Supramolecular hydrogen-bonded networks formed from copper(II) carboxylate dimers.

The well-known copper carboxylate dimer, with four carboxylate ligands extending outwards towards the corners of a square, has been employed to generate a series of crystalline compounds. In particular, this work centres on the use of the 4-hydroxybenzoate anion (Hhba) and its deprotonated phenolate form 4-oxidobenzoate (hba) to obtain complexes with the general formula [Cu(Hhba)(hba)L], where L is an axial coligand (including solvent molecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hydrogen bonds result in complexes which may be represented as [Cu(Hhba)(Hhba)L].

Complexes of 2,4,6-trihydroxybenzoic acid: effects of intramolecular hydrogen bonding on ligand geometry and metal binding modes.

This article describes a series of more than 20 new compounds formed by the combination of 2,4,6-trihydroxybenzoic acid (Hthba) with metal ions in the presence of a base, with structures that include discrete molecular units, chains, and two- and three-dimensional networks. As a result of the presence of two ortho-hydroxy groups, Hthba is a relatively strong acid (pK = 1.68).

Multi-Redox Responsive Behavior in a Mixed-Valence Semiconducting Framework Based on Bis-[1,2,5]-thiadiazolo-tetracyanoquinodimethane.

The two-dimensional (2-D) framework, [Cu(BTDAT)(MeOH)] {BTDAT = bis-[1,2,5]-thiadiazolo-tetracyanoquinodimethane}, possesses remarkable multi-step redox properties, with electrochemical studies revealing six quasi-stable redox states in the solid state. In situ electron paramagnetic resonance and visible-near infrared spectroelectrochemistry elucidated the mechanism for these multi-step redox processes, as well as the optical and electrochromic behavior of the BTDAT ligand and framework. In studying the structural, spectroscopic, and electronic properties of [Cu(BTDAT)(MeOH)], the as-synthesized framework was found to exist in a mixed-valence state with thermally-activated semiconducting behavior.

Mixed valency in a neutral 1D Fe-chloranilate coordination polymer.

The syntheses and structures of a pair of neutral one-dimensional (1D) Fe-anilate based coordination polymers, Fe(Fan)(4,4'-bipy) (Fan = deprotonated 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone; 4,4'-bipy = 4,4'-bipyridine) and Fe(Clan)(OPPh) (Clan = deprotonated 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone; OPPh = triphenylphosphine oxide), are reported. In the case of Fe(Fan)(4,4'-bipy), the Fe centre is in the +2 oxidation state and the Fan ligand is present in its quinoidal, dianionic form. In contrast, the structurally similar Fe(Clan)(OPPh) chain contains Fe centres and chloranilate ligands in oxidation states close to +3 and -3 respectively at low temperature.

Multifunctional Coordination Polymer Exhibiting Reversible Mechanical Motion Allowing Selective Uptake of Guests and Leading to Enhanced Electrical Conductivity.

A remarkably flexible, multifunctional, 2D coordination polymer exhibiting an unprecedented mode of reversible mechanical motion, enabling pores to open and close, is reported. Such multifunctional materials are highly sought after, owing to the potential to exploit coexisting electronic and mechanical functionalities that underpin useful technological applications such as actuators and ultrasensitive detectors. The coordination polymer, of composition Mn(FTCNQ)(py) (FTCNQ = 2,3,5,6-tetrafluoro-7,7,8,8-tetracycanoquinodimethane; py = pyridine), consists of Mn(II) centers bridged by FTCNQ dianions and coordinated by py molecules that extend above and below the 2D network.

Alkali metal salts of 4-hydroxybenzoic acid: a structural and educational study.

As part of an educational exercise designed to introduce school students to the technique of single-crystal X-ray diffraction and enhance their understanding of primary and secondary bonding, a group of nine secondary school students was given the opportunity to prepare new compounds and to solve and refine data collected on the crystalline materials they had prepared. Their investigation of the alkali metal salts of 4-hydroxybenzoic acid (Hhba) yielded nine new compounds and their structures are described in this article. Whilst the salts might be expected to have similar atomic arrangements, there are significant differences in their structures.

