18-membered Ring Research Articles

5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrakis[2-(2-chloroethoxy)ethoxy]-2,8,14,20-tetrasulfonylcalix[4]arene

Mol­ecules of the title compound, C56H76Cl4O16S4, have crystallographic C 2 symmetry and adopt a 1,3-alternate conformation where the four –OCH2CH2OCH2CH2Cl groups are located alternately above and below the virtual plane (R) defined by the four bridging S atoms. The dihedral angles between the plane (R) and the phenolic rings are 72.85 (7) and 74.57 (7)°. An unusual 24-membered macrocyclic ring is formed in the crystal structure with an array of eight intra­molecular C—H⋯O hydrogen bonds between the ether arm H atoms and the sulfonyl O atoms. In the supra­molecular structure, the mol­ecular components are linked into infinite zigzag one-dimensional chains by a combination of four inter­molecular C—H⋯O hydrogen bonds, forming R 2 2(13), R 2 2(16), R 2 2(21) and R 2 2(26) ring motifs. These chains are augmented into a wave-like two-dimensional network by weak C⋯O inter­actions. One tert-butyl group shows rotational disorder, and one CH2CH2Cl group is disordered over two orientations; the site-occupation factors are 0.756 (6) and 0.244 (6) for the two tert-butyl groups, and 0.808 (3) and 0.192 (3) for the two CH2CH2Cl units.

Synthesis of chiral threefold and sixfold functionalized macrocyclic imidazole peptides

Starting from 4-oxa- or 4-azasubstituted 2-amino-3-oxoesters and ( S)-valine, chiral imidazole diamino monocarboxylic acids as well as diamino dicarboxylic acids were prepared in a few synthetic steps. Macrolactamization of the side chain protected imidazole amino acids yields the corresponding 18- and 24-membered ring analogues of the naturally occurring cyclic peptide Westiellamide with various anchoring sites. The threefold functionalized scaffolds 2b– 4b and the sixfold functionalized scaffold 5 are versatile central modules for artificial receptors and ligands. Structural investigations of threefold functionalized scaffolds based on oxazole and N-methylimidazole units by DFT modeling are provided.

Bis{μ-3,3′-(1,3,4-thiadiazole-2,5-diyldithio)bis[pentanedionato(1−)]}bis[diaquanickel(II)] dimethylformamide disolvate trihydrate

The title compound, [Ni2(C12H12N2O4S3)(H2O)4]·2C3H7NO·3H2O, is made up of a centrosymmetric, bimetallic complex containing a 24-membered macrocyclic ring, two dimethyl­formamide and three water solvent mol­ecules. The Ni atom adopts a slightly distorted NiO6 octahedral geometry arising from two O,O-bidentate ligands and two water molecules. There are inter­molecular O—H⋯O and O—H⋯N inter­actions in the crystal structure. One of the uncoordinated water molecules is diordered over two sets of sites of equal occupancy.

Synthesis, conformational studies, and molecular dynamics calculations of two cyclic tetrapeptides with 17- and 18-membered rings

Two cyclic tetrapeptides [Boc-cyclo(-Xxx-Pro-Asn-Lys-)OMe (Xxx = Asp or Glu)] were synthesized and investigated by NMR spectroscopy. They were designed in order to mimic the salt bridge found in physalaemin. Isomers of the urethane bond were observed in DMSO solution. The ROESY spectrum allowed the assignment of many signals of the minor isomer of both compounds. Conformational studies based on the temperature gradients of the NH chemical shifts, coupling constants, and ROEs revealed a similar conformation for the Asp analogue as proposed for physalaemin. A beta I turn with Pro and Asn in the corner positions was found for the major isomer. No hydrogen bonds were detected for the major isomer of the cyclic Glu analogue. Molecular dynamics calculations, using the NMR based initial structures, yielded sets of conformations in agreement with the experimental data. It is concluded that the salt bridge in physalaemin is best approximated by a lactam formed from the original amino acids.

