EPR Spectra of Alkoxy and Mixed Alkyl-Alkoxy Substituted Aryl β Diketonates of Discotic Copper Complexes 1: Computer Analysis to Identify the Quadrupole Forbidden Transitions

Abstract

The solid state Q band EPR spectra of the mixed octyl-octyloxy substituted aryl β diketonate of Cu-(II) resemble to a great extent the quadrupole-cum-hyperfine spectrum of C₈OCu. Since the spectra in both cases arise from overlapping lines, one could not assign the quadrupole forbidden lines directly from the spectra. Thus two very weak hyperfine quartets from Δm = 0 in the computed spectra, is not observed in the experimental spectra, which start with a single line from Δm = ±1, followed by the first quadrupolar forbidden doublet (not resolved) from Δm = ±2 with admixture from Δm = ±1. The situation is the same on the other side. Between the first doublet and the partially resolved middle doublet lies the strong hyperfine line from Δm = 0. So also is the case between the middle doublet and the third unresolved doublet. The middle doublet (partially resolved in C₈OCu but not resolved in the mixed complex) results from two very strong Δm = ±2 lines with an admixture of a very weak Δm = ±1 for each line. So the present work identifies all the quadrupolar forbidden transitions present. Since the dimer is the basic repeating unit in both systems, the resemblance in the spectra is not unexpected. The subtle differences viz., partial splitting of the middle doublet in C₈OCu and presence of shoulders in the outer doublets as against symmetric doublets in the mixed complex, possibly arise from its larger hyperfine (B) term. However the ‘Q’ parameter has the same value in both cases.