Papers by Brendan Abrahams
Chemistry – A European Journal, 2019
A chiral, octahedral M12L12 cage, which is charge neutral and contains an internal void of about ... more A chiral, octahedral M12L12 cage, which is charge neutral and contains an internal void of about 2000 Å3, is reported. The cage was synthesised as an enantiopure complex by virtue of amino‐acid‐based dicarboxylate ligands, which assemble around copper paddlewheels at the vertices of the octahedron. The cage persists in solution with retention of the fluorescence properties of the parent acid. The solid‐state structure contains large pores both within and between the cages, and displays permanent porosity for the sorption of gases with retention of crystallinity. Initial tests show some enantioselectivity of the cage towards guests in solution.
Chemistry - A European Journal, 2015
The structure of Li(inox)⋅2/3 DMF (inox(-) =the N-oxide of the isonicotinate anion) consists of a... more The structure of Li(inox)⋅2/3 DMF (inox(-) =the N-oxide of the isonicotinate anion) consists of a 3D framework with solvent-filled, square cross-section channels of approximate dimensions 5.5×5.5 Å. Unfortunately, the Li(inox) framework is unstable upon removal of DMF from the channels. When the structurally related 4-hydroxybenzoic acid (H2 hba) was used in place of Hinox, and Zn(2+) in place of the Li(+) , a structurally similar but more robust network, Zn(hba), was obtained; the isostructural compound, Co(hba), may also be prepared. Longer ligands with phenolate and carboxylate functional groups at opposite ends, such as the dianions of 4-coumaric acid (H2 cma) and 4'-hydroxy-4-biphenylcarboxylic acid (H2 hbpc), in combination with Zn(2+) yield Zn(cma) and Zn(hbpc) frameworks, respectively, with the same PtS topology but with larger channels. The coordination polymers remain intact after desolvation and exhibit microporosity, showing the ability to sorb significant quantities of CO2 , CH4 , and H2 .
Crystal Growth & Design, 2014
Crystals of [Li(inox)(H 2 O)] (where inox − = the isonicotinate-N-oxide ion) are obtained from aq... more Crystals of [Li(inox)(H 2 O)] (where inox − = the isonicotinate-N-oxide ion) are obtained from aqueous solution. The Li + cations and the carboxylate anions form a two-dimensional (2D) sheet containing four-membered (−Li−O−Li−O−) rings and 16membered (−Li−O−C−O−) 4 rings; the sheets are linked to adjacent parallel sheets through hydrogen bonds. Crystals of solvent-free [Li(inox)], obtained from t-butanol, consist of a threedimensional network which can also be prepared in microcrystalline form by dehydration of [Li(inox)(H 2 O)] at 200°C. Crystals of [Ca(inox) 2 (H 2 O) 2 ] contain 2D sheets with 4,4 topology in which Ca 2+ ions, bound by trans water molecules, provide the 4-connecting nodes. The Ca(H 2 O) 2 2+ units are linked by carboxylate groups to generate 16-membered (−Ca−O−C−O−) 4 rings. Sheets are bound together by hydrogen bonds between the pyridine-N-oxide units and coordinated water molecules. [Ca(inox) 2 (H 2 O) 2 ] can be dehydrated at 190°C in a single crystal-to-single crystal transformation to give [Ca(inox) 2 ] whose structure is related to that of the hydrated precursor. A proposed solid-state mechanism for this single crystal-to-single crystal transformation, in which the N-oxide takes up the site on calcium vacated by water is proposed. ■ EXPERIMENTAL SECTION General Procedures. Commercially available reagents employed in the synthesis of the compounds reported were used without further
Journal of the Chemical Society, Dalton Transactions, 2002
The crystal structures of lanthanide complexes involving the dianions of dihydroxybenzoquinone (H... more The crystal structures of lanthanide complexes involving the dianions of dihydroxybenzoquinone (H2dhbq) or chloranilic acid (H2can) are presented. The complexes, Ln2dhbq3·24H2O (Ln = Y, La, Ce, Gd, Yb and Lu) are 2-D coordination polymers with metal centres linked by dhbq2− ligands. Each of these species contain a Ln2(H2O)18 pentagonal dodecahedral cage. Despite the variation in the radii of lanthanide ions this series is isostructural. In contrast, the hydrated structures of Ln2can3 (Ln = Sc, Y, La, Pr, Nd, Gd, Tb, Yb and Lu) show considerable structural variation. The crystal structures of the diamond-like networks Ycan2− and Thcan2 are also presented.
