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An amperometric sensor whose active layer is derived from a tetra core-substituted organic semiconductor, naphthalene diimide (NDI-CN4), has been evaluated for ammonia sensing at room temperature against the NDI devoid of core-substitution effects.

The optoelectronic properties of functional π-conjugated organic materials are affected by their ability to self-assemble within thin films of devices. There are limited reports that demonstrate the positive impact of self-assembly on the photovoltaic performance of organic solar cells. Here, we demonstrate that hydrogen-bonded supramolecular arrays of a cyanopyridone-based oligothiophene donor, CP6, show notable improvement in photovoltaic performance upon self-assembly into a nanofibrous network. The honeycomb-like blend network exhibited higher hole mobility, leading to efficient charge generation and transport. The photovoltaic performance of CP6 was superior to that of two structural analogues, CP5 and CP1, and was attributed to the enhanced capability of CP6 to self-assemble into a film morphology favorable for BHJ devices. The BHJ devices comprising CP6 and the conventional fullerene acceptor (PC71BM) exhibited an efficiency of 7.26%, which is greater than that of CP5 (5.19%) and CP1 (3.11%) and is among the best-performing, cyanopyridone-based oligothiophene donors described to date.

The development of perovskite solar cells (PSCs) as an efficient and cost-effective alternative to traditional approaches to solar energy transduction has received much recent attention, and there has been considerable progress made with reported power conversion efficiencies now surpassing 25%. This development is encouraging and is a result of intensive research on device design, factors affecting long-term stability of PSCs, and systematic material development in which electron transport layer (ETL) materials play a crucial role to afford high-performance PSC devices. ETL materials, including (6-(1,10-phenanthrolin-3-yl)naphthalen-2-yl)diphenylphosphine oxide (Phen-NaDPO), and n-type materials based on the naphthalene diimide (NDI) structure, appear to be amongst the most promising materials to date. This article provides an up-to-date review on organic n-type ETL materials, both polymeric and small molecules, based on NDI format, detailing reports of structures with key relevant parameters, such as the efficiency and stability of PSCs. The review is written from a perspective of organic chemistry and we believe this will provide fundamental advice on the future design of new ETL materials based on NDIs that will afford more efficient and stable PSCs.

Photocatalytic nitrogen reduction reaction (NRR) is a promising, green route to chemically reducing N2 into NH3 under ambient conditions, correlating to the N2 fixation process of nitrogenase enzymes. To achieve high-yield NRR with sunlight as the driving force, high-performance photocatalysts are essential. One-dimensional silicon nanowires (1D SiNWs) are a great photoelectric candidate, but inactive for NRR due to their inability to capture N2. In this study, we proposed SiNWs doped by p-block elements (B, C, P) to tune the affinity to N2 and demonstrated that two-coordinated boron (B2C) offers an ultra-low overpotential (η) of 0.34 V to catalyze full NRR, which is even much lower than that of flat benchmark Ru(0001) catalysts (η = 0.92 V). Moreover, aspects including suppressed hydrogen evolution reaction (HER), high-spin ground state of the B2C site, and decreased band gap after B-doping ensure the high selectivity and photocatalytic activity. Finally, this work not only shows the potential use of metal-free p-block element-based catalysts, but also would facilitate the development of 1D nanomaterials towards efficient reduction of N2 into NH3.

It is challenging to identify effective electrocatalysts for nitrogen reduction in order to advance electrochemical nitrogen fixation under ambient conditions using methods that are powered by renewable energy. Silicon carbide was investigated computationally as a metal-free, surface-derived catalyst for the electrocatalytic nitrogen reduction reaction. As demonstrated by first-principle calculations, Si-terminated and C-terminated surfaces, with the Si and C as active sites, are all reactive for dinitrogen capture and activation, resembling the catalytic behavior of popular B-based electrocatalysts, but the latter (C-terminated) offers an ultralow over-potential of 0.39 V, which is lower than most metals and alloys, while retarding hydrogen evolution. This research enriches the design of catalysts for dinitrogen fixation under ambient conditions, and also highlights a new direction for Si-based materials for nitrogen reduction.

A significant challenge of liquid phase exfoliation (LPE) of graphite to yield graphene resides in the fact that most conventional solvents used are high boiling points and thus extremely difficult to eliminate, especially during processing of graphene into composites or films. Here, we advance the ability to produce high yield graphene in a low boiling point organic solvent, chloroform, using core-substituted naphthalene diimides (cNDIs). Through the use of cNDIs it is possible to obtain high graphene concentrations of up to 0.13 mg/mL in chloroform. This yield represents a 69% improvement from graphene yields previously obtained in chloroform using unsubstituted NDIs. Characterisation of the products by UV-Vis, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) support the use of cNDIs as an appropriate exfoliating agent in chloroform.

