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[Display omitted] A systematic study of the UV light-induced degradation of a series of structurally similar conjugated polymers revealed important relationships between the molecular structure of the used building blocks and photostability of the resulting materials. These findings form a set of important guidelines for future rational design of new absorber materials for efficient and stable organic solar cells. [ABSTRACT FROM AUTHOR]

Owing to combination of chemical and thermal stability, favorable molecular packing, and efficient electron transport, naphthalene diimide derivatives (NDIs) are promising materials for n-channel organic field effect transistors (OFETs). For tuning the properties of n-conductive organic semiconductors, as well as for improvement of their air stability, fluorination is a frequently used approach. In this study, we demonstrate how very small modification of the molecular structure – fluorine substitution in the p-position of the phenyl rings of N,N′-diphenyl-NDI (Ph-NDI) – dramatically changes the crystal packing but almost does not affect electron transport. We show that this two-atom modification of Ph-NDI changes the molecular packing motif from π-stacking to a herringbone one, in contrast with usually observed improvement of π-stacking with fluorination. This unexpected behavior is mainly attributed to changes in the electrostatic potential of the phenyl rings as a result of fluorination, which alters their relative orientation and modifies the packing of the NDI cores. Nevertheless, though the herringbone packing is typically considered as less favorable for charge transport, the theoretical electron mobility is slightly higher in the fluorinated Ph-NDI. The results obtained improve the understanding of the relationship between the molecular and crystal structures of organic semiconductors and their impact on charge transport, which is of key importance for rational design of high-mobility materials for organic electronics. [ABSTRACT FROM AUTHOR]

A set of novel Y-shaped asymmetrical pyrimidines has been prepared on the basis of 2-hydroxy-4,6- dimethylpyrimidine used as a starting compound. All of them are the chromophores of D-π-A-π-D' motif where A is a central pyrimidine core; D, D' are the thiophene-2-yl, thiophene-3-yl, 9-ethyl-9H-carbazol-3-yl or 9H-carbazole-9-yl- fragments and a π-bridge is a vinyl or styryl moiety. We have studied their optical, electrochemical and electrophysical characteristics, as well as their polymerizability with the help of electrochemical oxidation. [ABSTRACT FROM AUTHOR]