Supra-molecular Chains Research Articles

Supramolecular association in Cu(II) coordination complexes involving energetically significant NO⋯NO π–hole interaction and cooperative π-stacked ternary assembly: Experimental and theoretical studies

Two new copper (II) coordination solids involving 1,10-phenanthroline (phen) and benzoate (bz) viz., [Cu(phen)(H2O)2(η2-NO3)]·NO3 (1) and [Cu(phen)2(η2-bz)]·2bzH·NO3 (2) [bzH = benzoic acid] have been synthesized and characterized by X-ray crystal structure analysis, FT-IR, electronic spectra, ESR and TGA. Theoretical calculations have been performed to analyse some unconventional non-covalent interactions observed in the solid state structures of compounds 1 and 2. In compound 1, 1D supramolecular chain is formed between the cationic moieties through the anti-parallel NO⋯NO π–hole interactions involving the coordinated nitrato co-ligands which have been scarcely describe in the literature. The NCI plot analysis reveals the existence of the anti-parallel NO⋯NO π–hole interaction for the supramolecular dimer of compound 1. The binding energy of the NO⋯NO π–hole interaction in the supramolecular dimer is −18.2 kcal/mol, thus, indicating a moderately strong interaction. In compound 2, a remarkable cooperative (π–π)2/(π–π)1/(π–π)2 type network for self-assembly progression of the ternary π-stacked assembly has been studied. The computation of the energetic features reveals that (π–π)1 is reinforced by the presence of (π–π)2 in compound 2. The microbial activities have been investigated for both the compounds.

Crystal structure of 2-[(2E)-2-methyl-3-phenyl-prop-2-en-1-yl-idene]-N-phenyl-hydrazinecarboxamide.

The title compound, C17H17N3O, crystallizes with two independent mol-ecules in the asymmetric unit. The semicarbazone moieties of these independent mol-ecules (I and II) are essentially planar [maximum deviation of 0.042 (1) Å in mol-ecule I and 0.041 (1) Å in mol-ecule II], with the terminal phenyl rings twisted away from the mean plane of the semicarbazone moiety, making dihedral angles of 60.26 (8) and 28.76 (9)° in mol-ecule I and 31.07 (9) and 35.45 (8)° in mol-ecule II. The mol-ecules both exhibit an E configuration with respect to the C=C and azomethine C=N bonds. In the crystal, two classical N-H⋯O hydrogen-bonding inter-actions are present between the two mol-ecules, forming a centrosymmetric dimer, while a weak C-H⋯O non-classical hydrogen-bonding inter-action, with a donor-acceptor distance of 3.476 (2) Å, inter-connects two neighbouring centrosymmetric dimers to form a cage-like structure. These cage structures are inter-connected by weak C-H⋯π inter-actions with an H⋯π distance of 2.790 Å, forming supra-molecular chains along the c-axis direction.

A supramolecular chain of dimeric Dy single molecule magnets decorated with azobenzene ligands.

We report the synthesis, ab initio calculations, magnetic and optical characterization of a DyIII-based dimeric compound named DyAZO. The dimers self-organize into a supramolecular chain decorated with photo-isomerizable azobenzene ligands. DyAZO displays single-molecule magnet (SMM) behavior. However, ab initio calculations highlight a quite strong admixture of MJ states of the 6H15/2 level of DyIII ions, the presence of low-lying excited MJ states and antiferromagnetic Dy-Dy dipolar coupling. This favors zero-field fast tunneling. Accordingly the Dy-doped analogue YDyAZO (5.5% Dy doping) displays enhanced magnetic relaxation with a hysteresis that is observed at 0.5 K. The influence of the cis- to trans-isomerization of the decorating azobenzene ligand on magnetic properties has been tested for both solid samples and solutions of DyAZO and YDyAZO. This provides hints for the synthesis of future Dy-based photo-isomerizable molecules.

