title: A solid state NMR study of layered double hydroxides intercalated with para-amino salicylate, a tuberculosis drug.
abstract: Para-amino salicylate (PAS), a tuberculosis drug, was intercalated in three different layered double hydroxides (MgAl, ZnAl, and CaAl-LDH) and the samples were studied by multi-nuclear ((1)H, (13)C, and (27)Al) solid state NMR (SSNMR) spectroscopy in combination with powder X-ray diffraction (PXRD), elemental analysis and IR-spectroscopy to gain insight into the bulk and atomic level structure of these LDHs especially with a view to the purity of the LDH-PAS materials and the concentration of impurities. The intercalations of PAS in MgAl-, ZnAl-, and CaAl-LDH's were confirmed by (13)C SSNMR and PXRD. Moreover, (13)C MAS NMR and infrared spectroscopy show that PAS did not decompose during synthesis. Large amounts (20-41%) of amorphous aluminum impurities were detected in the structure using (27)Al single pulse and 3QMAS NMR spectra, which in combination with (1)H single and double quantum experiments also showed that the M(II):Al ratio was higher than predicted from the bulk metal composition of MgAl-PAS and ZnAl-PAS. Moreover, the first high-resolution (1)H SSNMR spectra of a CaAl LDH is reported and assigned using (1)H single and double quantum experiments in combination with (27)Al{(1)H} HETCOR.
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark.
authors.forename: Nicholai Daugaard
authors.initials: ND
authors.lastname: Jensen
authors.affiliation: Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), University of Aarhus, Gustav Wiedsvej 14, 8000 Aarhus C, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Bjerring
authors.affiliation: Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark. Electronic address: ugn@sdu.dk.
authors.forename: Ulla Gro
authors.initials: UG
authors.lastname: Nielsen
mesh_terms: D006878:Hydroxides; D009682:Magnetic Resonance Spectroscopy; D012459:Salicylates; D014376:Tuberculosis; D014961:X-Ray Diffraction
chemical_list: D006878:Hydroxides; D012459:Salicylates
keywords: (1)H; (27)Al; Layered double hydroxides; Local environment; Nanocomposite; Para-amino salicylate solid state NMR; Para-amino salicylic acid