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The nanoporous structure of collagen-glycosaminoglycan (CG) hydrogels was studied using 1H NMR spectroscopy and thermally stimulated depolarisation (TSD) current with layer-by-layer freezing-out of bulk and interfacial water. The depression of the freezing point of water is related to the size of the nanopore, to which it is confined. Changes in the Gibbs free energy of the unfrozen interfacial water are related to the amount of bound water in the hydrogel matrix and to the re-arrangement of the 3D network structure of the biopolymer. Analysis of the thermodynamic properties of bulk and interfacial water using the layer-by-layer freezing-out technique combined with NMR and TSDC provides valuable information about the structural features of CG hydrogels that can be used for characterisation of different types of hydrogels and soft tissue scaffolds, artificial skin substitutes and other biomaterials.

We present a highly unusual example of self-assembly, specifically a polar, mixed-ligand cage which forms in preference to symmetrical homo-ligand products, and which suggests that steric effects can be exploited to obtain novel non-uniform polyhedral cages. In particular, reaction between the bulky tripodal triphosphine 2,4,6-tris(diphenylphosphino)triazine, L1, the non-bulky tripodal trinitrile 2,4,6-tris(cyanomethyl)trimethylbenzene, L2 and silver hexafluoroantimonate, AgSbF 6 , in a 3:1:4 ratio gives the mixed-ligand aggregate [Ag 4 (L1) 3 (L2)-(SbF 6 )] 3+ , 1-SbF 6 , instantly as the only product in quantitative yield. The X-ray crystal structure of complex 1-SbF 6 is consistent with the suspected solution-state structure. The cage derives from trigonal-pyramidal geometry, the basal vertices of which are defined by three bulky triphosphines, L1, and the apical vertex by the non-bulky trinitrile, L2. There is apical elongation amounting to 19% in comparison to the ideal uniform tetrahedron. The cage also encapsulates an SbF 6 anion. 19 F NMR spectra in solution for the analogous PF 6 complex [Ag 4 (L1) 3 (L2)-(PF 6 )] 3+ , 1-PF 6 , confirm that one anion is also encapsulated in solution. The synthesis of the analogous CF 3 SO 3 - complex, [Ag4(Ll)3(L2)(OTf)] 3+ , 1-OTf, in solution is also described, although 1-PF 6 and 1-OTf could not be isolated due to slow decomposition in solution. The selective formation of these mixed-ligand cages is discussed in terms of ligand-ligand and ligand-included anion steric repulsions, which we propose prevent the formation of the competing hypothetical homo-ligand tetrahedral structure [Ag 4 (L1) 4 -(SbF 6 )] 3+ , and thus favour the mixed ligand cage. "Cage cone angles" for L1 and L2 are estimated at 115° and 101°, respectively. Variable-temperature 31 P NMR spectroscopy shows that complex 1-SbF 6 and the related previously reported partial tetrahedral complex [Ag 4 (L1) 3 (anion)] 3+ undergo dynamic twisting processes in solution between enantiomeric C 3 -symmetry conformations.

A polymeric metal–organic gel is described, which acts as a template in the preparation of macroporous polymethylmethacrylate, and can be easily removed post-polymerisation.

The X-ray crystal structure of [Pd(η3-ally)dppn)]BF4·CH2Cl2 (1) where dppn = 1,8-bis(diphenylphosphino)naphthalene is reported. Comparison of the conformation of the ligand in 1 with that in the free state shows that there is a relief of strain on complexation analogous to the relief of strain observed upon protonation of proton sponge.

