An electron spin resonance study of the structure of dinuclear titanium-(III), vanadyl, and copper(II) chelates of tetrakis(aminomethyl)methane

Abstract

The triplet-state X-band e.s.r. spectra, recorded at sample temperatures of 77 K, due to dinuclear titanium(III), copper(II), and vanadyl ion chelates of tetrakis(aminomethyl)methane which exist in frozen aqueous glycol solution have been interpreted in terms of an interaction spin Hamiltonian which takes into account the symmetry imposed on the paramagnetic ion-pair system by the ligand and which results in a non-parallel alignment of the g-tensor axes of the individual paramagnetic ions. Computer simulation of the lineshapes of the triplet-state e.s.r. spectra has been carried out for cases involving isotropic g-values and anisotropic g-values and in the presence and absence of hyperfine interactions. These calculations are relevant to the determination of the magnetic parameters associated with the dinuclear complexes of titanium(III), copper(II), and vanadyl ions formed by combination with the spiro-amine. The parameter of chief interest is the distance between the magnetic point dipoles which in each case has been related to the internuclear separation of the metal ions in the dinuclear complex by use of molecular models.