Two-dimensional layer structure

The structure of graphite. Graphite has a two-dimensional layer structure with weak dispersion forces between the layers. 

Pillared clays (MELS) are aLso covered in this review. MELS have three-dimensional network structure like zeolites, and, unlike clays, which have two-dimensional layered structures, pillared cationic and anionic clays have been studied. Phthalocyanins intercalated in anionic clays have given interesting results for wastewater purification (Vaccari, 1998). 

The presence of triethylenetetramine in the hydrothermal synthesis of open-framework zinc phosphates results in a number of frameworks with one- to three-dimensional structures. The structures include one-dimensional ladders, two-dimensional layer structures, and one structure where the tetramine is bound to the zinc center. The structural type was highly sensitive to the relative concentration of the amine and phosphoric acid.411 Piperazine and 2-methylpiperazine can be used as templating molecules in solvothermal syntheses of zinc phosphates. The crystallization processes of the zinc compounds were investigated by real time in situ measurements of synchrotron X-ray powder diffraction patterns.412... 

Bu et al. investigated the role of methyl amine as the organic template in thesynthesis of a series of zeotype germanates. In the absence of the template a two-dimensional layered structure was formed. In contrast, in the presence of methylamine a three-dimensional framework evolved from these sheets.1191... 

From the above discussions it is clear that the amine has an important role in the formation of open-framework metal phosphates. Recent studies from this laboratory have shown that in the family of zinc phosphates, almost all the members in the hierarchy of open-framework structures can be synthesized using the same structure-directing agent, triethylenetetramine (TETA) [32], In Fig. 7.18 we show all the structures obtained with TETA along with the relative concentrations of the amine and the phosphoric acid employed in the synthesis. We see that the one-dimensional (ladder) and the two-dimensional (layer) structures are obtained when the relative concentration of phosphoric acid is high with the ratio of concentrations of the acid and the amine in the range 3 1-4 1. This is in contrast to the three-dimensional structures where the ratio... 

Ndo.5[Nd2(SiWii039)(H20)ii]°- displays a two-dimensional layer structure, which is constructed by [Nd2(SiWii039)(H20)n] chains and additional neodymium linkers. The... 

Figure 5.24 The two-dimensional layer structure of [Ln2(H20)9(a2-P2 Vi706i)]" [36]. (Reprinted with permission fromY. Lu, etal., New polyoxometalate compounds built up of lacunary Wells-Dawson anions and trivalent lanthanide cations, Inorganic Chemistry, 45, no. 5, 2055-2060 (Figure 3), 2006. 2006 American Chemical Society.)...

Some of the stoichiometric rare earth materials such as NdAl3(B03)4 are known to have two-dimensional layered structures and thus may yield interesting results on the energy migration dynamics. 

Schroder and co-workers have successfully isolated a unique poly-catenated undulating molecular ladder that forms interwoven two-dimensional sheets (252). The reaction of [Cu(MeCN)4]PF6 with 1,4-bis(4-pyridyl)butadiyne (L93) in MeCN-CH2Cl2 yielded the complex [Cu2(MeCN)2(L93)3](PF6)2. The compound exists as a network of molecular ladders in which the two independent Cu1 centers are each coordinated in a tetrahedral geometry to three L93 groups and one MeCN molecule. The lattices are polycatenated to give a remarkable two-dimensional layer structure (Fig. 77). The sheets of interwoven molecules are separated by PF3 counteranions and solvent molecules. The structure is further stabilized by the tt—tt interactions between adjacent, symmetry-related ladders. 

The jS and y structures probably contain the same two-dimensional layer structure, except that the packing is such that the HPO4 groups in each layer are opposed to one another. An interlayer separation of 9.28 A is predicted for the anhydrous ]8 product. It is thought that the dihydrate is derived from the anhydrous structure by simple insertion of water molecules between the layers, giving an interlayer distance greater than 9.28 A. 

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