Infinite Helical Chains Research Articles

Antimicrobial Activity of Water-Soluble Silver Complexes Bearing C-Scorpionate Ligands.

The novel hydrosoluble silver coordination polymer [Ag(NO3)(μ-1κN;2κN',N″-TPMOH)]n (1) (TPMOH = tris(1H-pyrazol-1-yl)ethanol) was obtained and characterized. While single crystal X-ray diffraction analysis of compound 1 disclosed an infinite 1D helical chain structure in the solid state, NMR analysis in polar solvents confirmed the mononuclear nature of compound 1 in solution. Compound 1 and the analogue [Ag(μ-1κN;2κN',N″-TPMS)]n (2) (TPMS = tris(1H-pyrazol-1-yl)methane sulfonate) were evaluated with regard to their antimicrobial activities towards the Gram-negative Escherichia coli, Pseudomonas aeruginosa, and Burkholderia contaminans, the Gram-positive Staphylococcus aureus, and the fungal species Candida albicans and Candida glabrata. Compound 1 exhibited minimal inhibitory concentration (MIC) values ranging from 2 to 7.7 µg/mL towards the tested Gram-negative bacteria, 18 µg/mL towards the Gram-positive S. aureus, and 15 and 31 µg/mL towards C. albicans and C. glabrata, respectively. Compound 2 was less effective towards the tested bacteria, with MIC values ranging from 15 to 19.6 µg/mL towards the Gram-negative bacteria and 51 µg/mL towards S. aureus; however, it was more effective against C. albicans and C. glabrata, with MIC values of about 6 µg/mL towards these fungal species. The toxicity of compounds 1 and 2 was assessed by evaluating the survival of the Caenorhabditis elegans model organism to concentrations of up to 100 µg/mL. The value of 50% lethality (LD50) could only be estimated as 73.2 µg/mL for compound 1 at 72 h, otherwise LD50 was >100 µg/mL for both compounds 1 and 2. These results indicate compounds 1 and 2 as novel silver complexes with interesting antimicrobial properties towards bacterial and fungal pathogens.

Novel ternary Zintl phosphide halides Ba3P5X (X = Cl, Br) with 1D helical phosphorus chains: synthesis, crystal and electronic structure.

Black single crystals of two novel ternary phosphide halides, Ba3P5Cl and Ba3P5Br, were grown using molten metal Pb-flux high-temperature reactions. These compounds were structurally characterized with the aid of the single-crystal X-ray diffraction (SCXRD) method at 100(2) K. The SCXRD shows that both compounds are isostructural and adopt a new structure type (space group R3̄c, No. 167, Z = 6) with unit cell parameters a = 14.9481(16) Å, c = 7.3954(11) Å and a = 15.045(4) Å, c = 7.537(3) Å for Ba3P5Cl and Ba3P5Br, respectively. Cl- and Br- anions are octahedrally coordinated by Ba2+ cations, thus composing a face-sharing 1D infinite chain 1∞[XBa3]5+ running along the [001] direction. Moreover, the crystal structures feature peculiar one-dimensional disordered infinite helical chains of 1∞P-, composed of partially occupied phosphorous atoms, each being a superposition of three symmetrical copies of the ordered phosphorus chain, with continuity along the c-axis. Ba3P5X (X = Cl, Br) compounds are charge-balanced heteroanionic Zintl phases according to the charge-partitioning scheme (Ba2+)3[P-]5X-. The presumed semiconducting behavior of both compounds corroborates well with the results of the electronic structure calculations performed with the aid of the TB-LMTO-ASA code.

Purely single-bonded spiral nitrogen chains stabilized by trivalent lanthanum ions.

