Geometry of metal–flavin interactions: the crystal structure of bis-(10-methylisoalloxazine)copper(II) perchlorate tetrahydrate

Abstract

An octahedral copper(II) complex of 10-methyl-isoalloxazine is characterized by strong flavin–copper bonding in the flavin primary chelate site [Cu–H₂O = 1·939(7); Cu–O(4)= 2·029(7); and Cu–N(5)= 2·415(7)Å] serving as a model for enzymic metal–flavin complexes as well as controverting earlier suggestions that quinonoid flavin forms complexes only with metals which are capable of one-electron oxidation.