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.

scholarly journals A phenomenological model for structural phase transitions in incommensurate alkane/urea inclusion compounds

2018 ◽  
Vol 5 (6) ◽  
pp. 180058 ◽  
Author(s):  
Michel Couzi ◽  
François Guillaume ◽  
Kenneth D. M. Harris
Keyword(s):  
Structural Properties ◽  
Phenomenological Model ◽  
Inclusion Compounds ◽  
Structural Phase ◽  
Temperature Phase ◽  
Coupling Mechanism ◽  
Repeat Distance ◽  
Guest Molecules ◽  
Urea Inclusion Compounds ◽  
Urea Inclusion

n -Alkane/urea inclusion compounds are crystalline materials in which n -alkane ‘guest’ molecules are located within parallel one-dimensional ‘host’ tunnels formed by a helical hydrogen-bonded arrangement of urea molecules. The periodic repeat distance of the guest molecules along the host tunnels is incommensurate with the periodic repeat distance of the host substructure. The structural properties of the high-temperature phase of these materials (phase I), which exist at ambient temperature, are described by a (3 + 1)-dimensional superspace. Recent publications have suggested that, in the prototypical incommensurate composite systems, n -nonadecane/urea and n -hexadecane/urea, two low-temperature phases II and ‘III’ exist and that one or both of these phases are described by a (3 + 2)-dimensional superspace. We present a phenomenological model based on symmetry considerations and developed in the frame of a pseudo-spin–phonon coupling mechanism, which accounts for the mechanisms responsible for the I ↔ II ↔ ‘III’ phase sequence. With reference to published experimental data, we demonstrate that, in all phases of these incommensurate materials, the structural properties are described by (3 + 1)-dimensional superspace groups. Around the temperature of the II ↔ ‘III’ transition, the macroscopic properties of the material are not actually associated with a phase transition, but instead represent a ‘crossover’ between two regimes involving different couplings between relevant order parameters.

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

Definitive Structural Characterization of the Conventional Low-Temperature Host Structure in Urea Inclusion Compounds

1997 ◽  
Vol 53 (5) ◽  
pp. 822-830 ◽  
Author(s):  
L. Yeo ◽  
K. D. M. Harris
Keyword(s):  
Low Temperature ◽  
Inclusion Compounds ◽  
Temperature Phase ◽  
Temperature Structure ◽  
Tunnel Structure ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
Urea Inclusion Compounds ◽  
Urea Inclusion ◽  
Low Temperature Phase

Structural properties of the 1,10-dibromodecane/urea and 1,12-dibromododecane/urea inclusion compounds have been determined by single-crystal X-ray diffraction for both the high- and low-temperature phases. In the high-temperature phase both inclusion compounds have the conventional hexagonal urea tunnel structure, with substantial orientational disorder of the guest molecules. In the low-temperature phase the urea tunnel structure distorts to an orthorhombic structure, based on a distorted form of the orthohexaganol cell of the high-temperature structure and with the loss of the C centre. Within this tunnel structure there is evidence that the guest molecules have a narrow distribution of orientations (with respect to rotation about the tunnel axis) and the preferred orientation of the guest molecules correlates well with the observed distortion of the host tunnel. This represents the first accurate and reliable report of the conventional low-temperature structure of urea inclusion compounds. Previous powder X-ray diffraction studies have confirmed that the host structure in the low-temperature phase of 1,10-dibromodecane/urea is the same as that in the low-temperature phase of the alkane/urea inclusion compounds.

scholarly journals Reply to comment on Couzi et al . (2018): a phenomenological model for structural phase transitions in incommensurate alkane/urea inclusion compounds

2019 ◽  
Vol 6 (8) ◽  
pp. 190518 ◽  
Author(s):  
Kirsten Christensen ◽  
P. Andrew Williams ◽  
Rhian Patterson ◽  
Benjamin A. Palmer ◽  
Michel Couzi ◽  
...  
Keyword(s):  
Phase Ii ◽  
Phenomenological Model ◽  
Inclusion Compounds ◽  
Phase Iii ◽  
X Ray Diffraction ◽  
X Ray ◽  
Urea Inclusion Compounds ◽  
Full Support ◽  
Link Type ◽  
Urea Inclusion