The metal–organic framework [Co(INA)2]·0.5EtOH (INA = isonicotinate, NC5H4-4-CO2−), 1 was synthesised under solvothermal conditions. Its X-ray crystal structure shows channels containing ethanol guests which are hydrogen-bonded to carboxylate oxygens of the framework. The pyridyl rings of the framework alternate between ‘open’ and ‘closed’ positions along the channels resulting in large variation in the channel cross-sectional area from ca. 1.4 by 2.3 A at the narrowest point to 4.9 by 5.3 A at the widest. Despite the very small windows, the ethanol guests (of van der Waals diameter ca. 4.2–6.1 A) may be reversibly desorbed and sorbed into the structure quantitatively, as shown by in situ variable-temperture IR spectroscopy and XRPD. The single-crystal structure of the desolvated form [Co(INA)2] 2 shows that there is no change in the overall connectivity on desolvation, but the rotational positions of the pyridine rings are altered. This suggests that pyridyl rotation may occur to allow guests to pass in and out. When the synthesis was conducted in 1-propanol solvent [Co(INA)2]·0.5PrnOH·H2O 3, was obtained, and a single-crystal X-ray structure revealed the same overall connectivity as in 1 but with pyridine rings disordered over closed and open positions. There was no evidence of included guests from X-ray crystallography, suggesting that they are also highly disordered. Variable-temperature XRPD performed on bulk samples showed peaks which were unsymmetrical and exhibited shoulders, suggesting that for each pattern obtained the material actually consisted of several closely-related phases. The movements of the peaks during desolvation showed the presence of intermediate phases before the final desolvated product was formed. The peak positions of the intermediate phases matched more closely with the calculated pattern for 3 than with 1 or 2, suggesting that they may have disordered structures similar to 3. The results also suggest that the intermediate phase represents an initial increase in volume before a larger decrease in volume occurs to give the final desolvated material.

We report the first example of a monoclonal antibody-catalysed hydrolysis of a beta-lactam where the antibodies were generated by a simple transition-state analogue. A rat monoclonal antibody (1/91c/4d/26) generated by using an acyclic 4-nitrophenylphosphate immunogen catalysed the hydrolysis of corresponding 4-nitrophenyl carbonates but, more importantly, also catalysed the hydrolysis of N-(4-nitrophenyl)-azetidinone at pH 8 with k(cat)=8.7 x 10(-6)s(-1) and K(M)=35 microM. This is the first example of a rat monoclonal catalytic antibody.

Silver salts and triphosphine ligands with biphenyl substituents assemble to give coordination cages with four external aromatic channel receptors in a pseudo-tetrahedral arrangement.

Addition of anionic benzylsulfate dendrons to dynamic mixtures of Ag+ and triphosphine ligands results in the assembly of loosely-bonded cage-core dendrimers.

This aim of this study was to develop a microparticulate based oral drug delivery system, which could prolong gut transit time by binding via specific interactions to the gut mucus layer. Porcine gastric mucus was semi-purified and used as an antigen to raise a polyclonal antiserum in rabbits. The immunoglobulin fraction of this serum was isolated, purified and tested for homogeneity and cross reactivity. High cross-reactivity was displayed when the antiserum was challenged against types of mucus other than that used as an antigen, but no significant cross-reactivity occurred when challenged against some other common macromolecules. The antibody fraction of this serum was covalently linked to three types of albumin microspheres (MS) using 1-ethyl-3(3-dimethyl aminopropyl) carbodiimide. The MS employed had either a hydrophobic, a hydrophilic or a carboxymethylated surface, and were prepared and characterised as described earlier (MacAdam, A.B., Shafi, Z.B., Martin, G.P. and James, S.L. 1997. Preparation of hydrophobic and hydrophilic MS and determination of surface carboxylic acid and amino residues. Int. J. Pharm. 151, 47–55). Binding of these MS to both radioiodinated mucin in suspension and to isolated gut segments was measured. Hydrophilic and carboxymethylated MS with surface-associated antibody bound significantly more mucin from a suspension than did uncoated controls. Similarly, anti-mucus antibody-coated hydrophilic and carboxymethylated MS bound more strongly to an isolated gut segment than did uncoated controls or controls coated in an antibody specific for albumin. These results suggest anti-mucus antibody coated albumin MS may be a useful model to act as comparators in studies aimed at developing drug delivery systems with delayed gastrointestinal transit.