This review focuses on describing all known synthetic strategies leading to core-annulation of naphthalene diimides (NDIs). Strategies presented involve the formation of four-, five- and six-membered ring annulations bearing different heteroatomic and carbocyclic derivatives, including annulenes. The core-annulation method opens the possibility for obtaining designer molecules with tuneable electronic characteristics such as a reduced energy band gap, and enhanced intermolecular overlap of π-systems that improve electronic coupling between molecules-which is highly desirable for charge transport properties summarised in the final pages for applications in electronic devices such as organic field-effect transistors (OFETs) and organic photovoltaic (OPV) cells. Molecular recognition in pH and fluoride sensing, or as a DNA probe, are some of additional applications of core-annulated NDIs presented here. Additionally, recent advances in core modification of NDIs are presented, opening an entire new chemical avenue to be explored. Finally, the outlook on the future prospect of annulated NDIs in various applications is summarised.

Crown ethers are effective at binding cations and through substitution onto the core of photoactive naphthalene diimide molecules (NDIs), cation binding can be detected via changes in UV-visible absorption and/or fluorescence emission. In this work, two new NDI-crown ether cation sensors (aza-15-crown-5 ether NDI, 5, and aza-18-crown-6 ether NDI, 6) have been synthesised and changes in UV-visible and fluorescence spectra upon addition of various cations investigated. A substantial blue shift in the UV-visible absorption of 75 nm was observed for 6 with a 1 : 1 addition of Na+ or K+, providing a clear colourimetric readout, however, no significant spectral changes were observed for 5 with the cations trialled at this level of analyte. Calcium cations do, however, elicit a response from 5 at substantially higher molar ratios, with some perturbation of the absorption spectrum observable, and an approximately six-fold increase in fluorescence emission. Theoretical calculations indicate that for 6, K+ and Na+ bind to the ether oxygens resulting in a blue shift similar to that observed experimentally. Ca2+ however, was found to bind quite differently with 5via both the ether oxygens and the carbonyl group on the NDI. This observation highlights how small structural changes can lead to different and unexpected behaviour and that investigation of underlying binding mechanisms is important to inform the rational design of future systems.

This work reports synthesis, thin film characterizations, and study of an organic semiconductor 2-aminoanthraquinone (AAq) for humidity and temperature sensing applications. The morphological and phase studies of AAq thin films are carried out by scanning electron microscope (SEM), atomic force microscope (AFM), and X-ray diffraction (XRD) analysis. To study the sensing properties of AAq, a surface type Au/AAq/Au sensor is fabricated by thermally depositing a 60 nm layer of AAq at a pressure of ~10&minus, 5 mbar on a pre-patterned gold (Au) electrodes with inter-electrode gap of 45 &micro, m. To measure sensing capability of the Au/AAq/Au device, the variations in its capacitance and resistance are studied as a function of humidity and temperature. The Au/AAq/Au device measures and exhibits a linear change in capacitance and resistance when relative humidity (%RH) and temperature are varied. The AAq is a hydrophobic material which makes it one of the best candidates to be used as an active material in humidity sensors, on the other hand, its high melting point (575 K) is another appealing property that enables it for its potential applications in temperature sensors.

The replacement of the imide oxygen atoms with sulfur atoms in the naphthalene diimide (NDI) framework is an attractive strategy for tuning of the electronic properties of such molecules. Here we report the synthesis and characterization of the full series of six thionated NDI molecules with branched side chains. In order to provide a direct comparison with the unthionated parent molecule, a top-gate, bottom contact geometry is adopted, with work function-modified gold electrodes facilitating electron injection. The highest electron mobility was observed for the S2-cis molecule, with a mobility of 0.20 cm2/Vs compared to 0.068 cm2/Vs for the parent molecule. Mobilities slightly lower than that achieved for the S2-cis molecule were also achieved for the S2-trans and S3 derivatives, with the S1, S4 and S2-cis imide derivatives showing mobilities lower than the parent molecule. The thin film microstructure of these molecules has also been explored using a combination of grazing-incidence wide-angle X-ray scattering and near-edge X-ray absorption fine-structure spectroscopy. The performance and microstructure of thin films deposited either by spin-coating or blade coating are also compared.

