Structural studies of trans-N 2S 2 copper macrocycles

Abstract

The X-ray crystal structures of two related trans-N 2S 2 copper macrocycles are reported. One was isolated with the copper in the divalent form and the other with copper in its univalent form affording a valuable insight into the changes of geometry and metrical parameters that occur during redox processes in macrocyclic copper complexes. A variable temperature NMR study of the copper(I) complex is reported, indicative of a chair-boat conformational change within the alkyl chain backbone of the macrocycle. It was possible to extract the relevant kinetic and thermodynamic parameters (ΔG ‡, 57.8 kJ mol −1; ΔH ‡, 52.1 kJ mol −1; ΔS ‡, −19.2 J K −1 mol −1) for this process at 298 K. DFT molecular orbital calculations were used to confirm these observations and to calculate the energy difference (26.2 kJmol −1) between the copper(I) macrocycle in a planar and a distorted tetrahedral disposition.