Trouble Simulating Broadened Features

[camgran]

Hello,

I am working on a S =1/2 system for a DPPZ ligand that is chelated to a tungsten metal. I have electrochemically reduced the complex by one electron so that the spin density is on the pyrazinyl nitrogen. For this system, I do not anticipate any spin density to be localized on the metal. Below is an epr spectrum of my reduced complex.

I am trying to simulate this structure using easyspin, but I'm not sure how to account for the broadened features. The system is isotropic and was performed at room temperature. What could be causing very broad features on the edges of the spectrum while retaining well-resolved splitting in the center of the graph?

I have attached my code below. So far, treating each hydrogen with a unique hyperfine splitting has given me the closest representation.
I appreciate any advice on how to make sense of this.
Best, camgran

Code: Select all

SysH.S = 1/2;
SysH.g = 2.0029;
SysH.Nucs = '14N,14N,1H,1H,1H,1H,1H,1H,1H,1H,1H,1H';
SysH.n = [2 2 1 1 1 1 1 1 1 1 1 1];
SysH.A = [5.4,0.54,1.60629,1.16398,1.52297,1.01448,1.12659,1.093,1.0369,1.0889,0.9809,0.9528]; % MHz
SysH.lwpp = [0.0135 0.013]; % mT
ExpH.mwFreq = 9.83; % GHz
ExpH.Range = [348 353]; % mT
garlic(SysH,ExpH);
[B,spcH] = garlic(SysH,ExpH);

[imasen]

Maybe you can try a slow motion simulation with anisotropic spin parameters.
Here is a simplified example:

Code: Select all

clear,clf,clc;

SysH.S = 1/2;
SysH.g = [2.002 2.0029];
SysH.Nucs = '14N,14N,1H,1H,1H,1H,1H,1H,1H,1H';
SysH.A = [0.24 30;0.24 30;0.1 2;0.1 2;0.1 2;0.1 2;0.1 2;0.1 2;0.1 2;0.1 2]; % MHz
SysH.lwpp = [0.015 0.018]; % mT
ExpH.mwFreq = 9.83; % GHz
ExpH.Range = [349.5 352]; % mT

logtcorr = [-12:0.5:-9]; % definiton log10(tcorr/seconds)

for k = 1:numel(logtcorr)
    SysH.logtcorr = logtcorr(k);
    [B,spcH(k,:)] = garlic(SysH,ExpH);
end

stackplot(B,spcH);

2023-08-15 162819.png (49.26 KiB) Viewed 1083 times

[camgran]

Hi imasen,

Thanks so much for your reply. I think this is helping me find the right path.

Cheers

[katarkon]

It looks as lite inequivalence at least of two nitrogens in the quintet 1:2:3:2:1.