V-shaped Ligand Research Articles

Synthesis, Crystal Structure and DNA-binding Properties of a Nickel(II) Complex with 2, 6-Bis(2-benzimidazolyl)pyridine

A novel complex of nickel(II) picrate (pic) with the V-shaped ligand 2, 6-bis(2-benzimidazolyl) pyridine (bbp) was synthesized and characterized by elemental analysis, electrical conductivity, and IR and UV/Vis spectral measurements. The crystal structure of the nickel(II) complex ([Ni(bbp)2](pic)2·2DMF) has been determined by single-crystal X-ray diffraction. The Ni(II) cation is bonded to two bbp ligands through six nitrogen atoms, resulting in a distorted octahedral geometry. The DNA-binding properties of the nickel(II) complex were investigated by electronic absorption and fluorescence spectra and by viscosity measurements. The experimental results suggest that the nickel(II) complex binds to DNA in an intercalation mode.

A V-shaped ligand 2,6-bis(2-benzimidazolyl)pyridine and its picrate Mn(II) complex: Synthesis, crystal structure and DNA-binding properties

A V-shaped ligand 2,6-bis(2-benzimidazolyl)pyridine (bbp) and its picrate Mn(II) complex have been synthesized and characterized by elemental analysis, molecular conductivities, 1H NMR, IR, UV–vis spectra and X-ray single crystal diffraction. The crystal structure of [Mn(bbp) 2](pic) 2·2DMF is six-coordinated forming a distorted octahedron. The DNA-binding properties of the two compounds were investigated by electronic absorption spectra, fluorescence spectra and viscosity measurements. The experimental results suggest that the two compounds bind to DNA in an intercalation mode. The main reason of the DNA-binding behaviors may be the large coplanar aromatic rings in the V-shaped ligand. As compared to the DNA-binding affinities of the two compounds, the Mn(II) complex is stronger than bbp. This may be due to the V-shaped angle changed.

Two Molecular Spheres

Viruses form highly symmetrical coat structures, capsids, through the assembly of multiple lower-symmetry protein precursors. Recently, chemists have sought to emulate this process on a smaller scale, relying on the assembly of organic molecular struts and metal ions, rather than proteins. Sun et al. (p. [1144][1], published online 29 April; see the Perspective by [Stefankiewicz and Sanders][2] ) now demonstrate that a mixture of palladium ions and V-shaped bridging ligands can self-assemble into a hollow, nearly spherical polyhedron with 24 vertices and a central diameter of 4 nanometers. The assembly process was highly sensitive to the ligand angle; a subtle average decrease generated instead a smaller 12-vertex product. [1]: /lookup/doi/10.1126/science.1188605 [2]: /lookup/doi/10.1126/science.1190821

Reversible de-/resolvation and accompanied magnetism modulation in a framework of topologically ferrimagnetic [Co3(μ3-OH)2]n chains linked by a V-shaped ligand 4,4′-dicarboxybiphenyl sulfone

A dynamic metal-organic framework consisting of topologically ferrimagnetic [Co(3)(mu(3)-OH)(2)](n) chains connected by V-shaped 4,4'-dicarboxybiphenyl sulfone ligands, exhibits reversible de-/resolvation and accompanied magnetism modulation.

Diverse Ni(ii) MOFs constructed from asymmetric semi-rigid V-shaped multicarboxylate ligands: structures and magnetic properties

Novel nickel(II) coordination polymers have been constructed from asymmetric semi-rigid V-shaped multicarboxylate ligands with the help of 4,4′-bipyridine (4,4′-bpy) ligand. The hydrothermal reaction between 3-(4-carboxy-phenoxy)-phthalic acid (H3L1) and Ni(OAc)2·4H2O led to the formation of [Ni3(L1)2(μ-4,4′-bpy)3(H2O)2]n·(4,4′-bpy)n·(H2O)5n (1). In contrast, the same reaction using 3-(2-carboxy-phenoxy)-phthalic acid (H3L2) as a starting material instead of H3L1 resulted in [Ni3(L2)2(H2O)4(μ-4,4′-bpy)3]n·(H2O)2n (2) and [Ni3(L2)2(H2O)4(μ-4,4′-bpy)4]n·(H2O)2n (3) at 120 and 150 °C, respectively, revealing the effect of reaction temperature on the structure of the coordination polymer formed from the semi-rigid V-shaped ligand of L2. Single-crystal X-ray diffraction analysis reveals that complex 1 shows a 3D framework structure assembled from right- and left-handed helices together with isolated tubes. This compound represents the first metal–organic hybrid tube constructed from an asymmetric semi-rigid V-shaped multicarboxylate ligand. Compound 2 also exhibits a 3D network composed of discontiguous trinuclear Ni(II) clusters, while the 3D architecture of 3 consisting of isolated Ni(II) ions separated in a long distance is constructed by two kinds of 2D (6,3) networks. Magnetic studies reveal the overall antiferromagnetic interaction between the neighbouring Ni(II) ions in 1–3.

