Electron paramagnetic resonance of Cu2+ in dibarium zinc formate tetrahydrate

Abstract

X-Band e.p.r. spectra of Cu²⁺-doped single crystals of fully deuteriated dibarium zinc formate tetrahydrate, Ba₂Zn(DCO₂)₆,4D₂O, have been investigated at 77°K. Spectra of magnetically dilute single crystals (Cu : Zn = 1 : 1000) have been analysed in terms of an axially symmetric spin Hamiltonian with the following parameters: g_∥= 2·391 ± 0·003; g_⊥= 2·079 ± 0·003; A(⁶³Cu)=±0·0130 ± 0·0001 cm.^–1, B(⁶³Cu)=∓0·0020 ± 0·0001 cm.^–1; Q′(⁶³Cu)=∓0·00093 ± 0·00006 cm.^–1; A(⁶⁵Cu)=±0·0139 ± 0·0001 cm.^–1; B(⁶⁵Cu)=∓0·0020 ± 0·0001 cm.^–1. Superhyperfine interaction with ¹³C present in labelled formate ligands has been detected and the isotropic contribution to this coupling found to be 0·00068 ± 0·00001 cm.^–1. The spin Hamiltonian parameters have been equated to the atomic orbital coefficients in some of the molecular orbitals involved in bonding in the complex ion [Cu(DCO₂)₄2D₂O]^2– in the paramagnetic species encountered in this compound. Spin Hamiltonian parameters and electron distributions in this ion are compared with those deduced for the complex ions [Cu(DCO₂)₆]^4– and [Cu(DCO₂)₂,4D₂O] present in deuteriated cupric formate dihydrate. Spin polarisation in [Cu(DCO₂)₄2D₂O]^2– is discussed.