STM Exploration of the Diverse Polymorphs for Tri‐Substituted Anthraquinone Derivatives via Alkyl Chain Elongation

Abstract

solvent, [ 3d,10 ] concentration, [ 5,11 ] voltage, [ 12 ] and temperature, [ 13 ] are considered as powerful methods to regulate the assembled patterns. Moreover, it is well known that in some circumstance, even tiny change of the structural units in a molecule can result in dramatic change of the nanopatterns. Hence for the alkyl chain substituted system, it is easy to change the networks by increasing or decreasing the chain length.The emergence of chain-length effect is often associated with the van der Waals interactions between the interdigitated alkyl chains and the molecule-substrate. The self-assembly of dehydrobenzo[12]annulene derivatives has been widely probed by De Feyter et al., [ 3e,14 ] and received extensive attention. By tuning the chain length, different nanostructures, i.e., honeycomb, linear, Kagomé, zigzag, polymer, etc., were obtained, and alkyl chain interdigitation was proved to act a vital function on stabilizing the networks. Furthermore, self-assembly is associated with the gain in system energy contributed from both enthalpy and entropy difference between the initial and fi nal states. [ 13b,15 ] Therefore, the appearance of structural diversity to the system as the chain length changes has direct relation with the change of Gibbs free energy. Miyake et al. systematically reported the 2D supramolecular structures of a series of N , N ′-bis( n -alkyl)-naphthalenediimides (NDIs) that the chain length spans from C 3 to C 18 . [ 16 ] They found that C 3 -and C 4 -NDIs adopted lamellar structures, C 4 -to C 12 -NDIs showed honeycomb structure, and the lamellar patterns were observed again when the chain is longer than C 12 . The drastic structural change was explained by the balance of entropy and enthalpy terms. On the whole, the self-assembly process is under both kinetic and thermodynamic control. Even though the relationship between the molecular confi gurations and the alkyl chain length has gained attention from lots of research groups and been extensively explored, it still needs further study from the viewpoint of its structural diversity, the formation mechanism, and effi cient regulation.In this contribution, we systematically investigate the formation of nanostructures of 1,2,4-tri( n -alkoxy)-9,10-anthracenedione (1,2,4-A-3OC n , Scheme 1 , synthesis is shown in Supporting Information as Figures S1 and S2) on the highly Fabrication of structural diversity in self-assembled monolayers has gained considerable attention, not only due to its signifi cance in interface science but also because of its potential application in designing nanomaterials. Here, systematical characterization of the molecular self-assembly of tri-substituted anthraquinone derivatives at the 1-octanoic acid/HOPG interface is provided. Different nanopatterns of Linear I, Butterfl y-like, and Linear II are recorded for 1,2,4-A-3OC 16 by gradually changing the solution concentration. Diverse polymorphs are also obtained by alkyl chain elongation, meaning that 1,2,4-A-3OC 15,17,18 adopt Dimer-Linear, Linear...

Effects of alkyl chain number and position on 2D self-assemblies

“…S1 †). As we previously reported, [24][25][26][27][28] monosubstituted anthraquinone derivatives 1-A and 2-A can selfassemble into linear structures, denoted as linear I ( Fig. 1a) and linear II ( Fig.…”

“…We have previously reported self-assemblies of anthraquinone derivatives with one, 24,25 two, 26 and three side chains. 27,28 These studies emphasized the diverse assembled structures induced by changing the alkyl chain lengths. However, self-assemblies of anthraquinone derivatives with different numbers of alkyl chains in different positions have not been explored and compared, and their potential mechanisms have yet to be discussed.…”

One Chain Fixed, One Chain Modified by −C5H10–: An Efficient Strategy on Fabricating Structural Diversity for 2D Self-Assembly

“…Disordered self-assembly networks are always observed for molecules with long side chains, and this phenomenon has been reported several times. 19,28,31,38 The longer alkyl chain causes stronger molecule−substrate interaction and thus can restrict the adsorption−desorption behavior and in-plane mobility of the molecules.…”

Tale of Alkyl Chains: Chain-Length Effect-Directed Formation of Complex Self-Assembly Behaviors at the Liquid/Solid Interface for Unsymmetrically Substituted Fluorenone Derivatives

“…π-Conjugated molecules can self-assemble into monolayers on the surface via physisorption, with their largest face flatly lying on the substrate, which is facilitated for monitoring the intermolecular bonding types. , As has been previously reported, hydrogen bonds, van der Waals (vdWs) interaction, dipolar interaction, and metal coordination are the common driving forces during the self-assembly process. − The assembled structures are sensitive to the change of experimental conditions; thus the solvent, concentration, temperature, substrate, and voltage are the factors that exert important roles on determining the self-assembly configurations. − Moreover, except for these factors, the chain-length effect also seems to be an efficient method on inducing structural diversity, owing to the possibility of regulating the molecule–molecule, molecule–solvent, and molecule–substrate vdWs interactions. ,− …”