A series of entangled MOFs constructed from flexible dipyridyl piperazine and rigid dicarboxylate: interpenetration, self-penetration, and polycatenation

By employing a flexible dipyridyl piperazine and a rigid linear dicarboxylate, four MOFs with different entangled structures involving a 3D inclined polycatenane and a 3D self-penetrated framework incorporating cyclic [3]catenane were isolated.

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.

Variation of topologies and entanglements in metal–organic frameworks with mixed tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide and dicarboxylate ligands

Six metal–organic frameworks with variation of topologies and entanglements have been successfully synthesized with mixed tris[4-(1H-imidazol-1-yl)phenyl]phosphine oxide and dicarboxylate ligands.

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.

Formation of a Dicopper Platform Based Polyrotaxane Whose "String" and "Bead" Are Constructed from the Same Components

The combination of the dicopper platform [Cu2(L)2(THF)2] (1·2THF), where H2L is 1,1'-(1,3-phenylene)-bis-4,4-dimethylpentane-1,3-dione, and 1,4-bis(4-pyridyl)piperazine (bpp), afforded the first example of a one-dimensional polyrotaxane {[(1)(μ2-bpp)][(1)2(bpp)2]}n whose "string" and "bead" are constructed from the same components. The bead of stoichiometry [(1)2(bpp)2] has a large rectangular cavity of dimensions 7.40 × 15.64 Å and is threaded onto a stair-like string of composition [(1)(μ2-bpp)]n. The formation of the polyrotaxane is driven by π-π stacking between the string and the beads with precise electronic and steric complementarity between these components. A pathway for the formation of the polyrotaxane is proposed.

Chiral crystallization and optical properties of three metal complexes based on two non-centrosymmetric tripodal ligands

Chiral coordination polymers have attracted much attention due to their special properties and significant applications. In this work, we synthesized two non-centrosymmetric ligands, N,N-bis(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)aniline (DIMPPA) and N-(4-(1H-imidazol-1-yl)phenyl)-4-(pyridin-4-yl)-N-(4-(pyridin-4-yl)phenyl)aniline (MIDPPA), via structural modification of two reported centrosymmetric ligands; after that achiral → chiral induction occurred in the construction of three coordination polymers namely {[Cd(DIMPPA)(5-OH-bdc)](H2O)}n (1), {[Co(DIMPPA)(5-OH-bdc)](H2O)}n (2) and {[Cd2(MIDPPA)2(D-ca)2(H2O)2](H2O)5}n (3), when replacing the reported centrosymmetric ligands with non-centrosymmetric ligands (5-OH-H2bdc = 5-hydroxyisophthalic acid, D-H2ca = D-camphoric acid). Isostructural complexes 1 and 2 exhibit chiral 2D → 3D frameworks with the coexistence of polyrotaxane and parallel polycatenation features. Complex 3 shows two-fold interpenetrating 3D chiral architecture with cds-type topology. The luminescence emissions of both complexes 1 and 3 are mostly assignable to the internal π→π* electron transition in DIMPPA and MIDPPA, respectively. Complex 3 can satisfy the fundamental requirement of second-order nonlinear optical materials.

A series of MOFs based on a triangular tri(4-pyridylphenyl)amine ligand combined with carboxylate or nitrate auxiliary ligands

A series of new metal–organic frameworks based on a triangular tri(4-pyridylphenyl)amine (TPPA) ligand that possess novel structures and features have been successfully synthesized and structurally characterized in detail.

Diverse topologies of seven d10 coordination polymers constructed from a long ligand and different carboxylates

Seven d¹⁰ coordination complexes exhibiting diverse architectures from 1D chain to 3D entangled frameworks based on long flexible 1,10-bis(1,2,4-triazol-1-yl)decane and different carboxylate anions have been synthesized and characterized by single-crystal X-ray diffraction analyses.

Poly[diaqua-[μ-1,4-bis-(1H-imidazol-1-yl)benzene-κ(2)N(3):N(3')](μ-fumarato-κ(2)O(1):O(4))nickel(II)]

In the title compound, [Ni(C₄H₂O₄)(C₁₂H₁₀N₄)(H₂O)₂]_n, the Ni^II ion has a distorted octa­hedral coordination geometry. The asymmetric unit is composed of an Ni²⁺ ion, located on a twofold rotation axis, one half of a 1,4-bis­(1H-imidazol-1-yl)benzene (BIMB) ligand and one half of a fumarte (fum²⁻) dianion, both ligands being located about inversion centers, and a coordinating water mol­ecule. The Ni^II ions are linked by two BIMB ligands and two fum²⁻ dianions, forming a four-connected layered structure parallel to (010) with a 4⁴-sql topology. Within each layer, there are rhombic grids with dimensions of ca 13.5 × 9.0 Å and approximate angles of 109 and 70°. The crystal packing features a two-dimensional → two-dimensional parallel/parallel interpenetration in which one undulating layer is catenated to another equivalent one, forming a new bilayer. Moreover, the entangled two-dimensional layers are connected by O—H⋯O and C—H⋯O hydrogen bonds, generating a three-dimensional structure.