The Effect of Sterically Active Ligand Substituents on Gas Adsorption within a Family of 3D Zn-Based Coordination Polymers.

An investigation of the adsorption properties of two structurally related, 3D coordination polymers of composition Zn(2-Mehba) and Zn(2,6-Mehba) (2-Mehba = the dianion of 2-methyl-4-hydroxybenzoic acid and 2,6-Mehba = the dianion of 2,6-dimethyl-4-hydroxybenzoic acid) is presented. A common feature of these structures are parallel channels that are able to accommodate appropriately sized guest molecules. The structures differ with respect to the steric congestion within the channels arising from methyl groups appended to the bridging ligands of the network.

Effects of Mixed Valency in an Fe-Based Framework: Coexistence of Slow Magnetic Relaxation, Semiconductivity, and Redox Activity.

A 2-D coordination framework, (NEt)[Fe(fan)] (; Hfan = 3,6-difluoro-2,5-dihydroxy-1,4-benzoquinone), was synthesized and structurally characterized. The compound is structurally analogous to a formerly elucidated framework, (NEt)[Fe(can)] (Hcan = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone), and adopts a 2-D (6,3) topology with the symmetrical stacking of [Fe(fan)] sheets that are held in position by the NEt cations between the sheets. The investigation of the dc and ac magnetic properties of revealed ferromagnetic ordering behavior and slow magnetization relaxation, as evinced from ac susceptibility measurements.

Square Grid Metal-Chloranilate Networks as Robust Host Systems for Guest Sorption.

Reaction of the chloranilate dianion with Y(NO ) in the presence of Et N in the appropriate proportions results in the formation of (Et N)[Y(can) ], which consists of anionic square-grid coordination polymer sheets with interleaved layers of counter-cations. These counter-cations, which serve as squat pillars between [Y(can) ] sheets, lead to alignment of the square grid sheets and the subsequent generation of square channels running perpendicular to the sheets. The crystals are found to be porous and retain crystallinity following cycles of adsorption and desorption.

Self-assembly of a Si-based cage by the formation of 24 equivalent covalent bonds.

A robust, nano-sized covalent cage, of composition, [(PhSi)(ctc)] (Hctc = cyclotricatechylene) has been prepared in a simple reaction in good yield. The tetrahedral anionic cage is stable in both the solid and solution state and exhibits an affinity for Cs ions which bind to the internal surface of the cage.

Mixed Valency in a 3D Semiconducting Iron-Fluoranilate Coordination Polymer.

A pair of coordination polymers of composition (NBu)[M(fan)] (fan = fluoranilate; M = Fe and Zn) were synthesized and structurally characterized. In each case the compound consists of a pair of interpenetrating three-dimensional, (10,3)-a networks in which metal centers are linked by chelating/bridging fluoranilate ligands. Tetrabutylammonium cations are located in the spaces between the two networks.

Tunable Porous Coordination Polymers for the Capture, Recovery and Storage of Inhalation Anesthetics.

The uptake of inhalation anesthetics by three topologically identical frameworks is described. The 3D network materials, which possess square channels of different dimensions, are formed from the relatively simple combination of Zn centres and dianionic ligands that contain a phenolate and a carboxylate group at opposite ends. All three framework materials are able to adsorb N O, Xe and isoflurane.

Lightweight Ionic Networks Composed of Li or Mg Centres Linked Together by Dicarboxylate Ligands.

The combination of lightweight metal cations with a range of dicarboxylate ligands has led to the generation of ionic network materials that possess channels occupied by solvent molecules. The compounds [Li (2,2-bpdc)(DMF) ] and [Mg(2,2-bpdc)(DMF) ] (2,2-bpdc=2,2-dipyridyl-4,4-dicarboxylate) adopt a similar structure in which parallel metal-carboxylate chains are linked to four equivalent chains to generate a 3 D network in which DMF molecules occupy channels. [Li (3,5-pdc) (DMF)]⋅solvate (3,5-pdc=3,5-pyridine dicarboxylate) adopts a similar structure but the chains are more complex.