Dihydrogenphosphate anionic template-assisted hydrogen bonded networks in 2-benzylaminopyridinium and 4-ethyoxyanilinium dihydrogenphosphate salts

In the title compounds, namely 2-benzylaminopyridinium dihydrogenphosphate C12H13N2+⋅H2PO4–, (I) and 4-ethoxyanilinium dihydrogenphosphate C8H12NO+⋅H2PO4–, (II), the H2PO4– anions form a one-dimensional chain and a two-dimensional supramolecular sheet built through O—H⋯O hydrogen bonds. The asymmetric unit of II consists of two symmetry-independent molecules with almost similar geometrical parameters, differing in the orientation of cations with respect to the anions. The 2-benzylaminopyridinium cations of I are linked to the anionic one-dimensional chain, while the 4-ethoxyanilinium cations of II are anchored to the anionic two-dimensional sheet through N—H⋯O hydrogen bonds. These anion-cation interactions lead to the formation of an organic-inorganic supramolecular one-dimensional chain and two-dimensional sheets in I and II respectively. In dihydrogenphosphate salts the formation of anionic supramolecular motifs and networks are very much influenced by the nature of cations and their interaction with the H2PO4– anions.

Supramolecular assembly of functional peptide–polymer conjugates

The following review gives an overview about synthetic peptide-polymer conjugates as macromolecular building blocks and their self-assembly into a variety of supramolecular architectures, from supramolecular polymer chains, to anisotropic 1D arrays, 2D layers, and more complex 3D networks. A selection of recent literature examples using linear, coiled-coil and cyclic peptide motifs is provided. The reversible nature of the unimer-to-supramolecular polymer transition provides unique opportunities to investigate mechanistic aspects of the supramolecular assembly, with respect to the thermodynamic or kinetic parameters and furthermore provides exciting opportunities for non-equilibrium assembly strategies. Using specific examples we also highlight some of the biological or mechanical function that arises from this versatile class of supramolecular biomaterials.

Crystal structure and Hirshfeld surface analysis of N,N'-[ethane-1,2-diylbis(-oxy)]bis-(4-methyl-benzene-sulfonamide).

In the mol-ecule of the title compound, C16H20N2O6S2, the mid-point of the C-C bond of the central ethane moiety is located on a twofold rotation axis. In the crystal, mol-ecules are linked by N-H⋯O hydrogen bonds into supra-molecular chains propagating along the [101] direction. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (43.1%), O⋯H/H⋯O (40.9%), C⋯H/H⋯C (8.8%) and C⋯C (5.5%) inter-actions.

A one-dimensional supramolecular chain based on [H2V10O28]4− units decorated with 4-dimethylaminopyridinium ions: an experimental and theoretical characterization

One-dimensional supramolecular structure with [H2V10O28]4− units was synthesized and experimental-theoretical characterized as potential releasing prodrug of the decavanadate ion.

Binding of gold(iii) with silver(i) dipropyldithiocarbamate: supramolecular self-assembly (role of secondary Au…S and Ag…S bonds) and thermal behavior of the ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n

The double ionic-polymer complex ([Au(S2CNPr2)2][AgCl2])n (1) was prepared as an individual fixation form of gold(III) from NaCl solutions with silver(I) dipropyldithiocarbamate and was characterized by single-crystal X-ray diffraction and 13C magic-angle spinning (MAS) NMR spectroscopy. The structure of 1 comprises two nonequivalent centrosymmetric complex cations [Au(S2CNPr2)2]+ (A and B) and the discrete linear anion [AgCl2]–. Gold(III) cations are linked by pairs of unsymmetrical secondary Au…S bonds to form linear supramolecular chains (…A…B…)n. Neighboring cations are additionally linked by [AgCl2]– anions via secondary Ag…S and Cl…S bonds, the anions being involved in the overall stabilization of the supramolecular structure. The cation–anion interactions lead to a distortion of the linear configuration of the [AgCl2]– anion. The character of thermolysis of 1 accompanied by quantitative regeneration of bound Au and Ag was established by simultaneous thermal analysis.

