Charge-assisted Hydrogen Bonds Research Articles

Cover Picture: Lithium [Bis{benzoyl‐W(CO)5}(μ2‐hydrogen)] − A Charge‐Assisted H+‐Bridged Organometallic Complex Prepared by Selective Li+ Ion Replacement (Eur. J. Inorg. Chem. 21/2003)

AbstractThe cover picture shows the crystal structure of lithium bis[benzoyl‐W(CO)5][μ2‐hydrogen] (orange: tungsten; red: oxygen; blue: lithium; grey: carbon), a new class of hydrogen‐bridged organometallic complexes exhibiting strong, charge assisted hydrogen bonds between anionic metal−acyl moieties in Fischer‐type carbene precursors. The novel cation‐exchange procedure used here could find application in future organometallic crystal engineering studies involving carbonylmetal fragments. Details are discussed in the article by H. G. Raubenheimer et al. on p. 3861 ff. Dedicated to E. O. Fischer on the occasion of his 85th birthday

Highly sensitive luminescent metal-complex receptors for anions through charge-assisted amide hydrogen bonding.

Two structurally simple and easily synthesized luminescent anion receptors featured with an amide-type anion binding site and rhenium(I) tricarbonyl pyridine signaling units have been developed, and they display outstanding sensitivity and selectivity toward a variety of anionic species. These complexes are highly emissive in solution. Upon anion binding, the emission intensity was significantly quenched. The sensitivities of these complexes are so high that the emission intensity can be effectively quenched by as much as 10% even in the presence of only 10(-8) M cyanide or fluoride anions. The ability of formation of intramolecular hydrogen bonding between the amide protons and central pyridine is believed to be responsible for the observed high selectivity.

N-(3-Phenoxy-4-pyridinio)methanesulfonamidate

The title compound, C(12)H(12)N(2)O(3)S, is a strict pyridine analogue of nimesulide, a selective inhibitor of cyclooxygenase-2. The structure is characterized by a pyridinium ring with a deprotonated sulfonamide group. An intermolecular charge-assisted hydrogen bond between these two groups is observed within the crystal packing, linking the molecules into an infinite chain running along the b-axis direction.

Self-Association Of Benzene-1,3,5-Tris-(Methylenephosphonic Acid): Evidence of Charge-Assisted Hydrogen Bonds

The synthesis and the solid-state structure of benzene-tris-(methylene-phosphonic acid) is reported in the following article. Surprisingly the three methylenephosphonic acid groups are located on the same side of the benzene ring leading to the formation of an octopus shaped molecule. Furthermore the number of proton per phosphonic acid function is different from the expected value of two per phosphophonic acid function. The single crystal X-ray diffraction reveals that this interesting behaviour arises from the formation of a dimer in the solid-state. Interestingly both charge-assisted hydrogen bonds and hydrogen bonds are observed in this dimer.

Associations of squaric acid and its anions as multiform building blocks of hydrogen-bonded molecular crystals.

Squaric acid, H(2)C(4)O(4) (H(2)SQ), is a completely flat diprotic acid that can crystallize as such, as well as in three different anionic forms, i.e. H(2)SQ.HSQ(-), HSQ(-) and SQ(2-). Its interest for crystal engineering studies arises from three notable factors: (i) its ability of donating and accepting hydrogen bonds strictly confined to the molecular plane; (ii) the remarkable strength of the O-H...O bonds it may form with itself which are either of resonance-assisted (RAHB) or negative-charge-assisted [(-)CAHB] types; (iii) the ease with which it may donate a proton to an aromatic base which, in turn, back-links to the anion by strong low-barrier N-H+...O(1/2-) charge-assisted hydrogen bonds. Analysis of all the structures so far known shows that, while H(2)SQ can only crystallize in an extended RAHB-linked planar arrangement and SQ(2-) tends to behave much as a monomeric dianion, the monoanion HSQ(-) displays a number of different supramolecular patterns that are classifiable as beta-chains, alpha-chains, alpha-dimers and alpha-tetramers. Partial protonation of these motifs leads to H(2)SQ.HSQ(-) anions whose supramolecular patterns include ribbons of dimerized beta-chains and chains of emiprotonated alpha-dimers. The topological similarities between the three-dimensional crystal chemistry of orthosilicic acid, H(4)SiO(4), and the two-dimensional one of squaric acid, H(2)C(4)O(4), are finally stressed.

