Hexamethylenetetramine: An old new building block for design of coordination polymers

The design of new coordination polymers is nowadays a challenging research topic that attracts increasing interest due to the unique structural and functional properties of such metal-organic materials. In contrast to the recognized use of some N-donor ligands for the construction of coordination polymers, the application of hexamethylenetetramine (hmt) as a simple, commercially available, water-soluble and highly versatile cagelike building block has so far been explored to a lesser extent, although a considerable number of hmt-driven metal-organic networks have been reported in the last few years. Given the high potential of hmt for future developments of this research field, the present review summarizes the main structural and topological types of coordination polymers bearing hmt. These compounds feature a high diversity of topologies that include linear, zigzag, double, triple and quadruple 1D chains, rectangular grids, flat and undulating 2D layers, as well as layer-pillared, octahedral, zeolite-like, honeycomb-like and other complex 3D nets, in which hmt acts as a linker or spacer, pillar or connector, stabilizer and/or supporting ligand. The most common synthetic strategies are reviewed, showing that a diversity of metal-organic networks can be generated by facile self-assembly routes in aqueous medium and using rather simple chemicals. The main types of auxiliary ligands necessary for the construction of hmt-driven coordination networks are also identified. The additional structural features such as the formation of supramolecular networks and water clusters are described, and the selected properties and potential applications of hmt-containing coordination polymers as porous, magnetic or photoluminescent materials are highlighted.     

Synthesis and characterization of electron-deficient and highly soluble (Bis)indenofluorene building blocks for n-type semiconducting polymers

New electron-deficient and soluble indenofluorene-based and bisindenofluorene-based ladder-type building blocks embedding carbonyl and dicyanovinylene functionalities were synthesized, and their optical and electrochemical properties were characterized. These derivatives exhibit optical band gaps of 1.83 to 2.44 eV and low LUMO energies of -3.24 to -4.30 eV, representing a promising new building block class for n-type polymeric electronic materials.     

Cardanol: A promising building block for biobased polymers and additives

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Synthesis of a new trans-A2B2 phthalocyanine motif as a building block for rodlike phthalocyanine polymers

Polyphthalocyanines have potential application in the development of electronic materials. One-dimensional polyphthalocyanines are accessible through monomers having a trans-A2B2 structure, but the preparation of a truly linear polyphthalocyanine is challenging because of limitations imposed by the geometry of phthalocyanines and the methodology for their synthesis. Benzimidazoporphyrazines are a known class of extra-annulated phthalocyanines. A trans-A2B2 benzimidazoporphyrazine is geometrically suitable for the preparation of rodlike polymers. A new synthesis of benzimidazoporphyrazines is presented as a stepping stone to the synthesis of trans-A2B2 benzimidazoporphyrazines.     

PAs3S3 cage as a new building block in copper halide coordination polymers

First examples of the coordination chemistry of the PAs(3)S(3) cage were obtained from solutions of PAs(3)S(3)·W(CO)(5) (1) in CH(2)Cl(2) or CH(2)Cl(2)/toluene and CuX (X = Cl, Br, I) in MeCN through interdiffusion techniques. Crystals of [Cu(PAs(3)S(3))(4)]X (2, X = Cl; 3, X = Br) and [(Cu(2)I)(PAs(3)S(3))(3)]I (4) were obtained and characterized by Raman spectroscopy (2) and single-crystal X-ray crystallography. The solid-state structures reveal an unexpected coordination versatility of the PAs(3)S(3) ligand: apical phosphorus and bridging sulfur atoms interact with copper, while As···X interactions determine the dimensionality of the frameworks. The structures of 2 and 3 contain tetrahedral [(PAs(3)S(3))(4)Cu](+) cations as secondary building units (SBUs), which are arranged by interactions with Cl(-) or Br(-) anions into two- and three-dimensional substructures. These interpenetrate into a (2D + 3D) polycatenane. Compound 4 is built up by a one-dimensional [(Cu(2)I)(PAs(3)S(3))(3)](n)(n+) ribbon with PAs(3)S(3) cages as P,S-linkers. The As atoms of the exo PAs(3)S(4) linkers interact with iodide counterions (3.35 < d(As-I) < 3.59 ?). The resulting two-dimensional layer is organized by weak As···I interactions (d(As-I = 3.87 ?) into a 3D network.     