Self-Organization Processes in Aqueous Solution of Polyvinyl Alcohol, L-Cysteine, and Silver Nitrate

The self-organization processes in aqueous solution of polyvinyl alcohol (PVA), L-cysteine, and silver nitrate treated with sodium sulfate were studied by a complex of methods (viscometry, UV and IR spectroscopy, pH measurements, and dynamic light scattering). It was shown that PVA macromolecules interact with [—Ag−S(R)—Ag−S(R)—]n supramolecular chains based on cysteine and silver (where R is the cysteine residue) by the formation of hydrogen bonds. The increase in PVA concentration leads to the increase in viscosity of the obtained hydrogels; the thixotropic properties become more pronounced; the intensity of the main absorption bands of the UV spectrum corresponding to the formation of supramolecular structures becomes higher; the pH increases; the average hydrodynamic sizes of particles increase; the electrical conductivity of the system decreases. Scanning electron microscopy showed the formation of a regular macroporous structure of dried hydrogels. It was established that both the density of the spatial network and the porosity of dried hydrogel can be controlled by changing the PVA concentration in solution. A superporous structure of dried hydrogel was observed at high PVA concentration (2%) in solution.

Anion-π Architectures of HAT(CN)6 and 5d Polycyanidometalates: [W(CN)8]3–, [Re(CN)7]3–, and [Pt(CN)6]2–

Homoleptic polycyanido-complexes of 5d metal ions with high coordination numbers (C.N.), 8 for [W(CN)8]3–, 7 for [Re(CN)7]3–, and 6 for [Pt(CN)6]2–, are found to form supramolecular anion-π chains with the multisite anion receptor HAT(CN)6 (hexaazatriphenylenehexacarbonitrile). The chains adopt a zigzag topology in the case of (XPh4)3[W(CN)8]·HAT(CN)6 (X = P: 1, X = As: 2) and (PPh4)3[Re(CN)7]·HAT(CN)6 (3), and a linear arrangement in the case of (PPh4)2[Pt(CN)6]·HAT(CN)6·0.5CH3CN·2Et2O (4). The anion-π interactions consist of 3-fold {M–C≡N–···δ+centroidpyrazine,ring}3 or single {M–C≡N–···δ+centroidpyrazine,C–C bond} intermolecular contacts with separation distances in the range of 2.79–3.20 A. An M-(CN)− → HAT(CN)6 charge transfer (CT) along these anion-π contacts is evidenced in the solid state by the appearance of new absorptions in the visible range of UV–vis electronic absorption spectra, as compared to the starting materials, and by dispersion-corrected density functional theory studies. The CT anio...

2-{[2,8-Bis(tri-fluoro-meth-yl)quinolin-4-yl](hy-droxy)meth-yl}piperidin-1-ium tri-chloro-acetate: crystal structure and Hirshfeld surface analysis.

The asymmetric unit of the centrosymmetric title salt, C17H17F6N2O+·C2Cl3O2 -, comprises a single ion-pair. The hy-droxy-O and ammonium-N atoms lie to the same side of the cation, a disposition maintained by a charge-assisted ammonium-N-H⋯O(hy-droxy) hydrogen bond [the Oh-Cm-Cm-Na (h = hy-droxy, m = methine, a = ammonium) torsion angle is 58.90 (19)°]. The piperidin-1-ium group is approximately perpendicular to the quinolinyl residue [Cq-Cm-Cm-Na (q = quinolin-yl) is -178.90 (15)°] so that the cation, to a first approximation, has the shape of the letter L. The most prominent feature of the supra-molecular association in the crystal is the formation of chains along the a-axis direction, being stabilized by charge-assisted hydrogen-bonds. Thus, ammonium-N+-H⋯O-(carboxyl-ate) hydrogen bonds are formed whereby two ammonium cations bridge a pair of carboxyl-ate-O atoms, leading to eight-membered {⋯O⋯HNH}2 synthons. The resulting four-ion aggregates are linked into the supra-molecular chain via charge-assisted hydroxyl-O-H⋯O-(carboxyl-ate) hydrogen bonds. The connections between the chains, leading to a three-dimensional architecture, are of the type C-X⋯π, for X = Cl and F. The analysis of the calculated Hirshfeld surface points to the importance of X⋯H contacts to the surface (X = F, 25.4% and X = Cl, 19.7%) along with a significant contribution from O⋯H hydrogen-bonds (10.2%). Conversely, H⋯H contacts, at 12.4%, make a relatively small contribution to the surface.

