Brendan F. Abrahams

Ni(tpt)(NO3)2—A Three-Dimensional Network with the Exceptional (12,3) Topology: A Self-Entangled Single Net

The shortest circuits in the three-dimensional network with (12,3) topology of solvated Ni(tpt)(NO3 )2 pass through one another (see picture). This network based upon interlinked double helices occupies a unique position in the set of (n,3) nets. tpt=tri-4-pyridyl-1,3,5-triazine.

A Robust (10,3)‐a Network Containing Chiral Micropores in the AgI Coordination Polymer of a Bridging Ligand that Provides Three Bidentate Metal‐Binding Sites

Framework integrity is retained when water molecules replace the nitromethane molecules in the coordination polymer [Ag(hat)ClO4 ]⋅2 CH3 NO2 (see picture for structure), which are arranged in a helical fashion within the chiral micropores of the three-dimensional [Ag(hat)+ ]n network with a (10,3)-a topology. Remarkably, this is also the case after subsequent displacement of the water by nitromethane molecules. hat=1,4,5,8,9,12-hexaazatriphenylene.

Highly Efficient Separation of a Solid Mixture of Naphthalene and Anthracene by a Reusable Porous Metal–Organic Framework through a Single-Crystal-to-Single-Crystal Transformation

The three-dimensional crystalline porous metal-organic framework [Ni(2)(μ(2)-OH(2))(1,3-BDC)(2)(tpcb)](n) (1) [1,3-H(2)BDC = 1,3-benzenedicarboxylic acid; tpcb = tetrakis(4-pyridyl)cyclobutane] was used to separate a solid mixture of naphthalene and anthracene at room temperature via selective adsorption of naphthalene. The process involved a single-crystal-to-single-crystal transformation. The guest naphthalene molecules could be exchanged with ethanol, and the host, 1, could be regenerated by removal of the guest ethanol molecules.

A {CrIII2DyIII2} Single‐Molecule Magnet: Enhancing the Blocking Temperature through 3d Magnetic Exchange

It would therefore be of greatsignificance to develop this class of materials such that thisbehavior can be observed at substantially higher temper-atures, thus greatly improving the application prospects. Thiscan potentially be achieved by increasing the anisotropyassociated with the ground state, which results in longerrelaxation times. Increases in the magnetic-anisotropy barrierhave recently been achieved by the use of lanthanide ions,which possess large single-ion magnetic anisotropies. This hasresultedinthedevelopmentofseveralmono-andpolynuclearcompounds displaying energy barriers to magnetic reversal ofupto938 K,

A Cluster Rearrangement of an Open Cubane (Cu4Br4) to a Prismane (Cu6Br6) in a Copper(I)–Olefin Network†

The rational design and self-assembly of copper(i)±olefin coordination polymers possessing high thermal stability has been the focus of intense interest in recent times.[1] While these materials possess many of the general features normally associated with coordination polymers, the inclusion of bridging ligands that are capable of p bonding offers the possibility of unusual and novel properties. The CuI±olefin complexes examined so far have demonstrated an ability to act as fluorescent sensors,[1] and have potential applications in areas such as olefin separation[2] and enantioseparation.[3] To the best of our knowledge, the presence of clusters, such as cubanes, within Cu±olefin coordination polymers is unknown, however there are a number of metal±organic frameworks with clusters acting as connecting units. Such materials have demonstrated gas-storage capabilities as well as exhibiting magnetic and catalytic properties.[4±6] The successful generation of networks incorporating olefin coordination to a copper cluster represents an exciting challenge in modern supramolecular and organometallic chemistry. With this in mind, we have studied the reactions of triallyl-1,3,5-triazine2,4,6(1H,3H,5H)-trione (TTT) with CuBr at different temperatures. Herein we report the synthesis, solid-state structures, and some electrochemical properties of two materials generated from such reactions. The reaction between TTT and CuBr in methanol at 50± 60 8C in a sealed tube yielded a product with the formula [Cu4Br4(TTT)2]n (1), which was examined by single-crystal X-ray diffraction.[7] In this complex, Cu4Br4 clusters are linked by TTT ligands to form a polymeric chain (Figure 1). The Cu

A Simple Lithium(I) Salt with a Microporous Structure and Its Gas Sorption Properties

