NMR Contact Shift and Line-Broadening Studies of Some Transition Metal-DMSO Complexes.

Dimethylsulfoxide (DMSO) is known to be a good ligand towards the formation of DMSO-complexed compounds. This work is concerned with the evaluation of the magnetic and kinetic properties of these compounds in DMSO solution. DMSO-complexed compounds of the transition metal ions, Cu(II), Ni (II), Co (II), Fe (II), Mn (II), Fe (III), and Cr(III) were studied.From the nmr spectra of these compounds, it is noted that the peak of the methyl proton shifts downfield with respect to that of the pure DMSO. The electron spin-nuclear spin coupling constants, An, were calculated to be all positive in sign. Unpaired electrons must be transferred either from the metal ion to the ligand or from the ligand to the metal ion to cause the corresponding contact shift. Different mechanisms are postulated to explain the possible electron transfer. It is found that the unpaired electron can be transferred only through the σ-system in Cu(II) and Ni(II) ions. For Co (II), Fe (II) and Mn(II) ions, the unpaired electrons can be transferred through both the σ and π systems.The exchange rate between the coordinated DMSO and bulk solvent DMSO molecules is studied for all metal ions from the line-width of the nmr spectra. The exchange rate constants, k1, together with the corresponding activation parameters, ∆H* and ∆S*, were calculated. 4 It is observed that the rate constants range from 103 sec-1 to 104 sec-1 for the divalent metal ions. In the case of Mn (II), only an upper limit rate constant can be obtained at the temperature range studied. The exchange rates are relatively slow for the trivalent metal ions and the observed value for Cr(III) is interpreted by the postulation of second layer exchange. Crystal Field Stabilization Energy (C.F.S.E.) is applied as one criterion to explain the exchange rates for all the metal ions studied.

Level thesis:degree_level

Thesis

Year

1970

Author dc:creator

• Ng, Patrick K

• DMSO-complexed compounds
• Dimethylsulfoxide
• Spin-nuclear spin coupling
• Metal ions

Repository record dc:identifier

https://digitalcommons.library.uab.edu/etd-collection/6951

OAI identifier oai:identifier

oai:digitalcommons.library.uab.edu:etd-collection-7943