Journal of the American Chemical Society
Journal of the American Chemical Society, 2005
The two major types of interactions employed by supramolecular chemists to engineer a variety of ... more The two major types of interactions employed by supramolecular chemists to engineer a variety of nets, both finite and infinite, are metal-ligand bonding and hydrogen bonding. The guanidinium cation, C(NH 2) 3 + , is a particularly potent structure-determining template in the formation of both coordination polymer networks and hydrogen-bonded networks. Because of its internal symmetry, it is able to form three pairs of strong hydrogen bonds to various oxyanions, as in 1, and thus can act as a 3-connecting node in the formation of a number of networks. Outstanding examples are provided by the extensive family of guanidinium sulfonates devised and studied by Ward and co-workers, in which the sulfonate components, as well as the guanidinum units, act as 3-connecting nodes to generate a variety of solids having a common, predictable, yet pliable underlying hydrogen-bonded 3-connected sheet structure with the (6,3) (or hexagonal grid) topology. 1 We have recently discovered 2 a new family of hydrogen-bonded frameworks, of composition [C(NH 2) 3 ][N(CH 3) 4 ][XO 4 ] (X) S, Cr, or Mo), related to the guanidinium sulfonates, in which the guanidinium cation again plays the 3-connecting role in 1 and the XO 4 2ion acts as a second type of 3-connecting node; now, the network generated is the most symmetrical 3D 3-connected network possible, namely, the (10,3)-a net, 3 rather than the most symmetrical 2D 3-connected network possible seen in the sulfonates. The guanidinium cation again plays the structural role 1 (Z) C) in an extensive family of carbonate-bridged coordination polymers, thereby promoting the generation of highly symmetrical metal-carbonate networks with cubic symmetry and sodalite-like topology. 4 We report here a series of guanidinium borate derivatives in which the guanidinium cation yet again acts as in 1 (Z) B), and again, a network of high symmetry (cubic) is formed, in this case with the boracite topology.
Inorganic Chemistry, 2006
Inorganic Chemistry, 2003
Reaction of Ag(tcm), tcm = tricyanomethanide, C(CN)(3)(-), with a range of terminal and bridging ... more Reaction of Ag(tcm), tcm = tricyanomethanide, C(CN)(3)(-), with a range of terminal and bridging ligands results in formation of a series of new coordination polymers. Recrystallization of Ag(tcm) from acetonitrile generates Ag(tcm)(MeCN), which is composed of corrugated (6,3) sheets displaying two-fold 2D --> 2D parallel interpenetration and is topologically identical to the parent Ag(tcm) structure. Ag(tcm)(L) species, L = 1,4-diazobicyclo-[2.2.2]-octane (dabco) or 4,4'-bipyridine (bipy), contain two interpenetrating 3D networks composed of 3-connecting (tcm) and 5-connecting (Ag) centers. The structure of Ag(tcm)(bpe), bpe = 1,2-bis(4-pyridyl)ethene, contains 1D ladderlike polymers connected by weak Ag-tcm interactions into two interpenetrating 3D nets. Ag(tcm)(Mepyz)(3/2), Mepyz = methylpyrazine, also contains 1D ladders, while Ag(tcm)(Me(4)pyz)(1/2), Me(4)pyz = tetramethylpyrazine, contains 2D sheets composed of Ag(tcm) 1D "tubes" linked by bridging Me(4)pyz ligands. Ag(tcm)(hmt), hmt = hexamethylenetetramine, has a 3D network structure in which the hmt ligands are 3-connecting, the tcm anions are 2-connecting, and the silver atoms are 5-connecting. The topology is the same as displayed by Ag(tcm)(L), L = dabco or bipy.