Iron(iii) coordination induced novel 18-metallacrown-6 complex: esterification and isolation of the ligand

The trianionic heptadentate ligand, (Z)-3-(salicylhydrazinocarbonyl) propenoic acid ((Z)-H(4)shcpa) (1), has been synthesized in good yield and reacted with FeCl(3).6H(2)O, to produce the complex [Fe(III)(6) (C(12)H(9)N(2)O(5))(6)(H(2)O)(2)(CH(3)OH)(4)] x 6CH(3)OH (2). The complex has been characterized by single-crystal X-ray diffraction. In the self-assembly process the ligand was esterified and transferred into (Z)-methyl 3-(salicylhydrazinocarbonyl) propenoate ((Z)-H(3)mshcp) (3). In the structure, the neutral Fe(III) complex contains a 18-membered metallacrown ring consisting of six Fe(III) and six trianionic ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Fe(III)-N-N]. Due to the meridional coordination of the ligands to the Fe(3+) ions, the ligands enforce the stereochemistry of the Fe(3+) ions as a propeller configuration with alternating Lambda/Delta form. The metallacrown can be treated with SnCl(2) to obtain purified ester. In addition, we have also obtained reduced esterified ligand, methyl 3-(salicylhydrazinocarbonyl) propanoate (H3mshcp) (4) with another reductant Zn powder.

Synthesis, structures and properties of Mn(II) coordination frameworks based on R-isophthalate (R = –CH3or –C(CH3)3) and various dipyridyl-type co-ligands

Five new Mn(II) metal–organic coordination polymers, [Mn(tbip)(bipy)]n (1), {[Mn(tbip)(dpe)]·1.5H2O}n (2), [Mn(tbip)(bpa)]n (3), [Mn(mip)(bpa)]n (4) and {[Mn3(mip)2(Hmip)2(bpp)2(H2O)2]·2H2O}n (5), were prepared through hydrothermal reactions of Mn(II) acetate with H2tbip (H2tbip = 5-tert-butyl isophthalic acid) or H2mip (H2mip = 5-methylisophthalic acid) in the presence of different dipyridyl co-ligands (bipy = 4,4′-bipyridine, dpe = 1,2-bi(4-pyridyl)ethene, bpa = 1,2-bi(4-pyridyl)ethane and bpp = 1,3-di(4-pyridyl)propane). All these compounds were characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. The structures of 1 and 2 are constructed of [Mn2(tbip)2]n layers, which consist of alternate left- and right-handed helical chains, and further pillared by bipy or dpe ligands into a 3D porous framework. Interestingly, there are two different sizes of pores in 1 and 2. From the topology point of view, both complexes 1 and 2 exhibit the rare rob network based on the dimeric [Mn(COO)]2 subunits as the 6-connected nodes. The ribbon-like chains having 8- and 16-membered rings in 3 and 4 result from dimeric Mn(II) units bridged by H2tbip or H2mip ligands, which are connected by the flexible dpa into 2D open layers. Complex 5 contains rare isophthalato-bridged trimanganese clusters as building units, which are further linked by mip anions to form a one-dimensional ladder-like chain with less common unidentate coordinated bpp decorated as pendants. The thermal stabilities and X-ray powder diffraction studies indicate that the microporous framework of 2 can keep stable even after the loss of guest water molecules. In addition, dominant antiferromagnetic coupling was observed in compounds 1–3 and 5.

Ligand Design and Metal Ion Recognition: Comparison of the Interaction of Zinc(II) and Cadmium(II) with 17,18-Membered N3O2 Donor Macrocycles

The interaction of zinc(II) and cadmium(II) with 17- and 18-membered ring macrocycles incorporating nitrogen and oxygen hetero-atoms is reported. These ligands constitute an array of related macrocyclic structures in which the position of the donor atoms, their spacing and the macrocyclic ring size all vary in a systematic manner. Physical measurements confirm the 1:1 metal to ligand stoichiometry of the respective complexes. The complexes, [ML 172 H2O] X2; [M ¼ Zn(II) or Cd(II); X ¼ Cl or NO3], have been synthesized via the templated cyclocondensation reactions of salicylaldehyde with 1,2-dibromoethane or 1,3-dibromopropane and diethylenetriamine in 2:1:1 molar ratio. The stoichiometries and coordination modes of the complexes have been deduced from IR, 1 H, and 13 C NMR, conductivity and microanalytical data. Tetrahedral geometry is suggested for Zn(II) compounds, where three nitrogen atoms are coordinated to the metal and the fourth being occupied by a water molecule, while octahedral geometry is suggested for Cd(II) where three nitrogen and two oxygen atoms are coordinated to the metal, the sixth being occupied by a water molecule.