A Generic Method for Preparing Hollow Mesoporous Silica Catalytic Nanoreactors with Metal Oxide Nanoparticles inside Their Cavities

AbstractWe report a facile and generic method for the synthesis of hollow mesoporous silica nanoreactors (HMSNs) with small‐sized metal oxide nanoparticles (NPs) inside their cavities. They were made by deposition of silica onto metal‐containing charge‐driven polymer micelles and subsequent calcination. The micelles consist of 1) negatively charged supramolecular polyelectrolyte chains of bis‐ligand‐bound metal ions, and 2) water‐soluble, neutral/positive diblock copolymers. Owing to the facile coordination between transition‐metal ion and the employed bidentate ligand, a series of HMSNs with <2 nm MxOy NPs inside cavities (M=Mn, Co, Ni, Cu, or Zn) were obtained by simply varying the metal ions inside the micelles. The developed method circumvents the pre‐ and post‐synthesis of metal oxide NPs; after calcination, hollow mesoporous nanostructures containing small‐sized metal oxide NPs inside their cavities are directly obtained. The CoxOy‐functionalized HMSNs catalyze the degradation of various dyes with H2O2.

A Generic Method for Preparing Hollow Mesoporous Silica Catalytic Nanoreactors with Metal Oxide Nanoparticles inside Their Cavities.

We report a facile and generic method for the synthesis of hollow mesoporous silica nanoreactors (HMSNs) with small-sized metal oxide nanoparticles (NPs) inside their cavities. They were made by deposition of silica onto metal-containing charge-driven polymer micelles and subsequent calcination. The micelles consist of 1) negatively charged supramolecular polyelectrolyte chains of bis-ligand-bound metal ions, and 2) water-soluble, neutral/positive diblock copolymers. Owing to the facile coordination between transition-metal ion and the employed bidentate ligand, a series of HMSNs with <2 nm Mx Oy NPs inside cavities (M=Mn, Co, Ni, Cu, or Zn) were obtained by simply varying the metal ions inside the micelles. The developed method circumvents the pre- and post-synthesis of metal oxide NPs; after calcination, hollow mesoporous nanostructures containing small-sized metal oxide NPs inside their cavities are directly obtained. The Cox Oy -functionalized HMSNs catalyze the degradation of various dyes with H2 O2 .

Imaging the Solvation of a One-Dimensional Solid on the Molecular Scale.

We have observed the inversion of the solvation environment of a one-dimensional solid by low-temperature scanning tunneling microscopy. Adsorption of 3-methoxy-9-diazofluorene on Ag(111) yields highly oriented supramolecular chains, which are then exposed to water molecules. The annealing of dry and water-decorated chains results in diametrically opposed outcomes. While the former simply leads to an increase in chain length and number, the latter results in a complete loss of order and produces water clusters decorated with the organic molecule.

Two new cobalt(II) rhodamine 6G hydrazone complexes: structure, fluorescence and magnetism.

Two new CoII complexes, namely bis{N-[(6-bromopyridin-2-yl)methylidene]-2-[6-ethylamino-3-(ethyliminiumyl)-2,7-dimethyl-3H-xanthen-9-yl]benzene-1-carbohydrazonate}cobalt(II) bis(perchlorate)-dichloromethane-methanol (1/1/2), [Co(C32H30BrN5O2)2](ClO4)2·CH2Cl2·2CH3OH or [CoII(L)2](ClO4)2·CH2Cl2·2CH3OH, (1), and the bis(tetrafluoridoborate) salt, [Co(C32H30BrN5O2)2](BF4)2·CH2Cl2·2CH3OH or [CoII(L)2](BF4)2·CH2Cl2·2CH3OH, (2) (L is commonly 6-bromopyridine-2-carbaldehyde rhodamine 6G hydrazone), have been successfully constructed and characterized. The crystal structure analysis revealed that complexes (1) and (2) are mononuclear and have a CoIIN4O2 distorted octahedral structure. The large π-conjugated xanthene moiety of the L ligand causes strong intermolecular π-π stacking interactions, yielding a supramolecular one-dimensional chain. Complexes (1) and (2) display an obvious fluorescence emission near 560 nm in the solid state. Magnetic investigations show that both (1) and (2) are paramagnetic, dominated by the structural distortion and spin-orbit coupling of CoII.

