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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Modulated structure of the composite crystal urea n-heptadecane
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Modulated structure of the composite crystal urea n-heptadecane

机译：复合晶体尿素正十七烷的调制结构

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The structure of the composite crystal urea/heptadecane was determined by single crystal X-ray diffraction. The lattice constants of the hexagonal substructures are a = 8.218(2), b = 8.218(3), c(h) = 11.017(3) Angstrom for the urea (host) structure and c(g) = 23.713(1)Angstrom for the heptadecane (guest) structure, respectively, The (3+1)-dimensional space group is . Refinements on 786 reflections converged to wR = 0.0232 for 608 main host reflections, wR = 0.1506 for 10 main guest reflections, wR = 0.0328 for 49 common main reflections and wR = 0.753 for 119 pure satellite reflections. A comparison of the refinement of only the urea substructure and a refinement of the whole composite crystal, including the guest subsystem and the mutual modulations of both subsystems, shows that the main reflections, previously assigned to the urea host exclusively, are affected by a nonnegligible contribution of the heptadecane satellite scattering. The modulation of the guest structure has a maximum when the CH2 groups of the heptadecane molecule are facing the channel walls at heights corresponding to troughs in this wall. Thus, the modulation of the guest structure can be interpreted by an adaptation of the guest molecules to the host structure. The modulation of the host structure was found to be very weak, as the satellite scattering of the host structure is low. psi-scans of the 00l reflections revealed that the observed violation of the 6(1) screw axis extinction rule of the host structure and guest structure modulation can be explained by considerable umweganregung.
机译：通过单晶X射线衍射确定复合晶体脲/十七烷的结构。六角形子结构的晶格常数为a = 8.218（2），b = 8.218（3），c（h）= 11.017（3）埃（主体）结构的埃，c（g）= 23.713（1）埃对于庚烷（客体）结构，（3 + 1）维空间组为。对786个反射的细化收敛为608个主主机反射的wR = 0.0232，对10个主要来宾反射的wR = 0.1506，对49个普通主反射的wR = 0.0328和对119个纯卫星反射的wR = 0.753。仅尿素亚结构的细化与整个复合晶体（包括客体子系统和两个子系统的相互调制）的细化的比较表明，以前专门分配给尿素主体的主反射受到不可忽略的影响庚烷卫星散射的贡献。当庚烷分子的CH 2基团面对通道壁的高度对应于该壁中的波谷时，客体结构的调节最大。因此，客体结构的调节可以通过客体分子对主体结构的适应来解释。发现主体结构的调制非常弱，因为主体结构的卫星散射较低。对00l反射的psi扫描显示，观察到的违反主体结构和客体结构调制的6（1）螺旋轴消光规则可以用相当多的umweganregung来解释。

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