Electron spin resonance spectra and conformations of Group 2 ion complexes with a semidione ligand

Abstract

The triplet states of the complexes formed between the semidione 1,1,4,4-tetramethyltetralin-2,3-dione and Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Zn²⁺ have been studied by e.s.r. spectroscopy in frozen solutions of 2-methyltetrahydrofuran. The e.s.r. spectrum of [Al(tmtd)₃][tmtd = 1,1,4,4-tetramethyltetralin-2,3-dionate(1–)] has been attributed to a quartet state. The zero-field splitting parameters for the [M(tmtd)₂] complexes have been obtained and compared with those calculated by electron dipole–dipole interaction for a number of conformations of the complexes. The conformations giving the best fit are reported. The discrepancy between experimental and calculated zero-field splitting parameters for the complexes of Sr²⁺ and Ba²⁺ has been explained by an additional spin–orbit contribution.