2-[4-(4,5-Dihydro-1H-pyrrol-2-yl)phenyl]-4,5-dihydro-1H-imidazole

The mol­ecule of the title compound, C12H14N4, lies about a crystallographic inversion centre. The five- and six-membered rings are twisted from each other, forming a dihedral angle of 18.06 (7)°. In the crystal structure, neighbouring mol­ecules are linked by inter­molecular N—H⋯N hydrogen bonds into one-dimensional infinite chains forming 18-membered rings with R 2 2(18) motifs. The crystal structure is further stabilized by weak inter­molecular π–π stacking [centroid–centroid distance = 3.8254 (6) Å] and C—H⋯π inter­actions.

Macrolactin S, a New Antibacterial Agent with Fab G-inhibitory Activity from Bacillus sp. AT28

In the course of screening for FabG inhibitors from microbial sources, a new 24-membered ring lactone named macrolactin S, along with the known compound macrolactin B, has been isolated from the mycelium of liquid fermentation cultures of Bacillus sp. AT28. The structure of macrolactin S was determined on the basis of MS and NMR data. Macrolactin S showed a dose-dependent inhibition of Staphylococcus aureus FabG, not inhibiting S. aureus FabI. Also macrolactin S inhibited the growth of S. aureus, Bacillus subtilis, and Escherichia coli.

Thiamacrocyclic Lactones: New Ag(I)-Ionophores

The syntheses of novel adamantane thialactones 5-12 are reported, and the results of the heavy- and transition-metal cation extraction experiments are described. The results are compared with those obtained with similar thiamacrocyclic ligands that have flexible chains of methylene groups incorporated into the macrocyclic framework as in 13-20. The results show that most of the hosts studied are very good in complexing the Ag(+) ion. The formation of complexes has also been demonstrated using NMR titration experiments for macrocycles 13 and 14 with AgTFA. Introduction of a single polycyclic molecule into the 15- to 18-membered rings increases the rigidity and preorganizes the ligand for complexation. However, two adamantane molecules embedded in the ring usually diminish the complexing ability of the ligand, primarily due to sterical effects of the bulky adamantane moiety that obstructs formation of an optimal geometry for binding the desired metal ion. The structures of macrocycles 5, 7, 9, 11, and 19 were determined by X-ray structure analysis, and their conformational properties are discussed. In the solid state, 7, 11, and 19 are organized into tubular fashion using C-H...O interactions. Also, two silver complexes with thialactone 13, Ag13 and Ag(13)(2), were prepared and characterized. The structure analysis of Ag13 and Ag(13)(2) reveals the formation of mononuclear and binuclear species with silver in ambivalent, tetrahedral coordination via sulfur and oxygen from trifluoroacetate anion.

Rasagiline ethanedisulfonate: an inhibitor for monoamine oxygenase B (MAOB)

Rasagiline is a selective and potent drug used for the treatment of Parkinson's disease. The first crystal structure of a salt of rasagiline, the title compound, bis[(1R)-N-prop-2-ynyl-2,3-dihydro-1H-inden-1-aminium] ethanedisulfonate, 2C(12)H(14)N(+).C(2)H(4)O(6)S(2)(-), was determined from crystals grown by gas diffusion. The compound has monoclinic (C2) symmetry. The ethane group of the ethanedisulfonate anion is disordered over three positions. The C(2)-symmetric ethanedisulfonate anions are connected by four N-H...O hydrogen bonds to four rasagiline cations. This leads to large 18-membered rings which are arranged in ladders in the [010] direction. The extended hydrogen-bonding architecture may explain the stability of the structure. Rasagiline ethanedisulfonate is nonhygroscopic. During a polymorph screen, no hydrates, solvates or polymorphs were found.