The protective functions of mucus may chiefly be defined by its barrier and transport properties. These properties are largely, but not exclusively, determined by the physical characteristics of the mucus which, in turn, may be most usefully considered as its characteristic behaviour under physical stress, that is, its rheological properties [1]. Abnormalities in the rheological properties of respiratory mucus are reliable indicators of suboptimal transport properties. Increases in viscoelastic parameters, common in cystic fibrosis, for example, lead to poor mucociliary clearance, whilst it has been suggested that a reduction in viscoelastic parameters, a situation possibly found in fucosidosis, will also result in impaired clearance [2].

The disilylated compound 1,4-bis(trimethylsilyl)-2,3,5,6-tetrakis((dimethylamino)methyl)benzene, (Me3Si)2C2N4, 4, can be electrophilically palladated selectively at the C-Si bonds to afford the neutral 1,4-bis(palladium) complex [(AcOPd)2(C2N4)], from which the dicationic [(LPd)2(C2N4)]2+ (L = MeCN) organometallic species are accessible. The monosilylated species (Me3Si)(H)C2N4, 5, can be used for the preparation of the dicationic heterodinuclear platinum(II)-palladium(II) species [(LPd)(LPt)(C2N4)]2+ (L = MeCN) via a sequence of transmetalation of the organolithium derivative of 5 with [PtCl2(SEt2)2], followed by a C-Si bond palladation reaction.

The new diarylplatinum complex cis-[Pt(PEt3)2{C6H3(CH2-NMe2)2-3,5}2] 1, containing four free amine coordination sites, undergoes directed lithiation with ButLi and subsequent transmetallation with [PtCl2(SEt2)2] to give a triplatinum species 3 which reductively eliminates the diplatinum complex [ClPt{2,6-(Me2NCH2)2C6H2–C6H2(CH2NMe2)2-2,6}PtCl] 4.

Mechanochemical synthesis has the potential to provide more sustainable preparative routes to catalysts than the current multistep solvent-based routes. In this review, the mechanochemical synthesis of catalysts is discussed, with emphasis placed on catalysts for environmental, energy and chemical synthesis applications. This includes the formation of mixed-metal oxides as well as the process of dispersing metals onto solid supports. In most cases the process involves no solvent. Encouragingly, there are several examples where the process is advantageous compared with the more normal solvent-based methods. This can be because of process cost or simplicity, or, notably, where it provides more active/selective catalysts than those made by conventional wet chemical methods. The need for greater, and more systematic, exploration of this currently unconventional approach to catalyst synthesis is highlighted.

Rigid organic iminospherand cages are rendered meltable by multiple alkylation; below their melting points they can take the form of permanently porous crystals, crystals unstable to desolvation or non-porous glassy solids depending on chain length and branching; melting points as low as 50 °C are observed and a fully Newtonian liquid phase is obtained above 80 °C. Thin glassy fibres can be drawn out from a molten phase.

Electrodeposition of metals onto conductive supports such as graphite potentially provides a lower-waste method to form heterogeneous catalysts than the standard methods such as wet impregnation. Copper electrodeposition onto pressed graphite disc electrodes was investigated from aqueous CuSO4–ethylenediamine solutions by chronoamperometry with scanning electron microscopy used to ascertain the particle sizes obtained by this method. The particle size was studied as a function of pH, CuSO4–ethylenediamine concentration, and electrodeposition time. It was observed that decreasing the pH, copper–ethylenediamine concentration and time each decreased the size of the copper particles observed, with the smallest obtained being around 5–20 nm. Furthermore, electroless aerobic oxidation of copper metal in the presence of ethylenediamine was successfully coupled with the electrodeposition in the same vessel. In this way, deposition was achieved sequentially on up to twenty different graphite discs using the same ethylenediamine solution, demonstrating the recyclability of the ligand. The materials thus prepared were shown to be catalytically active for the mineralisation of phenol by hydrogen peroxide. Overall, the results provide a proof-of-principle that by making use of aerobic oxidation coupled with electrochemical deposition, elemental base metals can be used directly as starting materials to form heterogeneous catalysts without the need to use metal salts as catalyst precursors.

