A set of terms, definitions, and recommendations is provided for use in the
classification of coordination polymers, networks, and metal–organic frameworks
(MOFs). A hierarchical terminology is ...recommended in which the most general term
is coordination polymer. Coordination networks are a subset of coordination
polymers and MOFs a further subset of coordination networks. One of the criteria
an MOF needs to fulfill is that it contains potential voids, but no physical
measurements of porosity or other properties are demanded per se. The use of
topology and topology descriptors to enhance the description of crystal
structures of MOFs and 3D-coordination polymers is furthermore strongly
recommended.
Coordination polymers (CPs) and metal-organic frameworks (MOFs) are among the most prolific research areas of inorganic chemistry and crystal engineering in the last 15 years, and yet it still seems ...that consensus is lacking about what they really are, or are not.
Polyrotaxane metal-organic frameworks (PMOFs) Yang, Jin; Ma, Jian-Fang; Batten, Stuart R
Chemical communications (Cambridge, England),
2012-Aug-18, Volume:
48, Issue:
64
Journal Article
Peer reviewed
Polyrotaxane metal-organic frameworks (PMOFs), a relatively rare branch of entangled networks, have received significant attention due to their unusual entanglement topologies. The PMOFs we described ...here are still at an early stage of development. This feature article summarizes the recent developments in structural types of PMOFs from our own group and others. We make some generalizations about the various classes of PMOFs, and develop the definitions and nomenclature of these entanglements, including classification into trivial and nontrivial polyrotaxanes, and limits on what constitutes a (nontrivial) polyrotaxane. Finally, the synthetic strategies toward the design and preparation of new PMOFs are elucidated.
In this feature article, we make some generalizations about the various classes of polyrotaxane metal-organic frameworks (PMOFs), and develop the definitions and nomenclature of these entanglements, including classification into trivial and nontrivial polyrotaxanes, and limits on what constitutes a (nontrivial) polyrotaxane.
Coordination polymers containing dicyanamide (N(CN)
2
−, dca) or tricyanomethanide (C(CN)
3
−, tcm) bridging ligands are described from the perspective of their structure and magnetism. The binary ...compounds α-M(dca)
2 form an isostructural series (M=Cr, Mn, Fe, Co, Ni, Cu) having a single rutile-like network that involves μ
1,3,5-dca bridging. They display quite diverse types of long-range magnetic order viz. canted-spin antiferromagnets (Cr, Mn, Fe), ferromagnets (Co, Ni, Cu). An up-to-date review is given of the diverse range of physical measurements made on the α-M(dca)
2 series together with interpretations for the different net exchange coupling and consequent 3D order. The doubly interpenetrating rutile network M(tcm)
2 series generally do not show long-range order except for a few members at very low temperatures. The ‘mixed’ self-penetrating network compounds M(dca)(tcm) do show long-range order (M=Co, Ni), albeit at lower
T
c values than for the M(dca)
2 parents. Modification of the M–dca networks is possible by incorporation of coligands into the structures. Ternary species of type M(dca)
2(L)
n
, where L is a terminal (e.g. pyridine, MeOH) or a bridging (e.g. pyrazine, 4,4′-bipyridine) coligand, display a diverse range of 1D, 2D and 3D structural types. With a few exceptions, the large number of compounds structurally characterised contain μ
1,5-dca bridging and display very weak antiferromagnetic coupling (
J<ca. −1 cm
−1), typical of this bridging mode. Compounds such as Mn(dca)
2(pyrazine) display a magnetic phase transition at low temperatures. This is also the case in the isostructural 2D layer compounds M(dca)
2(H
2O) · phenazine (M=Fe, Ni) which, perhaps not surprisingly, do not have coordinated phenazines but, rather, phenazines intercalated between layers of M(dca)
2(H
2O) in which μ
1,3,5 and μ
1,5-dca bridging exists. Anionic networks of types M(dca)
3
− and M(dca)
4
2− formed by templation around cations of the organic (e.g. Ph
4E
+, R
4N
+) or inorganic (M(2,2′-bipyridine)
3
2+) types are described. The latter display no magnetic interactions between the weakly antiferromagnetically coupled anionic sub-lattice and the paramagnetic cationic sub-lattice.
A distinct method, lanthanide(III)-doped pathway is for the first time utilized to replace lanthanide(III) MOFs for the access of MOF-based luminescent sensing of metal ions. The research results ...revealed that this strategy is highly effective and displays several outstanding features.
