The 2D NOESY (Nuclear Overhauser SpectroscopY) experiment offers a simple way to obtain all NOE information in a molecule by a single experiment and without prior knowledgment of the spectral assignment or molecular structure.

Easy implementation on any AVANCE spectrometer.

The basic pulse sequence of the NOESY experiment ( 79JCP4546 , 80MOP95 and 81JMR259-43 ) follows the same principles of the homonuclear 2D experiments. After an excitation 90º 1H pulse, transverse magnetization evolves during a free variable evolution t1 period. A 90º 1H pulse creates longitudinal magnetization and during the NOE mixing time magnetization transfer via cross-relaxation or chemical exchange can take place. A final 90º 1H proton pulse creates transverse magnetization which is detected as usual. Several modifications of the basic NOESY pulse schemes to remove multispin or spin diffusion effects and to remove undesired zero-quantum coherences (ZQC) ( 90JMR496-86 , and 90JMR423-89 ) have been also proposed.

Sometimes, the experiment is recorded using random variation of mixing time. The NOESY pulse sequence can also be combined with some solvent suppression scheme:

Pulsed field gradients can also be incorporated in the NOESY experiment (see ge-2D NOESY experiment).

The 2D NOESY can be recorded in routine/automation modes. The most important parameter to consider is the length of the mixing time. More details on practical implementation of 2D NOESY experiments on AVANCE spectrometers can be found in

Tutorials: 2D homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments in H₂O

NOESY experiment affords a 2D chemical shift correlation map similar in which through-space connectivites can be trace out. Diagonal peaks are positive, exchange cross-peaks are also positive and NOE cross-peaks are positive in the slow-tumbling or spin-difussion limit for large molecules (negative NOE) and negative in the extreme-narrowing limit (positive NOE). Thus, for small molecules chemical exchange and NOE effects have opposite signs and can be distinguished. A major problem is the presence of ZQC.

General Reading: 96ENC3262

NOE connectivites can be also established using the 2D ROESY experiment.

Related experiments:

2D homonuclear experiments

2D gradient-based homonuclear experiments