Using a small planetary ball mill, liquid-assisted grinding (LAG) of metal salts or oxides (ZnO, CdO, CdCO3, Cu(OAc)2·H2O, Co(OAc)2·4H2O, Mn(OAc)2·4H2O, Ni(OAc)2·4H2O, FeSO4·7H2O) with two equivalents of isonicotinic acid (HINA) and small amounts of water (up to 5.6 molar equivalents) gave discrete aquo complexes trans-[M(INA)2(OH2)4] (M = Zn, Cd, Cu, Fe, Co, Ni, Mn) efficiently within 30 min. For M = Zn, Cd and Cu these complexes readily undergo reversible formal dehydration to the extended network structures [M(INA)2] (M = Zn, Cu) or [Cd(INA)2(OH2)]·DMF by further LAG with non-aqueous liquids such as methanol or DMF. Overall, the mechanochemical dehydrations are more effective than heating or immersion in bulk solvents. The work demonstrates a two-step mechanochemical synthesis of coordination networks via discrete aquo complexes which may be preferable to single step reactions or grinding-annealing procedures in some cases. For example, the two step method was the only way to prepare [Cd(INA)2(OH2)]·DMF mechanochemically and the porous network Cu(INA)2 could not be obtained from the aquo complex by heating.

The chemoselective acylation of primary aliphatic amines has been achieved in under ten minutes (and for aromatic amines under 120 min) using vibration ball-milling, avoiding undesirable solvents which are typically employed for such reactions (e.g.DMF). Under optimised conditions, the synthesis of amides in the presence of both primary and secondary alcohol functions was achieved in high to excellent yields (65–94%). Overall, the methods described have significant practical advantages over conventional approaches based upon bulk solvents including greater yields, higher chemoselectivity and easier product separation.

Using a ball mill, rapid, atom-economic coupling between adenosine-5'-phosphoromorpholidate and phosphorylated ribose derivatives as their sodium or barium salts was achieved. Facile purification by reversed-phase HPLC enabled product isolation within hours.

Addition of anionic benzylsulfate dendrons to dynamic mixtures of Ag+ and triphosphine ligands results in the assembly of loosely-bonded cage–core dendrimers.

Liquid-assisted grinding in a ball mill for 20 minutes gives crystalline homo- and hetero-rare-earth(III) metal–organic frameworks by reaction between metal carbonates and benzene-1,3,5-tricarboxylic acid (H3BTC) in the presence of small amounts of DMF or water.

A series of enantiopure 2,2'-bipyridines have been synthesised from the corresponding cis-dihydrodiol metabolites of 2-chloroquinolines. Several of the resulting hydroxylated 2,2'-bipyridines were found to be useful chiral ligands for the asymmetric aminolysis of meso-epoxides leading to the formation of enantioenriched amino alcohols (-->84% ee). N-oxide and N,N'-dioxide derivatives of these 2,2'-bipyridines, including separable atropisomers, have been synthesised and used as enantioselective organocatalysts in the asymmetric allylation of aldehydes to give allylic alcohols (-->86% ee).

Porosity over a broad range (typically 0.001–300 μm in diameter) of tissue scaffolds provides appropriate conditions for diffusion and adsorption of small molecules and macromolecules, migration of cells through the scaffold, and adequate cell proliferative capacity. Characterisation of pores over this large range poses a problem especially when analysing soft polymer hydrogels, as no one methodology can adequately cover the entire range. This work describes a combined technique used for evaluation of the porous structure of a collagen hydrogel (dermal substitute Integra®) on the basis of NMR-cryoporometry (sensitive to nanopores) and confocal laser scanning microscopy (CLSM) imaging (sensitive to macropores). Thermodesorption of water, diffusion of proteins through a collagen membrane, migration and growth of normal primary human skin fibroblasts, and the interaction kinetics of 3T3 mouse fibroblast cells (using a quartz crystal microbalance) with collagen were analysed with respect to the porous structure of the material. The contribution to the total porosity of pores with a diameter of less than 100 nm is low, at approximately 3–5%, a figure estimated using the methods described above. However, these pores are the main contributor to the specific surface area (S ≈ 120 m2 g−1) as larger diameter macropores, with diameters of 20–200 μm, have a much lower surface area at S ≈ 0.4 m2 g−1 relative to their large pore volume V = 14.4 cm3 g−1.

