BINDING OF L-HISTIDINE TO VANADIUM - STRUCTURE OF EXO-[VO2(N-(2-OXIDONAPHTHAL)-HIS)]

The V(IV) complexes VO(H2O)L (2) (H2L is a Schiff base derived from o-hydroxynaphthalenecarbaldehyde and the amino acids glycine or phenylalanine) react with amines under aerobic conditions to V(V) complexes of the general composition VO(OH)L(amine) (5) (amine = imidazole, methylimidazole, pyrrole, pyridine, histidine, and histidine derivatives). With alcohols, the complexes VO(OR)L(ROH) (6) are formed. Histidine can also replace glycine in 2, forming the title compound 3 with the histidine moiety coordinating through one of the carboxylate-O moieties. Crystallographic data for 3: [VO2{O2CCH(CH2C3H4N2)N=CHC10H6O}], space group C2; Z = 4, a = 13.7077(17) angstrom, b = 6.7390(6) angstrom; c = 17.1851(15) angstrom, beta = 95.644(8)-degrees, V = 1579.8(3) angstrom3, R = 0.0325, R(w) = 0.0358, 3011 reflections (2916 with I > 2sigma-(I). The geometry around vanadium is square pyramidal. The two nitrogens of the imidazole unit are linked by intermolecular hydrogen bonds to the carboxylate oxygens and to the oxo group in the tetragonal plane. 3 models several of the active site features for vanadate-dependent haloperoxidases from marine brown algae.