Synthesis and Crystal Structure of a Novel Double-Chain Coordination Polymer [Zn2(bipy)2(btec)(H2O)2]n (bipy = 2,2′-bipyridine; btec = 1,2,4,5-benzenetetracarboxylate)

A novel aromatic polycarboxylate polymer, [Zn2(bipy)2(btec)(H2O)2]n (1), has been synthesized and structurally characterized by the single crystal X-ray diffraction. Compound 1 belongs to the triclinic crystal system, space group P-1; a = 7.7449(6) A, b = 8.9286(8) A, c = 10.7422(8) A, α = 80.95(1)°, β = 70.21(1)°, γ = 78.14(1)°, V = 680.93(10) A3, Z = 2. The coordination geometry of Zn(II) atom is distorted trigonal bipyramidal with two nitrogen atoms of one 2,2′-bipy group, two oxygen atoms from two different btec ligands, and one water. The 16-membered rings are alternately arranged forming an infinite 1-D double-chain structure. A 3-D network was constructed by interlayer C···H–O, O···H–O hydrogen bonds and π–π stacking interactions. Compound 1 exhibits fluorescence at room temperature in the solid state. A 1-D double-chain aromatic polycarboxylate polymer, [Zn2(bipy)2(btec)(H2O)2]n (1), has been synthesized and structurally characterized by the single crystal X-ray diffraction. A 3-D network was constructed by intermolecular C···H–O, O···H–O hydrogen bonds and π–π stacking interactions. Compound 1 exhibits fluorescence at room temperature in the solid state.

6,7,9,10-Tetrahydro-16,22-ethanooxyethano-5,8,11,19-tetraoxa-16,22-diazadibenzo[h,q]cyclooctadecine-17,21-dione: a benzylannelated macrobicyclic diamide

The macrobicyclic title compound, C24H28N2O7, has two tertiary diamide bridgehead atoms and is composed of a 12-membered ring (N2O2 donor set) and two 18-membered rings (N2O4 donor sets). The solid-state structure shows that each of the amide groups is not coplanar with the adjacent benzene ring and NMR studies indicate that this conformational relationship persists in solution.

Poly[[{μ3-tris[2-(4-phenyl-1,2,3-triazol-1-yl)ethyl]amine}silver(I)] hexafluoridophosphate

The title compound, {[Ag(L)]PF6)n {L is tris­[2-(4-phenyl-1,2,3-triazol-1-yl)eth­yl]amine, C30H30N10}, consists of alternating two-dimensional cationic layers of [Ag(L)]+ and anionic PF6 − layers. Each AgI atom is three coordinated in a T-shaped geometry by three N atoms from three ligands. Each ligand links three AgI atoms, generating a two-dimensional network structure with two different metallacycles, A and B. In A, eight coordination units from four ligands connect four AgI atoms, forming a 48-membered ring. In B, four coordination units from two ligands link two AgI atoms, forming a 24-membered ring. Each B ring is surrounded by four A rings, and each A ring has four A and four B rings as neighbours. This cationic layer thus generates a 4.82 topology network, with each AgI centre and ligand acting as a three-connected topological node.

A Series of Lead(II)-Organic Frameworks Based on Pyridyl Carboxylate Acid N-Oxide Derivatives: Syntheses, Structures, and Luminescent Properties

Six new lead coordination polymers, namely, [Pb(INO)2]·3H2O (1), [Pb(INO)2·NO3·H2O] (2), [Pb(INO)·Cl] (3), Na1.5[Pb2(INO)5]·0.5NO3 (4), [Pb3(NNO)4·(NO3)2·H2O] (5), and [Pb(NNO)2] (6), have been prepared by the reaction of Pb(NO3)2 with isonicotinic acid N-oxide (HINO), or nicotinic acid N-oxide (HNNO), and characterized by elemental analysis, IR, and single-crystal X-ray diffraction. Compound 1, consisting of a one-dimensional (1D) infinite chain, is a three-dimensional (3D) supramolecular framework with a 1D rectanglar channel in which free water molecules locate. The structure of 2 consists of 1D chains built by two parallel INO ligands bridging a pair of rhombic-planar [Pb2O2] units, which is further extended into a 2D supramolecular layer via hypervalent interactions and interlayer π-π interactions. Compound 3 consists of a two-dimensional (2D) inorganic layer containing 16-membered rings, which are further linked through μ-INO to generate a unique 3D open framework. In compound 4, the self-assembly b...