Triply-bridged disilver complexes [Ag2(μ2-dppa-P,P′)3(ani on)2] form selectively and are stabilised by many aromatic interactions.

Although phosphines have been less widely investigated in coordination self-assembly than have N- and O-donor ligands, interesting and unusual chemistry has been observed from their study in this context. This includes the selective formation of large rings, unsaturated as well as complete coordination cages, solvent- and anion-dependent aggregation, in addition to ring-opening polymerisation to give crystalline or non-crystalline coordination polymers. Important aspects which underpin this chemistry include (i) soft donor character, (ii) pyramidal geometry at the donor atom, (iii) highly bulky and irregular shapes, (iv) the applicability of (31)P NMR spectroscopy, and (v) their relevance to organometallic chemistry and homogeneous catalysis. In this critical review, findings which precede the concept of self-assembly as adopted by synthetic chemists as well as the latest 'supramolecular' chemistry of phosphines are discussed together in an attempt to give the current state of the topic in its historical context. Finally, some aspects and opportunities which may be of interest in the future are suggested (107 references).

Modification of Fe-tricarboxylate based metal–organic gels yielded tert-butyl substituted or phosphine-functionalised gels in alcohols or DMF, which were prepared from 5-tert-butylisophthalic acid and 5-diphenylphosphanylisophthalic acid, respectively. Owing to their permeability, such phosphine-functionalised metal–organic gels can act as a new type of functionalisable porous scaffold. The phosphorus-containing gel was subsequently functionalised with Pd(II) by immersion in a solution of Pd(COD)Cl2 (COD = 1,5-cyclooctadiene). The subsequently functionalised Pd(II)-immobilised gel and its xerogel/aerogel showed high activity in the catalysis of Suzuki C–C coupling comparable to unsupported complexes. The gel/xerogels could be reused under ambient atmosphere.

An array-based approach is put forward to obtain insight into reactivity under mechanochemical solvent-free conditions. We describe a survey of sixty potential reactions between twelve metal salts MX2 {(M = Cu, X2 = (OAc)2, (HCO2)2, (F3CCO2)2, (acac)2, (F6acac)2, (NO3)2, SO4; M = Ni, X2 = (OAc)2, (NO3)2, SO4; M = Zn, X2 = (OAc)2, (NO3)2} and five bridging organic ligands {isonicotinic acid (HINA), 1,4-benzenedicarboxylic acid (H2BDC), acetylenedicarboxylic acid (H2ADC), 1,3,5-benzenetricarboxylic acid (H3BTC), 4,4′-bipyridyl (BIPY). Reaction conditions involved a ball mill, applied for 15 min at 30 Hz, without external heating. When examined by XRPD, forty of the combinations gave detectable reactions, thirty-eight with crystalline products. Of these, twenty-nine reactions were quantitative (consuming all of at least one reactant). Comparison of XRPD patterns with patterns simulated from single crystal X-ray diffraction data in the Cambridge Structural Database allowed structural identification of six products. Of particular interest are the microporous framework materials [Cu(INA)2] and [Cu3(BTC)2] (HKUST-1) obtained by reaction of the corresponding carboxylic acids with copper acetate. Other non-porous polymers with 3-dimensional connectivity, [Ni(ADC)(H2O)4], or 1-dimensional connectivity, [Cu(acac)2(BIPY)] and [Cu(F6acac)(BIPY)] were also obtained. Reaction between zinc acetate and H2ADC gave a new product which had not previously been characterised by single-crystal X-ray crystallography, but whose XRPD pattern suggests that it is isostructural with the known nickel polymer [Ni(ADC)(H2O)4]. Two further isostructural nickel and zinc products were obtained in reactions between HINA and nickel nitrate and zinc nitrate. Trends observed within the array are discussed. Copper acetate and copper formate were the most effective starting materials for reaction with carboxylic acids, potentially related to the basicity of their anions and the solvating effects of the formic and acetic acid byproducts. Amongst the ligands there was a general negative corelation between melting point and reactivity. The issue of pore templating in microporous phases and the generation of new structures is also discussed in relation to the Cu(INA)2, Cu3(BTC)2 and nickel nitrate-BIPY systems. Overall, the study suggests that mechanochemical reactivity between metal salts and organic ligands under solvent free conditions is remarkably general. Use of array-based approaches as demonstrated here is advocated a useful way to reveal underlying trends in reactivity under solvent free mechanochemical conditions and to highlight particular cases for more detailed study.

