Epr study of the anisotropic interaction parameter of dichlorobis ( r|-cyclopentadienyl )‎ vanadium in chloroform

الملخص EN

The temperature dependent EPR line widths of a paramagnetic species, [dichlorobis(ri-cyclopentadienyl)vanadium] or [V(T|5-CJHJ)2C12], abbreviated as Cp2VCl2, were measured in chloroform at X band.

An analysis of the temperature dependent EPR line widths of Cp2VCl2 in chloroform in the motional narrowing region was carried out, using the four sets of the magnetic parameters available in the literature.

It was found that only those from Petersen and Dahl [J.

L.

Petersen and L.

F.

Dahl, /.

Am.

Chem.

Soc, 97 (1975), p.

6422.] could explain our line width data.

Our analysis in chloroform is in agreement with our results in toluene and suggests that Cp2VCl2 exhibits anisotropic rotational diffusion with N = 2.1 ± 0.7 at an axis z' = y, where N is the ratio RJRX; R^ is the rotational diffusion constant along the molecular z axis; and Rx is the rotational diffusion constant perpendicular to the molecular z axis.

This value is consistent with the TV value obtained from the Stokes-Einstein model (N = 3.3) and the allowed-values equation, AVE, with p, = 3.02 py - 7.18.

The AVE is not consistent with isotropic reorientation and is only consistent with axial symmetry if px = 1, py = 2.71.

The anisotropic interaction parameter k, which is a measure of the anisotropy of intermolecular interactions, was found to be 0.156.

The k value of 0.156 showed that Cp2VCl2 in chloroform is less slip than Cp2VCl2 in toluene (its k is 0.044).

Therefore, it seems that the K value increases with increasing solute-solvent interaction.

The stickiness factor (S) was calculated for Cp2VCl2 in chloroform and was found to be close to the slip limit (S - 0.1), indicating that there is very slight tendency for the chloroform solvent molecules to stick to the surface of the diffusing Cp2 VC12 particles.