Hyperfine coupling constants heteroatoms

It has been shown that triphenyl(p-cyanobenzyl)phosphonium tetrafluoroborate (16), which exhibits a a LUMO level localized predominantly on the heteroatom and benzylic carbon, gives products derived from out-of-solvent cage chemical reactions on direct irradiation (reaction 6). This behaviour is connected with the nuclear hyperfine coupling constant of the heteroatom in triphenylphosphine radical-cation171. 

Ammonium, phosphonium and arsonium salts may also possess a a LUMO and undergo PET bond cleavage reactions to provide products that depend largely upon the heteroatom nuclear hyperfine coupling constant [93]. 

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