Tris-(1,3-diaryltriazenide) complexes of rhodium: synthesis, structure and, spectral and electrochemical properties

Reaction of 1,3-diaryltriazenes (abbreviated in general as HL-R, where R stands for the para-substituent in the aryl fragment and H stands for the dissociable hydrogen atom, R = OCH3, CH3, H, Cl, NO2) with [Rh(PPh3)(2)(CO)Cl] in ethanol in the presence of NEt3 produces a series of tris-diaryltriazenide complexes of rhodium of type [Rh(L-R)(3)], where the triazenes are coordinated to rhodium as monoanionic, bidentate N,N-donors. Structure of the [Rh(L-OCH3)(3)] complex has been determined by X-ray crystallography. The complexes are diamagnetic, and show characteristic H-1 NMR signals and intense MLCT transitions in the visible region. They also fluoresce in the visible region under ambient condition while excited at around 400 nm. Cyclic voltammetry on these complexes shows a Rh(III)-Rh(IV) oxidation (within 0.84-1.67 V vs SCE), followed by an oxidation of the coordinated tri- and azene ligand (except the R = NO2 complex). An irreversible reduction of the coordinated triazene is also observed for all the complexes below -1.03 V vs SCE.

A new cyano-bridged one-dimensional (GdFeIII)-Fe-III coordination polymer with o-phenanthroline as the blocking ligand: synthesis, structure, and magnetic properties

Synthesis, structural characterization, and magnetic properties of a new cyano-bridged one-dimensional iron (III)-gadolinium (III) compound, trans-[Gd(o-phen)(2)(H2O)(2)(mu-CN)(2)Fe(CN)(4)], - 2no-phen (o-phen = 1,10-phenanthroline), have been described. The compound crystallizes in the triclinic P (1) over bar space group with the following unit cell parameters: a = 10.538(14) angstrom, b = 12.004(14) angstrom, c = 20.61(2) angstrom, alpha = 92.41(1)degrees, beta = 92.76(1)degrees, gamma = 11 2.72(1)degrees, and Z = 2. In this complex, each gadolinium (III) is coordinated to two nitrile nitrogens of the CN groups coming from two different ferricyanides, the mutually trans cyanides of each of which links another different Gd-III to create -NC-Fe(CN)(4)-CN-Gd-NC- type 1-D chain structure. The one-dimensional chains are self-assembled in two-dimensions via weak C-H center dot center dot center dot N hydrogen bonds. Both the variable-temperature (2-300 K, 0.01 T and 0.8 T) and variable-field (0-50 000 Gauss, 2 K) magnetic measurements reveal the existence of very weak interaction in this molecule. The temperature dependence of the susceptibilities has been analyzed using a model for a chain of alternating classic (7/2) and quantum (1/2) spins. (c) 2005 Elsevier B.V. All rights reserved.

Solvothermal syntheses, crystal structures and properties of five new thloantimonates(III) containing the [Sb4S7](2-) anion

Five new thioantimonates have been synthesized in the presence of organic amines under solvothermal conditions and their structures determined by single-crystal X-ray diffraction. All of the compounds are layered and contain antimony-sulphide anions of stoichiometry [Sb4S7](2-), but the structure of the anion formed is dependent on the amine used in synthesis. (H3N(CH2)(4)NH3)[Sb4S7] (1) contains [Sb4S7](2-) double chains directed along [010]. Weak interchain Sb-S interactions between neighbouring chains cause the double chains to pack into layers in the ab plane. In the [001] direction, the layers of double chains alternate with doubly protonated diaminobutane molecules to which the chains are hydrogen bonded. Compounds of general formula (TH)(2)[Sb4S7] (T= CH3(CH2)(2)NH2 (2), (CH3)(2)CHNH2 (3), CH3(CH2)(3)NH2 (4) and CH3(CH2)(4)NH2 (5)) adopt a more complex structure in which [Sb3S8](7-) units are linked by Sb-3(3-) pyramids to form chains, which in turn are bridged by sulphur atoms to create sheets containing large heterorings. Pairs of such sheets form double layers of four atoms thickness that are stacked along [001]. Protonated amine molecules are located between anionic antimony-sulphide layers to which they are hydrogen bonded. Thermal analysis reveals that the decomposition temperature of materials containing [Sb4S7](2-) anions is dependent both on the structure of the anion, the lowest decomposition temperature being that of the low-dimensional phase (1) and on the identity of the amine, the decomposition temperature decreasing with an increasing number of carbon atoms and decreasing density. (c) 2005 Elsevier Inc. All rights reserved.