Dimers and trimers of a fluorenone-appended porphyrin were prepared via Lindsey optimized Sonogashira coupling reaction. The photophysical properties of the oligomers were investigated upon excitation of the fluorenone arms which act as donors. The emission profiles of the covalently linked porphyrins suggest that the diphenylacetylene bonds are vital for efficient intramolecular energy transfer between the porphyrin units. Additionally, higher fluorescence quantum yields were recorded for the oligomers than for the individual units.

Transforming the naphthalene diimide (NDI) core into unusual aromatic systems has large potential for applications in which current NDI-based systems show promise. Treatment of N,N-dialkylNDIs under mild oxidizing conditions with ruthenium(III) chloride and sodium periodate affords the corresponding 1,4-diones in good yield. Interestingly, while aliphatic substituents at the N-imide positions allowed oxidation to take place easily, the presence of neutral, electron-rich or electron-deficient phenyl groups retarded the oxidation process under these reaction conditions. The chemistry of the 1,4-dione is then explored through reduction and condensation reactions. In two examples, reaction of the 1,4-dione with diamines gives an unusual, ring-contracted product 20, which has a high quantum yield. Additionally, the 1,4-dione can be converted into larger heterocycles such as 21 and 22 featuring an isoquinoline core. The 1,4-diones and their products have been investigated by spectroscopy, cyclic voltammetry, theoretical studies, and X-ray crystallography. The results obtained demonstrate the potential of the 1,4-dione to serve as an invaluable precursor for NDI-based research.

Carbon-based electrocatalysts for nitrogen fixation under ambient conditions has attracted tremendous attention but still encounter great challenges of low Faradic efficiency (FE) and a sluggish kinetics. Inspired by intrinsic defects (vacancies, edges and dislocation) on graphene showing activity towards oxygen reduction reaction (ORR) and nitrogen reduction reaction (NRR), here, two commonly exposed surfaces of diamond carbon, i.e., C(111) & C(110), were calculated for electrocatalytic nitrogen reduction reaction (eNRR) by the density functional theory (DFT) method, and calculations show that, compared with C(110), C(111) could be highly promising towards eNRR with a low over-potential (η) of 0.57 V (ΔGmax = 0.73 eV, η = 0.57 V), which are distinctly less than that (ΔGmax = 1.08 eV, η = 0.92 V) of flat benchmark Ru(0001) catalysts. Importantly, these two surfaces are shown to exhibit the suppression of hydrogen evolution reaction (HER). This work is the first reported indication that the low-coordinated carbons (LCCs) on sp3-hybridized diamond-carbon framework are active for eNRR, which gives a brand-new direction of designing/synthesizing sp3-configured diamond-carbon-composited catalysts for eNRR.

Two pendant-type naphthalene diimide (NDI) polymers bearing a polynorbornene backbone were prepared and their electrochemical properties explored. The NDI-based polymers displayed reversible redox responses in 1 M LiClO4 γ-butyrolactone electrolyte. Polymer 1, bearing a N-methyl group, exhibited remarkable charge-storage capabilities which demonstrated its potential usefulness as an organic cathode-active material in rechargeable devices with excellent performances such as large charge capacity, high rate capability, and charge-discharge cyclability.

Symmetrically and dissymmetrically core-substituted amino naphthalene diimides (cNDIs) with water-soluble substituents have been synthesised. The compounds display characteristic steady-state optical properties absorbing and emitting light in the visible part of the electromagnetic spectrum. Time-resolved fluorescence studies reveal long emission lifetimes of ∼10 ns in chloroform, ∼8 ns in methanol and ∼4 ns in water. Suitability for use in biophysical applications is demonstrated by encapsulation into reverse micelles and liposomes. Fluorescence lifetime is shown to indicate cavity size in the reverse micelles and fluorescence correlation spectroscopy measurements of cNDI loaded liposomes successfully determined diffusion coefficients and hydrodynamic radii of the liposomes.

Photocatalytic degradation of organic contaminants by self-cleaning textiles is an efficient method to create green environment and minimise energy consumption. In this work, the concept of dye-sensitised self-cleaning textiles has been introduced by incorporating monolayers of meso-tetra(4-carboxyphenyl)porphyrin (TCPP) on the surface of titania-coated cotton against methylene blue. Different complexes of TCPP (M = 2H, Fe, Co, Zn, Cu) have been trialled and evaluated for photocatalytic activity and stability. Cotton fabrics coated with TCPP show superior photochemical activity as compared to TiO2-coated fabrics under visible-light irradiation. The free base derivative availed the highest photocatalytic efficiency when compared to the metal complexes with Cu∼Fe > Co > Zn. In terms of stability, meso-tetra(4-car-boxyphenyl)porphyrinato copper(II) showed significant stabilisation under photocatalytic conditions when compared to the metal-free porphyrin and other metal complexes (Cu ≫ Co > 2H > Zn∼Fe). Porphyrins offer great potential in visible-light self-cleaning applications.

