A new cycloartane triterpenoid from the leaves and stems of Fritillaria hupehensis

A new triterpenoid has been isolated from the leaves and stems of Fritillaria hupehensis Hsiao et K.C.Hsia.Its structure wasestablished as(23Z)-9,19-cycloart-23-ene-3α,25-diol 1 through chemical and spectroscopic studies including 2D NMR.Anotherknown triterpenoid 9,19-cycloart-25-ene-3β,24ξ-diol 2 was also isolated.     

Metal coordination architectures of triazole-based ligands: Effect of the backbone of bridging ligands on the construction of polymers

In our efforts to investigate the influence of the backbone of different triazole-based bridging ligands on the structure of their metal complexes, four new coordination polymers, {[Cu(L¹)₂(H₂O)₂]Cl₂}_n (1), [Cu(L²)₂Cl₂]_n (2), [Co(L²)₂(SCN)₂]_n (3), and [Cu(L³)₂(NO₃)₂]_n (4), (L¹ = 1,2-bis(triazol-1-ylmethyl)benzene, L² = 1,3-bis(triazol-1-ylmethyl)benzene, L³ = 1,4-bis(triazol-1-ylmethyl)benzene), have been synthesized. All the complexes have been structurally characterized by IR, elemental analysis and single-crystal X-ray diffraction. Structural analyses show that 1 and 4 possess 2D coordination networks with (4,4) topology, and 1 shows a diagonal–diagonal inclined interpenetration. 2 and 3 are isostructural and feature 1D double chain, which further connected by C–H···Cl or π···π weak interactions to form 2D supramolecular frameworks. The results show that the structures of ligands (with different non-coordination backbone spacers) play important roles in the formation of such coordination architectures. Furthermore, EPR (Electron Paramagnetic Resonance) spectra of Cu^II complexes (1, 2, and 4) have been investigated in the solid state at room temperature.     

Rare configuration of tautomeric benzimidazolecarboxylate ligands in cadmium(II) and copper(II) coordination polymers

Two Cd(HBimc)-based isomers, [Cd(HBimc^N)(HBimc^T)(H₂O)]·3.5H₂O·EtOH (1a·3.5H₂O·EtOH, H₂Bimc=1H-benzimidazole-5-carboxylic acid) and [Cd(HBimc^N)(HBimc^T)(H₂O)] (1b), and two Cu(HMBimc)-based coordination polymers, [Cu(HMBimc^N)₂(H₂O)]·1/2H₂O (2·1/2H₂O, H₂MBimc=2-methyl-1H-benzimidazole-5-carboxylic acid) and [Cu(HMBimc^T)₂]·2THF·H₂O (3·2THF·H₂O), were self-assembled from Cd(ClO₄)₂·6H₂O/H₂Bimc and Cu(ClO₄)₂·6H₂O/H₂MBimc systems, respectively. Compound 1a adopts a ladder-like chain structure, comprised of a hydrogen-bond-stabilized Cd₂(HBimc^N)₂-metallocyclic stair and a 1D straight -(Cd-HBimc^T)_n- edge, whereas compound 1b exhibits a 2D (4,4)-rhombus layered structure, intercrossed by 1D -(Cd-HBimc^N)_n- chains and -(Cd-HBimc^T)_n- chains. Compound 2 shows a 1D double-stranded wave-like chain from two single-stranded wave-like -(Cu-HMBimc^N)_n- chains and compound 3 adopts a 2D (4,4)-topological layer structure, intercrossed by subunits of 1D -(Cu-HMBimc^T)_n- chains. Interestingly, a pair of tautomeric HBimc building blocks—normal (N or HBimc^N) and tautomer (T or HBimc^T)—is simultaneously included in the structures of 1a and 1b, whilst the N- and T-configured HMBimc building blocks are present as separate entities in Cu species, 2 and 3, respectively. The existence of only a tautomer (T) mode of the benzimidazolecarboxylate-based ligand in a Cu(II) network is observed for the first time.     

