The Group 13 metal complexes [M(L(2))(3)], where M is Al or Ga and L(2) is 1,3-di(4-pyridyl)-1,3-propanedionato, are hexatopic metalloligands that have been used to prepare mixed-metal-organic frameworks containing interpenetrated primitive cubic networks. In contrast, the europium complex [Eu(HL(2))(3)(H(2)L(2))]Cl(4) x EtOH forms a hydrogen-bonded network following partial protonation of the pyridyl groups.
The iron(III) and aluminium(III) complexes of 1,3-di(4-pyridyl)propane-1,3-dionato (dppd) and 1,3-di(3-pyridyl)propane-1,3-dionato (dmppd), [Fe(dppd)(3)] 1, [Fe(dmppd)(3)] 2, [Al(dppd)(3)] 3 and [Al(dmppd)(3)] 4 have been prepared. These complexes adopt molecular structures in which the metal centres contain distorted octahedral geometries. In contrast, the copper(II) and zinc(II) complexes [Cu(dppd)(2)] 5 and [Zn(dmppd)(2)] 6 both form polymeric structures in which coordination of the pyridyl groups into the axial positions of neighbouring metal centres links discrete square-planar complexes into two-dimensional networks. The europium complex [Eu(dmppd)(2)(H(2)O)(4)]Cl·2EtOH·0.5H(2)O 7 forms a structure containing discrete cations that are linked into sheets through hydrogen bonds, whereas the lanthanum complex [La(dmppd)(3)(H(2)O)]·2H(2)O 8 adopts a one-dimensional network structure, connected into sheets by hydrogen bonds. The iron complexes 1 and 2 act as metalloligands in reactions with silver(I) salts, with the nature of the product depending on the counter-ions present. Thus, the reaction between 1 and AgBF(4) gave [AgFe(dppd)(3)]BF(4)·DMSO 9, in which the silver centres link the metalloligands into discrete nanotubes, whereas reactions with AgPF(6) and AgSbF(6) gave [AgFe(dppd)(3)]PF(6)·3.28DMSO 10 and [AgFe(dppd)(3)]SbF(6)·1.25DMSO 11, in which the metalloligands are linked into sheets. In all three cases, only four of the six pyridyl groups present on the metalloligands are coordinated. The reaction between 2 and AgNO(3) gave [Ag(2)Fe(dmppd)(3)(ONO(2))]NO(3)·MeCN·CH(2)Cl(2)12. Compound 12 adopts a layer structure in which all pyridyl groups are coordinated to silver centres and, in addition, a nitrate ion bridges between two silver centres. A similar structure is adopted by [Ag(2)Fe(dmppd)(3)(O(2)CCF(3))]CF(3)CO(2)·2MeCN·0.25CH(2)Cl(2)13, with a bridging trifluoroacetate ion playing the same role as the nitrate ion in 12.
The highly porous nature of metal-organic frameworks (MOFs) offers great potential for the delivery of therapeutic agents. Here, we show that highly porous metal-organic frameworks can be used to deliver multiple therapeutic agents—a biologically active gas, an antibiotic drug molecule, and an active metal ion—simultaneously but at different rates. The possibilities offered by delivery of multiple agents with different mechanisms of action and, in particular, variable timescales may allow new therapy approaches. Here, we show that the loaded MOFs are highly active against various strains of bacteria.
A single-crystal to single-crystal transformable coordination polymer compound was hydrothermally synthesized. The structural rearrangement is induced by selecting a ligand that contains both strong and weaker coordinating groups. Both 10 hydrated and dehydrated structures were determined by single crystal X-ray analysis.In the last two decades, coordination polymer and Metal-Organic Frameworks have developed into a hot research topic, 1-3 due to 15 their potential application in areas such as gas adsorption, drug delivery, separation and catalysis. [4][5][6][7][8][9][10][11] Compared with traditional adsorbents and catalysts including zeolites and molecular sieves, MOFs present many unique properties due to their chemical nature and their intrinsic structures. The network structures of 20 MOF materials are built up by coordinate bonds between organic ligands and metal centres. It is possible, in a way, to target the synthesis of MOF materials with particular structures or properties by carefully selecting and designing the organic ligands. 12, 13 25 One particularly unusual feature of MOFs is their structural flexibility. This can lead to remarkable effects such as 'breathing', 14 pore-discriminating adsorption 15 and reversible single crystal to single crystal transformations. 16 The latter class of MOF materials responds to external stimuli such as heating or 30 guest exchange and reversible structure transformations can occur. [17][18][19] This kind of material is classified as "third generation" 20 and has attracted increasing attention in technical and research fields of gas adsorption, 21, 22 sensing, 23 and structure investigation. 24, 25 35 One strategy by which the transformations can be achieved uses ligands which form coordinating bonds of different binding strength. Once external stimulus is applied, the weaker bonds in the structure are more likely to be broken (and possibly reformed on removal or change of the stimulus), resulting in changes of 40 crystal structure. Meanwhile, the stronger coordinating bonds are more stable and strongly hold the whole framework so that the original structure can be recovered when the stimulus is stopped. One example of this strategy is the synthesis of Cu-SIP-3, a copper 5-sulfoisophthalate MOF that was reported by Xiao et 45 al. 24,26, 27 . The ligand molecule, 5-sulfoisophthalate, contains one sulfonate and two carboxylate groups. The sulfonate group is weaker than the strongly binding carboxylate groups. Coordinated water molecules leave the copper atoms upon dehydration and the sulfonate group changes its coordinating 50 mode, resulting in a structural transformation of Cu-SIP-3. We have dubbed this type of material a 'hemilabile MOF' by analogy with homogenous catalysis where multidentate ligands can have different coordinating groups of varying strengths. This property of hemilability leads directly to an unusual property for Cu-SIP-55 3; ultraselectivity towards the adsorption of coordinating gases such as NO, which is particularly interesting be...
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