by Nikolai V. Shokhirev
Prof. F. Ann Walker Research Group, Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
1D NMR Basics
2D NMR Basics
- Basic Pulse Sceme
- 2D time domain spectrum
- 2D frequency domain spectrum
- 2D spectrum of interacting subsystems
1D NMR with Chemical Exchange
The two dimensional (2D) NMR spectroscopy is based on the pulse variant briefly described in the previous section (1D NMR Basics).
Basic 3-pulses scheme for 2D spectroscopy
This stage is called evolution.
tm is called mixing time.
Here t2 = t - tm - t1. This stage is called acquisition.
Two-dimensional Fourier transformation converts this function into the two-dimensional function in the - domain:
The projections of this two-dimensional spectrum on each frequency axis has a well-known shape:
If a system consists of two non-interacting subsystems then its 2D spectrum has two peaks along the diagonal :
Its projection to each frequency axis again is 1D spectrum:
The advantage of the 2D spectroscopy becomes apparent for the systems with interaction. In addition to the diagonal peaks it has two cross-peaks:
The diagonal peaks are centered at and . The off diagonal peaks are situated at and :
The contour map of the 2D spectrum.
The 2D technique is a very useful tool for study of interactions accompanied by magnetization transfer. A chemical exchange is an example of the system with magnetization transfer due to chemical transformation.
©Nikolai V. Shokhirev, F. Ann Walker, 2001-2007