CrystEngComm, 2013
ABSTRACT
Crystal Growth & Design, 2008
Crystal Growth & Design, 2008
The structures of salts containing the ferrocenemonosulfonate anion and a range of nitrogen base ... more The structures of salts containing the ferrocenemonosulfonate anion and a range of nitrogen base cations are reported. It is found that electrostatic interactions, sometimes enhanced by hydrogen bonds, generally lead to layer-type structures with the sulfonate group playing a key role in the association with the cations.
Chemistry – A European Journal, 2004
The molten reaction of 2‐naphthol, 4‐(aminomethyl)pyridine, and 4‐pyridinecarboxaldehyde at about... more The molten reaction of 2‐naphthol, 4‐(aminomethyl)pyridine, and 4‐pyridinecarboxaldehyde at about 180 °C yields trans‐2,3‐dihydro‐2,3‐di(4′‐pyridyl)benzo[e]indole (1) which possesses two chiral centers, rather than an expected Betti‐type reaction product with only one chiral carbon center. The same reactions, using 3‐pyridinecarboxaldehyde, 4‐cyanobenzaldehyde, or 3‐ cyanobenzaldehyde instead of 4‐pyridinecarboxaldehyde produce the related compounds trans‐2,3‐dihydro‐2‐(4′‐pyridyl)‐3‐(3′′‐pyridyl)benzo[e]indole (2), trans‐2,3‐dihydro‐2‐(4′‐pyridyl)‐3‐(4′′‐cyanophenyl)benzo[e]indole (3), and trans‐2,3‐dihydro‐2‐(4′‐pyridyl)‐3‐(3′′‐cyanophenyl)benzo[e]indole (4), respectively. This reaction proceeds with a high degree of stereoselectivity with a trans/cis ratio of about 98:2 at elevated temperature. Compounds 1, 2, and 4 crystallize in a noncentrosymmetric space group (Pca21, Pca21, and Cc), while compound 3 has a chiral space group (P21). These successfully acentric packing arrangeme...
Chemistry - A European Journal, 2004
Under hydrothermal (solvothermal) reaction conditions chiral compounds 1, 2, and 3 and one acentr... more Under hydrothermal (solvothermal) reaction conditions chiral compounds 1, 2, and 3 and one acentric compound 4 were obtained by the reaction of Zn2+ or Cd2+ with racemic 3‐(3‐pyridyl)‐3‐aminopropionic acid (rac‐HPAPA). Compounds 1 and 2 crystallized in chiral space group P212121. At 105 °C, racemic 3‐pyridyl‐3‐aminopropionic acid (rac‐HPAPA) reacted with Zn(ClO4)2⋅6 H2O and dehydrogenated in situ to form the first chiral coordination polymer [Zn{(E)‐3‐C5H4NC(NH2)CHCOO}]ClO4 (1) with a β‐dehydroamino acid. Beyond 120 °C, the reaction of rac‐HPAPA with Zn(ClO4)2⋅6 H2O deaminates in situ to form chiral coordination polymer [Zn{(E)‐3‐C5H4NCHCHCOO}(OH)] (2). At relatively low temperatures (70 °C), the solvothermal reaction of Zn(NO3)2⋅6 H2O with rac‐HPAPA in methanol does not lead to any change in the ligand and results in the formation of a chiral (P212121) coordination polymer [Zn(papa)(NO3)] (3). The same reaction of Cd(ClO4)2⋅6 H2O with HPAPA also does not lead to any change in...
Chemistry of Materials, 2003
Chemical Communications, 2012
Angewandte Chemie International Edition, 2013
Angewandte Chemie International Edition, 2007
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Papers by Brendan Abrahams