Environment of Al3+ Ion and Transsolvation Process in Water–Urea Solutions of Aluminum Chloride

Abstract

Reaction of aluminum chloride crystalline hydrate AlCl₃(H₂O)₆ and urea in solid state and AlCl₃(H₂O)₆–CO(NH₂)₂–H₂O and AlCl₃(CO(NH₂)₂)₆–H₂O aqueous solutions has been studied. Analysis of IR spectra of studied samples showed that complete substitution of water molecules in the first coordination sphere of Al³⁺ ion by urea molecules occurs at the molar ratio Al : CO(NH₂)₂ = 1 : 6 in solid and liquid phase. Computation of structures, IR spectra, and energy parameters for (CO(NH₂)₂)₂, CO(NH₂)₂(H₂O)₂, CO(NH₂)₂(H₂O)₄, \({\text{Al}}\left( {{\text{CO}}{{{\left( {{\text{N}}{{{\text{H}}}_{2}}} \right)}}_{2}}} \right)_{6}^{{3 + }},\)\({\text{Al(CO(N}}{{{\text{H}}}_{2}}{{)}_{2}})_{{6\,\, + \,\,6}}^{{3 + }}\), and \({\text{Al(CO(N}}{{{\text{H}}}_{2}}{{)}_{2}}{{)}_{6}}({{{\text{H}}}_{2}}{\text{O}})_{3}^{{3 + }}\) complexes was performed using DFT (B3LYP-6-31++G(d,p)) method. On the basis of obtained data, competition between water and urea molecules in AlCl₃(CO(NH₂)₂)₆ aqueous solutions has been studied and experimental results have been explained.