Thin films of meso-tetra(4-carboxyphenyl)porphyrin with different metal centres (MTCPP, M = Fe, Co and Zn) in combination with anatase TiO2 have been formed on cotton fabric. Their self-cleaning properties have been evaluated by conducting the photocatalytic degradation of methylene blue under visible-light irradiation. All MTCPP/TiO2-coated cotton fabrics showed superior self-cleaning performance as compared to the bare TiO2-coated cotton. Among the three metal porphyrins, FeTCPP showed the highest photocatalytic activity with complete degradation of methylene blue in 180 min. The fabrics were characterized by FESEM, XRD, UV–vis and fluorescence spectroscopy.

Solutions of carboxymethyl sago pulp (CMSP) of various degree of substitution were irradiated with electron beam of various radiation doses. The gelation dose (Dg) and po/qo ratio (po is degradation density, qo is crosslinking density) is dependent on CMSP concentration and degree of substitution. In the range of concentrations of 10% to 80% (w/v) CMSP with degree of substitutions of 0.4, 0.6, and 0.8, the po/qo ratio decreases with increasing %CMSP showing that crosslinking processes are dominating and increasing the gel network of the CMSP hydrogel. The fourier transform infrared spectra of CMSP hydrogels of degree of substitutions of 0.4, 0.6, and 0.8 with percentage of gel fractions 25, 35, and ≥ 40 show differences in the intensity of the absorption bands at 1020–1100, 1326, and 1422 cm−1 with different degree of substitutions and percentage of gel fraction (%GF) that correspond to different extents of chain scission and crosslinking. The swelling behavior in water shows that CMSP hydrogels could absorb 3500–5300% of water by 1 g of CMSP hydrogel. The ability to absorb water increases with the decrease of degree of substitution and %GF of the CMSP hydrogels. It is also observed that the optimum pH for swelling CMSP hydrogel is at pH 7. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

The synthesis and spectroscopic characterisation of a new amino core-substituted naphthalene diimide is reported. The compound exhibits H + sensing properties leading to a change in optical output through both absorption and emission. On addition of trifluoroacetic acid, an increase in the fluorescence quantum yield from 0.5 to 0.67 and a ∼500–550 cm −1 blue shift of absorption and emission maxima are observed. Addition of triethylamine fully reverses these effects and the cycle is repeatable many times. The increase in fluorescence emission is attributed to protonation blocking weakly competitive photoinduced electron transfer operative in the neutral form of the molecule.

A protoporphyrin IX amphiphile bearing hydrophobic–hydrophilic functional regions was synthesised by coupling protoporphyrin IX with methoxytriethylene glycol using (3-(dimethylamino)propyl)ethyl carbodiimide hydrochloride/1-hydroxybenzotriazole followed by a double-cross metathesis with 1-undecene using second-generation Grubb's catalyst. The self-assembling behaviour of the amphiphile in varying concentration of CHCl3/MeOH was investigated, with well-defined nanostructures described as worm-like fibrils and particular aggregates being formed in 1:1 and 1:9 v/v of MeOH/CHCl3, respectively.

A tetrathiafulvalene donor has been attached to the naphthalene diimide core via a rigid bridge affording a new planar molecular dyad. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV–vis-NIR spectroscopy. Various electronic excited charge-transfer states are generated in different oxidation states, leading to almost full absorption in the visible to near-IR region with high extinction coefficients. The observed electronic properties are explained on the basis of density-functional-theory. In particular, the oxidized radical species show a strong tendency to undergo aggregation, in which the long-distance attractive interactions overcome the electrostatic repulsions.

