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 phenylal anine) react with amines under aerobic conditions to V(V) complexes of the general composition VO(OH)L(amine) (5) (amine = imidazole, methyl imidazole, pyrrole, pyridine, histidine, and histidine derivatives). W ith alcohols, the complexes VO(OR)L(ROH) (6) are formed. Histidine can also replace glycine in 2, forming the title compound 3 with the hist idine moiety coordinating through one of the carboxylate-O moieties. C rystallographic data for 3: [VO2{O2CCH(CH2C3H4N2)N=CHC10H6O}], space g roup 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) angstrom 3, R = 0.0325, R(w) = 0.0358, 3011 reflections (2916 with I > 2sigma-( I). The geometry around vanadium is square pyramidal. The two nitrogen s 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 h aloperoxidases from marine brown algae.