Conformational Properties of Guest Molecules in Constrained Solid-State Environments:  Bromine K-Edge X-ray Absorption Spectroscopy of 2-Bromoalkane/Urea Inclusion Compounds

1998 ◽  
Vol 10 (5) ◽  
pp. 1220-1226 ◽  
Author(s):  
Laurent Elizabé, ◽  
Lily Yeo ◽  
Kenneth D. M. Harris ◽  
Gopinathan Sankar ◽  
John Meurig Thomas
Keyword(s):  
Solid State ◽  
Absorption Spectroscopy ◽  
Inclusion Compounds ◽  
Guest Molecules ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Conformational Properties ◽  
Urea Inclusion ◽  
X Ray Absorption

Structural properties of the guest species in diacyl peroxide/urea inclusion compounds: an X-ray diffraction investigation

1990 ◽  
Vol 431 (1882) ◽  
pp. 245-269 ◽  
Keyword(s):  
Single Crystal ◽  
Structural Properties ◽  
Inclusion Compounds ◽  
X Ray Diffraction ◽  
Channel Axis ◽  
Guest Molecules ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Diacyl Peroxide ◽  
Urea Inclusion

In this paper we report single crystal X-ray diffraction studies of urea inclusion compounds containing diacyl peroxides (dioctanoyl peroxide (OP), diundecanoyl peroxide (UP), lauroyl peroxide (LP)) as the guest component. In these inclusion compounds, the host (urea) molecules crystallize in a hexagonal structure that contains linear, parallel, non-intersecting channels (tunnels). The guest (diacyl peroxide) molecules are closely packed inside these channels with a periodic repeat distance that is incommensurate with the period of the host structure along the channel axis. Furthermore, there is pronounced inhomogeneity within the guest structure: within each single crystal, there are regions in which the guest molecules are three-dimensionally ordered, and other regions in which they are only one-dimensionally ordered (along the channel axis). Although it has not proven possible to ‘determine’ the guest structures in the conventional sense, substantial information concerning their average periodicities and their orientational relationships with respect to the host has been deduced from single crystal X-ray diffraction photographs recorded at room temperature. For OP/urea, UP/urea and LP/urea, the guest structure in the three-dimensionally ordered regions is monoclinic, and six types of domain of this monoclinic structure can be identified within each single crystal. The relative packing of diacyl peroxide molecules is the same in each domain, and the different domains are related by 60° rotation about the channel axis. For each of these inclusion compounds, the offset between the ‘heights’ of the guest molecules in adjacent channels is the same ( ca . 4.6 Å (4.6 x 10 -10 m)) within experimental error, suggesting that the relative interchannel packing of the guest molecules is controlled by a property of the diacyl peroxide group. In addition to revealing these novel structural properties, the work discussed in this paper has more general relevance concerning the measurement and interpretation of single crystal X-ray diffraction patterns that are based on more than one three-dimensionally periodic reciprocal lattice. Seven separate reciprocal lattices are required to rationalize the complete X-ray diffraction pattern from each diacyl peroxide/urea crystal studied here.

Diffuse and satellite scattering in urea inclusion compounds with various alkane molecules

1996 ◽  
Vol 211 (4) ◽  
Author(s):  
Th. Weber ◽  
H. Boysen ◽  
M. Honal ◽  
F. Frey ◽  
R. B. Neder
Keyword(s):  
Inclusion Compounds ◽  
Diffuse Scattering ◽  
Room Temperature ◽  
Guest Molecules ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Urea Inclusion

AbstractX-ray diffuse scattering phenomena and satellite reflections in urea inclusion compounds with guest molecules of varying lengths (tridecane, tetradecane, pentadecane, heptadecane and a mixture of pentadecane and hexadecane) were investigated between room temperature and 30 K. It was found that diffuse

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