Poly-N-benzylaniline prepared in perchloric acid——a new soluble semiconducting polymer

Chemical or electrochemical oxidation of N-benzylaniline in perehloric acid solution yieldsa highly colored polymer——poly-N-benzylaniline (PBAn).The polymer has good solubility in a num-ber of organic solvents in either acid or base form.At room temperature,conductivity measurementson pressed pellets of the acid form PBAn give a conductivity of 9.3×10~(-6) S·cm~(-1).The soluble polymerwas analyzed using a variety of common experimental techniques including UV-vis,IR,NMR,ESRspectroscopy,elemental analysis and electrochemieal analysis.All experimental results showed thatPBAn has a structure similar to polyaniline with the elimination of some benzyl groups.     

Highly effective epoxidation of alkenes with Ti-containing soluble polymers

Ti-containing polysiloxane epoxidation catalysts have been prepared by controlled hydrolysis of titanium- and alkylsilane precursors. These polysilkoxanes exhibit very high yields to epoxides in the epoxidation reaction of primary alkenes with organic hydroproxides.     

Nanoscale molecular rods with a new building block for solubility enhancement

A new building block bearing a [1,3]dioxolo[4,5- f][1,3]benzodioxole core was developed to enhance the solubility of molecular rods by lateral alkyl chains. On incorporation in molecular rods with oligospiroketal structure, the straight geometry is retained, which was concluded from the X-ray crystal structure analysis of one of the rods. The determination of the solubility of a collection of rods bearing this building block revealed that already a butyl group efficiently hinders the aggregation of the rods and consequently causes a considerable enhancement of the solubility. Piperidine rings are located at the ends of the rods, which offer the opportunity for versatile functionalization. Thus, an N, N'-bis(azidoacetyl)-functionalized rod was prepared, which could serve as rigid linkage, initiated by a "Click" reaction.     

Acetyl-BINOL as mimic for chiral β-diketonates: a building block for new modular ligands

α-Acetyl-(S)-BINOL was prepared by ortho-lithiation and subsequent acetylation of acetal-protected (S)-BINOL. The β-hydroxyketone moiety of this compound is herein a structural mimic for a β-diketonate and forms six-membered chelates with transition metal ions. The second hydroxy-function was submitted to esterification with several carboxylic acids bearing another donor function, thus, new tridentate chiral ligands were obtained. Out of this library the l-proline-α-acetyl-(S)-BINOL-ester was identified to be most effective for the titanium-mediated addition of Et₂Zn to PhCHO yielding the respective secondary alcohol with up to 93% ee, which is better than with using (S)-BINOL itself. Besides a solvent dependency (use of MeCN is optimal), the proper choice of the counter-ion is crucial: anion exchange of bromide by trifluoroacetate gave a significant increase of enantioselectivity.     

3,4-Vinylenedioxythiophene (VDOT): a new building block for thiophene-based pi-conjugated systems

The synthesis of the title compound and its use as a building block in pi-conjugated systems are presented.     

beta(2,2)-Aminoxy acids: a new building block for turns and helices

The conformational properties of peptides 1-4 built from 3-aminoxy-2,2-dimethyl-propionic acid, a beta2,2-aminoxy acid, were investigated by NMR spectroscopy and X-ray crystallography. A novel beta N-O turn involving a nine-membered-ring intramolecular hydrogen bond between NHi+2 and COi was formed in diamides 1 and 2, which was further stabilized by another six-membered-ring intramolecular hydrogen bond between NHi+2 and NOi+1. Triamides 3 and 4 displayed a well-defined helical structure featuring two consecutive beta N-O turns. The X-ray structure of 4 revealed that the amide carbonyl group at position i+2 was twisted +65.9 degrees from that at i position, suggesting a novel 1.79 helix. Therefore, beta2,2-aminoxy acid can be used as a new building block for turns and helices.     

Perfluoro Allyl fluorosulfate (FAFS): a versatile building block for new fluoroallylic compounds

In this study we will present and discuss both the synthesis of CF(2) = CFCF(2)OSO(2)F (perfluoroallyl fluorosulfate, FAFS), focusing in particular on the important role of C(3)F(6)/SO(3) ratio, reaction temperature and boron catalyst/SO(3) ratio on FAFS' yield and selectivity, as well as a wide variety of ionic and radical reactions possible with FAFS. We focused our attention on reactions of FAFS with aliphatic and aromatic alcohols, acyl halides, halides, H(2)O(2), ketones and radicals whose synthesis and reaction mechanisms will be presented and discussed. Particular attention will be devoted to the novel diallyl-fluoroalkyl peroxide obtained. Factors such as pK(a) and Lowry and Pearson's Hard/Soft Acid-Base Theory which determine the selectivity between Addition/Elimination vs. Nucleophilic Substitution reaction mechanisms on FAFS will also be presented and discussed.     

