The effect of multiple pairs of meta-dicarboxyl groups on molecular self-assembly and the selective adsorption of coronene by hydrogen bonding and van der Waals forces

The prediction of two-dimensional molecular self-assembly structures has always been a problem to be solved.The molecules with meta-dicarboxyl groups can self-assemble into a specific hexagonal cavity,which has an important influence on the prediction of molecular self-assembly structures and the application of functional molecules with meta-dicarboxyl groups.Two kinds of molecules with four pairs of meta-dicarboxyl groups,1,3,6,8-tet「akis(3,5-isophthalic acid)pyrene(H_(8)TIAPy)and 4′,4′",4′"",4""-(ethene-1,1,2,2-tetrayl)tetrakis(([1,1′-biphenyl]-3,5-dicarboxylic acid))(H8ETTB)molecules were chosen to observe the self-assembly behavior at the heptanoic acid/highly oriented pyrolytic graphite(HA/HOPG)interface.H8TIAPy molecules self-assembled into well-ordered quadrilateral structures and could be regulated into kagome networks with hexagonal pores by coronene(COR)molecules.H8ETTB molecules self-assembled into lamellar structures and transformed into acid-COR-acid-COR co-assembled structures at low concentration of COR solution and acid-COR dimer-acid-COR dimer co-assembled structures at high concentration of COR solution.The reason that H8ETTB molecules could not be regulated into hexagonal porous architecture was attributed to the steric hindrance by the similar length and width of H8ETTB molecules.The H8ETTB templates had stronger adsorption for COR than that of hexaphenylbenzene(HPB),regardless of the order of molecular introduction.

Advances in the study of the host-guest interaction by using coronene as the guest molecule

Host-guest chemistry in two-dimensional (2D) networks has gained much interest for the new functionalities and potential applications, such as separation technology, photogenic crystals and biomimetic surfaces. Nanoporous supramolecular networks are assembled by a range of non-covalent forces like hydrogen bonds, van der Waals interactions and coordinate bonds, to immobilize guest molecules of different sizes and shapes. In this review, we mainly presented the effect of coronene on the host-guest architecture. Coronene (COR) is chosen to be the promising guest molecule and it can embed, cover, or change the host networks in different host-guest systems. All of the research in the review was finished with assistance of scanning tunneling microscope (STM). These studies were called upon impose controlling on host-guest systems and revealed the behaviors of COR clusters as guest molecules.

The self-assembly and structural regulation of a hydrogen-bonded dimeric building block formed by two N-H…O hydrogen bonds on HOPG

The self-assembled behavior of an unsymmetric molecule(BCDTDA)with one imidazole group as center and benzoic acid group as functional group is studied,and the regulatory behaviors of coronene(COR)and three bipyridine derivatives(named BP,PEBP-C4 and PEBP-C8)on BCDTDA self-assembly structures are also investigated.Based on highly oriented pyrolytic graphite(HOPG)substrate,scanning tunneling microscopy(STM)is used to observe the variation of assembled behaviors at the solid-liquid interface.Because of the concentration effect,BCDTDA molecules can assemble into grids and Kagomés structures in the form of N–H…O hydrogen bonded dimers.BCDTDA molecules still maintain dimeric structures in the regulation of COR and BP molecules to BCDTDA self-assembly.However,PEBP-C4 and PEBP-C8 destroy the structure of the dimers,and form a variety of co-assembled structures with BCDTDA.Different guest molecules coordinate the host molecules differently,which makes the experiment more meaningful.Combined with density functional theory(DFT)calculation,the discovery of molecular interactions provides a promising strategy for the construction of functional nanostructures and devices.

Advances in self-assembly and regulation of aromatic carboxylic acid derivatives at HOPG interface

Aromatic carboxylic acid self-assembly has been a hot research field for many scientists due to its strong coordination ability and flexible coordination mode.The hydrogen bond formed between aromatic carboxylic acids is a strong intermolecular force and has directionality and saturation,which plays a very important role in the self-assembly and regulation of aromatic carboxylic acids.In this review,we introduce surface organization formed by aromatic carboxylic acids with the aid of scanning tunneling microscopy(STM).These two-dimensional structures include molecular templates,host-guest systems,and photo-isomerization structures.We also emphasize the thermodynamics and dynamics,which are important research topics of current and future study.

Adsorption of helical and saddle-shaped oligothiophenes on solid surface

The arrangement of oligothiophenes is essential for understanding the relationship between structure and properties particularly in the organic electronic field. The self-assembly behaviors of helical(TMS)2-[7]helicene(T1), naphthalene-cored double(TMS)2-[7]helicene(T2), and saddle-shaped cyclooctatetrathiophene(T3), its derivative α,α,α,α-tetraphenyl-cyclooctatetrathiophene(T4) on solid surface are firstly investigated by using a combination of scanning tunneling microscopy(STM) and density functional theory(DFT) calculation. 1,3,5-Tris(10-carboxydecyloxy)-benzene(TCDB) is selected to build flexible host networks to immobilize these oligothiophenes in order to capture their molecular adsorption images successfully. The observed monodisperse or polydisperse filling and long-range alignment of oligothiophenes are described based on the non-covalent interactions and commensurate structure between olihothiophene and cavity. We speculate that those molecularly defined alignments could lead to significantly understanding the application of such ordered monolayer in organic electronic devices.

Selective adsorption behaviors of guest molecules COR in the hexamer host networks at liquid/solid interface

Here,the selective adsorption behaviors of guest molecule COR in two hexamer host grids were investigated by means of scanning tunnelling microscope(STM).The assembled structures of small functional organic molecules TTBTA and TATBA were thermodynamically stable.Interestingly,the introduction of the guest molecule COR destroyed the original hexamer structure of TTBTA and combined with it to form a new triangular host-guest system.Different from TTBTA,the introduction of the guest molecule COR did not affect the six-membered ring structure of TATBA.Furthermore,the co-assembly structure of TTBTA/TATBA/COR was established and the guest molecule COR showed preferential adsorption to the TATBA host grid.Density functional theory(DFT)calculations had been performed to disclose the mechanism of the involved assemblies.