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Metal–Organic Frameworks and Self-Assembled Supramolecular Coordination Complexes: Comparing and Contrasting the Design, Synthesis, and Functionality of Metal–Organic Materials

Interpretation of europium(III) spectra

Metal–organic frameworks (MOFs) are constructed from metal ions/clusters coordinated by organic linkers (or bridging-ligands). The hallmark of MOFs is their permanent porosity, which is frequently found in MOFs constructed from metal-clusters. These clusters are often formed in situ, whereas the linkers are generally pre-formed. The geometry and connectivity of a linker dictate the structure of the resulting MOF. Adjustments of linker geometry, length, ratio, and functional-group can tune the size, shape, and internal surface property of a MOF for a targeted application. In this critical review, we highlight advances in MOF synthesis focusing on linker design. Examples of building MOFs to reach unique properties, such as unprecedented surface area, pore aperture, molecular recognition, stability, and catalysis, through linker design are described. Further search for application-oriented MOFs through judicious selection of metal clusters and organic linkers is desirable. In this review, linkers are categorized as ditopic (Section 1), tritopic (Section 2), tetratopic (Section 3), hexatopic (Section 4), octatopic (Section 5), mixed (Section 6), desymmetrized (Section 7), metallo (Section 8), and N-heterocyclic linkers (Section 9).

Tuning the structure and function of metal–organic frameworks via linker design

Magnetism of lanthanides in molecular materials with transition-metal ions and organic radicals.

Strategies towards single molecule magnets based on lanthanide ions

The interplay of coordinative, hydrogen bonding and π–π stacking interactions in sustaining supramolecular solid-state architectures.

Heterometallic 3d−4f complexes are of high interest in molecular magnetism: the lanthanide ions bring large and, in most cases, anisotropic magnetic moments. The combination of 3d and 4f metal ions, which differ through their chemistries and stereochemical preferences, leads to a rich variety of heterometal complexes, ranging from discrete entities to 3-D coordination polymers. This paper reviews recent achievements in this field: (i) oligonuclear complexes for studying the nature of the 3d−4f exchange interaction; (ii) construction of single-molecule magnets; (iii) magnetic properties of 3d−4f coordination polymers.

3d-4f combined chemistry: synthetic strategies and magnetic properties.

The hexanuclear clusters [Ln 2 C 4 (fsaaep) 4 (NO 3 ) 6 ].0.5(CH 3 OH.H 2 O) (abbreviated as [Ln 2 Cu 4 ]) have been synthesized; Ln is a trivalent lanthanide and (fsaaep) 2- is the ligand deriving from 3-(N-2-(pyridylethyl)formimidoyl)salicylic acid. The crystal structure of the compound with Ln=Pr has been solved. This compound crystallizes in the orthorhombic system, space group P2 1 2 1 2 1 . The lattice parameters are a=18.746(4) A, b=24.196(4) A, c=17.053(4) A, and Z=4

Crystal structure and magnetic properties of [Ln2Cu4] hexanuclear clusters (where Ln = trivalent lanthanide). Mechanism of the gadolinium(III)-copper(II) magnetic interaction

Compartmental Schiff-base ligands--a rich library of tectons in designing magnetic and luminescent materials.

Heteronuclear cationic complexes, [LCuLn]3+ and [(LCu)2Ln]3+, were employed as nodes in designing high-nuclearity complexes and coordination polymers with a rich variety of network topologies (L is the dianion of the Schiff base resulting from the 2:1 condensation of 3-methoxysalycilaldehyde with 1,3-propanediamine). Two families of linkers have been chosen: the first consists of exo-dentate ligands bearing nitrogen-donor atoms (bipyridine (bipy), dicyanamido (dca)), whereas the second consists of exo-dentate ligands with oxygen-donor atoms (anions derived from the acetylenedicarboxylic (H2acdca), fumaric (H2fum), trimesic (H3trim), and oxalic (H2ox) acids). The ligands belonging to the first family prefer copper(II) ions, whereas the ligands from the second family interact preferentially with oxophilic rare-earth cations. The following complexes have been obtained and crystallographically characterized: [LCuII(OH2)GdIII(NO3)3] (1), [{LCuIIGdIII(NO3)3}2(μ-4,4′-bipy)] (2), [LCuIIGdIII(acdca)1.5(H2O)2]⋅13 H2O (3), [LCuIIGdIII(fum)1.5(H2O)2]⋅4 H2O⋅ C2H5OH (4), [LCuIISmIII(H2O)(Hfum)(fum)] (5), [LCuIIErIII(H2O)2(fum)]NO3⋅3 H2O (6), [LCuIISmIII(fum)1.5(H2O)2]⋅4 H2O⋅C2H5OH (7), [{(LCuII)2SmIII}2fum2](OH)2 (8), [LCuIIGdIII(trim)(H2O)2]⋅H2O (9), [{(LCuII)2PrIII}(C2O4)0.5(dca)]dca⋅2 H2O (10), [LCuIIGdIII(ox)(H2O)3][CrIII(2,2′-bipy)(ox)2]⋅9 H2O (11), and [LCuGd(H2O)4{Cr(CN)6}]⋅3 H2O (12). Compound 1 is representative of the whole family of binuclear CuII–LnIII complexes which have been used as precursors in constructing heteropolymetallic complexes. The rich variety of the resulting structures is due to several factors: 1) the nature of the donor atoms of the linkers, 2) the preference of the copper(II) ion for nitrogen atoms, 3) the oxophilicity of the lanthanides, 4) the degree of deprotonation of the polycarboxylic acids, 5) the various connectivity modes exhibited by the carboxylato groups, and 6) the stoichiometry of the final products, that is, the CuII/LnIII/linker molar ratio. A unique cluster formed by 24 water molecules was found in crystal 11. In compounds 2, 3, 4, 9, and 11 the CuII–GdIII exchange interaction was found to be ferromagnetic, with J values in the range of 3.53–8.96 cm−1. Compound 12 represents a new example of a polynuclear complex containing three different paramagnetic ions. The intranode CuII–GdIII ferromagnetic interaction is overwhelmed by the antiferromagnetic interactions occurring between the cyanobridged GdIII and CrIII ions.

Oligonuclear 3d-4f complexes as tectons in designing supramolecular solid-state architectures: impact of the nature of linkers on the structural diversity.

Marius Andruh

Papers

The interplay of coordinative, hydrogen bonding and π–π stacking interactions in sustaining supramolecular solid-state architectures.

3d-4f combined chemistry: synthetic strategies and magnetic properties.

Crystal structure and magnetic properties of [Ln2Cu4] hexanuclear clusters (where Ln = trivalent lanthanide). Mechanism of the gadolinium(III)-copper(II) magnetic interaction

Compartmental Schiff-base ligands--a rich library of tectons in designing magnetic and luminescent materials.

Oligonuclear 3d-4f complexes as tectons in designing supramolecular solid-state architectures: impact of the nature of linkers on the structural diversity.