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.

We describe herein that the self-assembled nanoobjects based on pyrimidinylene-phenylene macrocycles, 1 and 2, which possess the capability to respond to acid-stimuli by proton binding, can undergo reversible transformation of self-assemblies and fluorescence switching by protonation-deprotonation.

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In the title complex, [Pt(C15H11N4O)Cl3]·CH3CN, the PtIV ion adopts a distorted octa­hedral coordination geometry defined by a tridentate cyclo­metalated NCN ligand and three Cl atoms. In the crystal, individual mol­ecules are aggregated into a three-dimensional network by C—H⋯Cl hydrogen-bonding inter­actions and π–π stacking inter­actions between the tridentate ligands, the shortest ring centroid–centroid distance being 3.613 Å.

LI, R.; ZHANG, D.; HU, J.; XIAO, D.; LI, X.; XIANG, Y.; JIN*, W.; Tetrahedron 71 (2015) 47, 8871-8875, http://dx.