The use of an amino-pyridyl substituted beta -diketone, N-(2-pyridyl)-ketoacetamide (paaH), has allowed for the isolation of two new families of isostructural mononuclear lanthanide complexes with ...general formulae: Ln(paaH*) sub(2)(H sub(2)O) sub(4)Cl sub(3).2H sub(2)O (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5) and Y (6)) and Ln(paaH*) sub(2)(NO sub(3)) sub(2)(MeOH)NO sub(3) (Ln = Tb (7), Dy (8), Ho (9) and Er (10)). The dysprosium members of each family (3 and 8) show interesting slow magnetic relaxation features. Compound 3 displays Single Molecule Magnet (SMM) behaviour in zero DC field with an energy barrier to thermal relaxation of E sub(a) = 177(4) K (123(2) cm super(-1)) with tau sub(0) = 2.5(8) 10 super(-7) s, while compound 8 shows slow relaxation of the magnetization under an optimum DC field of 0.2 T with an energy barrier to thermal relaxation of E sub(a) = 64 K (44 cm super(-1)) with tau sub(0) = 6.2 10 super(-7) s. Ab initiomulticonfigurational calculations of the Complete Active Space type have been employed to elucidate the electronic and magnetic structure of the low-lying energy levels of compounds 2-5 and 8. The orientation of the anisotropic magnetic moments for compounds 2-5 are rationalized using a clear and succinct, chemically intuitive method based on the electrostatic repulsion of the aspherical electron density distributions of the lanthanides.
Entanglement is one of the most important features of coordination polymer frameworks and has attracted considerable attention due to its aesthetic and topological interest. Among entangled systems, ...interpenetrating frameworks represent an intriguing subset; however, there are few examples of materials containing very high levels of interpenetration. In this work a coordination polymer with 10(3)-srs topology, constructed from a star-like tridentate ligand, tri(4-imidazolylphenyl)amine, and Ag(I) ions, has been hydrothermally synthesized. It contains a record 54 interpenetrating networks.
An unexploited pentacarboxylate ligand, 2,5-bis(3',5'-dicarboxylphenyl)-benzoic acid (H5L), was designed and used for the preparation of metal organic material using Zn2+ as a node. The new compound, ...{(Me2NH2)Zn2(L)(H2O).0.5DMF}n (1) (DMF = dimethylformamide), has been synthesized and structurally characterized. The topology of the 5-connected anionic framework may be described as (44)(66) (Schlaefli symbol) based on {M2(CO2)5} molecular building blocks (MBBs) and L ligands in 1. It has been demonstrated that 1 can act as a fluorescent sensor for highly sensitive detection of nitroaromatics and Fe3+, with a detection limit of 0.54 ppm for 2,4,6-trinitrophenol (TNP) and 0.81 ppm for Fe3+. The possible emission quenching mechanism in the presence of nitroaromatics has been addressed by theoretical calculations.
Play ball! A family of discrete metallo‐supramolecular nanoballs (see picture) containing different divalent metals is produced by self‐assembly. These species have porous structures, similar to ...metal–organic frameworks. Stepwise desolvation results in bare metal sites which can be functionalized with organic molecules; the interball cavities show high affinity for hydrogen gas.
To systematically explore the higher‐dimensional network structures with mixed connectivity, a series of two‐dimensional (2D) and three‐dimensional (3D) metal–organic frameworks (MOFs) with unusual ...(3,6)‐connected net topologies are presented. These crystalline materials include {Mn(btza)2(H2O)2⋅2 H2O}n (1), {Zn(btza)2(H2O)2⋅2 H2O}n (2), {Cu(btza)2⋅H2O}n (3), and {Cd(btza)2⋅3 H2O}n (4), which have been successfully assembled through a predesigned three‐connected organic component bis(1,2,4‐triazol‐1‐yl)acetate (btza) with a variety of octahedral metal cores based on the modular synthetic methodology. The topological paradigms shown in this work cover the 2D CdCl2, 3D (42.6)2(44.62.87.102), and pyrite (pyr) types. That is, when properly treated with the familiar first‐row divalent metal ions, btza may perfectly furnish the coordination spheres for effective connectivity to result in diverse (3,6)‐connected nets. Beyond this, a detailed analysis of network topology for all known 3D (3,6)‐connected frameworks in both inorganic and inorganic–organic hybrid materials is described. Specific network connectivity of these MOFs indicates that the metal centers represent the most significant and alterable factor in structural assembly, although they show reliable and similar geometries. In this context, the combination of the distinct d10 AgI ion with btza in different solvents affords two isomorphous MOFs {Ag(btza)⋅glycol}n (5) and {Ag(btza)⋅CH3OH}n (6) with a binodal 4‐connected 3D SrAl2 (sra) topology. The network structures of MOFs 1–3 and 5 turn out to be more complicated and interesting if one considers the hydrogen bonding between the host coordination frameworks and the intercalated solvent molecules. Furthermore, the role of the included solvents in the generation and stabilization of MOFs 1–6 is also investigated.
Unusual network topologies: Assemblies of a well‐designed organic building block with octahedral centers allow the targeted construction of metal–organic frameworks with unusual (3,6)‐connected CdCl2, (42.6)2(44.62.87.102), and pyrite (pyr) topologies. The replacement of the metal node by AgI affords a pair of isomorphous 4‐connected SrAl2 (sra) networks (see scheme).
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