Aluminum chloride-urea ionic liquid was investigated by Lewis acid-base titration with chloride ions for its active species concentration with the aide of electronic spectroscopy. A coordination bonds between aluminum cationic species of the ionic liquid and the aromatic ring of toluene or benzene was assumed to be responsible for new bands formed in visible and ultraviolet regions.Upon Lewis acid-base titration these bands was found to disappear and the concentration of the acidic species therefore was elucidated to be around 75 mole % of the initial aluminum chloride used to prepare a 1.5 mole aluminum chloride to 1 mole urea ionic liquid. The product of this reaction was assumed to be between mole acidic species to mole chloride ion according to the mole fraction elucidated graph.The behavior of some transition metal compounds (chlorides and sulfates) of (Cu(II), Co(II) and Ni(II)) coordination in the ionic liquid was also investigated in this ionic liquid by electronic spectroscopy. Cobalt chloride showed a different behavior than the distorted octahedral geometry of copper chloride as it reacted with the anionic species to precipitate as form of a tetrahedral complex containing urea, aluminum and chloride ions. The behavior of nickel sulfate in the ionic liquid also showed an acid-base reaction with the acidic species of ionic liquid as the bands at 334 nm and 474 nm decreased with increasing the salt concentration. The coordination of Ni(II) cation was found to be an octahedral geometry with stronger ligand field effect. Similar strong ligand field was also observed with copper sulfate which showed four bands resulted from separating metal d-orbitals more obviously than the tetragonal John-Teller effect found with copper chloride in same ionic liquid.
