Complex assembly from planar and twisted π-conjugated molecules towards alloy helices and core-shell structures

Integrating together two dissimilar π-conjugated molecules into controlled complex topological configurations remains a largely unsolved problem owing to the diversity of organic species and their respective different assembly features. Here, we find that two structurally similar organic semiconductors, 9,10-bis(phenylethynyl)anthracene (BA) and 5,12-bis(phenylethynyl)naphthacene (BN), co-assemble into two-component helices by control of the growth kinetics as well as the molar ratio of BA/BN. The helical superstructures made of planar and twisted bis(phenylethynyl) derivatives can be regarded as (BA)(x)(BN)(1−x) alloys, which are formed due to compatible structural relationship between BA and BN. Moreover, epitaxial growth of (BA)(x)(BN)(1−x) alloy layer on the surface of BA tube to form BA@(BA)(x)(BN)(1−x) core-shell structure is also achieved via a solute exchange process. The precise control over composition and morphology towards organic alloy helices and core-shell microstructures opens a door for understanding the complex co-assembly features of two or more different material partners with similar structures.