Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 2 de 2
Filter
Add more filters










Database
Language
Publication year range
1.
Acta Crystallogr B ; 65(Pt 5): 639-46, 2009 Oct.
Article in English | MEDLINE | ID: mdl-19767686

ABSTRACT

The molecular and crystalline structure of ethyl 1',2',3',4',4a',5',6',7'-octahydrodispiro[cyclohexane-1,2'-quinazoline-4',1''-cyclohexane]-8'-carbodithioate (I) was solved and refined from powder synchrotron X-ray diffraction data. The initial model for the structural solution in direct space using the simulated annealing algorithm implemented in DASH [David et al. (2006). J. Appl. Cryst. 39, 910-915] was obtained performing a conformational study on the fused six-membered rings of the octahydroquinazoline system and the two spiran cyclohexane rings of (I). The best model was chosen using experimental evidence from 1H and 13C NMR [Contreras et al. (2001). J. Heterocycl. Chem. 38, 1223-1225] in combination with semi-empirical AM1 calculations. In the refined structure the two spiran rings have the chair conformation, while both of the fused rings in the octahydroquinazoline system have half-chair conformations compared with in-vacuum density-functional theory (DFT) B3LYP/6-311G*, DFTB (density-functional tight-binding) theoretical calculations in the solid state and other related structures from X-ray diffraction data. Compound (I) presents weak intramolecular hydrogen bonds of the type N-H...S and C-H...S, which produce delocalization of the electron density in the generated rings described by graph symbols S(6) and S(5). Packing of the molecules is dominated by van der Waals interactions.


Subject(s)
Cyclohexanes/chemistry , Quinazolines/chemistry , Spiro Compounds/chemistry , Crystallography, X-Ray , Electrochemistry , Hydrogen Bonding , Ligands , Molecular Conformation , Powder Diffraction , Synchrotrons
2.
Acta Crystallogr B ; 64(Pt 2): 217-22, 2008 Apr.
Article in English | MEDLINE | ID: mdl-18369293

ABSTRACT

A series of bidentate nitrogen-sulfur pro-ligands has been designed and synthesized with the purpose of introducing a structural modification that favours the tetrahedral site distortions of metalloprotein systems with metallic centers surrounded by ligands containing two N atoms and two S atoms as donor groups. Some of these new pro-ligands were obtained only as powders. Here we present the molecular and crystalline structure of cycloheptanespiro-3'(4'H)-6',7',8',9'-tetrahydrocyclohexa[b][1,4]thiazole-2'(5'H)-thione (I) solved and refined from powder synchrotron X-ray diffraction data. Two independent molecules comprising a total of 36 non-H atoms were obtained from the direct-methods solution and refined against the powder X-ray diffraction data using the Rietveld method. The molecular conformations of the heterocyclic benzothiazine ring, the fused heptenyl ring and the heptanyl spiro ring are thoroughly discussed and compared with VASP theoretical calculations and other related structures. The packing of molecules in (I) is based on hydrogen bonds of the type N-H...S and hydrophobic C-H interactions.


Subject(s)
Thiazoles/chemistry , Hydrogen Bonding , Molecular Conformation , Molecular Structure , Powder Diffraction , Synchrotrons
SELECTION OF CITATIONS
SEARCH DETAIL
...