Fabrication of 3-dimensional cellular constructs via microstereolithography using a simple, three-component, poly(ethylene glycol) acrylate-based system.

A novel method for the production of inhibitor- and solvent-free resins suitable for three-dimensional (3D) microstereolithography is reported. Using an exemplar poly(ethylene glycol)-based resin, the control of features in the X, Y, and Z planes is demonstrated such that complex structures can be manufactured. Human mesenchymal stem cells cultured on the manufactured scaffolds remained viable during the 7 day assessment period, with proliferation rates comparable to those observed on tissue culture polystyrene. These data suggest that this novel, yet simple, method is suitable for the production of 3D scaffolds for tissue engineering and regenerative medicine applications.

Structural and electronic modulation of magnetic properties in a family of chiral iron coordination polymers.

The complexes FeL(2) [L = bidentate Schiff base ligands obtained from (R)-(+)-α-phenylethanamine and 4-substituted salicylaldehydes, substituent R = H, (t)Bu, NO(2), OMe, CN, OH] react with ditopic proligands 1,4-pyrazine (pz) or 4,4'-bipyridine (bpy), to give a family of optically pure Fe(II) polymeric chain complexes of formula {FeL(2)(µ-pz)}(∞) and {FeL(2)(µ-bpy)}(∞). Crystallographic studies show that a range of structures are formed including unidirectional and bidirectional linear polymers and canted zigzag chains. Interchain interactions via π-contacts and hydrogen bonding are also observed. SQuID magnetometry studies on all of the complexes reveal antiferromagnetic interactions, the magnitudes of which are rationalized on the basis of substituent electronic properties and bridging ligand identity. For complexes with bridging pz, the antiferromangnetic interaction is enhanced by electron-releasing substituents on the Fe units, and this is accompanied by a contraction in the intrachain distance. For complexes bridged with the longer bpy the intrachain antiferromagnetic couplings are much weaker as a result of the longer intrachain distance. The magnetic data for this series of chain complexes follow a Bonner-Fisher 1D chain model, alongside a zero field splitting (ZFS) model for Fe(II) (S = 2) as appropriate. The intrachain antiferromagnetic coupling J values, g-factors, and the axial ZFS parameter D were obtained.

TTF salts of optically pure cobalt pyridine amidates; detection of soluble assemblies with stoichiometry corresponding to the solid state.

Optically pure anionic complexes of pyridinecarboxamide ligands, N(2),N(6)-bis((R)-α-methylbenzyl)pyridine-2, 6-dicarboxamide H(2)(R,R-L(1)) and N(2),N(6)-bis((S)-1-methoxypropan-2-yl)pyridine-2, 6-dicarboxamide H(2)(S,S-L(2)) have been synthesised and fully characterised. The complexes: (18-crown-6)K[Co(III)(R,R-L(1))(2)], (18-crown-6)K[Fe(III)(R,R-L(1))(2)] and K[Co(III)(S,S-L(2))(2)]·3H(2)O show interesting extended structures from 0D discrete units through 1D zigzag chains to 2D honeycomb layers. The complex anions were used in the synthesis of radical cation salts with tetrathiafulvalene (TTF). The salts (TTF)[Co(III)(R,R-L(1))(2)] and (TTF)[Co(III)(S,S-L(2))(2)]·EtOAc were characterised by single crystal X-ray diffraction and conductivity measurements. Both compounds comprise mono-oxidised TTF molecules and exhibit similar layered structures with no direct TTF stacking but in which phenyl substituents from the complex anion or co-crystallised ethyl acetate alternate with TTF(+) units. Solution spectroscopic and cyclic voltammetric evidence points to the formation of soluble assemblies between TTF(+) and the counterion which correspond to the stoichiometry observed by crystallography and other methods in the solid state.

Development of amino-oxazoline and amino-thiazoline organic catalysts for the ring-opening polymerisation of lactide.

The ring-opening polymerisation of lactide by a range of amino-oxazoline and amino-thiazoline catalysts is reported. The more electron-rich derivatives are demonstrated to be the most highly active and polymerisation is well controlled, as evidenced by the linear relationship between the molecular weight and both the monomer conversion and the monomer-to-initiator ratio. Mechanistic studies reveal significant interactions between the monomer, initiator and catalyst and that the polymerisation is first order with respect to each of these components. These observations indicate that the polymerisation operates by a general base/pseudo-anionic mechanism.

Chirality and diastereoselection in the mu-oxo diiron complexes L(2)Fe-O-FeL(2) (L = bidentate salicylaldiminato).

A number of bis(salicylaldiminato) (Schiff base) complexes of Fe(II) i.e. L(2)Fe with a variety of ligand substituents and functionality are synthesised, usually by salt metathesis but on one occasion via the (sal)(2)Fe complex, and characterised by standard methods. Two molecular structure determinations indicate the expected tetrahedral geometry. Treatment with dry oxygen yielded the Fe(III) complexes [(FeL(2))(2)-mu-O], generally in high yield and in the absence of hydroxylated impurities; one bulky complex L(2)Fe gave no oxidation product for steric reasons, and one hydroxyl-substituted compound gave an insoluble product. Five molecular structures of these [(FeL(2))(2)-mu-O] compounds were determined. All were homochiral in the sense that the absolute configuration at Fe was the same for both atoms. Three of the structures - those based on optically pure salicylaldimine ligands - were diastereomeric. For two, the diastereomers observed are those predicted on the basis of steric considerations, while a third highly distorted and congested structure represents the unexpected diastereomer. Powder X-ray diffraction confirms high phase purity of the bulk samples (i.e. they are diastereomerically pure to the level detectable). These investigations, coupled with molecular structure and NMR studies on model gallium complexes, indicate that the diastereoselection arises from cooperative interactions across the oxo bridge.

Synthesis of Poly(lactide)s with Modified Thermal and Mechanical Properties.

The use of poly(lactide)-based materials is, in part, limited by their physical and mechanical properties. This article reviews the methods that have been employed to enable enhancement of the materials properties through synthetic manipulation of the polymer structure including block copolymer synthesis and modification of the lactide monomer structure, focusing on the application of ring-opening polymerization. In turn the effect of these structural modifications on the properties of the resultant materials are reported.