The impact of ionic liquids on the coordination of anions with solvatochromic copper complexes

Abstract

Solvatochromic transition metal (TM)-complexes with weakly associating counter-anions are often used to evaluate traditional neutral solvent and anion coordination ability. However, when employed in ionic liquids (IL) many of the common assumptions made are no longer reliable. This study investigates the coordinating ability of weakly coordinating IL anions in traditional solvents and within IL solvents employing a range of solvatochromic copper complexes. Complexes of the form [Cu(acac)(tmen)][X] (acac = acetylacetonate, tmen = tetramethylethylenediamine) where [X] = [ClO], Cl, [NO], [SCN], [OTf], [NTf] and [PF] have been synthesised and characterised both experimentally and computationally. ILs based on these anions and imidazolium and pyrrolidinium cations, some of which are functionalised with hydroxyl and nitrile groups, have been examined. IL-anion coordination has been investigated and compared to typical weakly coordinating anions. We have found there is potential for competition at the Cu-centre and cases of anions traditionally assigned as weakly associating that demonstrate a stronger than expected level of coordinating ability within ILs. [Cu(acac)(tmen)][PF] is shown to contain the least coordinating anion and is established as the most sensitive probe studied here. Using this probe, the donor numbers (DNs) of ILs have been determined. Relative donor ability is further confirmed based on the UV-Vis of a neutral complex, [Cu(sacsac)] (sacsac = dithioacetylacetone), and DNs evaluated viaNa NMR spectroscopy. We demonstrate that ILs can span a wide donor range, similar in breadth to conventional solvents.

Investigation of Chromophoric Behavior of Water‐Soluble LaIII‐CuII Polynuclear Metallamacrocyclic 15‐MC‐5 Complex

“…Among the chromophoric metal complexes whose color changes arise from the d–d transitions, the copper(II) compounds are the most promising candidates for biomedical sensor applications . The solution behavior of the mixed‐ligand Cu II complexes in various media depends mainly on the coordination of solvent molecules or anions to the complex , . The classic solvatochromic Cu II mixed‐ligand chelate complexes developed by Fukuda bear diketonato and diamine ligands and belong to the Cu(O,O)(N,N) compounds .…”

Lignosulfonate/Dicationic Ionic Liquid Composite as a Task-Specific Catalyst Support for Enabling Efficient Synthesis of Unsymmetrical 1,3-Diynes with A Low Substrate Ratio

“…As we mentioned above, the polyanionic material sodium lignin sulfonate tended to react easily with polycationic species in water to generate the hydrophobic solid. Then a water-soluble dicationic imidazolium salt (DIS) was synthesized by the quaternization reaction of N -methylimidazole and bis­(2-chloroethyl)­amine hydrochloride in alcohol under reflux condition. , Afterward, the DIS was added dropwise to the aqueous solution of sodium lignosulfonate, thus generating a hydrophobic dicationic imidazolium salt/lignosulfonate solid composite via ion exchange process (denoted as DIS@LS, Figure ). To immobilize TMEDA fragment, the as-prepared DIS@LS composite was then treated with divinyl sulfone and N 1 , N 1 , N 2 -trimethylethane-1,2-diamine via a consecutive twice Michael addition reactions (Figure ).…”

Gutmann’s Donor and Acceptor Numbers for Ionic Liquids and Deep Eutectic Solvents

“…The probe ferrocyphen was purchased from BOC Science and used without further purifying. The probe Cu(acac)(tmen) + ClO 4 ⁻ was synthetized using the procedure indicated in the literature ( Kuzmina et al, 2017 ) and purified through hot filtration and recrystallization.…”