Size-Selective Recognition by a Tubular Assembly of Phenylene–Pyrimidinylene Alternated Macrocycle through Hydrogen-Bonding Interactions

Abstract

Study of artificial tubular assemblies as a useful host scaffold for size-selective recognition and release of guest molecules is an important subject in host-guest chemistry. We describe well-defined self-assembled nanotubes (NT6mer) formed from π-conjugated m-phenylene-pyrimidinylene alternated macrocycle 16mer that exhibit size-selective recognition toward a specific aromatic acid. In a series of guest molecules, a size-matched trimesic acid (G3) gives inclusion complexes (NT6mer⊃G3) in dichloromethane resulting in an enhanced and red-shifted fluorescence. (1)H nuclear magnetic resonance (NMR) titration experiments indicated that the complex was formed in a 1:1 molar ratio. Density functional theory (DFT) calculations and the binding constant value (K = 1.499 × 10(5) M(-1)) of NT6mer with G3 suggested that the complex involved triple hydrogen-bonding interactions. The encapsulated guest G3 molecules can be readily released from the tubular channel through the dissociation of hydrogen bonding by the addition of a polar solvent such as dimethylsulfoxide (DMSO). In contrast, 16mer could not form self-assembled nanotubes in CHCl3 or tetrahydrofuran (THF) solution, leading to weak or no size-selective recognizability, respectively.

Controlled Construction of an Exquisite Three-Component Co-assembly Supramolecular Structure at the Liquid–Solid Interface

“…The host molecule 1 6mer is a shape-persistent macrocycle with a large macrocyclic cavity and rich flexible long alkoxy side chains; these features make it an attractive candidate for constructing a stable host template with a nanoporous configuration that can be further used to host a variety of guest molecules. As previously reported, 2D porous networks self-assembled by 1 6mer were successfully obtained on the solid surface. , In this paper, we demonstrated the construction of an exquisite three-component co-assembly structure (1 6mer –COR–C 60 ) by adding COR and C 60 guest molecules into the 1 6mer host template. Through STM observations and DFT calculations, we found that the adding sequence of the guest molecules on the base of the 1 6mer host template plays a decisive role in the generation of the 1 6mer –COR–C 60 structure.…”

“…CHCl 3 , tetrahydrofuran (THF), trifluoroacetic acid (TFA), and 1-phenyloctane solvents were purchased from Aldrich. The 1 6mer host molecule was prepared according to previously reported procedures. , Coronene (COR) and C 60 fullerene guest molecules were purchased from Acros (chemical structures are shown in Scheme ). The solutions for the STM experiment were obtained by dissolving the host or guest molecule in a specific solvent.…”

Reversible transformation of self-assemblies and fluorescence by protonation–deprotonation in pyrimidinylene–phenylene macrocycles

“…More recently, we have reported that macrocycle 1 could self-assemble into welldefined nanotubes via p-p interactions in dichloromethane, which showed precision size-selective recognition toward trimesic acid (TMA) and formed an inclusion complex through hydrogenbonding interactions. 4 In the present work, we described that selfassemblies based on the pyrimidinylene-phenylene macrocyclic skeleton could interact with strong acids by protonation in the solution, which caused the disassembly or transformation of the self-assemblies through electrostatic repulsions and changes in planarity of macrocyclic backbones. Their morphologies were tuned back to the original state through simple deprotonation by addition of a base into the solution to recover p-p forces.…”

“…These changes were quite different from the phenomena in the previous work that the broad aromatic peaks of 1 NT remained and the proton signal of the pyrimidine ring disappeared with increasing addition of TMA. 4 On the other hand, fluorescence spectral changes were not observed when CF 3 COOCH 2 CH 3 , an esterification product of TFA, was added into the CH 2 Cl 2 solution of 1 NT (Fig. S2, ESI †).…”

“…S4, ESI †), as an example with six protons, showed the saddle-shaped structure, which twisted in a slightly greater degree than original macrocycle 1 alone. 4 Thus, it is rationalized that the disassembly of 1 NT was due to the electrostatic repulsions 8 between the charged skeletons of the macrocycle by protonation of nitrogen atoms in the pyrimidine ring and the changes in the planarity of the backbones before and after the protonation. Interestingly, after the treatment of the above 1 p with NaOH (in MeOH, 1 Â 10 À2 mol L À1 ), the TEM micrograph showed that the nanotubes reassembled (Fig.…”