Search

Abstract The structurally related odd and even numbered wheels [FeIII11ZnII4(tea)10(teaH)1(OMe)Cl8] (1) and [FeIII12ZnII4(tea)12Cl8] (2) can be synthesized under ambient conditions by reacting FeIII and ZnII salts with triethanolamine (teaH3), the change in nuclearity being dictated by the solvents employed. An antiferromagnetic exchange between nearest neighbors, J = ‐10.0 cm−1 for 1 and J = −12.0 cm−1 for 2, leads to a frustrated S = 1/2 ground state in the former and an S = 0 ground state in the latter.

A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li–Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA− (necessarily in a 1:1 ratio with the metal cation M+), barbituric acid, and water. All organic species and water molecules are coordinated to the metal centres via oxygen atoms as either terminal or bridging ligands. Coordination numbers range from 4 (for the Li complex) to 8 (for the Cs complex). Extensive hydrogen bonding plays a significant role in all the crystal structures, almost all of which include pairs of N–H···O hydrogen bonds linking BA− and/or BAH components into ribbons extending in one dimension. Factors influencing the structure adopted by each compound include cation size and reaction stoichiometry as well as hydrogen bonding.

A survey of the trends in metal–ligand coordination and hydrogen bonding has been carried out on complexes of singly deprotonated cyanuric acid CY− and alkaline earth metals, synthesised from aqueous solution and characterised by X-ray crystallography. The involvement of cyanurate in metal coordination increases from Mg through Ca and Sr to Ba relative to coordination by water, in parallel with increasing ionic radius and coordination number. The incidence of the bridging of metal centres by both water and cyanurate also increases in this series. The Mg complex [Mg(H2O)6][CY]2·2H2O contains hexaaqua-coordinated cations, uncoordinated CY− anions, and additional water molecules. The Ca and Sr complexes {[Ca(CY)(H2O)3][CY]}∞ and {[Sr(CY)2(H2O)4]}∞ feature polymeric chains of coordinated metal ions, the Ca complex with uncoordinated anions and the Sr complex with all potential ligands coordinated. The Ba complex {[Ba(CY)2(H2O)2]}∞ has a two-dimensional coordination network. Extensive hydrogen bonding plays a key role in generating a three-dimensional network in all four structures. The competition between cyanurate and water for coordination to the alkaline earth metal cations, and that between coordination and the hydrogen bonding propensities of the cyanurate anion, appear to be finely balanced, with the structural outcomes depending on the relative sizes and degrees of hardness of the four cations of the group.

Novel organometallic complexes Mn(benzene-1,2-diamine)(CO)3Br, Mn-1, Mn(3-methylbenzene-1,2-diamine)(CO)3Br, Mn-2, and Re(benzene-1,2-diamine)(CO)3Cl, Re-1, have been synthesized and characterized by IR, UV/Vis, 1H-NMR, EA and HRMS. The structures of Mn-2 and Re-1 were confirmed by X-ray crystallography. The three novel compounds were studied for their electrocatalytic reduction of carbon dioxide to carbon monoxide using cyclic voltammetry in acetonitrile solutions. Controlled potential electrolysis was used to obtain information on faradaic yield, with product formation being confirmed by GC. Using earth-abundant manganese, compounds Mn-1 and Mn-2 display turnover frequencies of 108 s−1 and 82 s−1, respectively, amid selective production of carbon monoxide (faradaic yields ~85%), with minimal co-production of dihydrogen (Re-1, displays no activity as an electrocatalyst for carbon dioxide reduction under identical conditions.

A metal organic framework Cu(tpt)BF4·¾H2O was synthesized as a potential carbon capture material, with the aim being to exploit the Lewis base interaction of the incorporated ligand functionalities with acidic gas. The material displays high thermal stability but an exceptionally low surface area; however, this contrasts starkly with its ability to capture carbon dioxide, demonstrating significant activated diffusion within the framework. The full characterization of the material shows a robust structure, where the CO2 sorption is 120% greater than current industrial methods using liquid amine solutions; the thermal energy required for sorbent regeneration is reduced by 65%, indicating the true industrial potential of the synthesized material.