In a recent paper (Couzi et al. 2018 R. Soc. open sci. 5 , 180058. ( doi:10.1098/rsos.180058 )), we proposed a new phenomenological model to account for the I↔II↔“III” phase sequence in incommensurate n -alkane/urea inclusion compounds, which represents an alternative interpretation to that proposed in work of Toudic et al. In a Comment (Toudic et al. 2019 R. Soc. open sci. 6 , 182073. ( doi:10.1098/rsos.182073 )), Toudic et al. have questioned our assignment of the superspace group of phase II of n -nonadecane/urea, which they have previously assigned, based on a (3 + 2)-dimensional superspace, as C222 1 (00 γ )(10 δ ). In this Reply, we present new results from a comprehensive synchrotron single-crystal X-ray diffraction study of n -nonadecane/urea, involving measurements as a detailed function of temperature across the I↔II↔“III” phase transition sequence. Our results demonstrate conclusively that “main reflections” ( h, k, l , 0) with h+k odd are observed in phase II of n -nonadecane/urea (including temperatures in phase II that are just below the transition from phase I to phase II), in full support of our assignment of the (3+1)-dimensional superspace group P2 1 2 1 2 1 (00 γ ) to phase II. As our phenomenological model is based on phase II and phase “III” of this incommensurate material having the same (3+1)-dimensional superspace group P2 1 2 1 2 1 (00 γ ), it follows that the new X-ray diffraction results are in full support of our phenomenological model.

Adsorption behaviour of a CdII–triazole MOF for butan-2-one in a single-crystal-to-single-crystal (SCSC) fashion: the role of hydrogen bonding and C—H...π interactions

2019 ◽  
Vol 75 (6) ◽  
pp. 806-811
Author(s):  
Jia Wang ◽  
Tianchao You ◽  
Teng Wang ◽  
Qikui Liu ◽  
Jianping Ma ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Single Crystal ◽  
Specific Binding ◽  
Supramolecular Interactions ◽  
Adsorption Behaviour ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Π Interactions ◽  
H Nmr

The adsorption behaviour of the CdII–MOF {[Cd(L)2(ClO4)2]·H2O (1), where L is 4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole, for butan-2-one was investigated in a single-crystal-to-single-crystal (SCSC) fashion. A new host–guest system that encapsulated butan-2-one molecules, namely poly[[bis{μ3-4-amino-3,5-bis[3-(pyridin-4-yl)phenyl]-1,2,4-triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C24H18N6)2](ClO4)2·1.5C4H8O} n , denoted C4H8O@Cd-MOF (2), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P43212. The specific binding sites for butan-2-one in the host were determined by single-crystal X-ray diffraction studies. N—H...O and C—H...O hydrogen-bonding interactions and C—H...π interactions between the framework, ClO4 − anions and guest molecules co-operatively bind 1.5 butan-2-one molecules within the channels. The adsorption behaviour was further evidenced by 1H NMR, IR, TGA and powder X-ray diffraction experiments, which are consistent with the single-crystal X-ray analysis. A 1H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO4 − anions and guest molecules in MOF 2 lead to a high butan-2-one uptake in the channel.

Temperature-dependent structural properties of a solid urea inclusion compound containing chiral guest molecules: 2-bromotetradecane/urea

1999 ◽  
Vol 77 (12) ◽  
pp. 2105-2118 ◽  
Author(s):  
Lily Yeo ◽  
Kenneth DM Harris
Keyword(s):  
High Temperature ◽  
Structural Properties ◽  
Inclusion Compound ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
Tunnel Structure ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
Urea Inclusion Compound ◽  
Urea Inclusion

Periodic structural properties of the 2-bromotetradecane/urea inclusion compound have been investigated as a function of temperature. Differential scanning calorimetry between 298 and 98 K identified three well-defined regimes, denoted the high-, intermediate-, and low-temperature phases. The structural properties of each phase (at 293, 207, and 142 K, respectively) have been investigated by single crystal X-ray diffraction. In the high-temperature phase, the inclusion compound has the hexagonal urea tunnel structure (P6122) characteristic of the conventional urea inclusion compounds, with substantial orientational disorder of the guest molecules. In the intermediate-temperature phase, the symmetry is lowered to orthorhombic (C2221), although the host structure remains close to the hexagonal tunnel structure of the high-temperature phase and there is no clear evidence for increased orientational ordering of the guest molecules. In the low-temperature phase, the urea tunnel structure is monoclinic (P21), and is based on a 2 × 2 × 1 supercell of the hexagonal cell of the high-temperature structure. There are four independent types of tunnel, three of which are strongly distorted from hexagonal geometry. Within these distorted tunnels, there is a comparatively narrow distribution of guest molecule orientations, which correlate well with the observed distortions of the tunnels. The 2-bromotetradecane/urea inclusion compound highlights several issues of wider relevance concerning the structural properties of solid inclusion compounds.Key words: urea inclusion compounds, X-ray diffraction, phase transitions, chiral recognition, incommensurate solid, 2-bromotetradecane/urea.

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