The first enantiopure 4,4′-bipyridyls, 6, 8, and 9 have been prepared in four or five steps via bacterial dioxygenase-catalysed cis-dihydroxylation of 4-chloroquinoline1 and C–C coupling; ligands 6 and 9 are found to be effective building blocks for the preparation of chiral metal–organic frameworks as demonstrated with the rational synthesis of two pillared-grid structures [Zn2(fumarate)2(L)], which exhibit interesting structural and dynamic aspects.

Persilylation of nucleoside hydroxyls was effected in quantitative yields under solvent-free conditions using a ball mill. In addition, one-pot persilylation and acylation of cytidine was performed as an exemplar reaction demonstrating the utility of solvent-free approaches to nucleoside chemistry.

Biphenyl dioxygenase-catalysed cis-dihydroxylation of 2-chloroquinoline, 2-chloro-3-methylquinoline and 2-chloro-6-phenylpyridine substrates yielded the corresponding enantiopure cis-dihydrodiols; enantiopure 2,2'-bipyridines, synthesised in four steps from 2-chloroquinoline, proved to be efficient chiral ligands in catalytic asymmetric allylic oxidation and cyclopropanation reactions of alkenes.

Cystic fibrosis (CF) is characterized by excessive amounts of thick and tenacious mucous secretions that obstruct organ ducts and passages. In the respiratory tract this is associated with chronic infection resulting in the hypersecretion of purulent sputum, which the patient finds difficult to clear. We have studied the rheologic properties of purulent sputum from six patients with CF and five patients with chronic bronchitis to assess whether CF is associated with increased sputum viscoelasticity. In addition, we have isolated the major rheologic determinants, mucous glycoproteins, from CF and chronic bronchitis sputa and, using a magnetic microrheometer, investigated the possibility that the altered properties of mucus in CF are associated with abnormalities in these glycoproteins. Creep compliance analysis indicated that the CF sputa possessed raised levels of both elasticity (p less than 0.01) and viscosity (p less than 0.01). These increases in both rheologic parameters were found to be associated with increases in the DNA content (p less than 0.01) and dry weight (p less than 0.05). Mucous glycoproteins were isolated from CF and chronic bronchitis sputum samples by gel filtration on Sepharose CL4B, followed by concentration to form 8% wt/wt gels. In the absence of other sputum components, no abnormality in the rheologic properties of CF mucin gels could be detected. However, when DNA was added, the CF gels responded with increases in both elasticity and viscosity of as much as 30% (p less than 0.05), an effect not observed in the chronic bronchitis gels. These results suggest that a subtle abnormality may exist in CF mucous glycoproteins and that this could have a role in the altered physical properties of mucous secretions in CF.

We describe a new interpenetrated pillared-grid structure based on Cu(II) paddle-wheels, 4,4′-biphenyldicarboxylate and 4,4′-bipyridine, with 51% non-framework volume and which retains the same structure on desolvation.

In the presence of templating anions, 2:3 molar mixtures of triphos and silver(I) cations unexpectedly give novel hexanuclear cages, which result from an unusual ‘endo-methyl’ geometry of the triphos ligands.

The reaction of [Pd(cod)Cl2] (cod = cycloocta-1,5-diene) with rac-diphenyl[2.2]paracyclophanylphosphine PPh2(C16H15) affords trans-[Pd{PPh2(C16H15)}2Cl2] and [Pd{PPh2(C16H15)}Cl2]2 in approximately equal yield which co-crystallise to form an unusual solid-state material.

