EasySpin forum

Hi everyone,

I am new to using the EPR simulation tool Easyspin and have recently grasped the basic aspects of simulation using this tool. However, I am encountering a bit of confusion regarding how to define the spin for a complex system.

To elaborate, I am working with a complex that includes a V(II) metal center coordinated to three bidentate ligands. These ligands have radical electrons delocalized over their pi-systems, amounting to three radical electrons in total. Given this setup, I am uncertain about the correct way to define the spin of the entire system.

Any guidance or insights on this matter would be highly appreciated. Thank you in advance for your help!

Best regards,

Sunil Kumar

If each ligand has one electron delocalised across its pi system, you simply model by a single s=1/2. So one s = 3/2 and three s=1/2 in total.

Thank you for your suggestion.
But I am getting some errors. I am not able to figure them out.
The input file is:

clear,clc,clf

[B,spc] = textread('fe_epr.txt','%f %f');
plot(B,spc)
Sys.g = [2.0791 2.0663 2.0075; 2.0023 2.0023 2.0023]
Sys.S = [2 1/2];
Sys.Nucs = 'Fe,14N, 14N';
Sys.n = [1 1 1];
Sys.J = 1.2;
Sys.lwpp = [0.01, 0.05];  % Lorentzian lines, mT
% Hyperfine couplings
A_anion =  unitconvert([2; 0.055; 0.55],'mT->MHz');

% Spectrometer settings
%--------------------------------------------------------------------------
Exp.mwFreq = 9.448;  % GHz

Exp.nPoints = length(B);
Exp.Range=[min(B) max(B)]

% Simulations
%--------------------------------------------------------------------------
Sys.A = A_anion;
[B,spca] = pepper(Sys,Exp);
plot(B, spc, B, spca)
SysVary.g = [0.015 0.015 0.015];
SysVary.lwpp = [0.001 0.05];
SysVary.A = [0.055, 0.055, 0.055];

and the error is :
Error using pepper
Size of Sys.A (2x1) is inconsistent with number of nuclei (2) and electrons (2).

Error in compisoloop

Error in pepper

Kindly help me to figure it out.
The complex is having Iron (II) and a radical electron ligand.

You system has two spin entities, a s=2 and an s=1/2, but Sys.nucs and Sys.A has three entries. That does not match - only one nucleus can be associated with each spin centre.