title: CH...Metal(II) axial interaction in planar complexes (metal=Cu, Pd) and implications for possible environmental effects of alkyl groups at biological copper sites.
abstract: Intramolecular M(II)...H-C interactions (M(II)=Cu(II), Pd(II)) involving a side chain alkyl group of planar d8 and d9 metal complexes of the N-alkyl (R) derivatives of N,N-bis(2-pyridylmethyl)amine with an N3Cl donor set were established by structural and spectroscopic methods. The methyl group from the branched alkyl group (R=2,2-dimethylpropyl and 2-methylbutyl) axially interacts with the metal ion with the M...C and M...H distances of 3.056(3)-3.352(9) and 2.317(1)-2.606(1) A, respectively, and the M-H-C angles of 122.4-162.3 degrees . The Cu(II) complexes showing the interaction have a higher redox potential as compared with those without it, and the (1)H NMR signals of the interacting methyl group in Pd(II) complexes shifted downfield relative to the ligand signals. Dependence of the downshift values on the dielectric constants of the solvents used indicated that the M(II)...H-C interaction is mainly electrostatic in nature and may be regarded as a weak hydrogen bond. Implications for possible environmental effects of the leucine alkyl group at the type 1 Cu site of fungal laccase are also discussed.
authors.affiliation: Unit of Chemistry, Faculty of Engineering, Kansai University, Suita, Osaka 564-8680, Japan. osamuy@ipcku.kansai-u.ac.jp
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamauchi
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Yajima
authors.forename: Rie
authors.initials: R
authors.lastname: Fujii
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Shimazaki
authors.forename: Masanobu
authors.initials: M
authors.lastname: Yabusaki
authors.forename: Masako
authors.initials: M
authors.lastname: Takani
authors.forename: Minoru
authors.initials: M
authors.lastname: Tashiro
authors.forename: Takeshi
authors.initials: T
authors.lastname: Motoyama
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Kakuto
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nakabayashi
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008744:Methylamines / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010165:Palladium / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
chemical_list: D000473:Alkanes; D008744:Methylamines; D011725:Pyridines; C121054:bis(2-pyridyl)methylamine; D010165:Palladium; D003300:Copper