Theoretical studies on thiophene-containing compounds

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 

Handbook of Thiophene-based Materials Applications in Organic Electronics and Photonics Edited by Igor F. Perepichka and Dmitrii F. Perepichka 2009 John Wiley Sons, Ltd 

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. 

Various molecular and solid-state quantum chemical methods have been used to predict the bandgaps of conjugated polymers [13-15]. Extrapolations based on oligomers provide an alternative way to calculate bandgaps. Here we will review the most recent papers on this topic. 

IPs and EAs are overestimated by up to 0.77 eV compared with experimental bulk values. Extrapolated bandwidths agree reasonably well with bandwidths from band structure calculations. The HOMO-LUMO gaps are significantly closer to experimental values with hybrid functionals than with LSDA and vertical excitation energies from UV spectra are reproduced to within 0.01-0.8 eV. 

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