Inspired by the single-bonded nitrogen chains stabilized by tetravalent cerium, pentavalent tantalum, and hexavalent tungsten atoms, we explored the possibility of single-bonded nitrogen polymorphs stabilized by trivalent lanthanum ions. To achieve this, we utilized the crystal structure search method on the phase diagram of binary La-N compounds. We identified three novel thermodynamically stable phases, the C2/c LaN3, P-1 LaN4, and P-1 LaN8. Among them, the C2/c phase with infinite helical poly-N6 chains becomes thermodynamically stable above 50GPa. Each nitrogen atom in the poly-N6 chain acquires one extra electron, and the spiral chain is purely single-bonded. The C2/c phase has an indirect band gap of ∼1.6eV at 60GPa. Notably, the band gap exhibits non-monotonic behavior, decreases first and then increases with increasing pressure. This abnormal behavior is attributed to the significant bonding of two La-N bonds at around 35GPa. Phonon spectrum calculations and AIMD simulations have confirmed that the C2/c phase can be quenched to ambient conditions with slight distortion, and it exhibits excellent detonation properties. Additionally, we also discovered armchair-like nitrogen chains in LaN4 and the armchair and zigzag-like mixed nitrogen chains in LaN8. These results provide valuable insights into the electronic and bonding properties of nitrides under high pressure and may have important implications for the design and development of novel functional materials.

Single-bonded nitrogen chain and porous nitrogen layer via Ce–N compounds

We explored the phase diagram of Ce–N compounds, and identified several interesting poly-nitrogen species, including the infinite helical chain, and porous poly-nitrogen layer.

Alkanes versus Oligosilanes: Conformational Effects on σ-Electron Delocalization.

Observations and computations both suggest that the extent and the conformational dependence of σ-electron delocalization in frontier molecular orbitals are quite different in alkanes CnH2n+2 and oligosilanes SinH2n+2, the isosteric and isoelectronic saturated chains built from carbon or silicon atoms, respectively. We find that the different conformational effects can be understood in simple intuitive terms. There are two modes of σ-electron delocalization, strongly conformation-sensitive skeletal delocalization through backbone X-X bonds (σ-conjugation and σ-hyperconjugation) and only weakly conformation-sensitive lateral delocalization through lateral X-H bonds (σ-hyperconjugation and σ-homoconjugation). In alkanes, both modes are active and complement each other, leading to delocalization in all conformations. In oligosilanes, only skeletal delocalization of holes is important in frontier orbitals, and the even simpler ladder C model provides an adequate intuitive description of the strong conformational dependence of σ-electron delocalization. Ultimately, the difference is primarily due to the similar electronegativity of carbon and hydrogen as opposed to the lower electronegativity of silicon, which causes a polarization of Si-H bonds. This understanding has been derived from an analysis of approximate algebraic solutions of a simple Hückel-level extended ladder H model for an infinite regular helical chain, using the effective mass of a hole as a measure of delocalization. This model is derived from the classical Sandorfy H model, and is parametrized by fitting to results of density functional or Hartree-Fock theory.

Unusual Metal-Organic Framework Topology and Radiation Resistance through Neptunyl Coordination Chemistry.

A Np(V) neptunyl metal-organic framework (MOF) with rod-shaped secondary building units was synthesized, characterized, and irradiated with γ rays. Single-crystal X-ray diffraction data revealed an anionic framework containing infinite helical chains of actinyl-actinyl interaction (AAI)-connected neptunyl ions linked together through tetratopic tetrahedral organic ligands (NSM). NSM exhibits an unprecedented net, demonstrating that AAIs may be exploited to give new MOFs and new topologies. To probe its radiation stability, we undertook the first irradiation study of a transuranic MOF and its organic linker building block using high doses of γ rays. Diffraction and spectroscopic data demonstrated that the radiation resistance of NSM is greater than that of its linker building block alone. Approximately 6 MGy of irradiation begins to induce notable changes in the long- and short-range order of the framework, whereas 3 MGy of irradiation induces total X-ray amorphization and changes in the local vibrational bands of the linker building block.

Iodine Adsorption in a Redox-Active Metal-Organic Framework: Electrical Conductivity Induced by Host-Guest Charge-Transfer.

