Chiral Pinwheel Heterojunctions Self Assembled from C60 and Pentacene

TL;DR

This study reports the self-assembly of chiral heterostructures from symmetric molecules C60 and pentacene, revealing new chiral supramolecular architectures with potential implications for molecular electronics.

Contribution

It demonstrates the formation of chiral pinwheel heterostructures from symmetric molecules, combining experimental STM imaging with theoretical calculations to understand their structure and charge transfer.

Findings

Chiral pinwheel structures formed from C60 and pentacene.

High agreement between observed and predicted chiral angles.

Charge transfer occurs from C60 to pentacene in the heterostructures.

Abstract

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 -- {\it chiral}. Pn was deposited on Cu(111) to monolayer coverage, producing the random-tiling ($R$) phase as previously described. Atop $R$-phase Pn, post-deposited 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 (STM) 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.