I'm working on Fe(II)porphyrin complexes. I realized that the center is already paramagnetic. When you try to get proton NMR spectra, you only see solvent peaks. After increasing the number of scans from 16 to 2048, I started barely to see proton peaks in the aromatic region. However, the resolution and peak intensity is very low, so I'm asking if I can find a way to see it or not.
You've said that the compd is paramagnetic in nature, so if it is highly paramagnetic in nature there is barely any chance that you will obtain any NMR peaks, but you try to record a spectrum at very low temperature and see if there is any change as compared to earlier ones.
You could try using a very short acquisition time and no delay between pulses. T1 will be short. This way you could signal average many more scans. This also means C-13 spectra may be possible since you can signal avenge much quicker.
It won’t hurt to increase the spectral width either.
Does anyone ever report H-1 data for similar compounds?
William C Hutton, I have already tried increasing spectral width, but beyond 10 ppm, I could say there is nothing even at 2048 scans. I can give it a try for a short acquisition time. In the literature, I could only manage to find diamagnetic proton NMR of similar compounds. However, with the paramagnetic effect, sometimes you may see a huge splitting of the peaks, i.e. one is 40 ppm, and another one is -50 ppm.
You may oxidize Fe(II) to Fe(III) with NOBF4 and acquire the NMR spectra of the corresponding Fe(III) diamagnetic complex
In that case you have an even number of electrons for sure. Low and high spin complexes are two extremes of a model which serve to justify paramagnetism/diamagnetism...but you should priorly trust experimental evidences. So, just try! If your spectrum looks better, then you may not be dealing with a low spin complex with an unpaired electron, as you predicted.
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