Not just size and shape: spherically symmetrical d5 and d10 metal ions give different coordination nets with 4,2′:6′,4″-terpyridines

Functionalized 4,2′:6′,4″-terpyridine ligands have been used to provide a divergent N,N′-donor set for the formation of coordination polymers containing {Zn2(µ-OAc)4} or {Mn3(µ-OAc)4(OAc)2} scaffolds. Single-stranded coordination polymers are produced from the reactions of 4′-(4-bromophenyl)-4,2′:6′,4″-terpyridine (1) and 4′-(4-methylthiophenyl)-4,2′:6′,4″-terpyridine (2) with Zn(OAc)2·2H2O. In [Zn2(1)(OAc)4]n and [Zn2(2)(OAc)4]n, the two outer nitrogen donors of the 4,2′:6′,4″-terpyridine ligands, bind to the axial sites of {Zn2(µ-OAc)4} units to generate coordination polymer chains which are π-stacked so that the V-shaped ligand domains are interleaved. When Mn(OAc)2·4H2O is treated with 4′-(4-bromophenyl)-4,2′:6′,4″-terpyridine, the triply stranded coordination polymer {[Mn3(1)3(OAc)6]·0.8MeOH·2.2H2O}n assembles in which the 4,2′:6′,4″-terpyridine ligands span between {Mn3(µ-OAc)4(OAc)2} units. Efficient face-to-face π-interactions between pairs of pyridine rings or pairs of bromophenyl rings are the dominant packing forces. The magnetic properties in {[Mn3(1)3(OAc)6]·0.8MeOH·2.2H2O}n are dominated by the presence of a weak antiferromagnetic interaction between the central Mn(II) ion and the two lateral ones within the linear trimeric unit, leading to an S = 5/2 ground state.

Rational Assembly of d10 Metal−Organic Frameworks with Helical Nanochannels Based on Flexible V-Shaped Ligand

Solvothermal reactions of Zn(II) or Cd(II) nitrates and V-shaped ligand of 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (H2hfipbb) in the presence or absence of 4,4′-bipy afforded four interesting d10 metal−organic frameworks with helical nanochannels, namely, Zn(hfipbb)·0.5H2O·0.5DMF enantiomers (P6222, 1a, and P6422, 1b), Zn(hfipbb)(4,4′-bipy)·DMF (2), and Cd(hfipbb)(DMF)·0.5DMF (3). The enantiomeric 1a and 1b exhibit similarly a (4,4)-connected 3D network with two types of helically 2-fold and 8-fold nanochannels along the c-axis, in which ultralong helical pitches are found in the 8-fold helical channels. Compound 2 features a 2D layered structure based on dizinc(II) paddle-wheel clusters with the appearance of left- and right-hand helical channels alternatively, while 1D double helical channels exist in the complicated structure of compound 3. The luminescent properties of all the compounds have also been studied.

Zn(II) Porous Material Assembled from V-Shaped Dicarboxylate Ligand and N-Donor Ancillary Ligand

A new porous metal-organic framework, [Zn(fipbb)(bpp)]n (1) (H 2 fipbb = (4,4′-(hexafluoroisopropylidene)bis(benzoic acid) and bpp = 1,3-bis(4-pyridyl)propane), constructed from mixed flexible co-liagnds, has been synthesized under mild condition and characterized by elemental analysis, IR and single-crystal X-ray diffraction analysis. Compound 1 exhibits (4,4) grid network containing multi-helical chains. Furthermore, two adjacent layers are displaced by about one half of the polymer period along the direction of extension and stacked with iterative sequence of ABAB. This result revealed that the coordination mode of fipbb and metal ion play important roles in controlling the resulting coordination framework.

Synthesis, Crystal Structure and Spectra Properties of the Nickel (II) Complex with 1,3-bis(1-benzylbenzimidazol2-yl)-2-Oxopropane

A novel complex of nickel (II) picrate with V-shaped ligand 1,3-bis(1-benzylbenzimidazol-2-yl)-2-oxopropane (Bobb) was synthesized and characterized by elemental analyses and electrical conductivity, IR and UV/visible spectra. The crystal structure of the complex has been determined by the single-crystal X-ray diffraction. In the complex, the Ni (II) ion is six-coordinated with a N4O2 ligand set, resulting in a distorted octahedron.