We report a comparative study of the binding of I2 (iodine) in a pair of redox-active metal–organic framework (MOF) materials, MFM-300(VIII) and its oxidized, deprotonated analogue, MFM-300(VIV). Adsorption of I2 in MFM-300(VIII) triggers a host-to-guest charge-transfer, accompanied by a partial (∼30%) oxidation of the VIII centers in the host framework and formation of I3– species residing in the MOF channels. Importantly, this charge-transfer induces a significant enhancement in the electrical conductivity (Δσ = 700000) of I2@MFM-300(VIII/IV) in comparison to MFM-300(VIII). In contrast, no host–guest charge-transfer or apparent change in the conductivity was observed upon adsorption of I2 in MFM-300(VIV). High-resolution synchrotron X-ray diffraction of I2@MFM-300(VIII/IV) confirms the first example of self-aggregation of adsorbed iodine species (I2 and I3–) into infinite helical chains within a MOF.

Novel organotin (IV) complexes derived from 4,4′‐oxybisbenzoic acid: synthesis, structure, in vitro cytostatic activity and binding interaction with BSA

Six novel organotin (IV) complexes, [(Me3Sn)2(H2O)2L] (1), [(R3Sn)2L]n (R = Me 2, R = n‐Bu 3), [(Ph3Sn)2L] (4), [Me2SnL]n (5), [(Me2Sn)2L(μ3‐O)]n (6) have been designed and synthesized by the reactions of 4,4′‐oxybisbenzoic acid (H2L) and triorganotin (IV) chloride or oxide. All the complexes have been characterized by elemental analysis, FT‐IR, NMR, ESI‐Mass, PXRD and X‐ray crystallography. The single crystal diffraction reveals that complexes 1 and 4 represent dinuclear tin monomers. Complexes 2 and 3 display 2D network structure and 2D corrugated framework respectively, which both contain tetranuclear 36‐membered macrocycles. Furthermore, 2D structures are linked into a 3D supramolecular structures through intermolecular C‐H···π interactions. Complex 5 shows 1D infinite helical chain and further constructs 3D ladder supramolecular architecture through additional Sn···O and C‐H···O intermolecular interactions. Complex 6 displays 1D infinite polymeric chain containing 28‐membered macrocyclic ring. Preliminarily in vitro cytostatic activity studies on cervical carcinoma cell lines (HeLa) and hepatocellular carcinoma cell lines (HepG‐2) by MTT assay for some complexes reveal that complexes 3 and 4 exhibit high cytostatic activity. Further, complexes 3 and 4 were selected to investigate interactions of bovine serum albumin (BSA) by fluorescence quenching spectra and synchronous fluorescence spectra, which indicates that the complexes could quench the intrinsic fluorescence of BSA in a static quenching process.

Effect of Conformation on Electron Localization and Delocalization in Infinite Helical Chains [X(CH3)2]∞ (X = Si, Ge, Sn, and Pb).

An intuitive explanation of the effects of conformation (backbone dihedral angle) on electron delocalization in infinite saturated regular helices [(CH3)2]∞Si, [(CH3)2Ge]∞, [(CH3)2Sn]∞, and [(CH3)2Pb]∞ is offered in terms of the simple Ladder C model and confirmed by density functional theory calculations. The effective hole mass, which ranges from near zero to infinity as a function of conformation, is used as a measure of the degree of delocalization and relates to the effects of chain length extension in finite systems. The position of the Fermi level in reciprocal space has a simple counterpart in systems of finite length and is used to characterize the dominant mechanism, σ conjugation (geminal interactions) or σ hyperconjugation (vicinal interactions, through-bond coupling). Constructive or destructive interference of the two mechanisms produces three different delocalization regimes as a function of the backbone dihedral angle and analogy is drawn to polycyclic π-electron systems consisting of fused Hückel or Möbius four-membered rings.

Iodine Clathrated: A Solid-State Analogue of the Iodine-Starch Complex.

Co-crystallizing iodine with a simple dicationic salt (1,8-diammoniumoctane chloride) results in the clathration of the iodine (I2 ) molecules inside trigonal and hexagonal helical channels of the crystal lattice with 72 wt % overall I2 loading. The I2 inside the bigger trigonal channel forms a I-I⋅⋅⋅I-I⋅⋅⋅I-I halogen-bonded infinite helical chain, while the I2 in the smaller hexagonal channel is disordered. In both channels the I2 interaction with the channel wall happens through I-I⋅⋅⋅Cl- halogen bonds. The helical channels in the crystal lattice are constructed via the strong charge-assisted H2 N+ H⋅⋅⋅Cl- hydrogen bonds between the dications and the chloride anions. The structure shows a marked similarity with the well-known starch-I2 system, and thus may provide insight for the yet unresolved structure of the I2 in the helical starch channel.

