Pteridine radicals

Pteridine radical cations, trihydrostructure, 3, 282 Pteridine radicals structure, 3, 282 Pteridine radicals, hydrostructure, 3, 282 Pteridine reds structure, 3, 283 Pteridines, 3, 263-327 biosynthesis, 3, 315, 320-322 catabolism, 3, 321... 

Reduction of pteridine by potassium allows the formation of the pteridine radical anion (10) for which a well-resolved ESR spectrum has been obtained <89JOM(362)37>. However, the low symmetry of the radical should show theoretically a hyperfine-splitting into 1296 lines and eight coupling constants, indicating that such a complex pattern cannot be analyzed by the experimental facts. 

In the case of molybdenum complexes of oxidized pterin and pteridine ligands, a similar argument leads to the formulation of these complexes as Mo(v) bound to a protonated, one-electron reduced pteridine radical, or Mo -(Hpterin ) (Scheme 2.18). This interpretation is consonant with earlier work on Ru"-flavin complexes. Radical character on flavin arising from intramolecular electron transfer was consistent with a structural distortion of flavin observed crystallographically, interpreted as partial Ru" -flavinsemiquinone character. Similarly, the Mo complexes of oxidized pterins and pteridines display short M=N5 bonds and bent flavin or pterin planes, consistent with a similar delocalized electronic structure. 

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