Much effort has been invested in studying the gas sorption properties of various classes of microporous materials such as zeolites, activated carbon materials, carbon nanotubes, polymers of intrinsic microporosity, and coordination polymers. At a time in the early 1990s when few coordination polymers had been deliberately constructed and characterized, their ability to sorb gases was a reasonable expectation. The first experimental measurements that heralded great promise of coordination polymers as materials for useful gas storage were reported by Kitagawa and co-workers in 1997. Subsequently, gas sorption by coordination polymers (more recently rebranded metal–organic frameworks (MOFs) by some) has become an intensively studied area. Low density is a most desirable characteristic of any gas storage material intended for mobile applications, and materials based on “light” metals (such as Li, Mg, and Al) are obvious targets for exploration. We report herein the synthesis, structure(s), and sorption properties of a simple salt of Li, lithium isonicotinate, which has a microporous structure and shows reversible gas uptake and release. Well-formed crystals of composition [(Li)(C6H4NO2 )]·0.5DMF (where C6H4NO2 is the isonicotinate anion, 1) can be readily obtained from DMF solution. The structure, which was determined by single-crystal X-ray diffraction, consists of a 3D [(Li)(C6H4NO2 )] network that contains microchannels occupied by DMF molecules. All the isonicotinate units are equivalent, and are associated with four Li centers, which are also all equivalent, and each associates with four isonicotinate anions. The structure can be readily envisaged in terms of [(Li)(C6H4NO2 )] chains (see Figure 1a), that are linked together by Li–N interactions into 2D sheets (see Figure 1b). The sheets in turn are linked together by Li–N interactions to form the 3D network (see Figure 1c). As can be seen in Figure 1a, each chain consists of alternating fourmembered rings (LiOLiO) and eight-membered rings (LiOCOLiOCO). The N centers of half of the pyridine units that

A wellsian ‘three-dimensional’ racemate: eight interpenetrating, enantiomorphic (10,3)-a nets, four right- and four left-handed

The crystal structure of solvated [Zn(tpt)2/3(SiF6)(H2O)2(MeOH)][tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine] is comprised of eight independent [Zn3(tpt)2]n networks with the (10,3)-a topology, four of one handedness and four of the other, which interpenetrate in a remarkable way, aspects of which were postulated by A. F. Wells almost twenty years ago.

α-Polonium coordination networks constructed from bis(imidazole) ligands

Two types of bis(imidazole) ligands – 1,4-bis(imidazol-1-ylmethyl)benzene (bix) and 1,4-bis(imidazolyl)-2-butyne (bib) – have been used to bridge octahedral metal centres and form simple cubic networks. Crystal structures of Cd(bix)3(ClO4)2, Cd(bix)3(NO3)2, Zn(bib)3(BF4)2 and Co(bib)3(NO3)2 reveal that all possess the α-polonium topology and are triply interpenetrating.

Cages with tetrahedron-like topology formed from the combination of cyclotricatechylene ligands with metal cations.

Cage the elephant: anionic tetrahedral assemblies, formed from the combination of cyclotricatechylene anions with transition metal ions, such as vanadium, contain large internal cavities that can act as hosts for alkali metal ions and solvent molecules. With appropriate metal centers, the anionic units can be linked together to form highly symmetric coordination polymers (V blue, O red, C black).

Heterometallic 3d–4f Single-Molecule Magnets: Ligand and Metal Ion Influences on the Magnetic Relaxation

Six tetranuclear 3d–4f single-molecule magnet (SMM) complexes formed using N-n-butyldiethanolamine and N-methyldiethanolamine in conjunction with ortho- and para-substituted benzoic acid and hexafluoroacetoacetone ligands yield two families, both having a butterfly metallic core. The first consists of four complexes of type {Co2(III)Dy2(III)} and {Co2(III)Co(II)Dy(III)} using N-n-butyldiethanolamine with variation of the carboxylate ligand. The anisotropy barriers are 80 cm–1, (77 and 96 cm–1—two relaxation processes occur), 117 and 88 cm–1, respectively, each following a relaxation mechanism from a single DyIII ion. The second family consists of a {Co2(III)Dy2(III)} and a {Cr2(III)Dy2(III)} complex, from the ligand combination of N-methyldiethanolamine and hexafluoroacetylacetone. Both show SMM behavior, the Co(III) example displaying an anisotropy barrier of 23 cm–1. The Cr(III) complex displays a barrier of 28 cm–1, with longer relaxation times and open hysteresis loops, the latter of which is not seen in the Co(III) case. This is a consequence of strong Dy(III)–Cr(III) magnetic interactions, with the relaxation arising from the electronic structure of the whole complex and not from a single DyIII ion. The results suggest that the presence of strong exchange interactions lead to significantly longer relaxation times than in isostructural complexes where the exchange is weak. The study also suggests that electron-withdrawing groups on both bridging (carboxylate) and terminal (β-diketonate) ligands enhance the anisotropy barrier.