Two novel d10 frameworks based on a new V-shaped ligand 2,4′-dipyridylamine and a flexible dicarboxylate ligand

Via hydrothermal synthesis, the self-assembly of d10 metal, 2,4′-dipyridylamine (L) and 1,3-adamantanediacetic acid (H2ADA) generated two unprecedented coordination polymers [Zn(ADA)(L)]n (1) and [Cd(ADA)(L)2]n (2). Complex 1 possesses a novel 1D looped-chain topology structure decorated with arms. Complex 2 shows an extended threaded framework involving 2D coordination layers of square (44) topology with dangling ligands, which gives the novel (2D → 3D) polythreaded array. To the best of our knowledge, complex 2 is the first example with four dangling arms coordinated in the axial sites of dinuclear nodes. In addition, both of the complexes show strong photoluminescence at room temperature, and may be good candidates for potential luminescence materials.

Synthesis, Crystal Structure and Electrochemical Properties of the Copper(Π) Complex with 1,3-bis(benzimidazol-2-yl)-2-oxopropane

A novel complex of Cu(pic)2 with V-shaped ligand 1,3-bis(benzimidazol-2-yl)-2-o- xopropane (OBB) was synthesized and characterized by elemental analyses and electrical conductivity, IR, UV/visible and 1H-n.m.r. spectra. The crystal structure of the complex has been determined by the single-crystal X-ray diffraction. In the complex, the Cu(Π) ion is six-coordinated with a N4O2 ligand set, resulting in a distorted octahedron.

Two coordination polymers displaying unusual threefold 1D→1D and threefold 2D→3D interpenetration topologies

Self-assembly of long V-shaped ligands and metal salts in the presence of a flexible bidentate ligand provides two types of three-fold interpenetrating networks showing unprecedented 1D→1D and 2D→3D motifs.

Microwave-Assisted Solvothermal Synthesis of a Dynamic Porous Metal-Carboxylate Framework

By treating Cu(NO3)2·3H2O with a V-shaped ligand 4,4ʼ-oxydibenzoic acid (H2oba), a dynamic metal-carboxylate framework [Cu2(oba)2(DMF)2]·5.25DMF (MCF-23) was synthesized, which features a wavelike layer with rhombic grids based on the paddle-wheel secondary building units. These layers stack via strong offset π-π stacking of the phenyl groups of oba ligands to give three-dimensional porosity. MCF-23 synthesized by conventional solvothermal methods always contains considerable and intractable impurities. In contrast, a microwave-assisted solvothermal method was proven to be a faster and greener approach to synthesize phase-pure MCF-23 in high yield. More interestingly, larger crystals suitable for single-crystal diffraction could be obtained by the multistep microwave heating mode. A powder X-ray diffraction study of MCF-23 reveals the dynamic structural transformation accompanying the release and reabsorption of the guest molecules. The N2 (77 K) and CO2 (195 K) gas sorption isotherms of the guest-free ph...

Exceptional Self-Penetrating Networks Containing Unprecedented Quintuple-Stranded Molecular Braid, 9-Fold Meso Helices, and 17-Fold Interwoven Helices

Self-assembly of long V-shaped ligands and d10 metal salts in the presence of a linear bidentate ligand affords two unprecedented self-penetrating coordination networks {[Zn4(bptc)2(bpy)4].(C5H3N).4H2O}n (1) and {[Cd2(sdba)2(bpy)(H2O)2].2H2O}n (2) (bptc = 3,3',4,4'-benzophenonetetracarboxylate, sdba = 4,4'-sulfonyldibenzoate, bpy = 4,4'-bipyridine). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, IR spectra, X-ray powder diffraction, and TG analyses. 1 adopts a novel 3D framework containing three types of molecular braids, among which the quintuple-stranded molecular braid represents the highest-stranded molecular braid presently known for entangled systems. 2 is an uncommon self-penetrating 2D network containing pseudo-Borromean links and double-stranded helices. More interestingly, when the strong hydrogen bonds between layers are taken into account, the resulting net of 2 becomes an eight-connected 3D self-penetrating network with an unprecedented (421.67) topology, which represents the highest connected topology presently known in self-penetrating systems. Furthermore, the photoluminescent properties of 1 and 2 were studied.

Hydrothermal synthesis and structural characterization of three helical coordination polymers constructed from V-shaped ligand

The syntheses, X-ray characterization and photoluminescent properties of three new metal-organic coordination polymers, [M(oba)(phen)] n ·H 2O (M=Zn ( 1), Cd ( 2)) and [Zn(oba)(2,2′-bpy)] n ( 3), (oba=4,4′-oxybis(benzoate), phen=1,10-phenanthroline), have been reported. They all exhibit one-dimensional helical structures that are further assembled into three-dimensional networks via aromatic π–π stacking interactions, and blue photoluminescence at room temperature. These results indicate that the geometry of ligand is one of the most important factors for the construction of helical motifs.