A new 3D nickel(II) framework composed of large rings: Ionothermal synthesis and crystal structure

Ionothermal reaction between Ni 2+ and 1,3,5-benzentricarboxylic acid (H 3BTC) with [AMI]Cl (AMI=1-amyl-3-methylimidazolium) as the reaction medium produced a novel 3D mixed-ligand metal-organic framework [AMI][Ni 3(BTC) 2(OAc)(MI) 3] (1) (MI=1-methylimidazole) with [AMI] + incorporated in the framework. The framework is formed by connecting 2D planes, made up of 32- and 48-membered rings, through 1D chains composed of 32-membered rings. The two BTC 3− ligands in 1 show the same connectivity mode with two bidentate and one μ 2 bridging carboxylic groups. This is a new connectivity mode to the already existing 17 in the Ni-BTC system. The role of MI and [AMI]Cl in the structure formation is discussed.

Self-Assembly of Discrete Metallocycle versus Coordination Polymer Based on Silver(I) and Di-2- and Di-3-pyridines with Flexible Spacer

Four flexible bis(pyridyl) ligands, namely, 1,3-bis(2-pyridylaminomethyl)benzene (L1), 1,3-bis(3-pyridylaminomethyl)benzene (L2), 1,4-bis(3-pyridylaminomethyl)benzene (L3), and 1,4-bis(2-pyridylaminomethyl)benzene (L4), have been synthesized, and the reactions of these ligands with AgX salts (X = NO3−, ClO4−) lead to the formation of six new complexes, [Ag(L1)]2(ClO4)2 (1), [Ag(L2)ClO4]n (2), [Ag(L1)NO3]n (3), [Ag(L3)(PPh3)2]n(NO3)n·nCH3OH (4), [Ag2(L4)(PPh3)2(NO3)2]n·nH2O (5), and [Ag(L4)NO3]n (6), exhibiting from zero-dimensional (0-D) to three-dimensional (3-D) frameworks. In complex 1, the L1 ligand bridges two silver atoms to form a dinuclear with a 24-membered macrometallacyclic ring, while the L1 ligand coordinates to silver atoms to generate a 2-D (4,4) network with two pyridine rings oriented in a divergent fashion (or trans conformation) in complex 3. With a similar trans conformation, L2 in complex 2, L3 in complex 4, and L4 in complex 5 connect the adjacent silver atoms or Ag2O2 units which formed by the bridging of nitrate anions in a η2:μ2 fashion to give rise to infinite helical chains, respectively. Complex 6 exhibits a 3-D framework with diamond topology, which is combined by two kinds of helical chains: one is a -Ag-NO3-Ag-NO3- chain with the nitrate anions in a η1:η1:μ2 fashion, and another is a -Ag-L4-Ag-L4- chain with the L4 ligand in trans conformation. All of these complexes are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor.

The Cyclic “Silver-Diphos” Motif [Ag2(μ-diphosphine)2]2+ as a Synthon for Building up Larger Structures

