Syntheses of new copper(II) mixed-ligand complexes and their chromotropic properties in solution and in the solid state

Abstract

Reaction of acetylacetone (Hacac) with aldehyde (RCHO; R =p-MeOC₆H₄, p-ClC₆H₄ or Ph) in 2 : 1 mol ratio resulted in the formation of new triketones (HL²), which were previously characterized as bis(β-diketones) of the type [(MeCO)₂CHCHRCH(COMe)₂](H₂L¹). Mixed-ligand copper(II) complexes with N,N,N′,N′-tetramethylethane-1,2-diamine (tmen) and the β-diketonate moiety of these triketones, [CuCl(L²)(tmen)], were synthesized and their solvatochromic properties in organic solvents (due to the acceptor properties of the solvent) investigated. The colour of these five-co-ordinated complexes in the solid state gradually changes from green in [CuCl(L²)(tmen)] through bluish green, [CuCl(L²)(tmen)]·CH₂Cl₂, to blue, [CuCl(L²)(tmen)]·MeOH·CH₂Cl₂. Crystallographic studies showed that this phenomenon arises from an intermolecular hydrogen bond between the co-ordinated chloride of one complex and the OH group of a triketonate ligand of an adjacent complex and/or cocrystallized MeOH molecule.