Syntheses, crystal structures, and electrochemical properties of binuclear copper(II,II)[Cu2L1Cl2][ClO4]2·4CH3CN and copper(I,I)[Cu2L1][ClO4]2 complexes {L1= 2,5-bis[N,N-bis(2′-pyridylethyl)aminomethyl]pyrazine}

Abstract

The binuclear copper(II,II) and copper(I,I) complexes [Cu₂L¹Cl₂][ClO₄]₂·4CH₃CN (1) and [Cu₂L¹][ClO₄]₂(2){L₁= 2,5-bis[N,N-bis(2′-pyridylethyl)aminomethyl]pyrazine} have been synthesized. Crystal structures of both complexes have been determined. Complex (1) crystallizes in the triclinic space group P with a= 13.140(3), b= 13.541(4), c= 8.217(2)Å, α= 101.43(4), β= 87.44(3), γ= 117.50(2)°, and Z= 1; complex (2) crystallizes in the triclinic space group P with a= 10.264(6), b= 12.473(5), c= 9.213(2)Å, α= 89.92(2), β= 113.19(3), γ= 113.74(3)°, and Z= 1. The complex cations in (1) and (2) have centrosymmetric binuclear structures with copper atoms in distorted square pyramidal and pyramidal geometries respectively. E.s.r. and magnetic susceptibility data of (1) show the absence of a strong magnetic interaction between the copper atoms. In acetonitrile complex (1) shows a quasi-reversible cyclic voltammogram with E_Pc and E_Pa values at –0.09 and 0.06 V vs. Ag–AgCl. Controlled-potential electrolysis upon complex (1) demonstrates that the process involves the transfer of two electrons. The two-step reduction potentials leading to Cu^II–Cu^I and Cu^I–Cu^I from Cu^II–Cu^II were estimated to be at 0.04 and –0.07 V, respectively.