Akkerman, Hylke B.Mannsfeld, Stefan C. B.Kaushik, Ananth P.Verploegen, EricBurnier, LucZoombelt, Arjan P.Saathoff, Jonathan D.Hong, SanghyunAtahan-Evrenk, SuleLiu, XueliangAspuru-Guzik, AlanToney, Michael F.Clancy, PauletteBao, Zhenan2014-08-072013Akkerman, Hylke B., Stefan C. B. Mannsfeld, Ananth P. Kaushik, Eric Verploegen, Luc Burnier, Arjan P. Zoombelt, Jonathan D. Saathoff, et al. 2013. Effects of Odd–Even Side Chain Length of Alkyl-Substituted Diphenylbithiophenes on First Monolayer Thin Film Packing Structure. Journal of the American Chemical Society 135 (30): 11006–11014.0002-78631520-5126http://nrs.harvard.edu/urn-3:HUL.InstRepos:12697374Because of their preferential two-dimensional layer-by-layer growth in thin films, 5,5′bis(4-alkylphenyl)-2,2′-bithiophenes (P2TPs) are model compounds for studying the effects of systematic chemical structure variations on thin-film structure and morphology, which in turn, impact the charge transport in organic field-effect transistors. For the first time, we observed, by grazing incidence X-ray diffraction (GIXD), a strong change in molecular tilt angle in a monolayer of P2TP, depending on whether the alkyl chain on the P2TP molecules was of odd or even length. The monolayers were deposited on densely packed ultrasmooth self-assembled alkane silane modified \(SiO_2\) surfaces. Our work shows that a subtle change in molecular structure can have a significant impact on the molecular packing structure in thin film, which in turn, will have a strong impact on charge transport of organic semiconductors. This was verified by quantum-chemical calculations that predict a corresponding odd–even effect in the strength of the intermolecular electronic coupling.en-USJournal Article2014-08-0710.1021/ja400015e