To gain more understanding into the mechanism that enables the dramatic resonant Raman enhancement of totally symmetric modes observed in hemozoin (malaria pigment) and other related heme supramolecular arrays when applying near-infrared excitation wavelengths, the iron(III) porphyrins Fe(TPP)Cl, [Fe(TPP)](2)O, Fe(OEP)Cl, and [Fe(OEP)](2)O along with β-hematin (synthetic hemozoin or malaria pigment) were analyzed in the solid state using resonance Raman spectroscopy. The critical finding was that from the model compounds investigated, all except [Fe(OEP)](2)O exhibited the enhancement of the totally symmetric mode ν(4) when exciting the molecules with 782 and 830 nm laser lines. Through a detailed comparison of X-ray crystallographic structures, it is proposed that intermolecular noncovalent interactions play an integral role in enabling excitonic interactions to occur in these heme supramolecular systems. Comparison of the solid- and solution-phase electronic spectra in the near-IR region indicated more absorbance in the solid state between 800 and 900 nm. The electronic spectrum of [Fe(OEP)](2)O shows minimal absorbance in this region compared to that of the other compounds. All heme derivatives investigated have similar structure with a five-coordinate high-spin iron(III) ion. The crystallographic data indicate no significant differences in porphyrin geometry between TPP and OEP derivatives studied. However, [Fe(OEP)](2)O contains less supramolecular interactions in comparison to the other species. The supramolecular bonding enhances the probability of through-space interactions between the transition dipoles from electronic transitions of extended π systems. Our results indicate that the intensity of ν(4) is in part strongly affected by C-H···X hydrogen bonding interactions when X is an electron-donating entity. Such information may have important implications in the design and monitoring of antimalarial drugs that specifically interfere with hemozoin formation.

The fabrication of increasingly smaller machines to the nanometer scale can be achieved by either a “top-down” or “bottom-up” approach. While the former is reaching its limits of resolution, the latter is showing promise for the assembly of molecular components, in a comparable approach to natural systems, to produce functioning ensembles in a controlled and predetermined manner. In this review we focus on recent progress in molecular systems that act as molecular machine prototypes such as switches, motors, vehicles and logic operators.

The synthesis and photophysics of two new aminopropenyl naphthalene diimide (SANDI) dyes are reported. A general and convenient method for the synthesis of the precursor mono-, di-, and tetrabrominated 1,4,5,8-naphthalene tetracarboxylic dianhydrides is described. The two core-substituted SANDIs exhibit many of the photophysical properties required for fluorescence labeling applications including high photostability and high fluorescence quantum yields (>0.5) in the visible region of the spectrum. The emission wavelength is sensitive to the number of substituents on the NDI core, and the fluorescence decay times are in the range of approximately 8-12 ns for both compounds in the solvents investigated. Preliminary fluorescence emission data from single molecules of the compounds embedded in poly(methyl methacrylate) films are also reported and show that single molecules have very low yields of photobleaching, particularly the di-substituted system. Furthermore, only a small proportion (

A discrimination study of the neurotransmitters 3,4-dihydroxy-L-phenylalanine (DOPA), adrenaline, noradrenaline, tyramine and serotonin in aqueous solution utilising hydrophobic and hydrophilic yoctowells bearing oligoethylene walls is reported. The catecholamines were bound selectively to the hydrophobic yoctowells. Serotonin showed a preference for hydrophilic yoctowells.

An approach to the formation of molecular timepieces is outlined based on differentiating between rotamers in diaxial Sn(IV) porphyrin phenolates. Two models are explored in detail. The first explores how the rates of rotation of the diaxial ligands is discriminated based on steric hindrance of the two porphyrin macrocycle faces at low temperature. The second model explores a ‘stopwatch’ function based on the ligation of Ag(I) ions to a 5,15-dipyridylporphyrinato tin(IV) complex bearing 3-hydroxypyridine ligands. The complexation inhibits rotation of the axial ligand, a result, which can be reversed by precipitation of Ag(I) using tetraethylammonium bromide. X-ray crystallography has also been used to characterize two Ag(I) 5,15-dipyridylporphyrinato tin(IV)complexes. The two isoforms differ in their supramolecular organization. One structure is formed through a cofacial stack linking each porphyrin by Ag(I) coordination. The other displays a sheet-like coordination polymer structure.

Intramolecular photoinduced electron transfer (PET) processes occurring in dyads with a free base porphyrin-tetraazaanthracene donor (P) and either a tetracyanonaphthoquinidodimethane (TCQ) or benzoquinone (BQ) acceptor linked by a rigid six σ-bond polynorbornane bridge ([6]) have been investigated. For P[6]BQ , PET in the polar solvent benzonitrile ( ɛ s = 25.9) occurs with a rate constant ( k PET ) of 1.6 × 10 8 s −1 but is not evident in solvents less polar than tetrahydrofuran ( ɛ s = 7.52). For P[6]TCQ , highly efficient forward PET occurs in both polar and non-polar solvents ( k PET > 2 × 10 10 s −1 ). For P[6]TCQ the lifetime of the resulting charge-separated state decreases markedly with increasing solvent polarity. The results are discussed in the context of the likely mechanisms for electronic coupling and current theories for PET processes in such linked molecular systems.