Modelling the use of lanthanides(III) as probes at calcium(II) binding sites in biological systems: Preparation and characterization of neodymium(III) and calcium(II) malonamato(-1) complexes

A bioinorganic approach into the problem of the isomorphous substitution of calcium(II) by lanthanide(III) ions in biological systems is discussed. Reactions of malonamic acid (H₂malm) with Ca^II and Nd^III sources under similar conditions yielded the compounds [Ca(Hmalm)₂]_n (1), [Nd(Hmalm)₂(H₂O)₂]_n(NO₃)_n (2) and [Nd(Hmalm)₂(H₂O)₂]_nCl_n·2nH₂O (3·2nH₂O). Their X-ray crystal structure data show that the malonamate(-1) ligand presents two different ligation modes and coordinates through the two carboxylate and the amide-O atoms, thus bridging three Ca^II ions in 1 and two Nd^III ions in 2 and 3·2nH₂O. Complex 1 is a 3D coordination polymer based on neutral repeating units, whereas 2 and 3·2nH₂O are 1D coordination polymers based on the same cationic repeating unit. Hydrogen bonding interactions further stabilize the 3D framework structure of 1 and assemble the 1D chains of 2 and 3·2nH₂O into 3D networks. The three complexes were characterized spectroscopically (IR, far-IR, and Raman) and the thermal decomposition of 2 and 3·2nH₂O was monitored by TG/DTA and TG/DTG measurements. Variable-temperature magnetic susceptibility data for 2 are also reported. The bioinorganic chemistry relevance of our results is discussed.     

Euphatexols A and B,two unusual euphane triterpenoids from the latex of Euphorbia resinifera

Two unusual euphane triterpenoids, named euphatexols A (1) and B (2), were isolated from the latex of Euphorbia resinifera. Their structures were elucidated based on the extensive analysis of spectroscopic data (HRMS, 1D and 2D NMR). Compound 1 possesses a rare tetrahydrofuran ring formed via C-1 and C-11, which is firstly reported in euphane triterpenoids. Compound 2 represents an unusual 27-nor-euphane triterpenoid. Moreover, compounds 1 and 2 showed significant cytotoxic activities against HepG2 cells with 87.0% and 87.4% inhibition rate at 1 μM, respectively.     

Synthesis of mono- and dihydroxy-substituted 2-aminocyclooctanecarboxylic acid enantiomers

(1R,2S,6R)-2-Amino-6-hydroxycyclooctanecarboxylic acid (?)-10 was synthesized from (1R,2S)-2-aminocyclooct-5-enecarboxylic acid (+)-2 via an iodolactone intermediate, while (1R,2S,3R,4S)-2-amino-5,6-dihydroxycyclooctanecarboxylic acid (?)-12 was prepared by using the OsO₄-catalyzed oxidation of Boc-protected amino ester (?)-5. The stereochemistry and relative configurations of the synthesized compounds were determined by 1D and 2D NMR spectroscopy (based on 2D NOE cross-peaks and ³J(H,H) coupling constants) and X-ray crystallography.     

Novel lead(II) carboxylate-arsonate hybrids

Hydrothermal reactions of lead(II) acetate with phenylarsonic acid (H₂L¹) (or 4-hydroxy-3-nitrophenylarsonic acid, H₃L²) and 5-sulfoisophthalic acid monosodium salt (NaH₂SIP) (or 1,3,5-benzenetricarboxylic acid (H₃BTC)) as the second metal linkers afforded three novel mixed-ligand lead(II) carboxylate-arsonates, namely, Pb₅(SIP)₂(L¹)₂(H₂O) 1, Pb₃(SIP)(L²)(H₂O) 2 and Pb(H₂L²)(H₂BTC) 3. The structure of 1 features a complicated 3D network composed of 2D double layers of lead(II) sulfoisophthalate bridged by 1D chains of lead(II) arsonates along b-axis, forming large tunnels along b-axis which are occupied by phenyl rings of the arsonate ligands. In 2, the Pb(II) ions are bridged by {L²}³⁻ anions into a 2D double layer whereas the interconnection of the Pb(II) ions via bridging and chelating SIP anions gave a 2D double layer. The cross-linkage of the above two building units leads to a complicated 3D network. In 3, the interconnection of the Pb(II) ions via bridging {H₂L²}⁻ and {H₂BTC}⁻ anions leads to a 1D double chain down a-axis. These 1D chains are further interconnected via hydrogen bonds among non-coordination carboxylate groups and arsonate oxygens into a 3D supramolecular architecture.     

