CIDNP

CIDNP (Chemically Induced Dynamic Nuclear Polarization) is a radical pairs. This mechanism, known as the Radical Pair Mechanism is currently accepted as the most common cause of CIDNP. There are, however, exceptions, and the DNP mechanism was found to be operational, for example, in many fluorine-containing radicals.

Radical Pair Mechanism

The generation of CIDNP in a typical photochemical system (target + photosensitizer, pH dependence.

The radical pair may either cross over to a singlet electron state and then recombine, or separate and perish in side reactions. The relative probability of these two pathways for a given radical pair depends on the nuclear spin state and leads to the nuclear spin state sorting and observable nuclear polarization.

Applications

Detected as enhanced absorptive or emissive signals in the folded states, and their interactions with molecules that modify the accessibility of the reactive side chains.

Although usually observed in liquids, the photo-CIDNP effect has also been detected in solid state, for example on 13C and 15N nuclei in photosynthetic reaction centres, where significant nuclear polarization can accumulate as a result of spin selection processes in the electron transfer reactions.

References

1. L.T. Muus, P.W. Atkins, K.A. McLauchlan, J.B. Pedersen (ed.), Chemically induced magnetic polarisation, D. Reidel, Dordrecht, 1977.
2. M. Goez, Photochemically induced dynamic nuclear polarization, Adv. Photochem. 23 (1997) 63-163.
3. R. Kaptein, Photo-CIDNP studies of proteins, Biol. Magn. Res. 4 (1982) 145-191.
4. R. Kaptein, K. Dijkstra, K. Nicolay, Laser photo-CIDNP as a surface probe for proteins in solution , Nature 274 (1978) 293-294.
5. P.J. Hore, R.W. Broadhurst, Progr. NMR Spec. 25 (1993) 345-402. Abstract
6. I. Kuprov, P.J. Hore, J. Magn. Res. 168 (2004) 1-7 Article
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