title: Powder X-ray diffraction, infrared and (13)C NMR spectroscopic studies of the homologous series of some solid-state zinc(II) and sodium(I) n-alkanoates.
abstract: A comparative study of the room temperature molecular packing and lattice structures for the homologous series of zinc(II) and sodium(I) n-alkanoates adduced from Fourier transform infrared and solid-state (13)C NMR spectroscopic data in conjunction with X-ray powder diffraction measurements is carried out. For zinc carboxylates, metal-carboxyl bonding is via asymmetric bridging bidentate coordination whilst for the sodium adducts, coordination is via asymmetric chelating bidentate bonding. All compounds are packed in a monoclinic crystal system. Furthermore, the fully extended all-trans hydrocarbon chains are arranged as lamellar bilayers. For zinc compounds, there is bilayer overlap, for long chain adducts (nc>8) but not for sodium compounds where methyl groups from opposing layers in the lamellar are only closely packed. Additionally, the hydrocarbon chains are extended along the a-axis of the unit cell for zinc compounds whilst for sodium carboxylates they are extended along the c-axis. These packing differences are responsible for different levels of Van der Waals effects in the lattices of these two series of compounds, hence, observed odd-even alternation is different. The significant difference in lattice packing observed for these two series of compounds is proposed to be due to the difference in metal-carboxyl coordination mode, arising from the different electronic structure of the central metal ions.
authors.affiliation: Department of Chemistry, University of the West Indies, Mona, Kingston 7, St. Andrew, Jamaica. Electronic address: chessnelo@yahoo.co.uk.
authors.forename: Peter N
authors.initials: PN
authors.lastname: Nelson
authors.affiliation: Department of Chemistry, University of the West Indies, St. Augustine, Trinidad and Tobago. Electronic address: Richard.Taylor@sta.uwi.edu.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Taylor
mesh_terms: D000473:Alkanes / Q000737:chemistry*; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D011208:Powders; D012964:Sodium / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry*
chemical_list: D000473:Alkanes; D011208:Powders; D012964:Sodium; D015032:Zinc
keywords: Bidentate coordination; Lamellar bilayer; Metal ions; all-trans Conformation; n-Alkanoates