The dinuclear, cyclic structural motif [Ag2(diphosphine)2](2+), here termed the "silver-diphos" motif, previously observed in many diphosphine-silver complexes, has been investigated as a synthon for building up larger structures such as coordination cages and polymers. A series of ligands containing one to four meta-substituted diphosphine groups, attached via a central core, has been synthesized from the corresponding fluoroarenes by reaction with KPPh2. Upon reaction with silver salts, the target synthon is adopted by meta-substituted diphosphines 1,3-bis(diphenylphosphino)benzene (L1), 2,6-bis(diphenylphosphino)benzonitrile (L2), and 3,5-bis(diphenylphosphino)benzamide (L3), each of which gives a single species in solution consistent with the expected dimeric complexes [Ag2L2(anion)2]. X-ray crystal structures of [Ag2(L1)2(OTf)2] and [Ag2(L2)2(SbF6)2] confirm the adoption of the silver-diphos motif in the solid state. Amide-functionalized diphosphine L3 forms a hydrogen-bonded chain structure in the solid state via the amide group. A discrete boxlike cage [Ag4(L4)2][SbF6]4 based on two silver-diphos synthons is formed when the tetraphosphine Ph2Sn{3,5-bis(diphenylphosphino)benzene}2 (L4) reacts with silver(I). Its single-crystal X-ray structure reveals a central cavity of minimum diameter, ca. 5.0 A, which contains a single SbF6(-) counterion disordered over two sites. In contrast to the highly selective behavior of the di- and tetra-phosphines L1-L4, the heptaphosphine P{3,5-bis(diphenylphosphino)benzene}3 L5 and the hexaphosphine PhSn{3,5-bis(diphenylphosphino)benzene}3 L6 give dynamic mixtures upon reaction with silver salts in solution. This nonspecific behavior is rationalized by the fact that their diphosphine groups are not appropriately disposed to form stable discrete structures based on the silver-diphos synthon. By contrast, the octaphosphine Sn{3,5-bis(diphenylphosphino)benzene}4 L7 does selectively form a single, discrete, highly symmetrical product in solution, [Ag4(L7)(OTf)4]. In this case, the ligand unexpectedly adopts an interarm tetra-chelating coordination mode, resulting in a continuous 24-membered ring around the periphery of the molecule. To understand the adoption of this unusual coordination mode, the alternative diphosphine Ph2Sn(3-diphenylphosphinobenzene)2 L8, which models a single interarm chelating site of L7, was also investigated. By contrast to L7, its coordination was nonspecific, giving mixtures of silver complexes upon reaction with AgOTf. The selective interarm chelation by L7 may therefore be stabilized by the continuous coordination ring in [Ag4(L7)(OTf)4]; that is, the four chelating sites can be thought of as acting in a cooperative manner. Alternatively, interarm steric repulsions between phenyl groups may favor interarm chelation. Overall, we conclude that, if the diphosphine groups are appropriately articulated to act independently (i. e., they are adequately separated and oriented), the silver-diphos synthon can be a useful tool for the coordination-based self-assembly of larger structures.

A layered cobalt phosphonate exhibiting ferrimagnetism and slow magnetic relaxation

Compound Co 3(hpyedpH) 2(H 2O) 4 · H 2O ( 1) (hpyedpH 4 = 1-hydroxy-2-(3-pyridyl)ethylidene-1,1-diphosphonic acid) has a layer structure where chains of {Co 3(hpyedpH) 2(H 2O) 4} n are connected by {CPO 3} tetrahedra, generating a layer containing 4-, 8- and 16-membered rings. Magnetic measurements show that compound 1 is a ferrimagnet with T c = 3.8 K. Slow magnetic relaxation is observed below 3.8 K, possibly due to the domain wall movement.

Two new d 10 2D layered frameworks based on 1,2,4-triazole bridge: Syntheses, structures, and fluorescence

Two new triazole-bridging d 10 2D layered frameworks, [Cd(H 2O) 2(Httr) 2](SiF 6) ( 1), [Zn(ttr)(OAc)] ( 2) (Httr = 3-amino-1 H-1,2,4-triazole), were synthesized with structures and fluorescence characterized. 1 is based on a kind of 16-membered ring with μ 2-1 κN:4 κN coordination mode of Httr and 2 is constructed from the fuse of different 6- and 16-membered rings with μ 3-1 κN:2 κN:4 κN mode of ttr −. The hydrogen bondings in 1 and 2 between the anions and ttr connect the 2D layers into 3D supramolecular architectures. The fluorescent studies of compounds 1 and 2 show an important difference, emission at 460 nm in 1 and a dual one at 334 and 462 nm in 2.