EasySpin forum

Dear Stefan,
I use your program EasySpin to simulate the rotational ESR spectra of TEMPO in different environment. The software works pretty well, however lately I got problem with simulation the one spectrum (please see attached file). I believe that in addition to the slow motional spectrum from TEMPO, the electron interact with 19F and that HFS is anisotropic. So I tried to write scrip including such interaction but I am not sure I am doing this correctly. Could you give me some advices how to write the correct script? Thank you in advance.
Sincerely,
KK
1 script
% slow-motional cw EPR spectrum simulation of a nitroxide radical
%==========================================================================
% bestvalues: [-4.9398 5 15.5461 97.4956 0.4000 0.3596 2.0085 2.0055 2.0013]

clear, clf
[exp,spc] = eprload('d:\data\pw\bud385_F_l-LN-KK4-bl.DTA'); % Bruker BES3T

% Parameters

% S
S.g = [2.0085 2.0055 2.0013];
S.Nucs = '14N';
S.A = [5 15.5461 97.4956];

% S - Dynamic parameters
S.lwpp = [0.4000 0.3596];
S.logtcorr = -4.9398;

HFS = struct('g',[2.0085 2.0055 2.0013],'Nucs','14N,19F');
AF = [800 800 2000];
HFS.A = [5 15.5461 97.4956; AF];
HFS.logtcorr = -7;
HFS.lwpp = [2 1];


% Experimental parameters
Exp.mwFreq = 9.363302;
Exp.Range = [285, 385];
Exp.nPoints = 2048;

% Next, we specify which parameter we want to be fitted
% and by how much the fitting algorithm can vary it approximately.

Vary1.logtcorr = 2
Vary1.A = [5 5 5];
Vary1.lwpp = [0.2 0.2];
Vary1.g = [0.0005 0.0005 0.0005];

Vary2.lwpp = [0.2 0.2];

Opt.Verbosity = 1;
SimOpt.Method = 'perturb';

% Calling the fitting function
FitOpt.Method = 'simplex fcn'; % simplex algorithm, normal spectra;
esfit('chili',spc,{S, HFS},{Vary1, Vary2},Exp,SimOpt,FitOpt);

2 script
% slow-motional cw EPR spectrum simulation of a nitroxide radical
%==========================================================================
% bestvalues: [-4.9398 5 15.5461 97.4956 0.4000 0.3596 2.0085 2.0055 2.0013]

clear, clf
[exp,spc] = eprload('d:\data\pw\bud385_F_l-LN-KK4-bl.DTA'); % Bruker BES3T

% Parameters

% S
S.g = [2.0085 2.0055 2.0013];
S.Nucs = '14N';
S.A = [5 15.5461 97.4956];

% S - Dynamic parameters
S.lwpp = [0.4000 0.3596];
S.logtcorr = -4.9398;

HFS = struct('g',[2.0085 2.0055 2.0013],'Nucs','14N,19F');
AF = [800 800 2000];
HFS.A = [5 15.5461 97.4956; AF];
HFS.logtcorr = -7;
HFS.lwpp = [2 1];


% Experimental parameters
Exp.mwFreq = 9.363302;
Exp.Range = [285, 385];
Exp.nPoints = 2048;

% Next, we specify which parameter we want to be fitted
% and by how much the fitting algorithm can vary it approximately.

Vary1.logtcorr = 2
Vary1.A = [5 5 5];
Vary1.lwpp = [0.2 0.2];
Vary1.g = [0.0005 0.0005 0.0005];

Vary2.lwpp = [0.2 0.2];

Opt.Verbosity = 1;
SimOpt.Method = 'perturb';

% Calling the fitting function
FitOpt.Method = 'simplex fcn'; % simplex algorithm, normal spectra;
esfit('chili',spc,{S, HFS},{Vary1, Vary2},Exp,SimOpt,FitOpt);

Can you describe the sample you are looking at? From your script, it appears to contain a 1:1 mixture of a normal and a fluorinated nitroxide. Is that correct?

TEMPO in not fluorinated but it is a ligand however phenyl ligand is fluorinated: [(C6F5)2Zn(TEMPO)2]
As an attachment please find the structure of the compounds (correct ext. CIF, Mercury file).
Best,
KK

From your sum formula then it appears you have two coupled nitroxide radicals, with each of them potentially having some hyperfine coupling to the fluorines on the phenyl ligands? You need to include F only if you see resolved F splittings in the spectrum. Also, if the two TEMPOs are coupled, you need to have them in the same spin system (Sys.S = [1/2 1/2]) and add some coupling (e.g. Sys.J).

Thx, I will try to simulate my spectrum according your suggestion.
Best,
KK