title: New hydrophobic L-amino acid salts: maleates of L-leucine, L-isoleucine and L-norvaline.
abstract: Crystals of maleates of three amino acids with hydrophobic side chains [L-leucenium hydrogen maleate, C6H14NO2(+)·C4H3O4(-), (I), L-isoleucenium hydrogen maleate hemihydrate, C6H14NO2(+)·C4H3O4(-)·0.5H2O, (II), and L-norvalinium hydrogen maleate-L-norvaline (1/1), C5H11NO2(+)·C4H3O4(-)·C5H12NO2, (III)], were obtained. The new structures contain C2(2)(12) chains, or variants thereof, that are a common feature in the crystal structures of amino acid maleates. The L-leucenium salt is remarkable due to a large number of symmetrically non-equivalent units (Z' = 3). The L-isoleucenium salt is a hydrate despite the fact that L-isoleucine is a nonpolar hydrophobic amino acid (previously known amino acid maleates formed hydrates only with lysine and histidine, which are polar and hydrophilic). The L-norvalinium salt provides the first example where the dimeric cation L-Nva...L-NvaH(+) was observed. All three compounds have layered noncentrosymmetric structures. Preliminary tests have shown the presence of the second harmonic generation (SGH) effect for all three compounds.
authors.affiliation: REC-008, Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russian Federation.
authors.forename: Sergey G
authors.initials: SG
authors.lastname: Arkhipov
authors.affiliation: REC-008, Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russian Federation.
authors.forename: Denis A
authors.initials: DA
authors.lastname: Rychkov
authors.affiliation: Institute of Automation and Electrometry SB RAS, pr. Akademika Koptyuga 1, Novosibirsk 630090, Russian Federation.
authors.forename: Alexey M
authors.initials: AM
authors.lastname: Pugachev
authors.affiliation: REC-008, Novosibirsk State University, Pirogova str. 2, Novosibirsk 630090, Russian Federation.
authors.forename: Elena V
authors.initials: EV
authors.lastname: Boldyreva
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D018360:Crystallography, X-Ray; D006639:Histidine / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007532:Isoleucine / Q000737:chemistry*; D007930:Leucine / Q000737:chemistry*; D008239:Lysine / Q000737:chemistry*; D008298:Maleates / Q000737:chemistry*; D015394:Molecular Structure; D014633:Valine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D000596:Amino Acids; D008298:Maleates; D007532:Isoleucine; D006639:Histidine; C005313:norvaline; D007930:Leucine; D014633:Valine; D008239:Lysine
keywords: SHG effect; crystal structure; l-amino acids; l-isoleucine; l-leucine; l-norvaline; l-norvaline–l-norvalinium dimer; maleate; noncentrosymmetric layered structures