Supramolecular hydrogen-bond structures and magnetic interactions in basal-apical, dinuclear, azide-bridged copper(II) complexes

The synthesis, characterisation, X-ray single crystal structures and magnetic properties of three new basal-apical mu(2)-1,1-azide-bridged complexes [(CuLN3)-N-1](2) (1), [(CuLN3)-N-2](2) (2) and [(CuLN3)-N-3](2) (3) with very similar tridentate Schiff-base blocking ligands {HL1 = N-[2-(ethylamino) ethyl] salicylaldimine; HL2 = 7-(ethylamino)-4-methyl-5-azahept-3-en-2-one; HL3 = 7-amino-4-methyl-5-azaoct-3-en-2-one} have been reported [complex 1: monoclinic, P2(1)/c, a = 8.390(2), b = 7.512(2), c = 19.822(6) Angstrom, beta = 91.45(5)degrees; complex 2: monoclinic, P2(1)/c, a = 8.070(9), b = 9.787(12), c = 15.743(17) A, beta = 98.467(10)degrees; complex 3: monoclinic, P2(1)/n, a = 5.884(7), b = 16.147(18), c = 11.901(12) Angstrom, beta = 90.050(10)degrees]. The structures consist of neutral dinuclear entities resulting from the pairing of two mononuclear units through end-on azide bridges connecting an equatorial position of one copper centre to an axial position of the other, The copper ions adopt a (4+1) square-based geometry in all the complexes. In complex 2, there is no inter-dimer hydrogen-bonding. However, complexes 1 and 3 form two different supramolecular structures in which the dinuclear entities are linked by H-bonds giving one-dimensional systems. Variable temperature (300-2 K) magnetic-susceptibility measurements and magnetisation measurements at 2 K reveal that all three complexes have antiferromagnetic coupling. Magneto-structural correlations have been made taking into consideration both the azido bridging ligands and the existence of intermolecular hydrogen bonds. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

Thermally responsive elastomeric supramolecular polymers featuring flexible aliphatic hydrogen-bonding end-groups

The present paper details the synthesis, characterization, and preliminary physical analyses of a series of polyisobutylene derivatives featuring urethane and urea end-groups that enable supramolecular network formation to occur via hydrogen bonding. These polymers are readily accessible from relatively inexpensive and commercially available starting materials using a simple two-step synthetic approach. In the bulk, these supramolecular networks were found to possess thermoreversible and elastomeric characteristics as determined by temperature-dependent rheological analysis. These thermoreversible and elastomeric properties make these supramolecular materials potentially very useful in applications such as adhesives and healable surface coatings.

Viscoelastic properties of high pressure and heat induced tofu gels

Tofu gels were rheologically examined to determine their storage or elastic (G′) and loss or viscous (G″) moduli as a function of frequency within their linear viscoelastic limits. The tofu gels were made using either glucono-δ-lactone (GDL) or calcium sulphate (CaSO4·2H2O), followed by either heat treatment (heated soymilk at 97 °C prior to coagulation and subsequently held at 70 °C for 60 min, HT) or high pressure treatment (400 MPa at 20 °C for 10 min, HP). The overall moduli values of the GDL gels and CaSO4·2H2O gels of both physical treatments were similar, each gave frequency profiles expected for weak viscoelastic materials. However, although both temperature and high pressure treatments could be used to produce tofu gels, the final products were not the same. Pressure formed gels, despite having a higher overall “consistency” (increasing values of their moduli), had a proportionately higher contribution from the loss modulus (increased tan δ). Differences could also be observed using confocal scanning laser microscopy. While such treatment may give rise to differing systems/structures, with new or modified organoleptic properties, the more “open” structures obtained by pressure treatment may well cause processing difficulties if subsequent reworking or moulding is required.

Antioxidant properties of kilned and roasted malts

Compounds possessing antioxidant activity play a crucial role in delaying or preventing lipid oxidation in foods and beverages during processing and storage. Such reactions lead to loss of product quality, especially as a consequence of off-flavor formation. The aim of this study was to determine the antioxidant activity of kilned (standard) and roasted (speciality) malts in relation to phenolic compounds, sugars, amino acids, and color [assessed as European Brewing Convention units (degrees EBC) and absorbance at 420 nm]. The concentrations of sugars and amino acids decreased with the intensity of the applied heat treatment, and this was attributed to the extent of the Maillard reaction, as well as sugar caramelization, in the highly roasted malts. Proline, followed by glutamine, was the most abundant free amino/imino acid in the malt samples, except those that were highly roasted, and maltose was the most abundant sugar in all malts. Levels of total phenolic compounds decreased with heat treatment. Catechin and ferulic acid were the most abundant phenolic compounds in the majority of the malts, and amounts were highest in the kilned samples. In highly roasted malts, degradation products of ferulic acid were identified. Antioxidant activity increased with the intensity of heating, in parallel with color formation, and was significantly higher for roasted malts compared to kilned malts. In kilned malts, phenolic compounds were the main identified contributors to antioxidant activity, with Maillard reaction products also playing a role. In roasted malts, Maillard reaction products were responsible for the majority of the antioxidant activity.

