The quantitative assessment of intermolecular interactions and their cooperative effects has been performed in spirohydantoin-based model compounds, 3-benzoyl-1,3-diazaspiro[4.5]decane-2,4-dione (1) and 3-(4-fluorobenzoyl)-1,3-diazaspiro[4.5]decane-2,4-dione (2), through single crystal X-ray crystallography and quantum chemical...
A series of cycloalkane-5-spirohydantoins bearing a halogeno substituted benzyl group (X = Cl and Br) in position 3 has been synthesized and their structures (1-6) have been determined by single crystal X-ray diffraction method. These compounds have multiple functional groups, which allow a greater competition and/or cooperation among the different intermolecular interactions in formation of their crystal structures. The molecules are linked together by paired N-H•••O hydrogen bonds in R2 2 (8) rings, while the C-H•••O interactions lead to their further association into double chains. The contribution of the cycloalkyl ring depends on its conformational flexibility and the multiple C-H donor implications. In the case of compounds 1-4 bearing the cyclopentyl or the cyclohexil ring, halogen bonding (X•••O) interactions give rise to a supramolecular pseudo-hexagonal network. In addition, the C-H•••X interactions with a higher degree of multifurcation at the halogen acceptor have an important role in formation of the crystal structure. Regarding compounds 5 and 6 with the cycloheptane ring, the X•••O interaction is absent and, along with the C-H•••X interactions, these compounds realize an alternative crystal structure with emphasis on the X•••π interactions. The lattice energies of all these crystal structures, as well as intermolecular pair energies, have been calculated using PIXEL and further partitioned into coulombic, dispersive, polarization and repulsive factors. The crystal structures have also been subjected to Hirshfeld surface analysis which reveals that approximately 75% of the close contacts correspond to relatively weak interactions. The application of both concepts has provided a new insight into relationships between molecular and crystal structure of the hydantoin derivatives.
Green hydroxyapatite ceramics were obtained by cold uniaxial and isostatic pressing of hydrothermally synthesized powders, pure hydroxyapatite and hydroxyapatite doped with Ag + , Cu 2+ and Zn 2+ ions. The ceramics were conventionally and microwave sintered and analyzed by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, X-ray diffraction analysis, and energy-dispersive X-ray spectroscopy. The effect of doping on the mechanical properties of the obtained hydroxyapatite/tricalcium phosphate ceramics was examined by comparing their average grain size, porosity and values of the hardness and fracture toughness. The results showed that doping with Cu 2+ ions caused the lowest porosity of the ceramics and the highest values of hardness and fracture toughness. The ceramics obtained from hydroxyapatite doped with Ag + and Zn 2+ ions exhibited worse mechanical properties due to the higher porosity even in the case of microwave sintering, which provide denser ceramics than conventional sintering.
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