Hexafluorosilicates of bis(aminopyridinium). The relationship between H-bonding system and solubility of salts

Pyridinium hexafluorosilicates of the composition (LH)₂[SiF₆] (I, II, IV, L = 2-aminopyridine, 3-aminopyridine, and 2,6-diaminopyridine) and (LH)₂[SiF₆]·H₂O (III, L = 4-aminopyridine) were separated as crystalline products of interaction of fluorosilicic acid with relevant aminopyridines. The compounds were characterized by IR, mass-spectrometry, potentiometry, solubility data, and in the case of I and IV by X-ray crystallography. The relationship between the salts structure and some physical properties is discussed.     

New star-shaped triarylamines: synthesis, mesomorphic behavior, and photophysical properties

A total of 18 compounds 1-6 derived from triphenylamine as core group were prepared and characterized, and their mesomorphic properties were also investigated. Compounds 1-4 and 5,6 were prepared from p,p′,p″-triformyltriphenylamine and p,p′-diformyltriphenylamine with appropriate alkoxyphenylamines. The phase behavior of these mesogenic compounds was characterized and studied by differential scanning calorimetry, polarized optical microscopy, and powder XRD diffraction. Compounds 1-3 exhibited columnar mesophase, however, compounds 4-6 were nonmesogenic. The mesophases observed in compounds 1-3 were found to be side dependent. Compounds 1a, 2a, and 3a appended with one, two, or three side chains exhibited lamellar columnar (Col_L) phases, and compounds 2b and 3b with four or six side chains formed hexagonal columnar (Col_h) phases. The formation of the mesophases, lamellar or columnar mesophases, was probably induced by H-bonding formed between -CH₂NH groups. The oxidation process determined by cyclic voltammetry showed two redox waves, one appeared at 220-255 mV and the other one at 503-677 mV, which gave energy to HOMOs range of 5.02-5.36 eV. The fluorescent properties of the compounds were examined. All λ_max peaks of the absorption and photoluminescence spectra of compounds occurred at ca. 307-392 nm and 368-456 nm, respectively. Compound 4a has a larger red shift due to a better conjugation linked by CC double bonds instead of -CH₂NH in other compounds.     

Synthesis and characterization of novel optically active poly(amide-imide)s via direct amidation

N,N′-Pyromelliticdiimido-di-l-methionine (3) was prepared from the reaction of pyromellitic dianhydride (1) with l-methionine (2) in glacial acetic acid and pyridine solution at refluxing temperature. The direct polycondensation reaction of the monomer diimide-diacid (3) with 1,3-phenylenediamine (4a), 1,4-phenylenediamine (4b), 2,6-diaminopyridine (4c), 3,5-diaminopyridine (4d), 4,4′-diaminodiphenylether (4e) and 4,4′-diaminodiphenylsulfone (4f) was carried out in a medium consisting of triphenyl phosphate, N-methyl-2-pyrolidone, pyridine and calcium chloride. The resulting poly(amide-imide)s having inherent viscosities 0.45-0.53 dl g⁻¹ were obtained in high yields and are optically active and thermally stable. All of the above compounds were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of these new optically active poly(amide-imide)s are reported.     

Cation-anion interactions involving hydrogen bonds: Syntheses and crystal structures study of hexafluorotitanate(IV) salts with pyridine and methyl substituted pyridines

Fluorotitanates (LH)₂[TiF₆]·nH₂O (1: R = pyridine, n = 1, 2: R = 2-picoline, n = 2, 3: R = 2,6-lutidine, n = 0, 4: R = 2,4,6-collidine, n = 0) and (LH)[TiF₅(H₂O)] (3a: L = 2,6-lutidine) have been synthesized by the reaction of pyridine or corresponding methyl substituted pyridines and titanium dioxide dissolved in hydrofluoric acid. The crystal structures of ionic compounds 1, 2, 3, 3a and 4 have been determined by single-crystal X-ray diffraction analysis. The hydrogen bonding led to the formation of discrete (LH)₂[TiF₆] units (4), chains (1-3), and layers (3a). The additional π-π interactions present in 1, 2, and 4 results in chain structures of 1 and 4 and in a layer structure of 2. The [TiF₆]²⁻ and [TiF₅(H₂O)]⁻ anions were observed by ¹⁹F NMR spectroscopy in aqueous solutions of 1, 2, 3, 3a and 4.     

