Hydrogen-Bonded Donor-Acceptor Arrays at the Solution-Graphite Interface

Effect of aromatic substituents on the H-bonded assembly of diketopyrrolopyrroles at solid-liquid interfaces

Hydrogen-bonded (H-bonded) self-assembly is a suitable approach for tailoring the solid-state packing and properties of organic semiconductors. Here we studied the H-bonded self-assembly of an important class of organic semiconductors, diketopyrrolopyrrole (DPP) derivatives, diselenophenylDPP (DSeDPP), dithiazolylDPP (DTzDPP), and dithienothiophenylDPP (DTTDPP), at solid-liquid interfaces using scanning tunneling microscopy (STM) and density functional theory (DFT). At the 1-octanoic acid/highly ordered pyrolytic graphite (HOPG) interface, DSeDPP and DTzDPP either co-assemble with the solvent via H-bonding between lactam and carboxyl groups or form homoassemblies through H-bonding between the lactam groups. However, DTTDPP forms two different homoassemblies involving H-bonding between lactam groups or weak H-bonding between the lactam group and the heteroaromatic ring. Enthalpic factors for the formation of homoassemblies and co-assemblies are investigated by evaluating the inter- and intramolecular interactions in the self-assembled lattices using DFT. A homoassembly with a twisted geometry of molecules with intermolecular π-interactions is only observed for DSeDPP. The absence of homoassembly with the twisted geometry of DTzDPP is attributed to the higher strain energy required to acquire out-of-plane twists in this molecule. Our study shows the profound effects aromatic substituents can impart in the supramolecular assembly of DPP molecules, which influences film morphology and hence its properties (e.g. charge transport).

Restructuring of Porphyrin Networks Driven by Self-Assembled Octanoic Acid Monolayer on Au(111)

We report time-dependent surface restructuring of bicomponent domain structures of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (H₂OEP) and cobalt(II) 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (CoOEP) (H₂/Co OEP) driven by self-assembled octanoic acid on the surface of Au(111). Scanning tunneling microscopy (STM) visualized molecular adsorption/desorption and rearrangement of supramolecular architectures in real-time in a solution of octanoic acid. We found that unique domain structures emerged at an initial state guided by adsorbed octanoic acid on the Au surface. Moreover, the desorption of octanoic acid occurred in solution, leading to the surface restructuring of porphyrin molecular networks. This molecular evidence is well-manifested in the time-dependent phase transitions, monitored by in situ STM.

Synthesis and photophysics of new pyridyl end-capped 3D-dithia[3.3]paracyclophane-based Janus tectons: surface-confined self-assembly of their model pedestal on HOPG

Once synthesized, these new tectons demonstrated both ionic and coordination bonding. Surprisingly, P forms a quasi-square self-assembly independently of the underlying HOPG lattice.

2D Co-crystallization of molecular homologues promoted by size complementarity of the alkyl chains at the liquid/solid interface

Co-crystallization of organic molecules is an important strategy for the fabrication of molecular materials. In this contribution, we investigated the mixing behavior of 5-(benzyloxy)-isophthalic acid homologues (BIC-Cn, n = 6, 8, 10, 12, and 14) at the liquid/solid interface using a scanning tunneling microscope. Deposition of the single component of BIC-Cn always results in typical honeycomb networks, whereas co-deposition of two BIC-Cn homologues leads to hybrid double-walled honeycomb networks or phase separation depending on the difference in the length of their alkyl chains. 2D co-crystallization can only be realized for BIC-C6/BIC-C10 or BIC-C8/BIC-C12 which have a four-methyl unit difference in their alkyl chains. The size complementarity of the alkyl chains in the two components suggests that it is responsible for the 2D co-crystallization, though hydrogen bonding contributes a lot both to the pristine honeycomb network and to the hybrid co-crystal. This result is of importance for understanding the role of van der Waals interaction and its interplay with hydrogen bonding in 2D co-crystallization.

Coordination-Driven Construction of Porphyrin Nanoribbons at a Highly Oriented Pyrolytic Graphite (HOPG)/Liquid Interface

Nanostructures were built at the solid/liquid interface by self-assembly and/or coordination bonds. Metalloporphyrins bearing two external coordination sites and long alkyl chains allowed the self-assembly of the compounds on highly oriented pyrolitic graphite. After addition of a metal ion, long transition-metal linked porphyrin nanoribbons were obtained and visualized by scanning tunneling microscopy. In these porphyrin ribbons electronic delocalization is possible through the d orbitals of the connecting metal ions.

Formation of multicomponent 2D assemblies of C 2v-symmetric terphenyl tetracarboxylic acid at the solid/liquid interface: recognition, selection, and transformation

We report on the two-dimensional self-assembly of C_2v-symmetric [1,1′:3′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (TPTA) at the solid/liquid interface by using scanning tunneling microscopy (STM). Two kinds of different self-assembly structure, i.e. a close-packed and porous rosette structure, are formed by TPTA molecules through intermolecular hydrogen bonds. When adding coronene (COR) as a guest into the TPTA assembly, structural transformation from a densely packed row structure to a rosette network structure is observed. It was found that two kinds of cavities with different sizes in the rosette network structure can be used to realize the selective co-adsorption of guest molecules with appropriate shape and size. Three-component 2D host–guest structures were successfully constructed by using 1,2,3,4,5,6-hexakis(4-bromophenyl)benzene (HBPBE) and copper phthalocyanine (CuPc) as guest molecules.

The formation process of multicomponent 2D assemblies of C_2v-symmetric terphenyl tetracarboxylic acid on a surface.

Dynamic Hierarchical Self-Assemble Small Molecule Structure Hexabenzocoronene for the High-Performance Anodes Lithium Ion Storage

This study examined the characteristics of small molecular structure nano-graphene in a dynamic hierarchical self-assembly and found that graphene is rearranged under its own pressure during dynamic aggregation and water ripples are formed by the d-spacing. The composition and structure were studied using a range of material characterization techniques. No covalent bonds were observed between molecules, and the self-assembled driving force was the only intermolecular interaction: Van der Waals' force in the intra-layer and π-π interactions between layers. The arranged-rearranged structures provided a range of lithium ion shuttle channels, including the space between layers and diffusing through the nanosheets, which decrease the diffusion distance of lithium ions remarkably and reduce the irreversible capacity of the battery.