Three 3D hybrid networks based on octamolybdates and different Cu/Cu-bis(triazole) motifs

Three 3D compounds based on octamolybdate clusters and various Cu^I/Cu^II-bis(triazole) motifs, [Cu^I₂btb][β-Mo₈O₂₆]_0.5 (1), [Cu^I₂btpe][β-Mo₈O₂₆]_0.5 (2), and [Cu^II(btpe)₂][β-Mo₈O₂₆]_0.5 (3) [btb=1,4-bis(1,2,4-triazol-1-yl)butane, btpe=1,5-bis(1,2,4-triazol-1-yl)pentane], were isolated via tuning flexible ligand spacer length and metal coordination preferences. In 1, the copper(I)-btb motif is a one-dimensional (1D) chain which is further linked by hexadentate β-[Mo₈O₂₆]⁴⁻ clusters via coordinating to Cu^I cations giving a 3D structure. In 2, the copper(I)-btpe motif exhibits a “stairs”-like [Cu^I₂btpe]²⁺ sheet, and the tetradentate β-[Mo₈O₂₆]⁴⁻ clusters interact with two neighboring [Cu^I₂btpe]²⁺ sheets constructing a 3D framework. In 3, the copper(II)-btpe motif possesses a novel (2D→3D) interdigitated structure, which is further connected by the tetradentate β-[Mo₈O₂₆]⁴⁻ clusters forming a 3D framework. The thermal stability and luminescent properties of 1-3 are investigated in the solid state.     

Hydrothermal syntheses, crystal structures and properties of three coordination frameworks based on a new semirigid ligand and benzenedicarboxylate

Three novel polymers, {[Cd(m-bdc)(L)]·H₂O}_n (1), [Co(m-bdc)(L)_0.5(H₂O)]_n (2) and [Zn₅(L)₂(p-bdc)₅(H₂O)]_n (3) based on 1,1′-bis(pyridin-3-ylmethyl)-2,2′-biimidazole (L) ligand and benzenedicarboxylate isomers, have been prepared and structurally characterized. Compound 1 exhibits a 2D architecture with (4²·6)(4²·6⁷·8) topology, which is synthesized by L and 1,3-benzenedicarboxylate (m-bdc) ligands. Compound 2 is constructed from 1D chains that are linked by L ligands extending a 2D (4,4) grid. Compound 3 is a 3D framework with (4³)(4⁶·6¹⁸·8⁴) topology, which is composed of trinuclear clusters and five-coordinated metal centers joined through 1,4-benzenedicarboxylate (p-bdc) and L ligands. Moreover, the fluorescent properties of L ligand, compounds 1 and 3 are also determined.     

Structural assemblies of four Cd(II) coordination polymers based on 5-methylisophthalic acid

Four new metal-organic coordination polymers, Cd(mip)(DMF)(1), Cd(mip)(EtOH)(2), Cd₂(mip)₂(H₂O)₅·3H₂O (3), Cd(mip)(bpp)(H₂O)·H₂O (4) (H₂mip = 5-methylisophthalic acid, bpp = 1,3-di(4-pyridyl)propane) have been hydro(solvo)thermally synthesized and characterized by IR, thermogravimetric (TG) analysis, powder X-ray diffraction and single-crystal X-ray diffraction. 1 and 2 are isostructural, and two adjacent Cd centers are bridged by four carboxylate groups in μ₂-carboxylato-κ¹O_.:κ¹O′ and μ₂Ο; κ²O,O′ fashion to form a linear (Cd–O–Cd)_n chain. The adjacent (Cd–O–Cd)_n chains are further connected by mip bridges to form a 3D framework. 3 features two types of chiral layers: One left-handed and another right-handed, which lead to racemic solid-state compound. 4 exhibits a two-dimensional wave-like (2D) (4,4) layer structure with infinite 1D linear chain. In addition, the luminescent properties of 1–4 are also discussed.     