Syntheses,characterizations and crystal structures of monomeric or macrocyclic compounds of di- or triorganotin (IV) moieties with 4,4′-thiodibenzenethiol

Six organotin compounds with 4,4′-thiodibenzenethiol (LH₂) of the type R_nSnL_4−nSnR_n (n = 3: R = Me 1, Ph 2, PhCH₂3, n = 2: R = Me 4, Ph 5, PhCH₂6) have been synthesized. All compounds were characterized by elemental analysis, IR and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectra. The structures of compounds 1, 2, 4, 5 and 6 were also determined by X-ray diffraction analysis, which revealed that compounds 1 and 2 were monomeric structures, compounds 4, 5 and 6 were centrosymmetric dinuclear macrocyclic structures, and all the tin(IV) atoms are four-coordinated. Furthermore, supramolecular structures were also found in compounds 1, 2, 4, 5 and 6, which exhibit one-dimensional chains, two-dimensional networks or three-dimensional structures through intermolecular C–H?S weak hydrogen bonds (WHBs), non-bonded Sn?S interactions or C–H?π interactions.     

Thio-ether-footed resorcin[4]arenes: self-assembly in solution and interaction with gold nanoparticles as viewed by diffusion NMR

In this paper we present the synthesis and characterization of a new family of thio-ether-footed resorcin[4]arenes (2-4). Diffusion NMR was used to follow the self-assembly of 2-4 in CDCl₃ and CHCl₃ solutions. We found that all three molecules self-assemble into hexameric capsules. These capsules can accommodate both tertiary alkylamines and ammonium salts. From the diffusion NMR data we could conclude that the hexameric capsules of compounds 2-4 are of nearly equal stability and prevail in other organic solvents, such as dichloromethane and benzene but not in tetrahydrofuran (THF). By measuring the diffusion coefficients of 2-4 in different concentrations, we found that further aggregation, beyond the hexameric aggregates, is obtained, especially in the case of 2 at high concentrations. Different diffusion NMR techniques revealed that water molecules are part of the hexameric capsules of 2-4 in chloroform solutions. In addition diffusion NMR was used to examine the interactions of compounds 2-4 with gold nanoparticles in chloroform solution and provided an unequivocal evidence for the attachment of 2-4 to the surface of gold nanoparticles. No evidence was found for the formation of higher aggregates on the gold nanoparticles.     

Assembly of novel phenanthroline-based cobalt(II) coordination polymers by selecting dicarboxylate ligands with different spacer length: From 1-D chain to 3-D interpenetrated framework

Three novel Co^II coordination polymers [Co(Dpq)₂(1,4-NDC)_0.5] · (1,4-HNDC) (1), [Co(Dpq)(2,6-NDC)] (2), and [Co₂(Dpq)₂(BPEA)₄(H₂O)] · H₂O (3) have been obtained from hydrothermal reaction of cobalt nitrate with the mixed ligands dipyrido[3,2-d:2′,3′-f]quinoxaline (Dpq) and three dicarboxylate ligands with different spacer length [1,4-naphthalene-dicarboxylic acid (1,4-H₂NDC), 2,6-naphthalene-dicarboxylic acid (2,6-H₂NDC) and biphenylethene-4,4′-dicarboxylic acid (BPEA)]. All these complexes are fully structurally characterized by elemental analysis, IR, and single-crystal X-ray diffraction analysis. Single-crystal X-ray analysis reveal that complex 1 is infinite one-dimensional (1-D) chains bridged by 1,4-NDC ligands, which are extended into a two-dimensional (2-D) supramolecular network by π-π interactions between the Dpq molecules. Complex 2 is a distorted three-dimensional (3-D) PtS network constructed from infinite Co-O-C rod units. Complex 3 has a 5-fold interpenetrated 3-D structure with diamondoid topology based on dinuclear [Co₂(CO₂)₂(μ₂-OH₂)N₄O₂] units and BPEA molecules. The different structures of complexes 1-3 illustrate the influence of the length of dicarboxylate ligands on the self-assembly of polymeric coordination architectures. In addition, the thermal properties of complexes 1-3 and fluorescent properties of complexes 2 and 3 have been investigated in the solid state.     

