Metal-complex assemblies constructed from the flexible hinge-like ligand H2bhnq: structural versatility and dynamic behavior in the solid state

Novel metal-complex assemblies constructed from the flexible hinge-like ligand H(2)bhnq (H(2)bhnq=2,2'-bi(3-hydroxy-1,4-naphthoquinone)) have been synthesized. The X-ray crystal structures of these compounds reveal that four types of architectures are accessible by variation of the metal ions. In copper(II) compounds 1-3, the chelating bhnq(2-) ions bridge copper(II) centers to form one-dimensional zigzag chains. The chains of 1-3 are arranged by hydrogen-bonding interactions and stacking interactions to produce porous structures. Cobalt(II) and zinc(II) compounds 4 and 5 form one-dimensional helical chains. In 4 and 5, the crystal packing induces spontaneous resolution of the helical chains with chiral cavities formed perpendicular to the helices. Nickel(II) compounds 6 and 7 form cyclic tetramers. The fourth architecture, a dimer (compound 8), is obtained by the reaction of zinc(II) and bhnq(2-) in MeOH. In these compounds, changes of the dihedral angles and the metal-coordination mode of the bhnq(2-) ion induce the structural versatility. The assemblies of the zigzag chains of the copper(II) compounds exhibit reversible vapochromic behavior. UV/Vis, powder X-ray diffraction, EPR, and adsorption isotherm measurements indicate that this vapochromic behavior is based on the hinge-like flexibility of the bhnq(2-) ion.     

Triple hydrogen bonds direct crystal engineering of metal-assembled complexes: the effect of a novel organic-inorganic module on supramolecular structure

Novel triply hydrogen bonded suprastructures based on [M(tdpd)2(L)2]2- (H2tdpd=1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarbonitrile, L=solvent) and melamine-analogous cations have been synthesized and characterized. The use of anions containing two AAA sets from [M(tdpd)2(L)2]2- together with cations containing one DDD set (A=hydrogen-bond acceptor, D=hydrogen-bond donor) leads to the formation of complementary triply hydrogen bonded modules in the solid state. In all cases, the building module is further extended via additional hydrogen-bonding interactions to produce a tape, and tapes are assembled into sheets. These results show that a hydrogen-bonded module consisting of different kinds of building blocks, one of which is a metal complex that includes hydrogen-bond acceptor sites and the other is a hydrogen-bond donor molecule, will be attractive for constructing metal-containing supramolecular systems by the self-assembly technique.     

Hydrogen bonding: How much anharmonicity?

In moderately strong hydrogen bonds, hydrogen bond formation increases the anharmonicity constant of the high frequency stretching vibration, significantly but not dramatically. This increase tends to increase with the strength of the hydrogen bond. The main cause of the fine structure and breadth of this band is, however, coupling with both the low frequency stretching and bending vibrations of the bridge, despite the smallness of the coupling constants. Second–order perturbation theory is sufficient to interpret the observed frequencies in the case of moderately strong hydrogen bonds. HCNHF, O–H:O, O–H:N, and N–H:N hydrogen bonds are considered.     

Die Gadoliniumcarbidhalogenide Gd4C2X3 (X = Cl,Br)

The Gadolinium Carbide Halides, Gd₄C₂X₃ (X = Cl, Br) The compounds Gd₄C₂X₃ (X = Cl, Br) and Tb₄C₂Br₃ have been prepared by reaction of the metals (RE), REX₃, and C in sealed Ta capsules at 1 100° and 1 300°C, respectively. Monophasic samples of Gd₄C₂Br₃ and Tb₄C₂Br₃ were obtained by reacting stoichiometric mixtures of the starting materials for five days. The needle shaped crystals are bronze-coloured and sensitive to air and moisture. Gd₄C₂X₃ crystallizes in the space group Pnma (No. 62) with lattice constants a = 1 059.6(4), b = 368.4(1), c = 1 962.7(8) pm (Gd₄C₂Cl₃), a = 1 084.4(1), b = 373.0(1), c = 2 036.1(1) pm (Gd₄C₂Br₃). According to Guinier photographs, Tb₄C₂Br₃ is isotypic (a = 1 074.3(2), b = 370.6(1), c = 2 019.4(1) pm). In the crystal structure C is octahedrally coordinated by Gd. The Gd₆ octahedra are linked via common edges to form corrugated layers. The X-anions coordinate all free edges and corners of these layers and connect them via Xⁱ? Xⁱ contacts parallel [001]. Gd₄C₂Br₃ shows metallic conductivity. The magnetic susceptibility follows at high temperatures a Curie Weiss law with an effective moment of 7.95 μ_B. At temperatures below 50 K antiferromagnetic order is observed.     