Au(CN)4]- as a supramolecular building block for heterobimetallic coordination polymers

A series of the first coordination polymers using the [Au(CN)(4)](-) anion as a building block has been prepared. The planar tetracyanoaurate anion uses one, two, or four cyano groups to bridge to Ni(II) or Cu(II) centers and exhibits weak Au(III)-N(cyano) interactions between anions. Ni(en)(2)[Au(CN)(4)](2).H(2)O (1, en = ethylenediamine) is a molecular compound with the two [Au(CN)(4)](-) anions coordinating in a trans orientation to Ni(II) without further cyanide coordination. Cu(dien)[Au(CN)(4)](2) (2, dien = diethylenetriamine) forms a similar molecular complex; however, the dimensionality is increased through weak intermolecular Au-N(cyano) interactions of 3.002(14) A to form a 1-D zigzag chain. Cu(en)(2)[Au(CN)(4)](2) (3) also forms a molecular complex similar to 1, but with elongated axial bonds. The complex further aggregates through Au-N(cyano) interactions of 3.035(8) A to form a 2-D array. In [Cu(dmeda)(2)Au(CN)(4)][Au(CN)(4)] (4, dmeda = N,N-dimethylethylenediamine) one [Au(CN)(4)](-) anion coordinates via two cis-N(cyano) donors to the axial sites of two Cu(II) centers to form a 1-D zigzag chain of alternating [Cu(dmeda)(2)](2+) and [Au(CN)(2)](-) units; the other [Au(CN)(4)](-) anion forms a 1-D chain via Au-N(cyano) interactions. In [Cu(bipy)(H(2)O)(2)(Au(CN)(4))(0.5)][Au(CN)(4)](1.5) (5, bipy = 2,2'-bipyridine) one [Au(CN)(4)](-) anion uses all four cyano moieties to bridge four different Cu(II) centers, creating a 1-D chain.     

Synthesis of a new conformationally constrained glycoamino acid building block

The synthesis of a suitably protected β-d-glucopyranosyl-(S)-α-methylserine derivative—a new conformationally constrained glycosylated quaternary amino acid analogue of β-d-glucopyranosyl-l-serine—is described. This compound can be used as an attractive building block for the synthesis of new, constrained glycopeptides.     

Morphology controllable conjugated network polymers based on AIE-active building block for TNP detection

Luminescent conjugated network polymer is one of the most promising chemo-sensors owing to their good chemical/optical stability and multiple functionalization.Herein,three conjugated network polymers were prepared by using aggregation-induced emission active 1,1,2,2-tetrakis(4-formyl-(1,1'-biphenyl))-ethane(TFBE) unit as monomer and hydrazine as linker.Through regulating the synthetical condition,the polyme ric network can form either unifo rm two-dimensional azine-linked nanosheets(ANS),conjugated microporous polymers(A-CMP) or covalent organic frameworks(A-COF).All of these polymers exhibited good stability and high fluorescence quantum efficiency with the quantum yield of6.31% for A-NS,5.26% for A-CMP,and 5.80% for A-COF,as well as fast and selective fluorescence quenching response to 2,4,6-trinitrophenol(TNP).And the best TNP sensing performance with the Stern-Volmer constants(K_(sv)) values up to 8 × 10~5 L/mol and a detection limit of 0.09 μmol/L was obtained for A-NS.The study explores various strategies to construct conjugated polymers with different nanoarchitectures based on the same building block for sensitive detection of explosives.     

Highly soluble germanium dioxide as a new source of germanium for derivatization with organic compounds

In modern germanium chemistry, toxic, corrosive and water- sensitive halogen and alkoxy derivatives, or poorly reactive polymeric dioxide are generally utilized. Recently developed highly water-soluble germanium dioxide was herein treated with diols and N-donor bases to produce novel highly reactive hydrophilic germanium source suitable for further derivatization.