Alkoxy substituted (E,E)-3,6-bis(styryl)pyridazine—a photosensitive mesogen for liquid crystals

(E,E)-3,6-Bis(styryl)pyridazines (3a-t) bearing 2, 4 or 6 alkoxy chains were prepared by applying the Siegrist reaction of 3,6-dimethylpyridazine (13) and the corresponding azomethines 10a-t. The transversal dipole moment of these calamitic compounds effects an extremely high tendency for self-organization in thermotropic LC phases (N, S_A, S_B, S_C, S_E, S_I/F, and Cub). The conjugated core structure represents moreover a chromophore with a high photosensitivity for (E,E)?(E,Z) isomerization reactions: this property makes the compounds interesting for optical imaging and switching techniques.     

Guest-encapsulation behavior in a self-assembled heterodimeric capsule

Tetra(4-pyridyl)-cavitand 1 and tetrakis(4-hydroxyphenyl)-cavitand 2 self-assemble into a heterodimeric capsule 1·2 via four PhOH?pyridyl hydrogen bonds in CDCl₃, wherein one molecule of 1,4-disubstituted-benzene as a guest is encapsulated to form a ternary complex, guest@(1·2). The X-ray crystallographic analysis of (methyl p-ethoxybenzoate)@(1·2) confirmed that the methyl ester and ethoxy groups of the encapsulated guest are oriented to the cavity ends of the 1 and 2 units, respectively. The scope and limitation of guest encapsulation in 1·2, including guest-binding selectivity and orientational isomeric selectivity, are described from the viewpoint of size complementarity and CH-π, CH-halogen, and halogen-π interactions between guest and the cavity of 1·2.     

N-heterocyclic carbene coordinated gallanes and chlorogallanes

The preparation of the N-heterocyclic carbene coordinated gallium complexes [GaH₃(IXy)] (1), [GaH₃(IDipp)] (2), [GaClH₂(IMes)] (3) and [GaCl₂H(IMes)] (4), where IXy = 1,3-bis(2,6-dimethylphenyl)imidazol-2-ylidene, IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene and IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene, are reported. All four complexes have been characterised by ¹H, ¹³C NMR and IR spectroscopy and, for complexes 2, 3 and 4, single crystal X-ray structure determination. These compounds represent some of the most thermally stable molecular gallium hydrides known, with 4 being the most thermally stable gallium hydride reported (dec. 274 °C). These remarkable thermal stabilities translate to significant aerobic stability such that all four compounds may be handled in dry air without significant decomposition. Compounds 2, 3 and 4 exist as distorted tetrahedra in the solid state with gallium to carbene C-donor bonds that shorten with increasing Lewis acidity of the gallium centre. Compound 2 co-crystallizes with 1 equiv. of 2,6-diisopropylphenylaniline and exhibits several weak intermolecular bonding interactions in the solid-state.     