Synthesis and Structural Analysis of Ammonium Orotate Hydrate Crystal

Single crystals of the title molecular salt, NH4 +. C5H3N2O4 ‒ . H2O, were isolated from the reaction of orotic acid, Dysprosium (III) Nitrate in a 1:1 molar ratio in 5 ml water 25% ammonia solution by hydrothermal reaction at 120oC for 3 days. In the crystal, the cations and anions are positioned alternately along an infinite helical chain and linked together through N---H...O hydrogen bonds between carboxylate oxygen and carbonyl oxygen of orotate ion. The water molecules of crystallization link the chains into (101) bilayers, with the cations organized in an isotactic manner.

A new copper(II) coordination polymer containing chains of interconnected paddle-wheel antiferromagnetic clusters.

The construction of supramolecular architectures based on inorganic-organic coordination frameworks with weak noncovalent interactions has implications for the rational design of functional materials. A new crystalline binuclear copper(II) one-dimensional polymeric chain, namely catena-poly[[[tetrakis(μ-4-azaniumylbutanoato-κ2O:O')dicopper(II)(Cu-Cu)]-μ-chlorido-[diaquadichloridocopper(II)]-μ-chlorido] bis(perchlorate)], {[Cu3Cl4(C4H9NO2)4(H2O)2](ClO4)2}n, was obtained by the reaction of 4-aminobutyric acid (GABA) with CuCl2·2H2O in aqueous solution. The structure was established by single-crystal X-ray diffraction and was also characterized by IR spectroscopy and magnetic measurements. The crystal structure consists of [{Cu2(GABA)4}{CuCl4(H2O)2}]+ cations and isolated perchlorate anions. Two symmetry-related CuII centres are bridged via carboxylate O atoms into a classical paddle-wheel configuration, with a Cu...Cu distance of 2.643 (1) Å, while bridging Cl atoms complete the square-pyramidal geometry of the metal atoms. The Cl atoms connect the paddlewheel moieties to a second CuII atom lying on an octahedral site, resulting in infinite helical chains along the c axis. The packing motif exhibits channels containing free perchlorate anions. The crystal structure is stabilized by hydrogen bonds between the perchlorate anions, the coordinated water molecules and the ammonium groups of the polymeric chains. The magnetic analysis of the title compound indicates a nontrivial antiferromagnetic behaviour arising from alternating weak-strong antiferromagnetic coupling between neighbouring CuII centres.

One-Dimensional Helical Metal Coordination Polymer: Synthesis and Structure of Infinite Chain of [Ag7(S2CNEt2)6] n + (as [SbF6]− salt) Composed of Ag6(S2CNEt2)6 Cluster Units Linked by Ag(I) Ions via Peculiar Chelating S–S Bites

A new polymeric silver cluster, formulated as [Ag7(S2CNEt2)6][SbF6] (1) was synthesized and characterized by single-crystal X-ray crystallography. The structure can be described as an infinite cationic polymeric helical chain consisting of two [Ag6(S2CNEt2)6] clusters linked by a silver ion tetrahedrally coordinated with four sulfur atoms, two from each of the constituent clusters. The stereochemistry of 1 is classified as a new ζ-modification of silver dithiocarbamate cluster. It is suggested that the constituent [Ag6(S2CNEt2)6] clusters in 1 can be used as building blocks in the construction of 1-D cluster-based metal coordination polymers as well as 2-D or 3-D cluster-based metal–organic frameworks. The paper reports the synthesis and single-crystal structure of an infinite helical chain of a cationic metal coordination polymer consisting of two [Ag6(S2CNEt2)6] clusters linked by a tetrahedrally coordinated silver ion. The implication of the utility of the constituent [Ag6(S2CNEt2)6] clusters as building blocks in the construction of other 1-D cluster-based metal coordination polymer as well as 2-D or 3-D cluster-based metal–organic-frameworks is discussed.