Crystal structures of the 1:1 salts of 2-amino-4-nitro-benzoate with each of (2-hy-droxy-eth-yl)di-methyl-aza-nium, tert-but-yl(2-hy-droxy-eth-yl)aza-nium and 1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-aminium.

The crystal and mol-ecular structures of the title mol-ecular salts, C4H12NO+·C7H5N2O4 -, (I), C6H16NO+·C7H5N2O4 -, (II), and C4H12NO3 +·C7H5N2O4 -, (III), are described. The common feature of these salts is the presence of the 2-amino-4-nitro-benzoate anion, which exhibit non-chemically significant variations in the conformational relationships between the carboxyl-ate and nitro groups, and between these and the benzene rings they are connected to. The number of ammonium-N-H H atoms in the cations increases from one to three in (I) to (III), respectively, and this variation significantly influences the supra-molecular aggregation patterns in the respective crystals. Thus, a linear supra-molecular chain along [100] sustained by charge-assisted tertiary-ammonium-N-H⋯O(carboxyl-ate), hy-droxy-O-H⋯O(carboxyl-ate) and amino-N-H⋯O(carboxyl-ate) hydrogen-bonds is apparent in the crystal of (I). Chains are connected into a three-dimensional architecture by methyl-C-H⋯O(hy-droxy) and π-π inter-actions, the latter between benzene rings [inter-centroid separation = 3.5796 (10) Å]. In the crystal of (II), a supra-molecular tube propagating along [901] arises as a result of charge-assisted secondary-ammonium-N-H⋯O(carboxyl-ate) and hy-droxy-O-H⋯O(carboxyl-ate) hydrogen-bonding. These are connected by methyl-ene- and methyl-C-H⋯O(nitro) and π-π stacking between benzene rings [inter-centroid separation = 3.5226 (10) Å]. Finally, double-layers parallel to (100) sustained by charge-assisted ammonium-N-H⋯O(carboxyl-ate), ammonium-N-H⋯O(hy-droxy) and hy-droxy-O-H⋯O(carboxyl-ate) hydrogen-bonds are apparent in the crystal of (III). These are connected in a three-dimensional architecture by amine-N-H⋯O(nitro) hydrogen-bonds.

Directed Supramolecular Organization of N-BAR Proteins through Regulation of H0 Membrane Immersion Depth

Many membrane remodeling events rely on the ability of curvature-generating N-BAR membrane proteins to organize into distinctive supramolecular configurations. Experiments have revealed a conformational switch in N-BAR proteins resulting in vesicular or tubular membrane shapes, with shallow membrane immersion of the H0 amphipathic helices of N-BAR proteins on vesicles but deep H0 immersion on tubes. We develop here a minimal elastic model of the local thinning of the lipid bilayer resulting from H0 immersion. Our model predicts that the observed conformational switch in N-BAR proteins produces a corresponding switch in the bilayer-mediated N-BAR interactions due to the H0 helices. In agreement with experiments, we find that bilayer-mediated H0 interactions oppose N-BAR multimerization for the shallow H0 membrane immersion depths measured on vesicles, but promote self-assembly of supramolecular N-BAR chains for the increased H0 membrane immersion depths measured on tubes. Finally, we consider the possibility that bilayer-mediated H0 interactions might contribute to the concerted structural reorganization of N-BAR proteins suggested by experiments. Our results indicate that the membrane immersion depth of amphipathic protein helices may provide a general molecular control parameter for membrane organization.