Structure and reactivity of mono- and dinuclear diiminate zinc alkyl complexes

The synthesis, structure and reactivity of several diiminate ligands are presented. The syntheses of five representative β-diiminate (BDI) zinc alkyl complexes and one β-oxo-δ-diiminate (BODDI) zinc alkyl are described. BDI ligands with varying backbone and N-aryl substituents display different solid state structures. [(BDI)ZnR] are synthesized by the reaction of (BDI)H with ZnR₂ in quantitative yield. Previously reported (BDI-1)ZnEt is a three-coordinate monomer in the solid state whereas [(BDI-3)ZnEt]_∞ [(BDI-3)=2-((2,6-diisopropylphenyl)amido)-3-cyano-4-((2,6-diisopropylphenyl)imino-2-pentene] and [(BDI-4)ZnEt]_∞ [(BDI-4)=2-((2,6-diethylphenyl)amido)-3-cyano-4-((2,6-diethylphenyl)imino-2-pentene] form one dimensional coordination polymers. The bimetallic complex [(BODDI-1)(ZnEt)₂] [(BODDI-1)=2,6-bis((2,6-diisopropylphenyl)amido)-2,5-heptadien-4-one] is prepared through the reaction of (BODDI-1)H₂ with two equivalents ZnEt₂. Both [(BDI)ZnEt] and [(BODDI)ZnEt] complexes react with acetic acid to give the acetate complexes in moderate to high yields, offering a superior synthetic route to these complexes. [(BDI)ZnR] [BDI=(BDI-3) or 1,1,1-trifluoro-2-((2,6-diisopropylphenyl)amido)-4-((2,6-diethylphenyl)imino-2-pentene), (BDI-5)] complexes react with MeOH to produce [{(BDI)Zn(μ-OMe)}₂Zn(μ-OMe)₂] in moderate yields. The molecular structures of [(BDI-3)ZnEt], [(BDI-4)ZnEt], [(BODDI-1)(ZnEt)₂], [(BODDI-1)Zn₂(μ-OAc)₂], [{(BDI-3)Zn(μ-OMe)}₂Zn(μ-OMe)₂] and [{(BDI-5)Zn(μ-OMe)}₂Zn(μ-OMe)₂] have been determined by X-ray diffraction.     

Synthesis, characterization and butadiene polymerization studies of cobalt(II) complexes bearing bisiminopyridine ligand

A series of 2,6-bis(imino)pyridyl Co(II) complexes of the general formulas [2,6-(ArNCMe)₂C₅H₃N]CoCl₂ (Ar = -C₆H₅, 3a; 2-MeC₆H₄, 3b; 2-EtC₆H₄, 3c; 2-ⁱPrC₆H₄, 3d; 2,6-ⁱPr₂C₆H₃, 3e; 4-ⁱPrC₆H₄, 3f; 4-FC₆H₄, 3g; 4-CF₃C₆H₄, 3h; 2-FC₆H₄, 3i; 2,6-F₂C₆H₃, 3j; 2-Me-4-FC₆H₃, 3k and 2,6-Me₂-4-FC₆H₂, 3l) and [2,6-(ArNCH)₂C₅H₃N]CoCl₂ (Ar = -C₆H₅, 3m; 2-EtC₆H₄, 3n and 4-ⁱPrC₆H₄, 3o) have been synthesized and characterized. The structures of new complexes 3a, 3f-3h and 3m-3o are further confirmed by X-ray crystallography. All complexes adopt distorted trigonal bipyramidal configuration with the equatorial plane formed by the pyridyl nitrogen atoms and the two chlorine atoms. In the complexes 3m and 3o, three aromatic rings are essentially coplanar, which is in sharp contrast to the other complexes, where three rings are almost orthogonal to each other. With methylaluminoxane (MAO) as cocatalyst in toluene at room temperature, the complexes show moderate to high conversion (42-99%) in butadiene polymerization, producing polybutadiene with tunable cis-1,4 structure (77.5-97%) and controllable molecular weight and molecular weight distribution. The catalytic activity, selectivity as well as the molecular weight and molecular weight distribution of the resultant polymer are found to be dependent on the size and nature of substituents on iminoaryl rings and their positions located. By deliberately tuning the ligand structure, more efficient catalyst in terms of high activity and high selectivity can be obtained.     

