Spin exchange through-bond interaction

Unpaired electronic density can be delocalized onto the various nuclei of the complex via through-bond scalar hyperfine interactions involving occupied orbitals containing s-character (direct interaction or polarization according to the Fermi mechanism, Wertz and Bolton (1986)). Random electron relaxation thus produces a flip-flop mechanism which affects the nuclear spin and increases nuclear relaxation processes (Bertini and Luchinat, 1996). Since these interactions are isotropic, they do not depend on molecular tumbling and re is the only relevant correlation time for non-exchanging semi-rigid complexes. Moreover, only electronic spin can be delocalized via hyperfine interactions (no orbital contribution) and the contact re-... 

Once a molecule (Fig. 11) has been added at the sample Node, the user can add atoms and subsequently bonds (see 2.14) through the Molecule menu or by a right mouse click on the Molecule Node. In this context, the term bond is loosely defined to include not only bonds but also interactions between electron spins and either nuelear spins (superhyperfine interaction) or other electron spins (exchange interaetion). Adding an atom displays a Periodic Table (Fig. 12) from which the user ean select an atom by clicking (left mouse button) on the appropriate element. The atom is then added to the Molecule in the Explorer. 

Through-Space and Through-Bond Orbital Interactions Leading to Spin Exchange... 

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