The structure of the title hydrated molecular salt, C14H23N2O4+·C2H3O2−·H2O, was determined as part of a wider study on the use of the molecule as a polydentate ligand in the synthesis of MnIII clusters with magnetic properties. The cation features intramolecular O—H...N and N—H...O hydrogen-bond interactions. The crystal structure features a range of intermolecular hydrogen-bonding interactions, principally O—H...O interactions between all three species in the asymmetric unit. An R24(8) graph-set hydrogen-bonding motif between the anion and water molecules serves as a unit which links to the cation via the diethanolamine group. Each O atom of the acetate anion accepts two hydrogen bonds.

In the title compound, [IrCl(C8H12)(C17H25N3)], the IrI ion has a distorted square-planar coordination geometry. The N-heterocyclic carbene ligand has an extended S-shaped conformation. The butyl group was refined using a two-part 1:1 disorder model. In the crystal, three unique weak C—H...Cl contacts are present. Two of these form a motif described as R21(6) in graph-set notation, while a third forms an R22(8) motif about a crystallographic inversion center. The result is a chain structure which extends parallel to the crystallographic a axis.

In the title compound, C22H24N4O, the aromatic moiety is essentially planar (r.m.s. deviation of a least-squares plane fitted through all non-H atoms = 0.0386 Å) and is rotated by 89.98 (4)° from the piperazine ring, which adopts the expected chair conformation. The propanol chain is not fully extended away from the piperazine ring. In the crystal, there are two unique hydrogen-bonding interactions. One is an O—H...N interaction which, together with an inversion-related symmetry equivalent, forms a ring motif. The second is an N—H...N interaction which links adjacent molecules by means of a chain motif which propagates in the c-axis direction. Overall, a two-dimensional hydrogen-bonded structure is formed.

In the title compound, [Rh(C8H12)(C7H12N2)2]BF4, the square-planar Rh complex cation and the BF4− anion are both bisected by a crystallographic twofold rotation axis. The Rh and B atoms lie on this axis and all others are in general positions. In the crystal, two unique C—H...F hydrogen-bonding interactions are present, which involve both imidazolin-2-ylidene H atoms. They form two separate C(5) motifs, the combination of which is a rippled hydrogen-bonded sheet structure in the ab plane.

The structure of the organic cation in the title compound, C15H16N3+·ClO4−, contains two essentially planar rings. Mean planes fitted through all non-H atoms of each ring system have an r.m.s. deviation of 0.019 Å for the imidazole-based ring and 0.016 Å for the 2,6-dimethylphenyl ring. The angle between the two planes is 86.76 (2)°. In the crystal structure, N—H...O interactions form a one-dimensional chain, which propagates in the b-axis direction. C—H...O interactions are also found in the crystal packing.

The V-shaped title compound, C11H10Br2N4, lies on a crystallographic twofold rotation axis which passes through the central C atom. In the crystal, an infinite tape motif, which propagates in the a-axis direction, is formed by inversion-related N—H...N hydrogen-bonding interactions. The structure confirmed the identity of the compound as a reaction side product.

There are two crystallographically unique molecules present in the asymmetric unit of the title compound, C14H16N6O; in both molecules, the seven-membered diazepinone ring adopts a boat-like conformation and the chair conformation piperidine ring is an axial substituent on the diazepinone ring. In the crystal, each molecule forms hydrogen bonds with its respective symmetry equivalents. Hydrogen bonding between molecule A and symmetry equivalents forms two ring motifs, the first formed by inversion-related N—H...O interactions and the second formed by C—H...O and C—H...N interactions. The combination of both ring motifs results in the formation of an infinite double tape, which propagates in the a-axis direction. Hydrogen bonding between molecule B and symmetry equivalents forms one ring motif by inversion-related N—H...O interactions and a second ring motif by C—H...O interactions, which propagate as a single tape parallel with the c axis.

