Collecting 13C NMR Spectra of Highly Paramagnetic Compounds

I am sometimes asked to acquire ¹³C NMR spectra of highly paramagnetic compounds. Those of you attempting to acquire such spectra for the first time should be aware of the following:
1. You should use a large spectra width as the ¹³C chemical shifts can be very extreme. In order to get a wide uniform excitation, use very short high power pulses.
2. Both the T₁'s and the T₂'s are short, so you can use short acquisition times and short recycle delays.
3. The ¹H chemical shift range for paramagnetic compounds can span hundreds of ppm. The ¹H decoupling schemes used to collect ¹³C data do not permit such a broad decoupling bandwidth and you may have to collect several ¹³C spectra with different ¹H offsets. It is always best to collect a proton spectrum first to evaluate the ¹H decoupling needs in the ¹³C spectrum.
4. The lines are often very broad and therefore many scans are needed to build up the signal-to-noise ratio.
5. The ²H lock signal may be shifted by the paramagnetic compound, so don't be surprised if your automatic locking routines do not work.