We describe the first solvent-free mechanochemical synthesis of a microporous metal–organic framework [Cu(INA)2] (INA = isonicotinic acid); the product has robust 3-dimensional connectivity and is obtained quantitatively by grinding together copper acetate and isonicotinic acid for 10 minutes without any applied heating—the high efficiency of the synthesis suggests that mechanochemical synthesis should be further investigated as a convenient method for the preparation of microporous metal–organic frameworks (MOFs).

Reaction of trans-[Pt(NC5H4CHBun2)2Cl2] 1 with an excess of HCCR (R = Ph, C6H4Me, C6H4NO2) affords the monomeric complex trans-[Pt(NC5H4CHBun2)2(CCR)2] (R = Ph 2a, C6H4Me 2b, C6H4NO2 2c), the trans arrangement of the alkynyl ligands being confirmed from spectroscopic data and by an X-ray analysis of 2c; when 1 is treated with 1 equiv. of HCCC6H2(Me)2CCH the polymer [Pt(NC5H4CHBun2)2CCC6H2Me2CC]n is formed, which is soluble in a range of organic solvents.

The new platinum complex [PtCl{C6H2(CH2NMe2)2-2,6-(CCH)-4}] exhibits a polymeric linear –CCH⋯ClPt–hydrogen-bonded structure in the solid state.

Tissue engineering involves seeding the patient's cells on to a three-dimensional temporary scaffold. It is becoming increasingly obvious that cells used to seed the scaffold have very specific requirements concerning the morphology and chemistry of the surface of the scaffold and its interconnectivity. A range of techniques has been examined in relation to key measurements such as pore size and porosity. Since capillary flow porometry measures a pore solely at its most constricted point, the method is unable to provide characterisation of other aspects of the pore. Scanning Electron Microscopy is limited to examining surface pores in ‘stiff’ scaffolds. Although cryo-SEM reduces the amount of ice-induced damage generated in ‘soft’ scaffolds upon freezing, the technique is limited to the same constraints. Images produced via scanning confocal microscopy are probably more representative of the true structure of the scaffold than that implied by cryo-SEM, although due to the diffuse nature of the image it is difficult to measure pore sizes.

The combination of directionality and unsaturated metal sites in bowl-shaped coordination clusters [Ag(4)L(3)(SbF(6))](3+){L = 2,4,6-tris(diphenylphosphino)triazine} results in the formation of discrete dimers on reaction with additional bridging ligands.

Recently, it has been found that the topologies of coordination polymers and their soluble discrete precursors are sometimes formally interrelated by ring-opening polymerisation (ROP), which has implications for the possible mechanisms by which coordination polymers form. Here, we describe unusual discrete bowl-shaped {Ag4L3} complexes which have a formal ROP relationship with a previously reported {Ag4L3}n porous 2-dimensional polymer (L = triphosphine). The discrete complexes are isolated for triphosphines based on heterocyclic cores [L = 1,3,5-tris(diphenylphosphino)triazine, or tris(diphenylphosphino)pyrimidine] whereas the previously-reported polymer was isolated for the corresponding benzene-cored ligand 1,3,5-tris(diphenylphosphino)benzene.

Metal-organic frameworks are a recently-identified class of porous polymeric material, consisting of metal ions linked together by organic bridging ligands, and are a new development on the interface between molecular coordination chemistry and materials science. A range of novel structures has been prepared which feature amongst the largest pores known for crystalline compounds, very high sorption capacities and complex sorption behaviour not seen in aluminosilicate zeolites. The development of synthetic approaches to these materials and investigations of their properties are reviewed.

The synthesis of the new diphosphine, 1,8-bis(diphenylphosphino) naphthalene ( 1a ), and its X-ray crystal structure are reported. Protonation of 1a gives a fluxional species to which a PP bonded structure is assigned. Despite the strain apparent in the solid state due to the proximity of the diphenylphosphino groups, it appears that 1a has a normal coordination chemistry with platinum(II) and palladium(II).