Crystalline bis(η5-cyclopentadienyl)bis(benzoato/carboxylato)titanium(IV) precursor-directed route to functional titanium dioxide nanomaterials

Five titanocene(IV) carboxylates of the general formula Cp2Ti(O2CR)2 viz., [Ti(η5-C5H5)2(O2CC6H5-4-CH3)2] (1), [Ti(η5-C5H5)2(O2CC4H3-2-O)2] (2), [Ti(η5-C5H5)2(O2CC4H3-3-O)2] (3), [Ti(η5-C5H5)2(O2CC(CH3)3)2] (4), and [Ti(η5-C5H5)2(O2C(CH)C(CH3)3)2] (5) have been synthesized. All the titanocene(IV) carboxylates have been characterized by IR, 1H, and 13C NMR spectroscopic techniques, and the crystal and molecular structures of 1–5 have been determined by single crystal X-ray crystallography. The structures present similar features with monodentate carboxylate ligands and tetrahedral Ti centers, assuming that each cyclopentadienyl (Cp) ring occupies one position only. The differences in the structures relate primarily to the relative orientations of the carboxylate ligands. In the molecular packing, non-conventional Cp-C–H···O(carbonyl) hydrogen bonds are observed in each case and lead to supramolecular chains in each of 1, 4, and 5. In 2, the 2-furyl-O atoms also participate in C–H···O interactions leading to a two-dimensional array. Finally, in 3, a two-dimensional array arises as a result of Cp-C–H···O(carbonyl) and 3-furyl-C–H···O(carbonyl) interactions. As representative example, 3 was used as starting material for the synthesis of TiO2 nanoparticles (NPs). An effective and simple wet-chemical method involving calcination and ultrasonication is suggested for obtaining pure anatase TiO2 NPs, which were confirmed from the powder XRD and imaging techniques such as SEM, TEM, and EDS.

Synthesis and structural characterization of a dumbbell-like phenylphosphonate-stabilized Ti7-oxide cluster.

In recent years, crystalline polyoxotitanium clusters (PTCs) have attracted increasing attention as a new kind of promising crystalline material. In this work, a PTC stabilized by phenylphosphonate ligands, i.e. hexa-μ-isopropanolato-hexaisopropanolatodi-μ3-oxido-hexa-μ3-phenylphosphonato-heptatitanium tetrahydrate, [Ti7(μ3-O)2(O3P-Phen)6(OiPr)12]·4H2O [PTC-54; H2O3P-Phen is phenylphosphonic acid, C6H5PO(OH)2, and HOiPr is isopropanol, C3H7OH], was obtained successfully through a facile one-step solvothermal reaction. The dumbbell-like core structure of PTC-54 can be described as two trinuclear {Ti3(μ3-O)} building units combined together by six phenylphosphonate ligands and one additional Ti atom, giving rise to a Ti7 cluster. Adjacent molecules of PTC-54 are further connected through π-π interactions between the phenyl groups to form a supramolecular one-dimensional chain.

Steric control of supramolecular association in structures of Zn(S2COR)2withN,N′-bis(pyridin-4-ylmethyl)oxalamide

AbstractThe crystal and molecular structures of the one-dimensional coordination polymer [Zn(S2COEt)2(4LH2)]n(1) and binuclear [Zn(S2COCy)2]2(4LH2) (2) are described, where4LH2is N,N′-bis(pyridin-4-ylmethyl)ethanediamide. In1, the Zn(S2COEt)2entities are linked by bidentate bridging4LH2ligands through the pyridyl-N atoms to generate a twisted supramolecular chain. As a result of monodentate xanthate ligands, the N2S4donor set defines a distorted tetrahedral coordination geometry and, crucially, allows the participation of the non-coordinating sulfur atoms in supramolecular association. Thus, in the crystal amide-N–H···O(amide) and amide-N–H···S(thione) hydrogen bonds link chains into a three-dimensional architecture. The substitution of the ethyl group in the xanthate ligand with a cyclohexyl group results in very different structural outcomes. In2, a binuclear molecule is observed with the coordination geometry for zinc being defined by chelating xanthate ligands and a pyridyl-N atom with the NS4donor set defining a highly distorted geometry. In the molecular packing, amide-N–H···S(thione) hydrogen bonds stabilise a supramolecular chain along the a-axis and these are connected into a three-dimensional arrangement by methylene-C–H···O and methylene-C–H···π(pyridyl) interactions. The relative importance of the specified intermolecular interactions and weaker, contributing contacts has been revealed by an analysis of the calculated Hirshfeld surfaces of1and2.