Electron Spin Relaxation in Solvated Manganese(II) Ion Solutions

Electron spin resonance (ESR) spectra were obtained for solutions of manganese(II) perchlorate in dimethylformamide (DMF), diethylformamide (DEF), dimethylsulfoxide (DMSO), and water. Variation of line shape with solvent and temperature was obtained and interpreted at low temperatures in terms of a model in which solvent fluctuations about the solvated ion modulate the ligand field and relax the electron spin through spin—orbit interaction. Relaxation times for Δm_s=1 transitions of the $\mathrm{S=}\frac{5}{2}$ system were calculated using a semiclassical density‐matrix formalism. In DMF, DEF, and DMSO solutions another contribution to relaxation was observed at high temperatures which may be attributable to ligand exchange or to internal motion in the complex ion. The high‐temperature process was not observed in aqueous manganese(II) solutions.