About oligothiophene self-assembly:: From aggregation in solution to solid-state nanostructures

Well-defined pi-conjugated oligomers play an important role in the field of organic electronics, because their precise chemical structure and conjugation length give rise to well-defined functional properties and facilitate control over their supramolecular organization. In this review, we present different complementary approaches for the control of molecular assembly into well-defined structures on the nanoscale, applied to oligothiophenes as a typical conjugated system. We consider self-assembly in solution, sublimation of individual molecules in the vapor phase, and aggregation in thin deposits from compounds molecularly dispersed in a solution. We demonstrate that the development of substituted, soluble pi-conjugated materials allows not only a control of their organization in the solid state but also the possibility of determining the degree of order in solution. During these self-assembly processes, the interplay between the conjugated molecules, the solvent, and the substrate surface is of primary importance. Depending on the interactions between the molecules and the substrate, one-dimensional (nanowires) or two-dimensional (platelets) objects can be generated. The self-organization of conjugated building blocks in solution or on surfaces, leading to the construction of nanoscopic and mesoscopic architectures, represents a starting point for the construction of molecular electronics or even circuits, through surface patterning with nanometer-sized objects.