Magnetic Susceptibility and Unpaired electrons

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SUMMARY

The discussion centers on calculating the magnetic susceptibility (XM) of Mn(acac)3 to determine the number of unpaired electrons using the Evans Method. The participant calculated XM as 4179.1878, but faced discrepancies due to the lack of data for Mn(III) and potential miscalculations involving frequency differences. The correct approach involves using Δv derived from the chloroform peaks and converting ppm to Hz by multiplying by the NMR frequency of 400 MHz. The participant realized the error in their calculations and is seeking confirmation on the corrected method.

PREREQUISITES
  • Understanding of magnetic susceptibility and its calculation methods
  • Familiarity with the Evans Method for determining unpaired electrons
  • Knowledge of NMR spectroscopy, specifically frequency conversions
  • Basic chemistry concepts related to coordination compounds and their magnetic properties
NEXT STEPS
  • Research the Evans Method for calculating magnetic susceptibility in coordination complexes
  • Learn about the magnetic properties of transition metals, specifically Mn(III)
  • Study NMR frequency conversions and their applications in magnetic susceptibility calculations
  • Explore literature on magnetic susceptibility values for various ligands and their contributions
USEFUL FOR

Chemistry students, researchers in coordination chemistry, and anyone involved in magnetic susceptibility measurements and analysis of unpaired electrons in transition metal complexes.

ReidMerrill
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Homework Statement


I'm am trying to find out the magnetic susceptibility,XM in order to calculate the number of unpaired electrons in Mn(acac)3 via the Evans Method

Homework Equations


XM = (477) Δv/(Qv1C)
XM= X'm+ XM(metal)+ XM (ligands)
Where X'M is the magnetic susceptibilty of just the unpaired electrons.
Δv is the frequency difference between the two chloroform peaks, 648.2 MHz (7.2722 ppm-5.6517 ppm)*400 MHz
Q=2 because a superconducting NMR was used
v1 is the frequency of the NMR, 400MHz
and c is the molarity of the solution used, 0.0948M
X'MT=(1/8)n(n+2) where n is number of unpaired electrons

The Attempt at a Solution


The XM I calculated is 4179.1878. I have nothing to base the accuracy of this off of.
the XM (metal) = 511. THis was for elemental Mn. I couldn't find anything for Mn(III) so this might be the problem. And from the lab manual the XM(ligands) is 3*52
Solving for X'M I got 3512.1878
This gives an unpaired electron count of of nearly 3,000 so this cannot be correct. Any help is greatly appreciated.
 
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Δν > ν1? Looks like you multiplied 1.6205*400. What about the "ppm"?
 
mjc123 said:
Δν > ν1? Looks like you multiplied 1.6205*400. What about the "ppm"?
1.6205 is the ppm. That's what the lab manual says to do.

EDIT: I see. the ppm x 400 MHz= Hz. I wasn't reading carefully. I'll see if this fixes things