The literature on open-framework materials has shown numerous examples of porous solids with additional structural, chemical, or physical properties. These materials show promise for applications ranging from sensing, catalysis and separation to multifunctional materials. This critical review provides an up-to-date survey to this new generation of multifunctional open-framework solids. For this, a detailed revision of the different examples so far reported will be presented, classified into five different sections: magnetic, chiral, conducting, optical, and labile open-frameworks for sensing applications. (413 references.)

Old materials with new tricks: multifunctional open-framework materials.

Six new coordination polymers, namely [Zn1.5(BTC)(L1)(H2O)2]·1.5H2O (1), [Zn3(BTC)2(L2)3] (2), [Zn3(BTC)2(L3)1.5(H2O)]·H2O (3), [Co6(BTC)4(L1)6(H2O)3]·9H2O (4), [Co1.5(BTC)(L2)1.5]·0.25H2O (5), and [Co4(BTC)2(L3)2(OH)2(H2O)]·4.5H2O (6), where L1 = 1,2-bis(imidazol-1-ylmethyl)benzene, L2 = 1,3-bis(imidazol-1-ylmethyl)benzene, L3 = 1,1‘-(1,4-butanediyl)bis(imidazole), and BTC = 1,3,5-benzenetricarboxylate anion, were synthesized under hydrothermal conditions. In 1−6, each of L1−L3 serves as a bidentate bridging ligand. In 1, BTC anions act as tridentate ligands, and compound 1 shows a 2D polymeric structure which consists of 2-fold interpenetrating (6, 3) networks. In compound 2, BTC anions coordinate to zinc cations as tridentate ligands to form a net with (64·82)2(86)(62·8)2 topology. In compound 3, BTC anions act as tetradentate ligands and coordinate to zinc cations to form a net with (4·62·83)2(8·102)(4·6·83·10)2 topology. In compound 5, each BTC anion coordinates to three Co cations, and the framework...

Syntheses and characterization of six coordination polymers of zinc(II) and cobalt(II) with 1,3,5-benzenetricarboxylate anion and bis(imidazole) ligands

Metal-organic frameworks represent the ultimate chemical platform on which to develop a new generation of designer magnets. In contrast to the inorganic solids that have dominated permanent magnet technology for decades, metal-organic frameworks offer numerous advantages, most notably the nearly infinite chemical space through which to synthesize predesigned and tunable structures with controllable properties. Moreover, the presence of a rigid, crystalline structure based on organic linkers enables the potential for permanent porosity and postsynthetic chemical modification of the inorganic and organic components. Despite these attributes, the realization of metal-organic magnets with high ordering temperatures represents a formidable challenge, owing largely to the typically weak magnetic exchange coupling mediated through organic linkers. Nevertheless, recent years have seen a number of exciting advances involving frameworks based on a wide range of metal ions and organic linkers. This review provides a survey of structurally characterized metal-organic frameworks that have been shown to exhibit magnetic order. Section 1 outlines the need for new magnets and the potential role of metal-organic frameworks toward that end, and it briefly introduces the classes of magnets and the experimental methods used to characterize them. Section 2 describes early milestones and key advances in metal-organic magnet research that laid the foundation for structurally characterized metal-organic framework magnets. Sections 3 and 4 then outline the literature of metal-organic framework magnets based on diamagnetic and radical organic linkers, respectively. Finally, Section 5 concludes with some potential strategies for increasing the ordering temperatures of metal-organic framework magnets while maintaining structural integrity and additional function.

Metal-Organic Framework Magnets.

Two novel three-dimensional complexes formulated as [M3(bime)2(μ3-OH)2(HO−BDC)2]n (M = Co, 1; Cu, 2) [bime = 1,2-bis(imidazol-1‘-yl)ethane, HO−H2BDC = 5-hydroxyisophthalic acid] have been hydrothermally synthesized and characterized Both 1 and 2 exhibit similar structural frameworks resulting from one-dimensional metal/oxygen chains extended by HO−BDC, but the bridging modes of HO−BDC and coordination environments of metal centers are different Complexes 1 and 2 crystallize in the orthorhombic system, space group Pbcn, a = 18458(2) [182119(12) for 2] A, b = 120616(14) [116847(7)] A, c = 114859(14) [120688(6)] A, and Z = 4 (4) Magnetic studies show that 1 displays a slow magnetic relaxation, a large hysteresis, and distinct finite-size effects and 2 contains an antiferromagnetic chain

Two Three-Dimensional Metal−Organic Frameworks Containing One-Dimensional Hydroxyl/Carboxylate Mixed Bridged Metal Chains: Syntheses, Crystal Structures, and Magnetic Properties

Two polyoxometalate-templated organic–inorganic hybrid porous frameworks, namely, [Cu2(H2O)2(bpp)2Cl][PM12O40]·∼20H2O (for 1, M = W; for 2, M = Mo; bpp = 1,3-bis(4-pyridyl)propane), were self-assembly obtained and structurally determined by elemental analyses, inductively coupled plasma analyses, infrared spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analysis of these crystals revealed that both of the structures are constructed from eight-connected three-dimensional coordination polymer hosts [Cu2(H2O)2(bpp)2Cl]n3n+ and ball-shaped Keggin-type guests [PM12O40]n3n− as templates. The polymer hosts resulted from a bcc-type framework with nanotubes, and the nanotubes can be regarded as a tetra-stranded helix structure. Furthermore, compounds 1 and 2 exhibit photoluminescent properties at ambient temperature, and the compound 2 bulk-modified carbon paste electrode (2-CPE) displays good electrocatalytic activity toward the reduction of nitrite.