The synthesis of a Zn (II) porphyrin-fullerene dyad in which the two chromophore units are tethered by a conformationally-flexible linker, is described. The synthesis is highlighted by the use of a cross metathesis strategy to prepare the linker between the chromophores. Photoexcitation of the Zn (II) porphyrin unit of the dyad in tetrahydrofuran leads to substantial (77%) quenching of porphyrin fluorescence. The multiple exponentials fluorescence decay kinetics observed are attributed to different rates of electron transfer from photoexcited porphyrin to fullerene in the various conformers present. A charge-separated state with a 330 ns lifetime is observed by transient spectroscopy.

The synthesis, characterization, and photophysical properties of a series of supramolecular triads consisting of a tin(IV) porphyrin with axial ligands of ortho-, meta-, and para-hydroxyphenyl naphthalenediimides are presented. For the meta- and parahydroxyphenyl derivatives, efficient and solvent-viscosity- dependent quenching of porphyrin fluorescence is observed. Experimental and theoretical studies demonstrate that, in these compounds, photoinduced electron transfer from the phenolate to the porphyrin is modulated by large amplitude rotational motions of the naphthalenediimide. These compounds are novel examples of fluorescent molecular rotors, and their potential use as environmental probes of local viscosity and temperature are discussed. © 2007 WILEY-VCH Verlag GmbH &. Co. KGaA.

The preparation and characterisation of the free-base and zinc metallated derivatives of 5,10,15,20-tetrakis(4-(2-(2-hydroxyethoxy)ethoxy)phenyl)porphyrin 1 is described. The X-ray crystal structure of the Zn(II) adduct 2 dimerises in the solid state via an intermolecular polyether oxygen–Zn(II) interaction (O…Zn = 2.124(4) A). The porphyrin dimers form discrete layers defined by a distance of 5.10 A between the porphyrin planes in adjacent layers. A bilayer sheeting arrangement of the porphyrin macrocyclic units is achieved through cooperative hydrogen bonding of the ethoxyethanol arms to form 11-membered macrocycles containing four hydrogen bonds.

The fluorescence decay kinetics from a benzonitrile solution of a dibenzo-18-crown-6 ether bridged porphyrin-fullerene dyad has been studied in the presence of a range of metal ions. Dual-exponential fluorescence decay behaviour has been attributed to conformational flexibility of the molecule influencing quenching interactions between the photo-excited porphyrin and fullerene. Additions of sodium, potassium and lithium ions significantly modulate the observed fluorescence decay processes while the larger tetrabutylammonium ion has only a minor affect. The results are discussed in terms of ion inclusion within the crown ether affecting both the bridge conformational properties and donor-acceptor electronic interactions.

Several blood-feeding organisms, including the malaria parasite detoxify haem released from host haemoglobin by conversion to the insoluble crystalline ferriprotoporphyrin IX dimer known as haemozoin. To date the mechanism of haemozoin formation has remained unknown, although lipids or proteins have been suggested to catalyse its formation. We have found that β-haematin (synthetic haemozoin) forms rapidly under physiologically realistic conditions near octanol/water, pentanol/water and lipid/water interfaces. Molecular dynamics simulations show that a precursor of the haemozoin dimer forms spontaneously in the absence of the competing hydrogen bonds of water, demonstrating that this substance probably self-assembles near a lipid/water interface in vivo.

Sago pulp (57% w/w) isolated from sago waste was converted to carboxymethyl cellulose (CMC) by etherification using sodium monochloroacetate and sodium hydroxide. The reaction was optimized against temperature, concentration and reaction time. The optimized product has a large degree of substitution (DS) of 0.821, which compared favorably to other forms of cellulose. Fourier Transform Infrared spectra (FTIR) were used to characterize the product and starting sago pulp. Digital photographs of sago waste and sago pulp showed the expected rough woody structure while that of the CMC generated from the pulp showed a smooth surface morphology.

A modular synthetic approach to preparing a family of triaminotriazine receptors bearing porphyrin chromophores is described. The porphyrin-appended triaminotriazines are prepared in a stepwise manner employing either cyanuric chloride or fluoride and 5-(4′-aminophenyl)-10,15,20-triphenylporphyrin in the first step. Reaction of the porphyrintriazine with excess 1-pentylamine leads to a triazine core programmed for three-point hydrogen bonding. Addition of a complementary naphthalene diimide yields a supramolecular donor–acceptor dyad. Photophysical studies in CH2Cl2 solvent show efficient quenching of porphyrin fluorescence within the dyad, consistent with an electron transfer process. Copyright © 2006 John Wiley & Sons, Ltd.

