Self-assembly of chiral amphiphiles with π-conjugated tectons into one-dimensional helical nanostructures offers great potential applications in the biological,physical,and material sciences.In this review,the recent development of supramolecular self-assembly of chiral amphiphiles with π-conjugated tectons has been discussed on the basis of experimental exploration by elegantly utilizing cooperative noncovalent forces such as π-π stacking,hydrophobic interaction,hydrogen bond and electrostatic interaction,and the potential applications of these self-assembled helical nanostructures in chiral recognition,asymmetric catalysis,electrical conduction,switchable interfaces and soft template for the fabrication of one-dimensional hard materials are described by a representative example.Meanwhile,some scientific and technical challenges in the development of supramolecular self-assembly of chiral amphiphiles with π-conjugated tectons are also presented.It is hoped that this review can summarize the strategies for self-assembling soft nanomaterials by using chiral amphiphiles with π-conjugated tectons,and also as a guideline for design functional nanomaterials for various potential applications.
Amino acids are basic units to construct a protein with the assistance of various interactions.During this building process,steric hindrance derived from amino acid side groups or side chains is a factor that could not be ignored.In this contribution,adsorption behaviors of C-terminal amino acid derivatives with amino acid residues fused in 3,4,9,10-perylenetetracarboxylic dianhydride were investigated by scanning tunneling microscopy(STM)and density functional theory(DFT)calculations at various liquid/solid interfaces.STM results at 1-phenyloctane/HOPG interface show that N,N'-3,4,9,10-perylenedicarboximide(GP)and N,N'-methyl-3,4,9,10-perylenedicarboximide(AP)formed linear and herringbone structures,respectively.The driving force could be attributed to different H-bonding sites induced by steric hindrance at side groups.N,N'-Benzyl-3,4,9,10-perylenedicarboximide(PP)generates both linear and herringbone structures because steric hindrance changes the H-bonding sites between PP molecules,whereas N,N'-isopropyl-3,4,9,10-perylenedicarboximide(LP)failed to be imaged because of strong steric hindrance coming from larger side group.To further investigate the impact of steric hindrance,we utilized octanoic acid(OA)as solvent to capture the adsorption details of LP and PP.We found that OA molecules drag PP and LP molecules in a different direction to generate linear structure,impeding the molecular rotation.The structure–solvent relationship shows that the steric hindrance is brought by the large side group,which makes it easier to recognize OA molecules at the interface.These results demonstrate that steric effect plays a significant role in altering interaction sites of the compounds during the adsorption process at the liquid/solid interface.
Yunzhi XieChunhua LiuLinxiu ChengYulan FanHuifang LiWei LiuLei ZhuXun LiKe DengQingdao ZengShoufa Han
We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.
The precise localization of organic molecules in controllable positions is an important step towards constructing functional nanostructures via the bottom-up strategy. Herein, supramolecularly organized C70-fullerene assemblies on macrocycle-modified surfaces were investigated using scanning tunneling microscopy （STM） in combination with theoretical calculations. The results revealed that an up-assembly of C70-fullerene adlayers was successfully formed on top of the bottom macrocycle arrays. Density functional theory （DFT） calculations confirmed that the macrocycle networks along with the co-adsorbed solvent 1-phenyloctane served as a selective template for trapping C70-fullerene molecules in the spectral sites and acted as a support for the C70-fullerene molecules. The periodical distribution of the C70-fullerene molecules should facilitate understanding of the strong dependence of the arrangement of C70-fullerene upon the specific interactions （apart from spatial recognition） derived from modification of the sub-monolayers.
The formation of coordinated dimeric complexes bridged by axial ligands on surface is observed with the help of a 1,3,5-tris（10-carboxydecyloxy）benzene（TCDB） template through scanning tunneling microscopy（STM）. STM images of molecular adlayers of zinc tetraphenylporphyrin（Zn TPP）, zinc phthalocyanine（Zn Pc）, and their mixture are reported. Zn TPP and Zn Pc can spontaneously form highly an ordered structure with a 1：1 molar ratio, which is different from that of individual Zn Pc. The coordinated bimolecular complexes bridged with axial ligands, simply as Zn Pc–DPP–Zn TPP and Zn Pc–DPE–Zn Pc, are presented and the corresponding surface structures are compared. Zn Pc and Zn TPP can be connected by an axial ligand DPP and formed assembled structures out of surface. Two types of arrays with entirely new structure are obtained for the Zn Pc–DPE–Zn Pc complex. These bridged hybrid complexes provide an example of design of self-organized crystals on the basis of coordination through non-covalent interactions.
Yan-Fang GengShi-Li WuJing XuHong-Liang DaiXiao-Kang LiKe DengQing-Dao Zeng
Individual titanyl phthalocyanine(TiOPc)molecules on ultrathin sodium chloride striped films grown on Cu(110)exhibit two different topographies with 8-lobes and 6-lobes when imaged by scanning tunneling microscopy(STM).Direct images of the molecular orbitals of the molecules with 8-lobes are obtained,indicating that the electronic structure of the TiOPc molecule are decoupled from the metallic substrate.For the TiOPc molecule with 6-lobes,the STM images at negative and positive bias polarities show the same structures as 2-fold symmetry except for the 90°rotation with respect to each other.This phenomenon may be attributed to the splitting of the two former degenerate lowest unoccupied molecular orbitals due to the negative charging of the molecule.The identification of the molecular orbital splitting on the ultrathin insulating layer could deepen the understanding of the intrinsic properties of semi-conducting molecules.
