Biomedical subjects
Publications and source records attributed to Mark R Sambrook.
We have produced the fullerene dimers C(120), C(120)O, and C(120)O(2) by a high-speed vibration milling technique. The thermal stability of C(120), C(120)O, and C(120)O(2) has been studied in the temperature range 150-350 degrees C for up to 4 h under vacuum. The bridging oxygen atoms were found to substantially increase the stability of the fullerene dimer molecules.
In this communication we demonstrate a directly-bonded crystalline fullerene superlattice and show that the incorporation of spin-active N@C60 endohedral fullerenes is readily achieved to give an atomic-molecular hybrid spin-active superlattice material.
Anion templation is used to develop a general method for rotaxane synthesis. The anion-templated synthesis of three new [2]rotaxanes containing positively charged pyridinium axles and neutral isophthalamide macrocyclic components is described. The incorporation of electron withdrawing substituents, such as the nitro group, into the 5-position of an isophthalamide bis-vinyl acyclic precursor results in a significant improvement in [2]rotaxane assembly yields. Rotaxane anion binding strengths are also enhanced whilst the rotaxane's unique interlocked binding domain ensures selectivity for chloride--the templating anion--is maintained.
The rational development of a general anion templation strategy for the construction of a variety of interpenetrated and interlocked molecular structures based upon the coupling of anion recognition with ion-pairing is described. The success of this anion templation methodology is demonstrated with the halide anion directed assembly of a series of novel [2]pseudorotaxanes containing pyridinium, pyridinium nicotinamide, imidazolium, benzimidazolium and guanidinium threading components and anion binding macrocyclic ligands. Interlocked [2]rotaxane and [2]catenane molecular structures are also synthesised using this anion templation protocol. These interlocked structures feature unique topologically defined hydrogen bond donating binding domains that exhibit a high degree of selectivity for chloride, the templating anion. A series of rhenium(I) bipyridyl containing [2]pseudorotaxane assemblies and a [2]rotaxane further highlight the potential this strategic anion templation approach has in future chemical sensor design and fabrication.
A wide range of pseudorotaxane assemblies containing positively charged pyridinium, pyridinium nicotinamide, imidazolium, benzimidazolium and guanidinium threading components, and macrocyclic isophthalamide polyether ligands have been prepared using a general anion templation procedure. In noncompetitive solvent media, coupling halide anion recognition by a macrocyclic ligand with ion-pairing between the halide anion and a strongly associated cation provides the driving force for interpenetration. Extensive solution 1H NMR binding studies, thermodynamic investigations, and single-crystal X-ray structure determinations reveal that the nature of the halide anion template, strength of the ion-pairing between the anion template and the cationic threading component, and to a lesser extent favorable second sphere pi-pi aromatic stacking interactions between the positively charged threading component and macrocyclic ligand, together with macrocyclic ring size, affect the efficacy of pseudorotaxane formation.
The first example of a [2]catenane structure to be synthesized using anion templation is described. The nature of the anion template is demonstrated to be crucial to the assembly process, with only chloride anion producing the [2]catenane in acceptable yield. Anion binding studies reveal a dramatic catenation effect on anion selectivity properties as compared to a noncatenated acyclic receptor.
A series of new photo-active rhenium(i) bipyridyl based pseudorotaxane complexes is assembled via halide anion templation.
The development of an acyclic chloride anion template in which the chloride anion is coordinatively unsaturated and available for subsequent complexation to various hydrogen bond donating components is described. This template orients a neutral hydrogen bond donating ligand and a pyridinium cation orthogonally to one another. Incorporation of second-sphere interactions between the ligand and the pyridinium cation improved the efficacy of the chloride template. These results were exploited in the construction of a chloride anion-templated [2]rotaxane which, after anion template removal, was studied with regards to its anion recognition properties. Encirclement of the neutral macrocycle around the dumbbell-shaped pyridinium cation in the [2]rotaxane produced a dramatic increase in its selectivity for chloride anions as compared to the noninterlocked cation. This is interpreted as a function of the anion template used to create the [2]rotaxane superstructure.