Trigonal pyramidal Cu^IN₄ cores assembled by a family of tetradentate N-donor Schiff bases. Substituent effects on the Cu(II/I) potential

Abstract

Copper(I) complexes of 1:3 condensates of tris(2-aminoethyl)amine and <i>p</i>-X-benzaldehydes (X = H, Cl, NMe₂ and NO₂) of the type [Cu(ligand)]ClO₄ are synthesised. The X-ray crystal structures of the copper(I) complexes with X = H, Cl and NMe₂ are determined. In these complexes copper(I) is found to have trigonal pyramidal N₄ coordination sphere with the

apical N forming a longer bond (2.191-2.202Å) than the trigonal ones (2.003-2.026Å). The Cu(II/I) potentials in these complexes span a range of 0.71-0.90 V vs SCE increasing linearly with the resonance component of the Hammett σ for the <i>para </i>substituent X. It is concluded that trigonal pyramidal geometry is destabilising for copper (II).