Buckled structures

Characteristic UV wavelengths have also been utilized in the determination of planar and buckled structures <1989J(P1)2495, 1989CC1137>. 

Since the deformation of the porphyrin ring proved to be the main factor governing the acceleration of the metalloporphyrin formation (Lavallee, 1985 Tabata Tanaka, 1991), this can also be achieved by substituents at the porphyrin core or at the peripheral ring. Thus, e.g., the peripheral or substituted octabromoporphyrins display a buckled structure due to steric hindrance between the substituents (Bhyrapp>a Krishnan, 1991 Mandon et al., 1992 Herding et al., 1993 Brinbaum et al, 1995). Such a deformation profoundly enhanced the reactivity of the porphyrin even towards Hg2+ (Nahar Tabata, 1998), the ionic radius of which is rather large an)rway. 

In comparison to carbon, the absence of an sp hybridisation in silicon complicates the stabilization of a silicon monolayer. As a result, silicon layers have a buckled structure, which additionally have free valences. These have to be saturated, e.g. by hydrogen, in order to stabilize the systems. " ... 

Fig. 5 (a) Carbon nanotube and (b) silicon nanotube. The lattice is distorted due to a large ionic radius of a silicon atom and forms a buckled structure in the sihcon nanotube (reproduced with permission of EPL (Europhysics Letters)— lOP science, M. Ezawa et al., EPL [24])... 

Soares, G.C. 1988. Uncertainty modelling in plate buckling. Structural Scfety 5(1) 17-34. 

All complexes of cytosine - isocytosine base pairs dramatically change the geometry when they interact with six water molecules. They become strongly nonplanar and adopt a buckling structure. For example, the buckle angle amounts to 3.6", 6.1 , 3.2" and 31.2" for isolated, two-, four- and six-hydrated iCCl complexes, respectively. The same effect has been observed for seven water molecules hydrating the AU complexes. 

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