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H2O)m] · nH2O (M = Co, Cd or Zn)

Three novel metal-organic frameworks [M(1,3-BDC)(Dpdq)(H₂O)_m] · nH₂O, (M = Co^II (1), Cd^II (2) or Zn^II (3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π-π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1-3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.     

meta-Phenylene-bridged double Schiff base copper(II) complexes as building blocks for 1D coordination polymers: Synthesis,crystal structure and magnetic properties

The new double Schiff-base ligands H₆ipa-hyhb and H₆ipa-hyhh were synthesized by condensation of a 4,6-diformylresorcinol derivative (ipa) with 4-hydroxy-butanoic acid hydrazide (hyhb) and 6-hydroxy-hexanoic acid hydrazide (hyhh). The reaction with copper(II) perchlorate in the presence of an appropriate co-ligand (Him = imidazole, Hpz = pyrazole) leads to the novel coordination polymers {[Cu₂(H₄ipa-hyhb)(Hpz)₂](ClO₄)₂}_n (1), {[Cu₂(H₄ipa-hyhb)(Him)₂](ClO₄)₂}_n (2), and {[Cu₂-(H₄ipa-hyhh)(Hpz)₂](ClO₄)₂}_n (3). These coordination polymers are composed of primary building blocks with the general formula [Cu₂(H₄ipa-X)(L)₂]²⁺ (X = hyhb, hyhh; L = Him, Hpz) which are linked by coordination of the hydroxyl groups of the ligand side chains at the apical position of copper(II) centers of adjacent building blocks. The resulting chains possess different topologies and therefore different supramolecular structures due to the variation in length of the ligand alkyl side chains. For the complexes 1 and 2 double hydroxyalkyl-bridged distorted ladder like chains are formed. Whereas in case of complex 3 single hydroxyalkyl-bridged chains are obtained which assemble to hydrogen bonded double chains. In the case of 1 and 2 these chains are cross-linked by hydrogen bonding interactions with the perchlorate counterions, whereas for 3 additional π–π stacking interaction are observed. The temperature-dependent magnetic measurements indicate weak antiferromagnetic interactions with coupling constants J = −26.1 cm⁻¹ (1), J = −28.2 cm⁻¹ (2), and J = −26.5 cm⁻¹ (3). The magnetic exchange interaction is solely the result of a coupling within the dinuclear complex moieties through the central resorcinol moiety.     

Tubular structures bearing channels in organic crystals composed of adamantane-based macrocycles

Five macrocyclic molecules (1–5) were efficiently synthesized from the dimerization and trimerization of di-substituted adamantane derivatives, which were composed of three different aromatic units and two different linker groups. Three single-crystals were obtained from these macrocyclic molecules, including a set of pseudopolymorphs (3a and 3b) of macrocycle 3 and another macrocycle 5 (5a). Single crystal X-ray analysis revealed that the three monocyclic compounds were rectangular or square in shape with solvent molecules in the cavity. Macrocycle 3 in 3a formed stacks to produce tubular structures with channels that assembled into three-dimensional networks through CH/π interactions.     

Molecular engineering. Part 9: Enhanced binding ability and selectivity of C2v cavitands

Two new C_2v cavitands with protective side chains were synthesized and their binding properties for small molecules were studied. Cavitand 7 having benzyl side chains binds ethanol most strongly with K_a = 1508 M⁻¹ at 20 °C in CDCl₃, which was driven entropically. Cavitand 8 having coumarinyl side chains showed weaker binding due to its steric hindrance. ¹H NMR spectra show that carceroisomers of ethanol or acetonitrile@cavitand 7 exist in 3:1 ratio at 20 °C. The binding tendencies of the guest molecules were increased in nonpolar solvent media.     

New interlocked molecules generated from a podand containing urea units and imidazolium salts using an anion template

A podand containing urea units (L) was found to form interlocked structures with 2,5-dihexylamide imidazolium salts (3·X), 2,5-dihexyl imidazolium salts (4·X), and 2,5-dihexyl benzoimidazolium salts (5·X), where X=Cl⁻, Br⁻, and PF₆⁻ using anions as templates. The binding ability of L and guest molecules was evaluated by ¹H NMR titrations in CDCl₃. It was found that L could form complexes with guest molecules in the following order, 3·X > 5·X > 4·X. Stabilities of the complexes also depended on shape of the templated anions: Cl⁻>Br⁻?PF₆⁻. Hydrogen bonding and π-π stacking interactions played an important role in the self-assembling of these interlocked molecules.     

