Chiral 'pinwheel' heterojunctions self-assembled from C _(60) and pentacene

摘要

We demonstrate the self-assembly of C_(60) and pentacene (Pn) molecules into acceptor-donor heterostructures which are well-ordered and -despite the high degree of symmetry of the constituent molecules -chiral. Pn was deposited on Cu(111) to monolayer coverage, producing the random-tiling (R) phase as previously described. Atop R-phase Pn, postdeposited C_(60) molecules cause rearrangement of the Pn molecules into domains based on chiral supramolecular "pinwheels". These two molecules are the highest-symmetry achiral molecules so far observed to coalesce into chiral heterostructures. Also, the chiral pinwheels (composed of 1 C_(60) and 6 Pn each) may share Pn molecules in different ways to produce structures with different lattice parameters and degree of chirality. High-resolution scanning tunneling microscopy results and knowledge of adsorption sites allow the determination of these structures to a high degree of confidence. The measurement of chiral angles identical to those predicted is a further demonstration of the accuracy of the models. van der Waals density functional theory calculations reveal that the Pn molecules around each C_(60) are torsionally flexed around their long molecular axes and that there is charge transfer from C_(60) to Pn in each pinwheel.