Green Chemistry aims to modify chemical processes so that they are more
friendly to the environment. The 9th principle of Green Chemistry emphasises the
use of catalytic reagents in chemical processes. One way in which ionic liquids
can implement this principle is in two-phase catalytic processes. A major
drawback of homogenous catalysis processes is associated with the separation of
the catalyst from the products. This can be solved by the use of biphasic catalysis,
in which the catalyst can be reused several times without any significant changes
in its catalytic performance.
However, it is vital to understand how catalysts interact with the solvents in a
biphasic solvent system. On one hand, it is advantageous to use an ionic form of
catalyst (e.g Cu2+) because this improves the retention of the catalyst in the ionic
liquid. However, using charged ions affects their catalytic performance, because
their coordination characteristics are changed. Many catalysts are transition metal
complexes. Therefore, a solvatochromic transition metal is an ideal probe to study
the behaviour of ionic liquid, specifically how do the non-coordinating anions in
ionic liquids coordinate to metal centres?
In this thesis, a set of solvatochromic copper complexes with different charges
were synthesised and characterised. The monocationic complexes had the form
[Cu(acac)(tmen)]X (acac = acetylacetonate, tmen = tetramethylethylenediamine)
where X were Cl⁻, [NO3]⁻, [SCN]⁻, [OTf]⁻, [NTf2]⁻ and [PF6]⁻. The neutral complex
was Cu(hfac)2 (hfac = hexafluoroacetonate). A set of non-functionalised ionic
liquids and functionalised ionic liquids (FIL) containing hydroxyl, nitrile and
ketone groups were also synthesised and characterised. The Kamlet-Taft multi
parameter polarity scales were used to study the solvent-solute interactions of the
ionic liquids by means of dipolarity/polarizability (π*), hydrogen bond donating
ability (α) and hydrogen bond accepting ability (β). The UV-Vis absorption
spectra of the complexes were measured in solid state, dichloroethane and ionic
liquid solutions. Analysis of these spectra suggested all these weakly coordinating
anions coordinate with the copper centre in a different manner depending on the
How do Non-coordinating Anions in Ionic Liquids coordinate to Metal Centres
coordinating ability of the anion and also the charge of the copper centre. The
coordination mode and the order of binding strength for the individual anions
were fully studied and analysed. The correlation between νmax and solvent donor
number was investigated by measuring UV-vis spectra in a range of molecular
solvents, and was used to predict the donor numbers of the ionic liquid solvents.
The apparent donor number of ionic liquids was also predicted using the value
from the spectra measured in ionic liquids. The effect of functionalised groups in
ionic liquids on donor ability has also been investigated by comparing the results
from non-functionalied and functionalised ionic liquids