Supramolecular solid-state structure, potential energy surfaces and evaluation of antiproliferative effect of 2-benzothiazolylhydrazone derivatives in vitro

The in situ condensation reaction of 2-hydrazinobenzothiazole with salicylaldehyde, 3,4-dihydroxybenzaldehyde, 2,4-dihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2-methoxy-1-naphthaldehyde, 4-methoxy-1-naphthaldehyde and 6-methoxy-2-naphthaldehyde produced 9 hydrazone Schiff bases (L1–L9, respectively) which were identified and characterized by elemental analysis, IR and NMR spectroscopy. The crystal and molecular structures of four Schiff bases (L1, L7–L9) have been determined by the single-crystal X-ray diffraction method confirming the imino form of L1 and the amino tautomeric form of L7–L9 compounds. Molecular structure analysis also confirmed that reported compounds are E-isomers relative to exo C = N imino bond. The Nhydrazino–H group of amino tautomers forms Nhydrazino–H···Nthiazolyl intermolecular hydrogen bonds shaping molecules into R22(8) rings, while imino tautomer of L1 forms C(4) infinite helical chains via Nthiazolyl–H···Nhydrazino type of intermolecular hydrogen bond. The methoxy group (L7–L9) further shaped these primary supramolecular synthons into different supramolecular arrangements via C–H···O, C–H···N and C–H···S intermolecular hydrogen bonds. The role of aryl substituents in the shaping and stabilization of supramolecular architectures of L1, L7–L9 is supported by quantum chemical calculations. Strong antiproliferative effects on tumor cells and cytotoxic effects on fibroblasts are shown for all ligands L1–L9 with exception of L6 and L7 that had no effect on fibroblast cells.

1D infinite helical water chain encapsulated in a supramolecular complex based on amino acid derivate

ABSTRACTAn oligonuclear complex based on amino acid derivate had been synthesized and structurally characterized, which exhibits a three-dimensional (3D) supramolecular framework constructed from the mono-cobalt units and helical water chains stabilized in this complex. Additionally, the compound was characterized by thermogravimetric analysis (TGA), IR spectroscopy, and elemental analysis.

Synthesis, Crystal Structure, and NLO Property of the Chiral Sulfide Sm4InSbS9

AbstractThe chiral sulfide Sm4InSbS9 was prepared from a stoichiometric mixture of the elements at 1223 K in an evacuated silica tube. It crystallizes in the chiral tetragonal space group P43212 with a = 10.0042(4) Å, c = 27.6810(15) Å, V = 2770.4(2) Å3, and Z = 8. The structure features infinite helical chains of [In2Sb2S1110–]∞ propagating along the c direction that are separated by Sm3+ cations and S2– anions. It shows the second harmonic generation with an intensity of 0.75 times that of benchmark AgGaS2 at 2.05 µm laser in type I phase matchable behavior. UV/Vis diffuse reflectance spectroscopy study shows its optical gap of around 2.13 eV.

Step-by-step strategy from achiral precursors to polyoxometalates-based chiral organic-inorganic hybrids.

Using two types of triol ligands, several novel asymmetrically triol-functionalized Anderson organic hybrids have been efficiently synthesized in high purity and good yields via a convenient two-step esterification reaction. These organic-inorganic hybrids are chiral and can be spontaneously resolved with suitable solvents. Their molecular and crystal structures have been confirmed by single-crystal X-ray diffraction studies. Stable solid-state chirality of the corresponding enantiopure crystals has also been confirmed definitively by CD spectra. Interestingly, these organic-inorganic hybrids possess a layer-by-layer structure, forming solvent-accessible nanoscale chiral channels via a 1D infinite helical chain substructure. TGA measurements indicated that the species of the central heteroatoms significantly effects the stability of these compounds.

