Selective and Competitive Adsorptions of Guest Molecules in Phase-Separated Networks

The formation of crystalline multicomponent 2D lattices, containing more than two different organic molecular building blocks, has been rarely achieved because optimized recognition and selection processes require us to achieve the targeted multicomponent surface confined patterns. In this Article, we show that tetraacidic azobenzene (NN4A) and 1,3,5-tris(10-carboxydecyloxy)-benzene (TCDB) molecules can exclusively form 2D phase-separated nanoporous networks via hydrogen bonds between carboxyl groups at the liquid–solid interface, which have two types of cavities with different size and symmetry. These networks can serve as organic templates for the accommodation of fullerene (C60), coronene, and copper(II) phthalocyanine (CuPc) molecules. The experimental and calculated results indicate that coronene can be immobilized in the cavities formed by both NN4A and TCDB, whereas CuPc can be immobilized only in the cavity formed by TCDB and C60 can be immobilized only in the cavity formed by NN4A. Moreover, in the phase-separated networks, the coronene can be preferentially immobilized in NN4A. These results could benefit the studies on highly selectively molecular recognition and separation

Photo-Induced Polymerization and Isomerization on the Surface Observed by Scanning Tunneling Microscopy

In this paper, an azobenzene derivative containing two diacetylene groups is synthesized and its self-assembly at a surface investigated using scanning tunneling microscopy (STM). Both the azo-benzene and diacetylene groups are photoactive, and the results show that surface assemblies of the targeted compound undergo polymerization following irradiation at 254 nm and reversible isomerization following alternating irradiation at 365 nm and with visible light. This is the first report of a STM investigation observing both photopolymerization and photoisomerization simultaneously for the same molecular assembly at an interface. The target molecule allows one to induce sequential and reversible structural changes to surface assemblies via multiple optical treatments, and is thus of both fundamental interest for surface science and engineering. These results provide experimental and theoretical guidance for the fabrication of future molecular optoelectronic devices

Triphenylene Substituted Pyrene Derivative: Synthesis and Single Molecule Investigation

A novel donor–acceptor material based on pyrene derivative with two substituted triphenylenes (Py-TP2) is synthesized via the Sonogashira coupling reaction. The structure and physical chemistry properties of the target molecule have been discussed, ranging from the traditional ¹H NMR and high-resolution mass spectroscopy (HRMS), over UV and PL spectra, and to the surface science research. The results revealed that the Py-TP2 molecule shows a narrowed energy gap between LUMO–HOMO and a bathochromic shift of 27 nm in the solid state as compared to that in solution, which is important for its practical applications in optoeletronic devices. Moreover, combined with DFT calculations, our STM results clearly show that the Py-TP2 molecule assembled into a stable long-ranged zigzag structure on HOPG surface. The interesting results in this contribution will boost the physical chemistry study of other functional materials under such methods