Novel porphyrin-quinone architectures via 1,3-dipolar cycloaddition reactions

Porphyrinic pyridinium ylides react with 1,4-benzoquinone and 1,4-naphthoquinone to afford novel meso-substituted indolizine porphyrins.     

Novel architectures in porous materials based on clays

Modification of layered clays in view to develop porous materials, mainly for catalytic applications, has been afforded in the past via intercalation reaction of aluminum and other polyoxycations or through generation of mesoporous silica between the layers of the silicate. In this paper it is introduced examples of an alternative route for the preparation of porous nanoarchitectures based on the sol–gel method that profits from the swelling ability of organoclays in organic solvents to incorporate silicon and/or other metal (e.g., Ti, Al,…) alkoxides in the interlayer region of the silicates where they are hydrolyzed in a controlled manner. Their further polycondensation originates the formation of an oxide matrix and after a thermal treatment is possible the consolidation of oxide nanoparticles between delaminated smectites and vermiculites. It is also showed how this colloidal route can be applied to the generation of oxide nanoparticles bonded to the external surface of fibrous clays, such as sepiolite. Finally, it is also summarized with various examples the potential interest of the resulting porous clay nanoarchitecture materials in applications as acid catalysts, photocatalysts or nanofillers in polymer–clay nanocomposites.     

Novel hybrid hetero-sandwich architectures via stoichiometric control of host-guest self-organization

Thiocyanate cadmium and methylviologen hybrid host-guest compounds give two novel multiple sandwich architectures with regular or irregular grids of the anionic layer in the structures as effected by the molar ratios of starting ingredients, and show evidence of charge-transfer to the organic dications.     

Novel macromolecular architectures: Globular block copolymers containing dendritic components

The synthesis of three different macromolecular architectures, dendritic segment-block, layer-block, and surface-block copolymers, all of which can be regarded as new types of block copolymers, is discussed. The factors determining the physical properties of each of these unusual materials are studied and related to the dendritic structure.     

Novel side-chain liquid crystalline polymer architectures produced by the Wittig-Horner reaction

We have investigated the use of the Wittig-Horner reaction in the preparation of novel side-chain liquid crystalline (SCLC) polymers. The simplicity and versatility of the Wittig-Horner methodology makes it another useful synthetic route in preparing SCLC polymers with polar groups being positioned along the polymer backbone. This new methodology will now be used to synthesise a range of novel ferroelectric SCLC polymers.     

Novel fluorinated block copolymer architectures fuelled by atom transfer radical polymerization

Block copolymers based on poly(pentafluorostyrene), PFS, in various numbers and of different lengths, and polystyrene are prepared by atom transfer radical polymerization (ATRP). Di- and triblock copolymers with varying amounts of PFS were synthesized employing either 1-phenylethylbromide or 1,4-dibromoxylene as initiators for ATRP. Diverse bromo(ester) (macro)initiators were also devised and involved in the formulation of fluorinated pentablock as well as amphiphilic triblock copolymers with a central polyether segment. Amphiphilic star-shaped fluoropolymers, hydrophobic fluorinated nanoparticles, or segmented fluorinated star-shaped block copolymers are further designed by use of different multifunctional initiators. The composition of the novel materials with PFS is determined by combination of SEC and ¹H NMR. Glass transition temperatures and thermal stabilities of the hydrophobic star-shaped PFSs on a six arm dipentaerythritol core are investigated in a wide range of molecular masses and further discussed.     

Novel rearranged acetophenone derivatives possessing diverse architectures from the leaves of Melicope ptelefolia

Melicolones C–K (1–9), nine acetophenone derivatives with three unprecedented architectures, were characterized from the leaves of Melicope ptelefolia. Among them, melicolone C (1) was a novel acetophenone analogue possessing a highly rearranged spiro skeleton. Melicolones D-F (2–4) were three novel acetophenone congeners bearing unusual octalactone ring. Melicolones G-K (5–9) were five new prenylated acetophenone derivatives featuring a 9-oxatricyclo [3.2.1.13, 8]nonane core. Their structures were established by extensive spectroscopic analysis and ECD spectra. These different structures were presumably derived from the same precursor via three major biosynthetic pathways. Compounds 5–9 exerted moderate effects to reverse multidrug-resistance in MCF-7/ADR cells with reversal fold values ranging from 6.2 to 13.3.     

