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

Abstract

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.

Organic multicomponent microparticle libraries

“…Specifically, a series of 3 / 4 stock solutions with variable molar ratio were injected into ethanol/H 2 O (v/v) mixtures to induce their co-assembly. As described previously 30 , the binary microparticles would undergo structural transformation from straight rods to twisted ribbons upon increasing the content of 4 (Supplementary Fig. 7 ).…”

“…(ii) The constituent materials with different structural compatibility enable the construction of multicomponent assemblies with diverse phase behavior. For instance, we found that the combination of 3 and 4 can assemble into binary alloy ribbons with variable composition 30 . Moreover, the material combination of 1 and 2 which show a similarity in molecular configuration and size can also form two-component alloys by substitution of 1 with a small molar ratio of 2 52 , 53 .…”

“…4c, d ), due to their highly similar π-conjugated molecular skeletons. Moreover, the molecular structure of 3 and 4 has a nearly identical length ( L 3 = 18.332 Å; L 4 = 18.361 Å) and relatively small differences in width ( W 3 = 8.905 Å; W 4 = 11.411 Å), thus facilitating the substitution of 3 by 4 into 34 alloys 30 , 31 . By means of the crystallographic data of 3 , we simulated the molecular packing mode of 34 alloys and found that 4 molecules would randomly occupy the lattice sites of 3 host (Fig.…”

“…15a . Well-matched energy levels as well as suitable intermolecular distances between 3 and 4 enable high-efficiency energy transfer (ET) process in 34 alloy assemblies, leading to tunable emissions toward 4 30 . Notably, compounds 1 and 2 also possess similar molecular packing patterns and effective energy level matching (Supplementary Fig.…”

“…Compared to inorganic analogs, organic microparticles and nanoparticles made of multiple π-conjugated molecules have also drawn considerable attention due to their promising performance in photonics and electronics applications 22 – 39 . Until now, relevant studies in this context mainly focus on binary mixtures that exist in an ordered (host–guest complexes 22 – 24 , cocrystal 25 – 29 ) or random stacking fashion (alloy phase 30 – 33 ) or in a phase separated state 34 – 39 . For instance, assemblies made of alloys of two structurally similar oligo-phenylenevinylenes (OPVs) exhibit tunable lasing action upon adjusting the stoichiometric ratio between them 40 .…”