Self-assembly of organic-inorganic hybrid materials constructed from eight-connected coordination polymer hosts with nanotube channels and polyoxometalate guests as templates.

Two polymeric malonato-bridged manganese(II) complexes of formula [Mn(mal)(H(2)O)(2)](n)() (1) and [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) have been synthesized and characterized (mal = malonate dianion; 4,4'-bipy = 4,4'-bipyridine). The crystal structure of complex 1 was already known. Complex 2 crystallizes in monoclinic space group P2(1)/n, Z = 2, with unit cell parameters of a = 7.2974(10) A, b = 18.7715(10) A, c = 7.514(3) A, and beta = 91.743(12) degrees. The structure determination reveals that the complex [Mn(2)(mal)(2)(4,4'-bipy)(H(2)O)(2)](n)() (2) is a 3D network being composed of Mn-malonate sheets which are pillared by bidentate 4,4'-bipy spacer forming small voids. The Mn-Mn distances through Mn-mu-(O3-C8-O4)-Mn, Mn-mu(O1-C6-O2)-Mn, and Mn-mu-4,4'-bipy-Mn bridges are 5.561, 5.410, and 11.723 A, respectively. The magnetic behaviors of complexes 1 and 2 in the temperature range 300-2 K are very close, corresponding to a weak antiferromagnetic coupling. The magnetic pathways of complex 1 are through two Mn-O-C-O-Mn with anti-anti conformation and two Mn-O-C-O-Mn with syn-anti conformations and in complex 2 through all Mn-O-C-O-Mn with syn-anti conformations. Both syn-anti and anti-anti conformations create weak antiferromagnetic coupling, and the susceptibility data are fitted by the expansion series of Lines and the Curely formula for an S = 5/2 antiferromagnetic quadratic layer, based on the exchange Hamiltonian H = -Sigma(nn)()JS(i)()S(j)(). The best fit is given by the superexchange parameters J = -0.32 cm(-)(1) and g = 2.00 for complex 1 and J = -0.14 cm(-)(1), J(inter) = -0.031 cm(-)(1), and g = 2.00 for complex 2. Finally, in both the complexes there is a magnetic pathway Mn-O-C-C-C-O-Mn, and this pathway through the three carbon atoms of the malonato-bridging ligand could be considered negligible.

Magneto-structural xorrelations in 2D and 3D extended structures of manganese(II)-malonate systems.

Three supramolecular networks are synthesized by the combination of Mn(II) and flexible ligands [1,2-bis (4-pyridyl) ethane (bpe); 1,3-bis (4-pyridyl) propane (bpp); 4,4‘-bipyridyl disulfide (bpds)], characterized by single-crystal X-ray analysis All three complexes have extended solid-state structure formed by π−π interactions, and there is an excellent opportunity to elucidate the difference in the formation of extended networks in these three complexes Complex 1, which is reported in a paper earlier by our group, is an unprecedented three-dimensional (3D) “honeycomb”-like architecture constructed from a novel sinusoidal one-dimensional (1D) chain [Mn(bpe)(H2O)4]2+ through π−π interactions in which bpe is used as a bidentate bridging ligand Complex [{Mn(bpp)3Cl2}(H2O)2]n 2 generates a “standing wave”-like architecture by π−π interactions from a neutral zigzag 1D chain of [Mn(bpp)3Cl2] Complex [{Mn(bpds)2(dca)2(H2O)2}(H2O)4(bpds)]n 3 is a neutral monomer [Mn(bpds)2(dca)2(H2O)2], which is self-assembl

Novel solid-state molecular self-assemblies of manganese (II) constructed with flexible-ligands: Influences of π-π and C-H...π interactions on their crystal packing

A one pot reaction of MnCl2, acetylene dicarboxylate (C4O42-), and 1,2-bis(4-pyridyl)ethane (bpe) leads to a compound formulated as [{Mn(bpe)(H2O)4}(C4O4)·4.5H2O] and has been shown by single crystal structure analysis to be a three-dimensional network with hexagonal and rhombohedral channels encapsulating C4O42- and water molecules, constructed by the one-dimensional “sinusoidal” [Mn(bpe)(H2O)4]n2+ cationic chains through extensive hydrogen-bonding and π−π interactions.

Tian-Huey Lu

Papers

Magneto-structural xorrelations in 2D and 3D extended structures of manganese(II)-malonate systems.

Novel solid-state molecular self-assemblies of manganese (II) constructed with flexible-ligands: Influences of π-π and C-H...π interactions on their crystal packing

A Three-Dimensional Honeycomb-Like Network Constructed with Novel “Sinusoidal” One-Dimensional Chains via Hydrogen Bonding and π−π Interactions