Alkaloids of NIRAM,natural dye from Polygonum tinctorium,and their anti-inflammatory activities

Phytochemical investigation of EtOH extract of NIRAM, natural dye from Polygonum tinctorium, resulted in the purification of nine alkaloid compounds (1–9) including four new compounds (1–4). Structures of these new compounds were elucidated by 1D and 2D NMR (¹H and ¹³C NMR, ¹H–¹H COSY, ¹H–¹³C HSQC, ¹H–¹³C HMBC), IR, UV, HR-ESI-MS, and ECD spectra. Isolated compounds (1–9) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated BV-2 cells. Compounds 1–3, 5, and 7 showed potent NO production inhibitory activities, with IC₅₀ values of 3.88–22.87 μM.     

Chains,helices, sheets and unusual 3D nets: Diverse structures of the flexible,ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazolyl)ethane

The flexible ditopic ligand 1,2-bis(3-(4-pyridyl)pyrazol-1-yl)ethane (L^4Et) displays remarkable versatility in the complexes that it forms with transition metals with products ranging from 1D chains to interpenetrating 3D networks. The L^4Et ligand itself crystallises in the space group P2₁, adopting a helical twist, although it is found in a variety of other conformations in its complexes. Coordination polymers containing the L^4Et ligand vary from almost straight, parallel 1D chains of [Ag₂(L^4Et)₂(ClO₄)₂(DMF)]·DMF (1), through interdigitating helical complexes containing tetrahedral Zn(II), [Zn(NCS)₂(L^4Et)]·DMF·H₂O (2) to 2D sheets of [Cu(L^4Et)₂(H₂O)₂](PF₆)₂·xH₂O (3) and the three-fold interpenetrating 3D network of [Co(L^4Et)₂(NCS)₂] (4). The 3D network adopts an unusual 3D 4-connected dmp (6⁵.8) topology. Dimensionality can be limited by the use of chelating co-ligands, demonstrated by the formation of the dinuclear complex [{Cu(py-2,6-CO₂)(H₂O)}₂(L^4Et)] (5).     

1D coordination polymers of silver(I) and copper(II) based on bis(N-heterocyclic carbene) ligands: Synthesis and structural studies

The alkyl chain-linked diimidazolium (or dibenzimidazolium) salts, 1,1′-diethyl-4,4′-tetramethylene-diimidazolium-diiodide (L¹H₂·I₂) and 1,1′-diethyl-3,3′-trimethylene-dibenzimidazolium-diiodide (L²H₂·I₂), and their silver(I) and copper(II) coordination polymers, [L¹AgI]_n (1) and [L²Cu₂I₄]_n (2), have been prepared and characterized. Complex 1 is a 1D helical polymer generated by bidentated carbene ligands (L¹) and Ag(I) atoms. The 1D polymer of 2 is formed by bidentated carbene ligands (L²) and coplanar quadrilateral Cu₂I₂ units. 3D supramolecular frameworks in the crystal packings of 1 and 2 are formed via intermolecular weak interactions, including C–H···π contacts, π–π interactions and C–H···I hydrogen bonds.     

