A new 2D→2D interpenetrating polymer containing polyrotaxane- and polycatenane-like motifs: The tilt of local distortion axes for the magnetic behavior

Construction of 2D Interdigitated Polyrotaxane Layers and their Transformation to a 3D Polyrotaxane by a Photocycloaddition Reaction between Wheels

Following the pioneering work of Sauvage and Stoddart on rotaxanes, construction of higher dimensional polyrotaxanes in metal-organic frameworks (MOFs) via a modified protocol is challenging. We present the formation of a two-dimensional (2D) polyrotaxane and its conversion to a three-dimensional (3D) polyrotaxane MOF via a photoreaction between interdigitated "olefin wheels". For this purpose, a 2-fold entangled 2D MOF [Pb₂(bpp)(sdc)₂] (1), showing a 2D + 2D → 2D polyrotaxane motif, has been synthesized from the solvothermal reaction of lead(II) nitrate, 3,3'-stilbenedicarboxylic acid (H₂sdc) containing an olefin group, and 1,4-bis(4-pyridyl)piperazine (bpp). The single-crystal X-ray diffraction analysis of 1 revealed that the adjacent entangled 2D layers are interdigitated, with the separation of 3.72 Å between C═C bond pairs in adjacent layers satisfying Schmidt's criteria for the occurrence of a [2 + 2] photocycloaddition reaction. Irradiation of the single crystals of 1 under UV light resulted in formation of a 3D polyrotaxane, [Pb₂(bpp)(rctt-tccb)]_n (2), due to a [2 + 2] photocycloaddition reaction between two wheels via a single-crystal to single-crystal transformation. The photocycloaddition and partial thermal cleavage reaction between 1 and 2 were confirmed by ¹H NMR and powder X-ray diffraction (PXRD) in solution and the solid state, respectively. The present approach could contribute to the understanding of the construction of higher dimensional polyrotaxanes which are not accessible by the traditional routes.

A cadmium(II) coordination polymer with both polyrotaxane and polycatenane features constructed by a V-shaped semi-rigid ligand: synthesis and fluorescence properties

One of the most interesting phenomena in coordination polymers (CPs) is the co-existence of different interlaced motifs. However, CPs having two different interlaced motifs at the same time are still rare. Colourless block-shaped crystals of the two-dimensional polymer poly[[aqua(μ₂-naphthalene-2,6-dicarboxylato){μ₂-4,4'-[oxybis(4,1-phenylene)]dipyridine}cadmium(II)] monohydrate], {[Cd(C₁₂H₆O₄)(C₂₂H₁₆N₂O)(H₂O)]·H₂O}_n, (I), was synthesized under hydrothermal conditions by the self-assembly of 4,4'-[oxybis(4,1-phenylene)]dipyridine (OPY) with Cd^II in the presence of naphthalene-2,6-dicarboxylic acid (H₂ndc). Each Cd^II ion is six-coordinated by two N atoms from the pyridine rings of two OPY ligands and by four O atoms, three of which are from two ndc^2- ligands and one of which is from a water molecule. In (I), every two identical two-dimensional (2D) 6³ layers are interpenetrated in a parallel fashion, resulting in an interesting 2D→2D framework with both polyrotaxane and polycatenane characteristics. The extension of these sheets into a three-dimensional supramolecular net is via O-H...O hydrogen bonds. The solid-state photoluminescence properties of (I) are also discussed.

Synthesis, structures and magnetic properties of isoreticular polyrotaxane-type two-dimensional coordination polymers

The variable temperature magnetic properties have been investigated for two isoreticular polyrotaxane-type coordination polymers of Co(ii) with bent and two linear dinitrogen spacers.

Thermodynamically stable MOF showing a highly rare four-connected hxg-d-4-Cccm net with self-penetration, polyrotaxane, and polycatenane multi-features

Herein, we report the first case of MOFs showing the coexistence of self-penetration, polyrotaxane, and polycatenane multi-features.

Two isoreticular metal–organic frameworks with CdSO4-like topology: selective gas sorption and drug delivery

In this work, we have also investigated the binding mode of 5-FU to these frameworks, which provides an atomic level view of host–guest interactions.

Different interpenetrated coordination polymers based on flexible dicarboxylate ligands: topological diversity and magnetism

This work evidently indicates that the effect of the secondary ligands, molar ratios and geometric preferences of the metal centers are critical on the resulting entangled motifs.