The title compound, C24H30N2O6, a Schiff base, adopts an extended conformation in which the methoxy groups are essentially coplanar with the aromatic ring to which they are bonded (mean planes fitted through the non-H atoms of each methoxyphenyl group have r.m.s. deviations of 0.078 and 0.044 Å) and the angle between mean planes fitted through the aromatic rings is 87.57 (10)°. An intramolecular N—H...N hydrogen bond keeps the imine and amide groups essentially coplanar. A mean plane fitted through these groups has an r.m.s. deviation of 0.0545 Å. Additional O—H...O hydrogen bonding parallel with the a axis links the molecules into a hydrogen-bonded chain in the crystal. C—H...O and C—H...π interactions are found within the crystal packing. The compound has been assigned the S,S configuration on the basis of the chemical synthesis, which used pure homotopic l-amino acids, and we have no reason to believe that the compound has epimerized.

In the title compound, [Ir(C8H12)(C7H12N2)(C18H15P)]BF4·CH2Cl2, the Ir(I) atom has a square-planar conformation with normal bond lengths. One of the phenyl rings, and the solvent dichloromethane molecule, were refined using separate two part disorder models, each in an approximately 1:1 ratio.

The title compound, C8H13Br2NO3, crystallizes as a non-merohedral twin with twin law −0.6 0 0.4/0 − 1 0 /1.6 0 0.6, and the structure has a refined twin domain ratio of 0.546 (5). The structure shows a compact conformation, with the ester unit roughly coplanar with a mean plane fitted through the non-H atoms of the pyrrolidine ring [dihedral angle = 8.23 (9)°]. In the crystal, inversion dimers linked by pairs of O—H...O hydrogen bonds generate an R22(12) motif.

The title compound, C21H21N3O2, was obtained following a five-step synthetic procedure yielding weakly diffracting rod and needle-shaped crystals which crystallized concomitantly. Structural analysis of a rod-shaped crystal showed that the central seven-membered heterocyclic ring adopts a conformation that is perhaps best described as a distorted boat, with the H-bearing (CH2 and NH) atoms lying well out of the least-squares mean plane fitted through the other five atoms in the ring (r.m.s. deviation 0.075 Å). In the crystal, the compound packs as a twisted chain, which propagates along the b axis by means of an R12(6) motif formed by one of the carbonyl O atoms acting as a bifurcated acceptor in an N—H...O and C—H...O interaction. No diffraction was observed from the needle-shaped crystals.

The title compound, C14H5F6NO3, was synthesized by condensation of tetrafluorophthalic anhydride and 2,4-difluoroaniline. It was then recrystallized from hexane to give a nonmerohedral twin with two crystallographically unique molecules in the asymmetric unit. The refined twin fraction is 0.460 (3). Torsional differences between the aryl rings and the central amide group account for the presence of two unique molecules. The compound packs as double tapes formed by O—H...O and N—H...O hydrogen-bonding interactions between each unique molecule and its symmetry equivalents.

The title compound, C28H34N2O8S2, was synthesized as part of a project to develop synthetic routes to analogues of sporidesmins, a class of secondary metabolite produced by the filamentous fungi Chaetomium and Pithomyces sp. The complete molecule is generated by crystallographic inversion symmetry: the methoxy group is essentially coplanar with the benzene ring to which it is bonded, a mean plane fitted through the non-H atoms of the aromatic ring and the methoxy group having an r.m.s. deviation of 0.0140 Å. Similarly, the ester group is also essentially planar (r.m.s. deviation of a plane fitted through all non-H atoms is 0.0101 Å). There is only one independent C—H...O interaction, which links together adjacent molecules into a two-dimensional sheet in the bc plane.

The synthesis of the title compound, C16H15N3O, is regiospecific and single-crystal X-ray diffraction provides the only means of unambiguous structural analysis, with the benzene ring bonded to the imine C atom. The phenyl ring and the essentially planar (r.m.s. deviation 0.0354 Å) methoxybenzene group are rotated by 29.41 (5) and 37.01 (5)°, respectively, from the central pyrazole ring. An intermolecular N—H...N hydrogen bond links symmetry-related molecules into a C(5) chain, which runs parallel to the b axis.