Syntheses and characterization of inorganic–organic hybrids with 4-(isonicotinamido)phthalate and some divalent metal centers

Four new inorganic–organic hybrid frameworks [Mn(L)(H₂O)₂]_n (1), {[Co(L)(H₂O)₃]·2H₂O·CH₃OH}_n (2), {[Zn(L)(H₂O)]·H₂O}_n (3) and [Cd(HL)₂]_n (4) [H₂L = 4-(isonicotinamido)phthalic acid] have been synthesized and characterized by single-crystal X-ray diffraction analysis. Complex 1 has three-dimensional (3D) structure and topology related to SrAl₂ (sra) with Schläfli symbol of (4²·6³·8). And 2 displays (3,3)-connected two-dimensional (2D) network with (4,8²) topology, while 3 exhibits a uninodal (3,3)-connected (6,3) 2D network, which is further linked by N–H?O hydrogen bonding interactions to give 3D structure with hms topology and Schläfli symbol of (6³)(6⁹·8). Complex 4 with partial deprotonated HL⁻ ligands also has a 2D network structure. In addition, the magnetic property of 1, nonlinear optical property of 3 and photoluminescence of 3 and 4 were investigated.     

Hydrothermal syntheses, crystal structures and fluorescent properties of five transition metal–organic hybrids incorporating an unsymmetrical benzotriazole carboxylate ligand

The hydrothermal reactions of nitrate or chloride salts of Co(II), Zn(II), Cd(II), Hg(II) and Ag(I) with an unsymmetrical benzotriazole derivative 1H-1,2,3-benzotriazole-1-propionic acid (Hbtap) afforded five new metal–organic coordination polymers with formula of [M(btap)₂(H₂O)₂] _n (M = Co 1, Zn 2, Cd 3), [Hg(btap)Cl] _n (4) and {[Ag(btap)]·H₂O} _n (5), which were characterized by X-ray diffraction and spectroscopic methods. The anionic btap^? ligands in these complexes assume the same anti conformation, but show different coordination behaviors toward transition metal ions. Complexes 1, 2 and 3 are isostructural and reveal infinite one-dimensional (1D) looped-chain structures constructed by hexacoordinated metal centers and 2-connected btap^? bridges. Complex 4 features 1D zigzag polymeric arrays, which are interlinked with each other resulting in a chiral three-dimensional (3D) 4-connected framework. In complex 5, the 3-connected ligands join Ag(I) atoms into a 1D ribbon motif. The photoluminescence spectra of three d¹⁰ metal complexes 2, 3 and 4 were measured at room temperature. The emission peaks of these complexes resemble that of the free ligand and can be ascribed to the intraligand π–π* transitions.     

Syntheses, structures and properties of five copper coordination polymers constructed by the triazole ligand

Reactions of different metal salts with 4-amino-3,5-bis(3-pyridyl)-1,2,4-triazole (3-abpt) gave rise to five new complexes, namely [Cu₄(CN)₄(3-abpt)₂]_n (1), [CuBr(3-abpt)]_n (2), [CuI(3-abpt)]_n (3), [Cu₃I₃(3-abpt)]_n (4) and [Cu(3-abpt)(SO₄)(H₂O)]_n (5). Compounds 1, 3, 4 and 5 are all 2D structures. Compound 1 is a double-layered polymer with an uncommon 3-nodal 3-connected (10³)(10².4)₄ network, 3 shows a 2D square layered structure, 4 is also a double-layered polymer with 2-nodal 4-connected (3.4.5.6².7)₂(3.4².5².7) network and 5 is a 2D structure which is ultimately stacked with an ABAB repeat pattern. Compound 2 is a 1D coordination polymer which exhibits a ladder-like network. The photoluminescence of 1-2 has also been investigated. The long emission lifetimes of 1-2 could be assigned to metal-to-ligand charge transfer triple excited states [MLCT].     