Bis(hydroxy)tin(IV) tetraphenylporphyrin (Sn(IV)TPP(OH) 2 , 2 ) condenses with two equivalents of tris( tert -butoxy)silanol (HOSi(O t Bu) 3 , 3 ) to form complex 2 . 3 2 in toluene. The product, which is air and moisture stable, has been characterised by 1 H, 29 Si and 119 Sn NMR spectroscopy and mass spectrometry. Application of this reaction in producing novel photochromic glasses is also discussed.

The novel bichromophoric crown ether N24C8NQ 3 has been synthesised in good yield by the conjugate addition of a polyether diol 1 to 2,3-dichloronaphthoquinone in the presence of base. Crown ether 3 was further reacted with malononitrile in the presence of TiCl4 to prepare the tetracyano-1,4-napthoquinodimethane derivative 4. Electrochemical and photophysical studies on 3 and 4 have been undertaken. The addition of alkali metal cations to the crown ether 3 causes significant changes in the first and second reduction potentials of the naphthoquinone (NQ) chromophore. In the case of the first process, a correlation exists between the reversible potential and cation fit. Crown ethers 3 and 4 exhibit red-shifted absorption bands attributed to intramolecular charge transfer interactions between the chromophores. Fluorescence from the naphthalene chromophore in 3 and 4 is quenched substantially (>80%) as compared to the model 5. The weak nature of the complex between 3 and the guest dibenzylammonium hexafluorop...

A novel dialkylammonium salt, 1.PF6, bearing a pyridyl group has been prepared and characterised by x-ray crystallography: triclinic space group P-1, a = 8.8141(1), b = 9.8902(2), c = 10.2611(1), A˚ and α = 82.008(1)°, β = 85.212(1)°, γ = 71.058(1)°, Z = 2, R = 0.0542 for 3902 independent reflections. The hydrogen-bonded tape generated within the crystal lattice is augmented by water molecules between the divided units in an N-H…O and O-H…Npy manner. The nature of the [2]pseudorotaxane formed upon the addition of DB24C8 to 1.PF6 (Ka = 2293 M−1) is characterised in the solid state (monoclinic space group P 21/c, a = 14.3808(4), b = 15.0194(4), c = 18.2599(6), A˚ and β = 95.723(1)°, Z = 4, R = 0.0766 for 9313 independent reflections) by hydrogen bonds between NH2 and CH2 groups of the guest with polyether oxygens of the crown ether. These hydrogen bond distances vary with close contacts between 2.01 and 2.58 A˚. 1H NMR spectroscopy and mass spectrometry further support the presence of the [2]pse...

This review describes the advances made in utilizing the unique recognition and structural characteristics of DNA to perform Boolean algebra using complex logic functions such as AND, XOR, NAND and INHIBIT based on chemical or photonic inputs. A comparison of these results to the action of novel 12-mer antisense peptide nucleic acid (PNA) constructs targeting the AMPA receptor in live motor neuron hybrids (NSC34) is made. In this case, a NOT function is displayed through downregulation of the GluR3 subunit, a result that impedes other cellular chemical processes. The consequence of cellular logic based on chemical inputs such as PNAs and their utilization as whole-cell machines whose biological output is chemical input-dependent is discussed briefly.

A naphthalene diimide acceptor 1 bearing a pyridine group linked directly (a series) or through a —CH2CH2— spacer (b series) coordinated axially to a metallotetraarylporphyrin (MP) undergoes fast photoinduced electron transfer (in the case of MP = Zn(II)TTP) while the kinetically more stable ruthenium complexes (MP = Ru(CO)TPP) have been used to illustrate the correlation between the distance of probe protons from the porphyrin plane and the change in chemical shift (Δδ) upon coordination. Changes in the emission spectra at 650 nm (λ ex= 400 nm) upon the addition of Zn(II) ions and/or 1b to TTPH2 can be interpreted in a truth table to illustrate a NAND gate.

Glutamate excitotoxicity is strongly implicated as a major contributing factor in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Excitotoxicity results from elevated intracellular calcium ion (Ca 2 + ) levels, which in turn recruit cell death signaling pathways. Recent evidence suggests that α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit (GluR) stoichiometry is a dominant factor leading to excess Ca 2 + loading in neurodegeneration. In particular, the Ca 2 + permeable glutamate receptor subunit 3 (GluR3) has been implicated in several neurologic conditions such as bipolar disorder and epilepsy. Recent proteomic analysis within our group on the copper zinc superoxide dismutase (SOD1) G 9 3 A transgenic mouse model of familial ALS (FALS) reveals a potentially deleterious upregulation of GluR3 in spinal cord compared to that in wild-type littermates. Based on this finding we designed a 12mer antisense peptide nucleic acid (PNA) directed against GluR3. This sequence significantly reduced levels of GluR3 protein and protected neuroblastoma x spinal cord (NSC-34) cells against death induced by the AMPA receptor-specific agonist (S)-5-fluorowillardiine. We subsequently treated SOD1 G 9 3 A mice thrice weekly with intraperitoneal injections of the antisense PNA (2.5 mg/kg) commencing at postnatal day 50. Mice treated with the antisense sequence had significantly extended survival compared to mice injected with a nonsense sequence. Western blot analysis, however, did not reveal a significant reduction in GluR3 protein levels in whole extracts of the lumbar spinal cord. These results suggest that interference with the GluR3 component of the AMPA receptor assembly may be a novel strategy for controlling excitotoxic destruction of motor neurons and may lead to new therapeutic opportunities for the treatment of human ALS.