Tricyclic ligands on cyclam core and X-ray crystallographic structure of hexachloro-(1,11:4,8-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,8-diazonia-4,11-diazacyclotetradecane) - dimanganese(II) dimethanol dihydrate solvate

The synthesis of tricyclic compounds on functionalized cyclam core is described. The addition of four methyl acrylate molecules and consecutive condensation of this derivative with ethylenediamine resulted in formation of 1,4,8,11-tetrakis(2-(N-(2-aminoethyl)carbamoyl)ethyl)-1,4,8,11-tetraazacyclotetradecane (3). Compound 3 was the substrate for further condensation with dialdehydes: iso-phthaldialdehyde and 2,6-pyridinedicarbaldehyde, resulting in spontaneous macrocycle ring closure to give tricyclic derivatives: 1,11:4,8-bis(benzene-1,3-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (4) in the reaction of 3 with iso-phthaldialdehyde and three isomers: 1,4:8,11-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5A), 1,11:4,8-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5B), and 1,8:4,11-bis(pyridine-2,6-diyl-bis(2-(N-(2-formidoylethylene)carbamoyl)ethylene))-1,4,8,11-tetraazacyclotetradecane (5C) when 2,6-pyridinedicarbaldehyde was used. The compounds 4, 5B, and 5C were identified crystallographically. The isolated 5A converted in solution into the mixture of 5B and 5C as monitored by the ¹H NMR spectroscopy. The tricycle 5 is able to accept two manganese(II) metal ions by reacting with manganese(II) dichloride with simultaneous diprotonation of 5. Structure of the resulting Mn₂(5BH₂)Cl₆·(CH₃OH)₂(H₂O)₂ was determined crystallographically.     

Oxime-substituted NCN-pincer palladium and platinum halide polymers through non-covalent hydrogen bonding (NCN = [C6H2(CH2NMe2)2-2,6])

The oxime-substituted NCN-pincer molecules HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 (2a) and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (2b) were accessible by treatment of the benzaldehydes H(O)C-4-C₆H₃(CH₂NMe₂)₂-3,5 (1a) and H(O)C-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 (1b) with an excess of hydroxylamine. In the solid state both compounds are forming polymers with intermolecular O-H?N connectivities between the Me₂NCH₂ substituents and the oxime entity of further molecules of 2a and 2b, respectively. Characteristic for 2a and 2b is a helically arrangement involving a crystallographic 2₁ screw axis of the HONCH-1-C₆H₃(CH₂NMe₂)₂-3,5 and HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6-Br-1 building blocks.The reaction of 2b with equimolar amounts of [Pd₂(dba)₃ · CHCl₃] (3) (dba = dibenzylidene acetone) or [Pt(tol)₂(SEt₂)]₂ (4) (tol = 4-tolyl) gave by an oxidative addition of the C-Br unit to M coordination polymers with a [(HONCH-4-C₆H₂(CH₂NMe₂)₂-2,6)MBr] repeating unit (5: M = Pd, 6: M = Pt). Complexes 5 and 6 are in the solid state linear hydrogen-bridged polymers with O-H?Br contacts between the oxime entities and the metal-bonded bromide.     

Ferrocene incorporating host-guest dyads with electrochemically controlled three-pole hydrogen bonding properties

We describe the electrochemically controlled hydrogen bonding interactions between the isobutyl flavin/2,6-diferrocenylamidopyridine (2·5) and 9,10-phenanthrenequinone/1-ferrocenyl-3-hexylurea (4·6) dyads. Cyclic and square wave voltammetry studies have shown that the binding efficiencies between these moieties can be electrochemically actuated in non-polar (CH₂Cl₂ for 2·5) or polar (DMF for 4·6) organic solvents between three distinct states.