Selective complexation of α-amino acids and simple peptides via their carboxylate groups.

摘要: The complexation of anions selected α-amino acids (alanine, valine, proline, tyrosine) and small peptides (L-alanyl-L-alanine, L-alanyl-L-alanyl-L-alanine, L-alanyl-L-alanyl-L-alanyl-L-alanine) by the dinuclear nickel(II) complex [LNi2(μ-Cl)]+ (1), where (L)2− represents a 24-membered binucleating hexamine-dithiophenolato ligand, has been investigated. following complexes were prepared, isolated as perchlorate or tetraphenylborate salts, characterized UV/Vis, IR, CD spectroscopy: [LNi2(μ-L-alaninato)]+ (2), [LNi2(μ-L-valinato)]+ (3), [LNi2(μ-L-prolinato)]+ (4), [LNi2(μ-L-tyrosinato)]+ (5a), [LNi2(μ-D-tyrosinato)]+ (5b), [LNi2(μ-L,D-tyrosinato)]+ (5c), [LNi2(μ-L-alanyl-L-alaninato)]+ (6), [LNi2(μ-(L-alanyl)2-L-alaninato)]+ (7), [LNi2(μ-(L-alanyl)3-L-alaninato)]+ (8). Compounds 4, 5a 6 additionally identified X-ray crystallography. In contrast to unsupported amino carboxylate which typically contain five membered NO chelate rings, [LNi2]2+ fragment selectively binds via μ1,3-bridging carboxylato groups. Coordination coligands in this way confers dissymmetry on complexes. spectra syn,syn-bridged structures are significantly different from those chelates, can distinguish between two coordination modes. encapsulation increases their solubility solvent system MeOH–MeCN up orders magnitude. This is discussed terms absence intermolecular hydrogen bonding interactions indicated structure 6.