Cyclometalation: 2,6-diphenylpyridine complexes of platinum

This thesis describes the synthesis and characterisation of novel cycloplatinated 2,6- diphenylpyridine complexes and an interesting platinum carbene complex formed by an unusual intermolecular C-H activation. 2,6-Diphenylpyridine, 2,6-bis(4'-alkoxyphenyl)pyridines, 4-(4-octyloxyphenyl)-2,6- diphenylpyridine and 2,4,6-tris-(4-alkoxyphenyl)-[1,3,5]triazine have all been mono- cycloplatinated to from chloride bridged dimers. These dimers have been cleaved with various ligands including trimethylphosphine, dimethylsulfoxide and carbon monoxide. The synthesis and characterisation of the cyclometalated products of 2- phenylpyridine, and subsequent oxidation to a platinum(IV) complex has been described. A novel high yield synthetic route to the di-cycloplatination of C"N"C type ligands involving a C-H activation induced by water has also been reported. The synthesis of di- cycloplatinated 2,6-diphenylpyridine, 2,6-bis( 4'-alkoxyphenyl)pyridines and 4-(4'- octyloxyphenyl)-2,6-diphenylpyridine ligands has been recorded. The lability of the dimethylsulfoxide ligand used in the di-cyclometalation reaction is demonstrated by its substitution with trimethylphosphine, carbon monoxide and the stilbazole ligand. Thermal analyses of all the ligands and cyclometalated products have been recorded. The mesogenic behaviour of four materials has been described and discussed. This report also includes a synthetic route to a platinum carbene dimer formed from a 2,6-bis(2',4'-alkoxyphenyl)pyridine ligand

Microfluidic-Based Formulation of Essential Oils-Loaded Chitosan Coated PLGA Particles Enhances Their Bioavailability and Nematocidal Activity

In this study, poly (lactic-co-glycolic) acid (PLGA) particles were synthesized and coated with chitosan. Three essential oil (EO) components (eugenol, linalool, and geraniol) were entrapped inside these PLGA particles by using the continuous flow-focusing microfluidic method and a partially water-miscible solvent mixture (dichloromethane: acetone mixture (1:10)). Encapsulation of EO components in PLGA particles was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction, with encapsulation efficiencies 95.14%, 79.68%, and 71.34% and loading capacities 8.88%, 8.38%, and 5.65% in particles entrapped with eugenol, linalool, and geraniol, respectively. The EO components’ dissociation from the loaded particles exhibited an initial burst release in the first 8 h followed by a sustained release phase at significantly slower rates from the coated particles, extending beyond 5 days. The EO components encapsulated in chitosan coated particles up to 5 μg/mL were not cytotoxic to bovine gut cell line (FFKD-1-R) and had no adverse effect on cell growth and membrane integrity compared with free EO components or uncoated particles. Chitosan coated PLGA particles loaded with combined EO components (10 µg/mL) significantly inhibited the motility of the larval stage of Haemonchus contortus and Trichostrongylus axei by 76.9%, and completely inhibited the motility of adult worms (p < 0.05). This nematocidal effect was accompanied by considerable cuticular damage in the treated worms, reflecting a synergistic effect of the combined EO components and an additive effect of chitosan. These results show that encapsulation of EO components, with a potent anthelmintic activity, in chitosan coated PLGA particles improve the bioavailability and efficacy of EO components against ovine gastrointestinal nematodes

Benign approaches for the synthesis of bis-imine Schiff bases

Pure bis-imine Schiff bases are readily accessible in high yield, typically >95%, when aliphatic diamine/aldehyde condensation reactions are carried out under solvent-free conditions or in poly(propyleneglycol) (PPG) as a recyclable reaction medium, with negligible waste

Cyclometallated platinum(II) complexes : oxidation to, and C-H activation by, platinum(IV)

A series of cyclometallated phenylpyridine platinum(II) complexes have been synthesised with a systematic variation in both the phenylpyridine and the ancillary ligand. Oxidation of one of the cyclometallated species leads to a number of isomeric platinum(IV) complexes, all of which eventually isomerise to a single compound. The route to these new compounds has been demonstrated to involve an initial slow oxidation followed by a rapid C-H activation to give doubly cyclometallated complexes. The solid state structures of a number of both the platinum( II) and the platinum(IV) species have been solved; many of the structures exhibited extended interactions that result in complex three dimensional packing