Structural, spectroscopic, and computational characterization of the cleavage product of dimolybdenum(II) core under aerobic conditions

Full characterization of the adduct isolated in crystalline form from a solution of tetrakis(μ-trifluoroacetato) dimolybdenum(II) and (2S,3S)-butane-2,3-diol is reported herein. For this purpose X-ray crystallographic, spectroscopic, and computational methods were conducted. The single crystal X-ray diffraction analysis clearly indicates the cleavage of the MoMo quadruple bond in the chiral complex initially formed in situ after mixing the components. Cleavage product 2 shows two coordinated, symmetrically unequivalent (2S,3S)-butane-2,3-diol ligands associated with one Mo atom with different MoO bond lengths and MoOC bond angles. This inequivalence most likely reflects the engagement of the coordinated butanediol ligands in an intermolecular hydrogen bonding interaction with solvating butanediol molecules leading to the formation of an infinite helical chain pattern. Density functional theory (DFT) and time-dependent DFT calculations were used to provide support for the proposed structural assignment of 2 in acetonitrile and chloroform solutions, which were made on the basis of experimental CD and NMR results. Additional studies under anaerobic conditions have shown that the cleavage of the quadruple MoMo bond takes place only under aerobic conditions. Thus, it has been demonstrated that the changes in the shapes of the ECD curves observed over time are associated with spontaneous, air-oxidative cleavage of the quadruple MoMo bond and conversion of the Mo(II) to Mo(VI) centers.

Syntheses, crystal structures and luminescent properties of six new d10 transitional metal coordination polymers based on bis(benzimidazole) ligands

Six new coordination polymers, [CdCl2(bbim)]n (1), [ZnCl2(bbbm)]n (2), [ZnCl(HCOO)(bbbm)]n (3), [Cd(PhCOO)2(bbim)]n (4), [Cd(PhCOO)2(bbbm)]n (5), and {[Zn(ip-OH)(bbim)]·DMF}n (6) [bbim=1,1′-(1,4-butanediyl)bis(2-methylbenzimidazole), bbbm=1,1′-(1,4-butanediyl)bis(benzimidazole), H2ip-OH=5-hydroxylisophthalic acid], have been prepared and characterized by elemental analysis, infrared spectra and X-ray single-crystal diffraction. Complexes 1–5 have one-dimensional (1D) chain structures. Complexes 1, 3 and 4 possess similar 1D meso-helical chain structures, which are extended into 2D or 3D supramolecular network through intermolecular hydrogen-bonding, C–H⋯π and π⋯π interactions. Complexes 2 and 5 exhibit similar 1D infinite helical chains. The 1D chains further form a three-dimensional (3D) supramolecular structure through intermolecular hydrogen-bonding and π⋯π interactions in 2, but form a 2D supramolecular layer via C–H⋯π interactions in 5. Complex 6 possesses a 2D 44-sql network. Furthermore, luminescent properties and thermal stabilities of 1–6 were also investigated.

Zinc(II) complexes with an imidazolylpyridine ligand: luminescence and hydrogen bonding

ZnLCl and [H2L]2[ZnCl4], based on 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine (HL), have been synthesized. There is a short intraionic O–H···N hydrogen bond between the hydroxyimidazolyl and pyridyl of H2L+ cations (N···O 2.608(2) Å) in the structure of [H2L]2[ZnCl4]. The formation of this rather strong hydrogen bond is confirmed by IR spectroscopy through a broad band at 3200–2200 cm−1 and a band at 1655 cm−1. HL crystallizes in the form of a hemihydrate, HL·0.5H2O. HL assemble into infinite helical chains due to N–H···O intermolecular hydrogen bonds between the NH of imidazole and O of the N-oxide (O···N 2.623(2) Å). An unusual mid-IR pattern with three broad bands at 3373, 2530, and 1850 cm−1 is typical for strong hydrogen bonds, explained by resonance-assisted hydrogen bonding occurring in the helical chains. On cooling to 5 K, noticeable changes in the IR spectra of [H2L]2[ZnCl4] and HL·0.5H2O were observed. ZnLCl and [H2L]2[ZnCl4] exhibit bright photoluminescence with maxima of emission at 458 nm (for ZnLCl) and 490 nm (for [H2L]2[ZnCl4]).