An indirect generation of 1D M(II)-2,5-dihydroxybenzoquinone coordination polymers, their structural rearrangements and generation of materials with a high affinity for H2, CO2 and CH4.

A series of solid-state structural transformations are found to accompany desolvation of relatively simple coordination polymers to yield materials that exhibit unexpected gas sorbing properties. Reaction of 1,2,4,5-tetrahydroxybenzene with M(II) salts (M = Mg, or Zn) in an alcohol/water solution in the presence of air affords cis-M(II)(C6H2O4(-II))(H2O)2·2H2O·xROH, (M = Mg, or Zn), crankshaft-like chains in which the absolute configurations of the chiral metal centres follow the pattern Δ Δ Λ Λ Δ Δ Λ Λ, and are hydrogen bonded together to generate spacious channels. When crystals of the crankshaft chain are air dried the crystals undergo a single crystal-to-powder rearrangement to form linear trans-M(II)(C6H2O4(-II))(H2O)2 chains.

A New Structural Family of Gas-Sorbing Coordination Polymers Derived from Phenolic Carboxylic Acids.

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.

Isomeric ionic lithium isonicotinate three-dimensional networks and single-crystal-to-single-crystal rearrangements generating microporous materials.

Reaction between LiOH and isonicotinic acid (inicH) in the appropriate solvent or mixture of solvents affords a family of variously solvated forms of a simple ionic lithium salt, viz., Li(+)inic(-)·S (where S = 0.5 morpholine, 0.

Electrochemically directed synthesis of Cu2(I)(TCNQF4(II-))(MeCN)2 (TCNQF4 = 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane): voltammetry, simulations, bulk electrolysis, spectroscopy, photoactivity, and X-ray crystal structure of the Cu2(I)(TCNQF4(II-))(EtCN)2 analogue.

The new compound Cu2(I)(TCNQF4(II-))(MeCN)2 (TCNQF4(2-) = dianion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) has been synthesized by electrochemically directed synthesis involving reduction of TCNQF4 to TCNQF4(2-) in acetonitrile containing [Cu(MeCN)4](+)(MeCN) and 0.1 M Bu4NPF6. In one scenario, TCNQF4(2-) is quantitatively formed by reductive electrolysis of TCNQF4 followed by addition of [Cu(MeCN)4](+) to form the Cu2(I)(TCNQF4(II-))(MeCN)2 coordination polymer.

Synthesis, structure and cation-binding properties of some [4 + 4] metallocyclic MO2(2+) (M = Mo or W) derivatives of 9-phenyl-2,3,7-trihydroxyfluor-6-one.

The trianion Z(3-) obtained from 9-phenyl 2,3,7-trihydroxyfluor-6-one, ZH3, affords dioxomolybdenum and dioxotungsten derivatives which contain [4 + 4] metallocycles of composition [(MO2)4Z4](4-) (M = Mo, W) in combination with a variety of counter cations. The syntheses, structures and ESMS of the following compounds are presented: compound 1, (MePPh3)3(NBu4)[(MoO2)4Z4]; compound 2, (MePPh3)3(NBu4)[(WO2)4Z4]; compound 3, (MePPh3)4[(WO2)4Z4]; compound 4, (PPh4)2(NBu4)2[(MoO2)4Z4]; compound 5, (AsPh4)3(NBu4)[(MoO2)4Z4]; compound 6, (AsPh4)2(NBu4)2[(WO2)4Z4]; compound 7, (Ph3PNPPh3)(NBu4)3[(MoO2)4Z4]; compound 8, (Ph3PNPPh3)(NBu4)3[(WO2)4Z4]; compound 9, (NEt4)(NBu4)3[(MoO2)4Z4]. The metallocycles in all of these compounds have similar structures, with the four metal centers located at the corners of a square slightly distorted, to varying degrees, toward a rhombus and also toward a tetrahedron.