Reaction of 4,4′-bipyridine (4,4′-bipy) with barbituric (BAH), orotic (ORH), and uracil-5-carboxylic acids (U5CAH) yielded three new products, which have been characterized by single-crystal X-ray diffraction. The products include a co-crystal of neutral species with Z′ = 2 (4,4′-bipy/BAH), an organic complex ion pair (4,4′-bipy/ORH) and a compound containing both ionic and hydrogen-bonded neutral species (4,4′-bipy/U5CAH). Partial proton transfer is observed in both of the ionic cases, and in all three structures the crystal packing arrangement is such that weak hydrogen bonding, π···π and molecular dipole interactions are optimized. [ABSTRACT FROM AUTHOR]

Three new complexes of the [Re6(μ3-Se)8]2+core-containing clusters with the water-soluble trialkylphosphine ligand 1,3,5-triaza-7-phosphaadamantane (PTA), [Re6(μ3-Se)8(PEt3)5(PTA)](SbF6)2(P5PTA, 1), [Re6(μ3-Se)8(PEt3)5(PTAH)][Re6(μ3-Se)8(PEt3)5(PTA)](SbF6)5(2), and [Re6(μ3-Se)8(PEt3)5(PTAH)]2(HBr)(SbF6)2Br4(3) have been prepared and structurally characterized. Unexpected protonation of the cluster-bound PTA ligand was observed when coordination of 1with HgI2was attempted, affording compound 2featuring a protonated PTA ligand, PTAH. Deliberate acidification of 1with HBr produced compound 3, and the protonation was investigated by using 31P NMR spectroscopy. Crystallographic studies revealed distinct structural distortions of the ligand as a result of protonation. [ABSTRACT FROM AUTHOR]

The reactions of the previously reported cluster complexes [Re6(μ3-Se)8(PEt3)5I]I, trans-[Re6(μ3-Se)8(PEt3)4I2], and cis-[Re6(μ3-Se)8(PEt3)4I2] with the [Re6(μ3-Se)8]2+ core with CO in the presence of AgSbF6 afforded the corresponding cluster carbonyls [Re6(μ3-Se)8(PEt3)5(CO)][SbF6]2 (1), trans-[Re6(μ3-Se)8(PEt3)4(CO)2][SbF6]2 (2), and cis-[Re6(μ3-Se)8(PEt3)4(CO)2][SbF6]2 (3). Infrared spectroscopy indicated weakening of the bond in CO, suggesting the existence of backbonding between the cluster core and the CO ligand(s). Electrochemical studies focusing on the reversible, one-electron oxidation of the cluster core revealed a large increase in the oxidation potential upon going from the acetonitrile derivatives to their carbonyl analogs, consistent with the depleted electron density of the cluster core upon CO ligation. Disparities between the IR spectra and oxidation potential between 2 and 3 indicate that electronic differences exist between sites trans and cis to the location of a ligand of interest. The active role played by the Se atoms in influencing the cluster-to-CO bonding interactions is suggested through this result and density functional (DF) computational analysis. The computations indicate that molecular orbitals near the HOMO account for backbonding interactions with a high percentage of participation of Se orbitals. [ABSTRACT FROM AUTHOR]

Reaction in methanol or water of the organic base 1,8-bis(dimethylamino)naphthalene (often called “proton sponge”, PS) with four simple chemically related organic acids (HA), namely, violuric acid (VIH), cyanuric acid (CYH), barbituric acid (BAH), and orotic acid (ORH), gave rise to four new organic salts, 1−4, respectively, with very different crystal structures. Crystallographic problems (including disorder, weak diffraction, and rapid dissolution at ambient temperatures) were encountered with all four compounds and were successfully resolved in each case. Analysis of the crystal packing shows that weak C−H···O and π···π stacking interactions are important in maintaining the integrity of the structures. All four compounds have asymmetric units containing more than a single ion pair PSH+A- (i.e., Z‘‘ > 2); for the chemically simple compound PS+VI-·MeOH (1), Z‘ = 1 and Z‘‘ = 3, but for the more complicated compound PS+OR- (4), Z‘ = 8 and Z‘‘ = 16 (counting only the species that have been modeled with discrete atoms and ignoring others that are highly disordered in “voids” of the structure) with an extensive network of weak intermolecular interactions holding the structure together. [ABSTRACT FROM AUTHOR]