From bio-based to halide-free, greener ionic liquids: synthesis and application.

During this PhD thesis, we focused on the possibility to obtain greener ionic liquids using halide- free alkylating agents or bio-based feedstocks. A systematic study of viscosities and refractive indices has been carried out on 1-alkyl- 3- methylimidazolium based ionic liquids (alkyl = methyl, butyl and hexyl) combined with three phosphorous containing anions, i.e. dimethylphosphate, methyl methylphosphonate and methylphosphonate. Despite the structural similarity of these anions, the resulting ILs show significantly different viscosities which increase on increasing alkyl chain length on cation. On the contrary, no correlation between refractive index and IL structure was observed. Ab initio theoretical calculations have been carried out to rationalized the observed behavior. These ILs have been employed with success in essential oil extraction from different matrices (cinnamom cortex, fennel seeds and cumin seeds) using different techniques (microwave, ultrasound). We also report a detailed study on the application of dimethylimidazolium methylphosphite as phosphorilating agent in carbohydrate chemistry. Furthermore, chiral ILs and Bio-based ILs have been prepared in high yield and high purity using commercial propylene oxide and natural chiral alcohols as building blocks. The impact of alkyl chain length and the chiral center in cation on the physico-chemical properties of the resulting salts has been evaluated. Circular Dichroism (CD) and X-ray Photoelectron Spectroscopy (XPS) have been used to demonstrate the assembly and layering of these ionic liquids. The self-assembly at the interface IL/vacuum, investigated for some couples of enantiopure and racemic CILs, show that the presence of a chiral centre on the cation side chain and the enantiomeric purity of the related imidazolium based CILs can affect the orientation and layering of the liquid components in the outmost regions of the interface. Furthermore, we have studied the influence of the obtained bio based ionic liquids as solvents and/or directing morphology agents in the synthesis of some metal oxides. The influence of the employed ILs over the morphology and crystal structure of the nanoarchitectures was investigated by TEM, STEM-EDX measurements.