3d-Metal derivatives of the [Cu(I)(SO3)4]7- ion: structure and magnetism.

The Cu(SO(3))(4)(7-) anion, which consists of a tetrahedrally coordinated Cu(I) centre coordinated to four sulfur atoms, is able to act as a multidentate ligand in discrete and infinite supramolecular species. The slow oxidation of an aqueous solution of Na(7)Cu(SO(3))(4) yields a mixed oxidation state, 2D network of composition Na(5){[Cu(II)(H(2)O)][Cu(I)(SO(3))(4)]}·6H(2)O. The addition of Cu(II) and 2,2'-bipyridine to an aqueous Na(7)Cu(SO(3))(4) solution leads to the formation of a pentanuclear complex of composition {[Cu(II)(H(2)O)(bipy)](4)[Cu(I)(SO(3))(4)]}(+); a combination of hydrogen bonding and π-π stacking interactions leads to the generation of infinite parallel channels that are occupied by disordered nitrate anions and water molecules.

Synthesis, structure and host-guest properties of (Et4N)2[Sn(IV)Ca(II)(chloranilate)4], a new type of robust microporous coordination polymer with a 2D square grid structure.

Reaction of chloranilic acid with SnCl(4), Ca(NO(3))(2) and Et(4)NBF(4) in aqueous acetone yields (Et(4)N)(2)[Sn(IV)Ca(II)(can)(4)]. 2 Me(2)CO which contains 2D coordination polymer sheets of composition [Sn(IV)Ca(II)(can)(4)](2-). Both metals are 8-coordinate and act as 4-connecting nodes to form a square grid containing "square" holes.

Closed and open clamlike structures formed by hydrogen-bonded pairs of cyclotricatechylene anions that contain cationic "meat".

Clamming up: The hexaphenolic compound cyclotricatechylene, which has a bowl-shaped cavity, forms clamlike pairs that encapsulate cations (see picture). Variable hydrogen bonding allows two linked cyclotricatechylene clamshells to be in a closed arrangement when smaller cations such Rb(+) or Cs(+) provide the clam meat, whereas larger cations such as NMe(4) (+) and NEt(4) (+) cause the clam to be partially opened.

In situ synthesis of trisubstituted methanol ligands and their potential as one-pot generators of cubane-like metal complexes.

Two different one pot routes to a variety of metal cubane compounds are reported; one route is based on an in situ benzilic acid type rearrangement and the other involves in situ nucleophilic attack at a ketone. Diketosuccinic acid in basic solution in the presence of certain divalent metal ions undergoes a benzilic acid type rearrangement to generate the carbon oxyanion, C(CO(2) (-))(3)O(-), which serves as a cubane-forming bridging ligand in a series of octanuclear complexes of composition [M(8){C(CO(2))(3)O}(4)](H(2)O)(12) (M=Mg, Mn, Fe, Co, Ni, Zn). At the heart of each of these highly symmetrical aggregates is an M(4)O(4) cubane core, each oxygen component of which is provided by the alkoxo centre of a C(CO(2) (-))(3)O(-) ligand.

Citrate, in collaboration with a guanidinium ion, as a generator of cubane-like complexes with a range of metal cations: synthesis, structures, and magnetic properties of [C(NH2)3]8[(M(II))4(cit)4].8H2O (M = Mg, Mn, Fe, Co, Ni, and Zn; cit = Citrate).

Aqueous reaction mixtures containing citric acid, guanidinium carbonate, and a range of metal cations (Mg2+, Mn2+, Fe2+, Co2+, Ni2+, and Zn2+) at room temperature give crystalline products of composition [C(NH2)3]8[(M(II))4(cit)4].8H2O (cit = citrate). In all cases, the crystals are suitable for single-crystal X-ray diffraction studies, which reveal that the compounds are isostructural (space group P4(2)/n; a approximately 16.