Novel fluoride transfer in the reaction of tricyclic epoxides with boron trifluoride

Reaction of the tricyclic epoxides ($\text{1a}$) and ($\text{1b}$) with boron trifluoride etherate leads to fluorohydrins ($\text{2a}$) and ($\text{2b}$) derived in the novel fluoride transfer, whereas ($\text{1c}$) undergoes isomerization to spiro ketone ($\text{3}$).     

Novel carboranyl C-glycosides for the treatment of cancer by boron neutron capture therapy

The synthesis of the novel unprotected carboranyl C-glycosides 2 and 20-24 starting from ethynyl C-glycosides 1, 5-8, 10, and 13 is described. The new compounds are highly water-soluble and display only a very low cytotoxicity, which makes them promising candidates for use in boron neutron capture therapy for the treatment of cancer.     

Novel carboranylporphyrins for application in boron neutron capture therapy (BNCT) of tumors

Condensation of a new carboranylpyrrole 1 with benzaldehydes leads to β-carboranylporphyrins 2 and 3 in good yields. These new porphyrins of high boron content (32-43%) have potential as boron delivery agents for BNCT. The X-ray structures of one β-carboranylporphyrin, of a carboranylpyrrole, and of a side-product are presented.     

Determination of boron and nitrogen in boron nitride

Improved techniques are described for the determination of boron and nitrogen in pure boron nitride. Controlled fusion of boron nitride with sodium carbonate in a muffle furnace is followed by a potentiometric titration of the boric acid. A special quartz vessel is described for the determination of nitrogen. The boron nitride is fused with sodium hydroxide and the resulting ammonia is swept into a receiver and titrated with standard hydrochloric acid. Boron and nitrogen values with their standard deviation are given for a typical pure boron nitride.     

Supramolecular architectures of cellulose derivatives

Several cellulose derivatives belong to a special class of polymers called hairy-rod macromolecules which are used to generate well-defined supramolecular architectures by the Langmuir-Blodgett (LB) technique. In particular trimethylsilyl cellulose (TMSC) forms monomolecular films on the Langmuir-trough and is transferred onto hydrophobic substrates with a constant transfer ratio, as it does not undergo chemical changes in the film-building process. Silylated celluloses was regenerated which represents a convenient method for the generation of homogeneous ultrathin films with hydrophilic surfaces. The adsorption of polymers and dyes as well as biomolecules onto regenerated and modified cellulose LB films have been studied. In addition, chemical reactions, such as cycloaddition, desilylation and crosslinking reactions within single monolayers have been performed.     

Microfabrication of three-dimensional bioelectronic architectures

The functionality and structural diversity of biological macromolecules has motivated efforts to exploit proteins and DNA as templates for synthesis of electronic architectures. Although such materials offer promise for numerous applications in the fabrication of cellular interfaces, biosensors, and nanoelectronics, identification of techniques for positioning and ordering bioelectronic components into useful patterns capable of sophisticated function has presented a major challenge. Here, we describe the fabrication of electronic materials using biomolecular scaffolds that can be constructed with precisely defined topographies. In this approach, a tightly focused pulsed laser beam capable of promoting protein photo-cross-linking in specified femtoliter volume elements is scanned within a protein solution, creating biomolecular matrices that either remain in integral contact with a support surface or extend as free-standing structures through solution, tethered at their ends. Once fabricated, specific protein scaffolds can be selectively metallized via targeted deposition and growth of metal nanoparticles, yielding high-conductivity bioelectronic materials. This aqueous fabrication strategy opens new opportunities for creating electronic materials in chemically sensitive environments and may offer a general approach for creating microscopically defined inorganic landscapes.     