Viscoelastic properties of high pressure and heat induced tofu gels

Tofu gels were rheologically examined to determine their storage or elastic (G') and loss or viscous (G '') moduli as a function of frequency within their linear viscoelastic limits. The tofu gels were made using either glucono-delta-lactone (GDL) or calcium sulphate (CaSO4 center dot 2H(2)O), followed by either heat treatment (heated soymilk at >= 97 degrees C prior to coagulation and subsequently held at 70 degrees C for 60 min, HT) or high pressure treatment (400 MPa at 20 degrees C for 10 min, HP). The overall moduli values of the GDL gels and CaSO4 center dot 2H(2)O gels of both physical treatments were similar, each gave frequency profiles expected for weak viscoelastic materials. However, although both temperature and high pressure treatments could be used to produce tofu gels, the final products were not the same. Pressure formed gels, despite having a higher overall "consistency" (increasing values of their moduli), had a proportionately higher contribution from the loss modulus (increased tan delta). Differences could also be observed using confocal scanning laser microscopy. While such treatment may give rise to differing systems/structures, with new or modified organoleptic properties, the more "open" structures obtained by pressure treatment may well cause processing difficulties if subsequent reworking or moulding is required. (c) 2007 Elsevier Ltd. All rights reserved.

Effects of calcium-chelating agents and pasteurisation on certain properties of calcium-fortified soy milk

Addition of 25 mM calcium chloride to soy milk reduced pH, increased ionic calcium and caused it to coagulate. The effects of different chelating agents were investigated on selected physicochemical properties of soy milk and on preventing coagulation. The soy milks were then pasteurised to examine how heat treatment changed some of these properties as well as to evaluate their effects on heat stability. Sediment formation and susceptibility to coagulation could be reduced by decreasing ionic calcium and increasing pH. To achieve this, the most effective chelating agents were tri-sodium citrate and disodium hydrogen phosphate. These chelating agents also reduce absolute viscosity and particle size. Sodium hexa meta phosphate was also effective, but less so; it reduced ionic calcium but had a less noticeable effect on pH. The disodium salt of ethylenediamine tetraacetic acid was not effective, as it decreased the pH of soy milk. Ionic calcium and pH are useful indicators of heat stability of calcium-fortified soy beverages. (C) 2009 Elsevier Ltd. All rights reserved.

Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9, trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9, trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9, trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg ( on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18: 0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsaturated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.

Effects of hydrocolloid addition and high pressure processing on the rheological properties and microstructure of a commercial ostrich meat product "Yor" (Thai sausage)

"Yor" is a traditional sausage like product widely consumed in Thailand. Its textures are usually set by steaming, in this experiment ultra-high pressure was used to modify the product. Three types of hydrocolloid; carboxymethylcellulose (CMC), locust bean gum (LBG) and xanthan gum, were added to minced ostrich meat batter at concentration of 0-1% and subjected to high pressure 600 Mpa, 50 degrees C, 40 min. The treated samples were analysed for storage (G) and loss (G '') moduli by dynamic oscillatory testing as well as creep compliance for control stress measurement. Their microstructures using confocal microscopy were also examined. Hydrocolloid addition caused a significant (P < 0.05) decrease in both the G' and G '' moduli. However the loss tangent of all samples remained unchanged. Addition of hydrocolloids led to decreases in the gel network formation but appears to function as surfactant materials during the initial mixing stage as shown by the microstructure. Confocal microscopy suggested that the size of the fat droplets decreased with gum addition. The fat droplets were smallest on the addition of xanthan gum and increased in the order CMC, LBG and no added gum, respectively. Creep parameters of ostrich yors with four levels of xanthan gum addition (0.50%, 0.75%, 1.00% and 1.25%) showed an increase in the instantaneous compliance (J(0)), the retarded compliance (J(1)) and retardation time (lambda(1)) but a decrease in the viscosity (eta(0)) with increasing levels of addition. The results also suggested that the larger deformations used during creep testing might be more helpful in assessing the mechanical properties of the product than the small deformations used in oscillatory rheology. (c) 2007 Elsevier Ltd. All rights reserved.

