Qingdao Zeng

Molecular Superlattices Induced by Alkyl Substitutions in Self-Assembled Triphenylene Monolayers

The configuration of the superlattices, formed from liquid-crystalline molecules on a graphite surface, are controllable through their alkyl substituents. This control may be attributed to the interplay of molecular steric interaction and the 2 D crystallization of alkyl chains. Two such lattices, as observed by STM, are shown in the accompanying graphic (C12- and (inset) C14-substituted molecules).

Self-assembled two-dimensional hexagonal networks

A new compound, 1,3,5-tris(carboxymethoxy)benzene, which forms infinite two-dimensional hexagonal networks, has been synthesized. Its self-assembly behavior at gas–solid interfaces has been studied by scanning tunneling microscopy.

Photoinduced organic nanowires from self-assembled monolayers

The self-assembled diacetylene molecular monolayer was prepared on highly oriented pyrolitic graphite and observed by scanning tunneling microscopy. Upon applying ultraviolet irradiation, the self-assembled conjugated polydiacetylene nanowires resulting from photoinduced topochemical reaction of diacetylene molecules were obtained. Control of the spacings between nanowires was achieved by a simple coadsorption method. The result presented here may supply a general method to obtain spacing-controllable organic nanowires.

Binding modes of thioflavin T molecules to prion peptide assemblies identified by using scanning tunneling microscopy.

The widely used method to monitor the aggregation process of amyloid peptide is thioflavin T (ThT) assay, while the detailed molecular mechanism is still not clear. In this work, we report here the direct identification of the binding modes of ThT molecules with the prion peptide GNNQQNY by using scanning tunneling microscopy (STM). The assembly structures of GNNQQNY were first observed by STM on a graphite surface, and the introduction of ThT molecules to the surface facilitated the STM observations of the adsorption conformations of ThT with peptide strands. ThT molecules are apt to adsorb on the peptide assembly with β-sheet structure and oriented parallel with the peptide strands adopting four different binding modes. This effort could benefit the understanding of the mechanisms of the interactions between labeling species or inhibitory ligands and amyloid peptides, which is keenly needed for developing diagnostic and therapeutic approaches.

The two-dimensional self-assembled n-alkoxy-substituted stilbenoid compounds and triphenylenes studied by scanning tunneling microscopy

Abstract We present a comparison of the assembling behavior of two series discotic molecules, n -alkoxy-substituted stilbenoid compounds ( E , E , E )-1,3,5- Tris [2-(3,4,5-trialkoxyphenyl) ethenyl] benzenes ( n TEB, n =12, 14, 16 and 18) and n -alkoxy-substituted triphenylenes, 2,3,6,7,10,11-hexakisalkoxytriphenylenes (H n T, n =9, 12, 14, 16, 18 and 20), on highly oriented pyrolytic graphite surface using scanning tunneling microscopy. Characteristic two-dimensional self-assembly structures, hexagonal structures and linear array structures, were observed with different alkyl chain length for both series of molecules. While linear lamellae structure prevails for long alkyl substituted species of both series, the hexagonal assembly pattern differs significantly. It was evident that 12TEB develops center-void hexagonal structures and H12T adopts center-filled hexagons. The difference of the assembling structure could be attributed to the steric effect associated with molecular cores.

Bipyridine conformations control the solid-state supramolecular chemistry of zinc(II) phthalocyanine with bipyridines

Two H-shaped supramolecular complexes (C32H16N8Zn)2·(C12H12N2)·0.96H2O (1), (C32H16N8Zn)2·(C12H10N2)·(DMF)2 n (2), and one T-shaped supramolecular complex C32H16N8Zn·C13H14N2 n (3) have been prepared from zinc(II) phthalocyanine with 1,2-bis(4-pyridyl)ethane (bipy-eta), 1,2-di(4-pyridyl)ethylene (dipy-ete) or 1,3-di(4-pyridyl)propane (dipy-pra), respectively, and characterized by single-crystal X-ray diffraction, electronic absorption spectra and fluorescence spectra; the conformation of the bipyridines plays an important role in the assembly processes.

Polymeric hydrogen-bonded supramolecules by self-assembling of adamantane derivatives with bipyridines

Eight new supramolecular structures have been prepared by 4,4′-(1,3-adamantanediyl)diphenol (ADP), 1,3-adamantanedicarboxylic acid (ADC) and/or 1,3-adamantanediacetic acid (ADA) with bipyridine bases 1,2-di(4-pyridyl)ethylene (dipy-ete), 1,2-bis(4-pyridyl)ethane (bipy-eta), 4,4′-dipyridyl sulfide (dipy-sul), 4,4′-dipyridyl disulfide (dipy-dis) and 4,4′-dipyridyl N,N′-dioxide (dipy-dox). These molecular complexes are (ADP)·(dipy-ete) n 1, (ADP)·(dipy-sul) n 2, (ADP)·(dipy-dox) n 3, (ADC)·(dipy-ete) n 4, (ADC)2·(bipy-eta) n 5, (ADC)·(dipy-dis) n 6, (ADA)·(dipy-ete) n 7, (ADA)·(bipy-eta) n 8, respectively. Their crystal structures have been determined by single-crystal X-ray diffraction. All these molecular complexes exhibit supramolecular structures via O–H⋯N or O–H⋯O hydrogen bondings. 1, 2, 3, 4 and 6 generate zigzag chain structures. 5, 7 and 8 form 1-D linear chain structures.

STM observation of 1,3,5-triazines bearing rod-like benzeneazonaphthalene moieties monolayers self-assembled on graphite surface

A series of 1,3,5-triazines incorporating benzeneazonaphthalene moieties have been synthesized and STM observations have clarified the geometrical configuration of the self-assembled molecules on a graphite surface.

Atomic force microscopy of the topochemical photopolymerization of diolefin crystals

The formation of regular nanostructures by photopolymerization of three diolefin derivative crystals, P2VB, DSP, and p-CPAEt, is investigated using atomic force microscopy (AFM) and known crystal packing data. AFM reveals that the crystal face (100) and (010) of P2VB exhibit volcanoes, whereas (100) and (010) of DSP give floelike structures. The main face and long side face of p-CPAEt give rise to volcanoes. All of those are guided by the crystal structure. Molecular interpretations of the AFM features of P2VB and DSP are given.

Structure of self-assembled monolayer of NPAN on Au(111) electrode

Adsorption of 4-(4-nitrophenylazo)-l-naphthol (NPAN), an azobenzene derivative, on Au(111) has been investigated in aqueous HC1O4 solution by using the cyclic voltammetry and scanning tunneling microscopy (STM). The molecule is found to form a stable monolayer on the electrode with a (6×4) structure relative to the underlying Au(111) lattice. Cyclic voltammograms show that the redox reactions occurring on the electrode are retarded by the formation of the monolayer. A structural model is proposed for the two-dimensional adlayer.