Synthesis,characterization and ethylene polymerization of 1-(2,6-dimethyl-4-fluorenylphenylimino)-2-aryliminoacenaphthylnickel bromides

A series of 1-(2,6-dimethyl-4-fluorenylphenylimino)-2-aryliminoacenaphthylene compounds (aryl = 2,6-di(Me)Ph (L1), 2,6-di(Et)Ph (L2), 2,6-di(i-Pr)Ph (L3), 2,4,6-tri(Me)Ph (L4), 2,6-di(Et)-4-MePh (L5)) was prepared and used to form their corresponding dibromonickel complexes (D1–D5). Both L1–L5 and D1–D5 were fully characterized by FT-IR and elemental analysis as well as NMR measurements in the case of ligands L1–L5. The molecular structure of the representative complex D5 was confirmed by single crystal X-ray diffraction revealing a distorted trigonal bipyramidal geometry around the nickel center. On activation with either ethylaluminium sesquichloride (Et₃Al₂Cl₃, EASC) or methylaluminoxane (MAO), all nickel complexes exhibited high activities up to 9.82 × 10⁶ g of PE (mol of Ni)⁻¹ h⁻¹ for ethylene polymerization. In comparison with the polyethylenes obtained with related Ni pre-catalysts, the polyethylenes obtained in this work possessed relatively higher molecular weights and lower levels of branching, highlighting the significant influence of the remote fluorenyl substituent.     

Synthesis,crystal structures and properties of three glutarato and adipato bridged manganese(II) coordination polymers under ambient conditions

Three Mn(II) polymers Mn(H₂O)₄(C₅H₆O₄) 1, [Mn(H₂O)₂(C₅H₆O₄)]·H₂O 2 and Mn(H₂O)(C₆H₈O₄) 3 were synthesized (H₂(C₅H₆O₄) = glutaric acid, H₂(C₆H₈O₄) = adipic acid) under mild ambient conditions. The [Mn(H₂O)₂]²⁺ units in 2 are interlinked by the glutarate anions with a η⁴μ₃ bridging mode to form 2D (4·8²) topological networks, which are stacked via interlayer hydrogen bonds into a 3D (4³·6⁵·8²)(4⁷·6³) topological net. Compound 3 crystallizes in the acentric space group P2₁ and exhibits significant ferroelectricity (remnant polarization Pr = 0.371 nC cm⁻², coercive field Ec = 0.028 kV cm⁻¹, saturation of the spontaneous polarization Ps = 0.972 nC cm⁻²). The adjacent MnO₆ octahedrons in 3 are one atom-shared to generate the Mn₂O₁₁ bi-octahedron, leading into 1D metal oxide chains. The resulting chains are interconnected by the η⁵μ₅ adipate anions to form new 2D (4⁸·6²) networks, which are held together via strong interlayer hydrogen bonds into 3D α-Po topological supra-molecular architecture. The temperature-dependent magnetic susceptibility data of 1–3 shows overall anti-ferromagnetic interactions between the metal ions bridged by the carboxylate groups.     

Ligand controlled structure of cadmium(II) metal-organic frameworks for fluorescence sensing of Fe3+ ion and nitroaromatic compounds

2-Fold interpenetrating 3D framework for selective adsorption of CO₂ over CH₄ and fluorescence detection of Fe³⁺ ions and nitroaromatic compounds through fluorescence quenching.     

Syntheses,IR spectra,thermal properties and crystal structures of novel cyano-bridged polymeric complexes of zinc and cadmium with tetracyanoplatinate

Two novel one-dimensional polymeric cyano-bridged platinum(II) complexes of N-(2-hydroxyethyl)-ethylenediamine (hydeten), [M^II(hydeten)Pt(CN)₂(μ-CN)₂]_n (M^II = Zn^II (1) and Cd^II (2)), were synthesized and characterized by physico-chemical methods (elemental analysis, IR spectroscopy and thermoanalytical measurements) and X-ray diffraction. Thermal behaviours of 1 and 2 were followed using TG and DTA (DSC) techniques. The 1D chain structures of 1 and 2 were verified by X-ray diffraction studies. According to the positions of the bridging cyano groups, in complex 1 the polymeric chains are built up via the 2,2-CT type, while in complex 2 the polymeric chains are built up via the 2,2-TT type.