cm2 V-1 s-1 for the former [76] and 1 cm2 V-1 s-1 for the latter [77]. 

A series of luminescent mercury(II) bis(alkynyl) complexes containing oligothiophenes have been synthesized by Wong via direct merciuation of the corresponding alkynes (see equation S). Most importantly, the optical properties of these species have been found to be easily tuned by modifying the... 

From the point of view of applications, a6T is by far the most important oligothiophene (see Section 6). Like aST, sexithiophene forms highly ordered or crystalline films on oxidic surfaces, depending on the preparation conditions. The trend of forming films with higher crystallinity by increasing the substrate temperature is even more pronounced. On the other hand, there are no reports on completely closed uniaxially oriented films. 

The electronic structure of oligothiophenes is characterized by UPS and MO calculations for the occupied states and by a variety of optical techniques for the transition between occupied and unoccupied levels. Because of the vast number of papers on optical measurements, only a selection demonstrating the most important features can be presented here. 

We have reviewed the calculations related to the most important properties of thiophene-containing materials, such as the HOMO-LUMO gap (or bandgap for polymers), twisting, the effect of substitution, the nature of charge carriers and IR, Raman and UV-Vis spectra. In addition, promising new classes of thiophene type compounds, such as quinoid oligothiophenes and cyclic oligothiophenes, have been reviewed. This review covers the literature up to mid-2007. 

From the point of applications a-6T is by far the most important oligothiophene. Like a-5T sexithiophene forms highly ordered or crystalline films on oxidic siuTaces,... 

Polythiophenes (including oligothiophenes) are one of the most studied and important classes of linear conjugated polymers [444,445], Versatile synthetic approaches to PTs (chemical [446] and electrochemical [447]), easy functionalization and unique, widely tunable electronic properties have been the source of tremendous interest in this class of polymers. 

We are aware of only two reviews (book chapters) devoted solely to the theoretical smdy of oligothiophenes and polythiophenes [2, 3]. Since these were published in 1998 [2] and 1999 [3], the present chapter covers mostly research published after 1998. Due to the significant number of pubiications over the last 10 years that include theoretical studies on thiophene-containing compounds, we have not attempted to write a comprehensive review and to cover all available publications. Rather, our aim is to provide an overview of the field. We decided to concentrate on representative case studies of thiophene-containing compounds and not necessarily on the deepest or most comprehensive studies hence some other important studies are not covered in this review. Most theoretical studies were performed on oligomers however, where polymer calculations are available, they are also included in this review. We note that, since around 1996-99, density functional theory (DFT) has become the most popular computational tool in chemistry in general and in material chemistry in particular. Earlier reviews, published before 2000, concentrated... 

Research on organic/polymeric FETs has not been confined to oligothiophene/ poly thiophene materials. Important advances have been made with other classes of materials such as fullerenes [12, 13], fused ring compounds such as pentacene [14, 15], and the phthalocyanines. While most of this chapter is focused on oligo-and poly-thiophene FETs, there are a few brief discussions of FETs with other organic materials to illustrate some key points. 

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