by Nikolai V. Shokhirev

Prof. F. Ann Walker Research Group, Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA

2D NMR Basics

1D NMR Basics

2D NMR Basics

Contents

Chemical Exchange

1D NMR with Chemical Exchange

Programs


Introduction

The two dimensional (2D) NMR spectroscopy is based on the pulse variant briefly described in the previous section (1D NMR Basics).

Basic Pulse Scheme

In 2D

Basic 3-pulses scheme for 2D spectroscopy

 Stages:

2D time domain spectrum

The x-component of the above magnetization as a function of t1 and t2 has the following shape:

 2D frequency domain spectrum

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:

Two-line 2D spectrum 

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:

2D spectrum of interacting subsystems

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.

References

  1.  R.R.Ernst, G.Bodenhausen, and A.Wokaun. Principles of nuclear magnetic resonance in one and two dimensions. Claredon Press, Oxford, 1987.

©Nikolai V. Shokhirev, F. Ann Walker, 2001-2007

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