Photoresponsive supramolecular systems: self-assembly of azodibenzoic acid linear tapes and cyclic tetramers

A new strategy to effect photoinduced control over molecular self-assembly is reported. This strategy uses the reversible trans-cis photoisomerization of a novel azobenzene system, where the trans- and cis-forms self-assemble into dramatically different higher-order structures. The trans-azobenzene form of this molecule associates into infinite hydrogen-bonded linear tapes, while the cis-azobenzene form undergoes hydrogen-bonded self-assembly into cyclic tetramers. This results in a second level of association, where the cis-hydrogen-bonded supramolecular cycles ultimately form long, rod-like aggregates through stacking interactions.     

The effect of the solvents on the specific intramolecular C-H...N interactions studied by1H NMR spectroscopy

The analysis of the effect of the solvents on the proton chemical shifts in¹H NMR spectra of 2-vinyloxypyridine indicates that the C—H...N interaction of weak intramolecular hydrogen bond type hinders the formation of intermolecular hydrogen C—H...X and C-H... bonds. The protonating solvents reduce the intramolecular C—H...N interaction due to association with the N atom of the pyridine cycle.Translated fromIzvestiya Akademii Nauk. Seriya Khimieheskaya, No. S, pp. 1202–1204, May, 1996.     

二氯四(苯丙酮-1, 2, 4-三唑)合钴六水配合物晶体结构

0IntroductionRecently,thecompoundscontaining1H-1,2,4-tr-iazolegrouphaveattractedmuchinterestbecauseoftheirexhibitingsomefungicidalactivityandplantgrowthregulatingactivity犤1犦,andshowingantibacterialactivityagainstPucciniareconditeandrootsgrowthregulationforcucumber犤2犦.Also,suchcompoundsareincreasinglybeingstudiedbecauseofthecoordinationchemistryofazolesactingasligandsintransitionmetalcompounds.Asamatteroffact,thetriazolederivativeshavebeenextensivelyusedasterminalandbridgingligands,andthey…     

Characteristic features of intra- and intermolecular interactions in crystals of pyrrole-2-carbaldehyde isonicotinoylhydrazone and its hydrate

Pyrrole-2-carbaldehyde isonicotinoylhydrazone (1) and its hydrate [1·H₂O] (2) were studied by single-crystal X-ray diffraction analysis. The introduction of the pyrrole substituent into N"-substituted isonicotinic hydrazide (INH) causes the intramolecular redistribution of the electron density compared to those in INHs studied earlier, which increases the basicity of the hydrazone nitrogen atom (N") involved in intermolecular hydrogen bonding. This effect has not been observed in the structures of N"-substituted INHs and benzhydrazides studied previously. Intermolecular hydrogen bonds play a decisive role in the formation of the crystal structures of 1 and 2.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

On the Importance of H-Bonding Interactions in Organic Ammonium Tetrathiotungstates

Summary. Four new organic ammonium tetrathiotungstates (N–Me–enH₂)[WS₄] (1), (N,N′-dm-1,3-pnH₂)[WS₄] (2), (1,4-bnH₂)[WS₄] (3), and (mipaH)₂[WS₄] (4), (N–Me–enH₂ = N-methylethylenediammonium, N,N′-dm-1,3-pnH₂ = N,N′-dimethyl-1,3-propanediammonium, 1,4-bnH₂ = 1,4-butanediammonium, and mipaH = monoisopropylammonium) were synthesized by the base promoted cation exchange reaction and characterized by elemental analysis, infrared, Raman, UV-Vis and ¹H NMR spectroscopy as well as single crystal X-ray crystallography. The structures of 1–4 consist of [WS₄]²⁻ tetrahedra which are linked to the organic ammonium cations via N–H⋯S hydrogen bonding. The strength and number of the S⋯H interactions affect the W–S bond lengths as evidenced by distinct short and long W–S bonds. The IR spectra exhibit splitting of the W–S vibrations, which can be attributed to the distortion of the [WS₄]²⁻ tetrahedron. From a comparative study of several known tetrathiotungstates it is observed that a difference of more than 0.033 ? between the longest and shortest W–S bonds in a tetrathiotungstate will result in the splitting of the asymmetric stretching vibration of the W–S bond.