434 KB29 KB199820252011Kaučič, VenčeslavMali, GregorUkmar Godec, Tinaletnik:no. 3str. 425-433številka:vol. 58ISSN:1318-0207COBISSID:4767770URN:URN:NBN:SI:doc-EHPL7107enSlovensko kemijsko društvoActa chimica slovenicaCPMASCRAMPSGIPAWindometacinindomethacinkemijska strukturakristalna strukturanuklearna magnetna resonancapolimorfijapolymorphismsolid-state NMRvodikova vezSolid-state NMR spectroscopy and first-principles calculations| a powerful combination of tools for the investigation of polymorphism of indomethacin|Two polymorphs of indomethacin were investigated by 1H MAS and CRAMPS, and 1H-13C CPMAS and HETCOR NMR techniques. The obtained spectra clearly elucidated the structural differences between the polymorphs, especially the different numbers of indomethacin molecules within the crystallographic asymmetric units and the different schemes of hydrogen bonding among the molecules. Known structure of indomethacin gamma was used in first-principles DFT/GIPAW calculations of 1H and 13C isotropic chemical shifts. Two packages, freely available Quantum Espresso and commercially available CASTEP, were employed. They both provided values that excellently agreed with the measured values, and thus allowed unambiguous assignment of 1H and 13C spectral linesZ NMR spektroskopijo 1H MAS in CRAMPS ter 1H-13C CPMAS in HETCOR smo preučevali dva polimorfa indometacina. Dobljeni spektri so jasno razkrili strukturne razlike med polimorfi, predvsem razlike v številu molekul indometacina v asimetričnih enotah kristala in v konfiguracijah vodikovih vezi med posameznimi molekulami modelne učinkovine. Meritve smo dopolnili s kvantno-mehanskimi izračuni izotropnih kemijskih premikov jeder 1H in 13C v okviru teorije DFT/GIPAW. Pri izračunih smo se omejili na polimorf gama, katerega struktura je dobro znana. Račune smo opravili s programskima paketoma Quantum Espresso (prosto dostopen) in CASTEP (komercialno dostopen). Rezultati izračunov z obema paketoma so odlično sovpadali z izmerjenimi vrednostmi, kar nam je omogočilo, da smo spektralne črte v 1H in 13C NMR spektrih nedvoumno pripisali jedrom na posameznih kristalografskih mestih v osnovni celici indometacina gamaTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaSlovensko kemijsko društvo