Selective and competitive adsorption behaviors of guest molecules in donor-acceptor conjugated macrocycles networks on liquid/solid interface

The selective competitive adsorption of guest molecules C-70 and coronene (COR) in the electron donor-acceptor conjugated macrocycles host systems were investigated by means of scanning tunneling microscope (STM). The assembled structures of macrocycle molecules 3B2A and 4B2A were thermodynamically stable. After introducing C-70 molecules into the host systems, C-70 molecules were immobilized into the cavities of macrocycles. As a result, new kinds of complexes 3B2A/C-70 with 3B2A: C-70= 1: 1 and 4B2A/C-70 with 4B2A: C-70= 1: 2 were formed. However, these balance were interrupted after adding the COR molecules into the systems. All the C-70 molecules were replaced by COR molecules. Interestingly, the COR molecules were immobilized not only in the cavities of macrocycles, but also in the voids formed through alkyl chains provided by the adjoining macrocycles molecules. Such synergetic responses lead to the formation of the complexes of 3B2A/COR with 3B2A: COR= 1: 3 and 4B2A/COR with 4B2A: COR= 1: 5. Furthermore, these complexes were identical to the binary structures formed by depositing COR molecules to the pure macrocycle patterns. Density functional theory (DFT) calculations had been performed to reveal the formation mechanism of the different assemblies. This work may provide a useful strategy for two dimensional molecular recognition and separation.