A strategy in preparing a family of hexameric porphyrin cubes based on the interplay of Sn(IV)-O and Ru(II)-N interactions is described. In this first iteration, we have prepared the heptamer [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 (4 = (E)-(3-(4-pyridyl)acrylate)) constituting a 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP) core and 5,10,15,20-tetraphenylporphyrin (TPP) faces and compared its formation by stepwise and "one-pot" strategies where up to nine components are assembled in a single step in a regiospecific manner. In one example, the heptamer is formed around the template [SnIV(TPyP)·(4)2] bearing pyridine groups in which the nitrogens radiate octahedrally along each vertex. The ability to modulate the axial vertex through choice of pyridine is also demonstrated. 1H NMR measurements on [SnIV(TPyP)·(4)2][Ru(CO)(TPP)]6 indicate that the protons on the core template are extremely shielded as a result of the anisotropy of the peripheral porphyrin units. Various NMR techniques, including NOESY experiments, have been used to characterise the heptamer in solution.

Re-expression of the death-signalling p75 neurotrophin receptor (p75NTR) is associated with injury and neurodegeneration in the adult nervous system. The induction of p75NTR expression in mature degenerating spinal motor neurons of humans and transgenic mice with amyotrophic lateral sclerosis (ALS) suggests a role of p75NTR in the progression of motor neuron disease (MND). In this study, we designed, synthesized and evaluated novel antisense peptide nucleic acid (PNA) constructs targeting p75NTR as a potential gene knockdown therapeutic strategy for ALS. An 11-mer antisense PNA directed at the initiation codon, but not downstream gene sequences, dose-dependently inhibited p75NTR expression and death-signalling by nerve growth factor (NGF) in Schwann cell cultures. Antisense phosphorothioate oligonucleotide (PS-ODN) sequences used for comparison failed to confer such inhibitory activity. Systemic intraperitoneal administration of this antisense PNA to mutant superoxide dismutase 1 (SOD1G93A) transgenic mice significantly delayed locomotor impairment and mortality compared with mice injected with nonsense or scrambled PNA sequences. Reductions in p75NTR expression and subsequent caspase-3 activation in spinal cords were consistent with increased survival in antisense PNA-treated mice. The uptake of fluorescent-labelled antisense PNA in the nervous system of transgenic mice was also confirmed. This study suggests that p75NTR may be a promising antisense target in the treatment of ALS.

Novel antisense peptide nucleic acid (PNA) constructs targeting p75NTR as a potential therapeutic strategy for amyotrophic lateral sclerosis (ALS) were designed, synthesised and evaluated against phosphorothioate oligonucleotide sequences (PS-ODN). An 11-mer antisense PNA directed at the initiation codon dose-dependently inhibited p75NTR expression and death signalling by nerve growth factor in Schwann cell cultures. Inhibition of p75NTR production was not detected in cultures treated with the nonsense PNA or antisense PNA directed at the 3'-terminus sequence. The 19-mer PS-ODN sequences also failed to confer any activity against p75NTR but, unlike the PNA sequences, were toxic in vitro at comparable doses.

Tin(IV)porphyrin phenolates are the stable product of the equilibrium-based condensation reaction of phenols with tin(IV)porphyrin dihydroxide in an organic medium. Their formation is characterised by significant shifts (1–5 ppm) of the phenolic protons within the recorded 1 H NMR spectra. To demonstrate the inherent simplicity of their formation and the flexibility in choice of phenolic ligand towards the design and fabrication of more elaborate assemblies and arrays we have constructed two different mixed porphyrin trimer families in which the porphyrin units differ in their orientation to the central porphyrin unit using Sn–O, Ru(III)–N and Zn(II)–N interactions. In one of these cases, 5 molecular components are self-assembled in one-pot to form a cofacially stacked mixed porphyrin trimer with high yield.