ChemInform Abstract: Intermolecular Interactions in Nonorganic Crystal Engineering

The utilization of noncovalent interactions to construct molecular crystals is evaluated in the context of inorganic and organometallic crystal engineering. The attention is focused on hydrogen-bonding interactions involving metal complexes in which the metal atoms participate in the bonding either directly or as ancillary systems. The role of ionic charges is discussed. It is shown, inter alia, that reproducible and transferable crystal synthesis strategies based on charge-assisted hydrogen bonds can be devised to build periodical supermolecules.

Intermolecular interactions in nonorganic crystal engineering.

The utilization of noncovalent interactions to construct molecular crystals is evaluated in the context of inorganic and organometallic crystal engineering. The attention is focused on hydrogen-bonding interactions involving metal complexes in which the metal atoms participate in the bonding either directly or as ancillary systems. The role of ionic charges is discussed. It is shown, inter alia, that reproducible and transferable crystal synthesis strategies based on charge-assisted hydrogen bonds can be devised to build periodical supermolecules.

Supramolecular co-ordination networks constructed via pi-stacking interactions and charge-assisted hydrogen bonds

The diprotic acid 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid, H2SQA) reacts with [(eta5-C5H5)2Co] in THF to form a hydrogen bonded co-ordination network in crystalline {[CoII(HSQA-HSQA)2(H2O)4]2-}{[(eta5-C5H5)2CoIII]+}2 (1) which contains CoII and CoIII metal centres and the supramolecular salt {[(eta5-C5H5)2CoIII]+}{[(HSQA)(H2SQA)]-} (2) depending on the solvent and on the stoichiometric ratio. The diprotic acid pyridine-2,6-dicarboxylic acid (dipicolinic acid, H2DPA) reacts with [(eta5-C5H5)2Co] and [(eta6-C6H6)2Cr] in THF or water to form the supersalt {[(eta5-C5H5)2Co]+}{ [(HDPA)(H2DPA)]-} (3) and the co-ordination complex {[(eta6-C6H6)2CrI]+}2{[(DPA)2CrIII]-}.2H2O (4), respectively. All compounds have been structurally characterised by single-crystal X-ray diffraction. The metal centres in the mixed valence species 4 are the paramagnetic 17 electrons CrI and 15 electrons CrIII, respectively. The crystalline edifices in all compounds are held together by pi-stacking interactions involving the flat organic moieties and by hydrogen bonding interactions of the O-H...O and/or O-H...O(-) type between the acid moieties, whether as metal co-ordinated ligands or as free ions and by charge assisted C-Hdelta+...Odelta- bonds between cations and anions.

Charge-Assisted Hydrogen Bonds and Halogen-Halogen Interactions in Organic Salts: Benzylammonium Benzoates and Pentafluorobenzoates

The enhanced influence of charge-assisted hydrogen bonds upon the resulting crystal structure in the presence of competing noncovalent interactions has been examined using single-crystal X-ray diffraction. The crystal structures of six organic salts are presented: 4-chlorobenzylammonium 2,4-dichlorobenzoate, 3-chlorobenzylammonium 2,4-dichlorobenzoate, 4-methylbenzylammonium pentafluorobenzoate, 4-chlorobenzylammonium pentafluorobenzoate, 3-methylbenzylammonium benzoate, and 4-chlorobenzylammonium benzoate monohydrate. All structures are dominated by charge-assisted \( - {\text{NH}}_{\text{3}}^{\text{ + }} \cdot \cdot \cdot ^ - {\text{OOC}} -\)hydrogen bonds that generate either one-dimensional ribbons or two-dimensional sheets. The structural influence of weaker intermolecular interactions is limited as there are very few short, halogen-halogen, π-π, or \({\text{C}} - {\text{H}} \cdot \cdot \cdot {\text{X}}\) distances in this series of compounds.