Honeycomb networks

Since their first discovery by Iijima in 1991 [1], carbon nanotubes have attracted a great deal of interest due to their very exciting properties. Their structure is characterized by cylindrically shaped enclosed graphene layers that can form co-axially stacked multi-wall nanotubes (MWNTs) or single-walled nanotubes (SWNTs). Like in graphite, carbon atoms are strongly bonded to each other in the curved honeycomb network but have much weaker Van der Waals-type interaction with carbons belonging to... 

A ligand-based emission is also proposed in the complex [PhC = CAu]n, which displays a honeycomb network with PhC = C pillars [16]. In this case, the Au-Au interactions are even shorter than in the previous cases (2.98(1)-3.26(1) A) and the emission spectrum displays a very complicated pattern with peak maxima at 413,468,... 

The geometries in the six-coordinate species, 25a and 25b, are also far from regular even a severely distorted octahedral description appears inappropriate. The DMIO derivative, 25a, forms a honeycomb network due to a combination of S — Sn and O —> Sn intermolecular interactions and the rings are formed from six molecules191. 

Fig. 8 (a) ZnOEP molecules trapped in the dehydro-DPDI honeycomb network. STM images were recorded at room temperature (left), 11K (middle), and 5 K (right), respectively, (b) model structures of the arrangement of the ZnOEP molecule inside the honeycomb dehydro-DPDI network on Cu(lll). Reprinted with permission from [112], Copyright (2007) The Royal Society of... 

Tadokoro and Nakasuji used the monoanionic 2,2 -biimidazoleate (HBim ) ligand in conjunction with divalent octahedral metal centres, M(II), to prepare 2D honeycomb networks based upon M(Hbim) ( building blocks linked by N-H---N hydrogen bonds in an R IO) synthon (Figure 24) [64], The overall crystal structure depends on the counter-cation used, and can be a layer structure or an interpenetrated network. The interligand N-H N hydrogen bonds can... 

Figure 24 2D honeycomb network constructed from Ni(Hbim)J building blocks (I IB ini = 2,2 -biimidazoleate) linked by N-H N hydrogen bonds in R (l 0) synthons as seen in crystal structure of [K(dibenzo-18-crown-6)][Ni(Hbim)3] 3CH3OH 2H20 [64], Nitrogen and key hydrogen atoms are shaded. 

Figure 32 Hydrogen-bonded honeycomb network found in crystal structure of [4,4 -bipy]2-trans-[Ni(0H2)(SCN)4][N03]2 [30e]. Oxygen, nitrogen and key hydrogen atoms are shaded.

Figure 15 Honeycomb network formed by the 2,6-dimethyl analogue of 1 and Cu(I).

The brick wall network is a distorted version of the above honeycomb network as the metal centers act as a T-shape node. This network was first observed to form between a more flexible ligand such as l,4-bis[(4-pyridyl)methyl]-2,3,5,6-tetrafluor-ophenylene and Cd(N03)2 (Figure 17) [38]. However, given the large nature of the... 

Figure 16 Honeycomb network formed by ligand 2 and CuCl.

Generally, the formation of two-dimensionally linked assemblies affords subunits possessing either four-connected points or a combination of two three-connected points. Figure 18 illustrates the way in which two dimeric subunits may be combined to form a planar honeycomb network. 

In principle, 1 3 stoichiometry offers the opportunity to generate honeycomb networks. As revealed by Figure 14a, motif A or B should be capable of propagating the trimesate anion into a honeycomb structure. Figure 14b reveals that the crystal... 

L. Rajput, K. Biradha, Design of cocrystals via new and robust supramolecular synthon between carboxylic acid and secondary amide honeycomb network with jailed aromatics, Cryst. Growth Des. 9 (2009) 40-42. 

In the middle of domains, the overlayers are well ordered, with a lattice parameter very close to that of metallic A1 (expansion of 4 % with respect to the registered state), and a small rotation (-1.4° with respect to the R state) with the epitaxial relationships (111)A1//(0001)A1203 and [Tl0]Al//(R1.4°)[1120]Al2O3. In the domain walls, large expansion and rotation, and even loss of honeycomb network topology were found. The observed structure was interpreted in the spirit of rotational epitaxy with non-linear distortions. 

Figure 7 STM-image of PtaSnf 111) of the mixed p(2x2) and ( /3 x /3) R30° structure taken after annealing to lOOOK, size (44A), U =0.9V, 1 =1. OnA. The image has been differentiated to enhance contrast. The small adatom islands mark the p(2x2) domain whereas in the lower right corner ( /3 x /3) R30° areas with the honeycomb-network remain. The larger clusters may be due to residual contaminants, below the AES-detection-limit. From Ref. [35].

The jS constituent f of the aluminium bronzes can exhibit two formations, firstly, a cellular or honeycombed network and, secondly, a considerably finer, lamellar, structure, analogous to the pearlite in annealed steels. 

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