Changes in the antioxidant properties of protein solutions in the presence of epigallocatechin gallate

beta-Casein and alpha-casein showed radical-scavenging activities in aqueous solution, whereas bovine serum albumin (BSA), alpha-lactalbumin and P-lactoglobulin showed much weaker antioxidant activity, when assessed by the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical-scavenging assay. However, beta-casein and alpha-casein showed reduced antioxidant activity after storage at 30 degrees C. An increase in radical- scavenging activity and a fall in fluorescence of the protein component were evident after 6 h, when BSA, beta-lactoglobulin or casein were mixed with EGCG, and excess EGCG was removed, indicating the formation of a complex with this protein on mixing. Storage of all the proteins with EGCG at 30 degrees C caused an increase in the antioxidant activity of the isolated protein component after separation from excess EGCG. This showed that EGCG was reacting with the proteins and that the protein-bound catechin had antioxidant properties. The reaction of EGCG with BSA, casein and beta-lactoglobulin was confirmed by the loss of fluorescence of the protein on storage, and the increase in UV absorbance between 250 and 400 nm. The increase in antioxidant activity of BSA after storage with EGCG was confirmed by the ferric reducing antioxidant potential (FRAP) and the oxygen radical antioxidant capacity (ORAC) assays. (c) 2006 Elsevier Ltd. All rights reserved.

Polymer-mediated disruption of drug crystallinity

Ibuprofen (IB), a BCS Class II compound, is a highly crystalline substance with poor solubility properties. Here we report on the disruption of this crystalline structure upon intimate contact with the polymeric carrier cross-linked polyvinylpyrrolidone (PVP-CL) facilitated by low energy simple mixing. Whilst strong molecular interactions between APIs and carriers within delivery systems would be expected on melting or through solvent depositions, this is not the case with less energetic mixing. Simple mixing of the two compounds resulted in a significant decrease in the differential scanning calorimetry (DSC) melting enthalpy for IB, indicating that approximately 30% of the crystalline content was disordered. This structural change was confirmed by broadening and intensity diminution of characteristic IB X-ray powder diffractometry (PXRD) peaks. Unexpectedly, the crystalline content of the drug continued to decrease upon storage under ambient conditions. The molecular environment of the mixture was further investigated using Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectroscopy. These data suggest that the primary interaction between these components of the physical mix is hydrogen bonding, with a secondary mechanism involving electrostatic/hydrophobic interactions through the IB benzene ring. Such interactions and subsequent loss of crystallinity could confer a dissolution rate advantage for IB. (C) 2006 Elsevier B.V. All rights reserved.

Hydrogen bond-induced pair formation of glycine on the chiral Cu{531} surface

Enantio-specific interactions on intrinsically chiral or chirally modified surfaces can be identified experimentally via comparison of the adsorption geometries of similar nonchiral and chiral molecules. Information about the effects of substrate-related and in interactions on the adsorption geometry of glycine, the only natural nonchiral amino acid, is therefore important for identifying enantio-specific interactions of larger chiral amino acids. We have studied the long- and short-range adsorption geometry and bonding properties of glycine on the intrinsically chiral Cu{531} surface with low-energy electron diffraction, near-edge X-ray absorption One structure spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed desorption. For coverages between 0.15 and 0.33 ML (saturated chemisorbed layer) and temperatures between 300 and 430 K, glycine molecules adsorb in two different azimuthal orientations, which are associated with adsorption sites on the {110} and {311} microfacets of Cu{531}. Both types of adsorption sites allow a triangular footprint with surface bonds through the two oxygen atoms and the nitrogen atom. The occupation of the two adsorption sites is equal for all coverages, which can be explained by pair formation due to similar site-specific adsorption energies and the possibility of forming hydrogen bonds between molecules on adjacent {110} and {311} sites. This is not the ease for alanine and points toward higher site specificity in the case of alanine, which is eventually responsible for the enantiomeric differences observed for the alanine system.

Self-assembled healable materials through a combination of pi-pi stacking and hydrogen bonding

The discovery of polymers with stimuli responsive physical properties is a rapidly expanding area of research. At the forefront of the field are self-healing polymers, which, when fractured can regain the mechanical properties of the material either autonomically, or in response to a stimulus. It has long been known that it is possible to promote healing in conventional thermoplastics by heating the fracture zone above the Tg of the polymer under pressure. This process requires reptation and subsequent re-entanglement of macromolecules across the fracture void, which serves to bridge, and ‘heal’ the crack. The timescale for this mechanism is highly dependent on the molecular weight of the polymer being studied. This process is in contrast to that required to affect healing in supramolecular polymers such as the plasticised, hydrogen bonded elastomer reported by Leibler et al. The disparity in bond energies between the non-covalent and covalent bonds within supramolecular polymers results in fractures propagating through scission of the comparatively weak supramolecular interactions, rather than through breaking the stronger, covalent bonds. Thus, during the healing process the macromolecules surrounding the fracture site only need sufficient energy to re-engage their supramolecular interactions in order to regenerate the strength of the pristine material. Herein we describe the design, synthesis and optimization of a new class of supramolecular polymer blends that harness the reversible nature of pi-pi stacking and hydrogen bonding interactions to produce self-supporting films with facile healable characteristics.