Novel dithioether-silver(I) coordination architectures: structural diversities by varying the spacers and terminal groups of ligands

An investigation into the dependence of the framework formation of coordination architectures on ligand spacers and terminal groups was reported based on the self-assembly of AgClO4 and eight structurally related flexible dithioether ligands, RS(CH2)nSR (Lan, R = ethyl group; Lbn, R = benzyl group, n= 1-4). Eight novel metal-organic architectures, [Ag(La1)3/2ClO4]n (1a), [Ag2(La2)2(ClO4)2]2 (2a), [AgLa3ClO4]n (3a), {[Ag(La4)2]ClO4}n (4a), [AgLb1ClO4]2 (1b), [Ag(Lb2)2]ClO4 (2b), {[Ag(Lb3)3/2(ClO4)1/2](ClO4)1/2}n (3b) and [Ag(Lb4)3/2ClO4]n(4b), were synthesized and structurally characterized by X-ray crystallography. Structure diversities were observed for these complexes: 1a forms a 2-D (6,3) net, while 2a is a discrete tetranuclear complex, in which the AgI ion adopts linear and tetrahedral coordination modes, and the S donors in each ligand show monodentate terminal and mu2-S bridging coordination fashions; 3a has a chiral helical chain structure in which two homo-chiral right-handed single helical chains (Ag-La3-)n are bound together through mu2-S donors, and simultaneously gives rise to left-handed helical entity (Ag-S-)n. In 4a, left- and right-handed helical chains formed by the ligands bridging AgI centers are further linked alternately by single-bridging ligands to form a non-chiral 2-D framework. 1b has a dinuclear structure showing obvious ligand-sustained Ag-Ag interaction, while 2b is a mononuclear complex; 3b is a 3-D framework formed by ClO4- linking the 2-D (6,3) framework, which is similar to that of 1a, and 4b has a single, double-bridging chain structure in which 14-membered dinuclear ring units formed through two ligands bridging two AgI ions are further linked by single-bridging ligands. In addition, a systematic structural comparison of these complexes and other reported AgClO4 complexes of analogous dithioether ligands indicates that the ligand spacers and terminal groups take essential roles on the framework formation of the AgI complexes, and this present feasible ways for adjusting the structures of such complexes by modifying the ligand spacers and terminal groups.     

Polysilanes with various architectures

Copolymers and homopolymers containing silicon atoms connected to three and four other silicon atoms have been prepared and characterized. We report the first evidence of dendritic polymers with silicon backbones. Copolymers made from RSiCl₃ and R¹R²SiCl₂ resemble hybrid materials of polysilyne and polysilanes. Polymers, which contain tetrasilyl-substituted Si atoms, [(SiMe₂)₄Si]_n and (Si)_m(Me₂Si)_n, have also been synthesized. These molecules appear to be the first hyperbranched polymers, which have applications based on their electronic properties. The properties of these molecules fit into the hierarchy of 1-D to 3-D topologies known for Si materials.     

Structure and stability of small boron and boron oxide clusters

To rationally design and explore a potential energy source based on the highly exothermic oxidation of boron, density functional theory (DFT) was used to characterize small boron clusters with 0-3 oxygen atoms and a total of up to ten atoms. The structures, vibrational frequencies, and stabilities were calculated for each of these clusters. A quantum molecular dynamics procedure was used to locate the global minimum for each species, which proved to be crucial given the unintuitive structure of many of the most stable isomers. Additionally, due to the plane-wave, periodic DFT code used in this study a straightforward comparison of these clusters to the bulk boron and B2O3 structures was possible despite the great structural and energetic differences between the two forms. Through evaluation of previous computational and experimental work, the relevant low-energy structures of all but one of the pure boron clusters can be assigned with great certainty. Nearly all of the boron oxide clusters are described here for the first time, but there are strong indications that the DFT procedure chosen is particularly well suited for the task. Insight into the trends in boron and boron oxide cluster stabilities, as well as the ultimate limits of growth for each, are also provided. The work reported herein provides crucial information towards understanding the oxidation of boron at a molecular level.