Honeycomb self-assembled network

Scheme 15.1 The honeycomb self-assembled network formed between tetra-carboxylic acid diimide 15.1 and melamine (15.2).

When one, or both, the interactive modules are tridentate, bidimensional (2D) architectures can be formed. A frequently recurring pattern is the (6,3) network (honeycomb structure), which is sometimes formed when onium halides self-assemble with dihalocarbons. Halide anions work as tridentate XB acceptors and occupy the nodes while the dihalocarbons work as bidentate XB donors and form the sides that space the nodes. Such architectures are present in the co-crystals l,4-DITFB/Ph4P+Br , l,4-DITFB/Me4N+r [155], and a,oo-diiodoperfluoroalkanes/K.2.2.2.cKI [128,189]. The less planar the trigonal arrangement around the nodes, the more corrugated the honeycomb structure (Fig. 9). 

Fig. 9 Honeycomb-like architectures formed on self-assembly of halide anions (which work as tridentate XB acceptors and sit at the networks nodes) with 1,4-DITFB (which works as bidentate donor and forms network sides) (A). The angles formed by the XBs around the halide anions determine the corrugation of the honeycomb architecture, a more planar arrangement around the halide anions (as is the case of the iodide anions in adduct l,4-DITFB/Me4P+r (B) with respect to the bromide anions in adduct l,4-DITFB/Ph4P+Br (C)) results in a less corrugated honeycomb architecture...

Figure 2.5.1 Schematic representation of some of the discrete and extended supramolecular architectures that can be prepared by metal-directed self-assembly (a) 1D polymeric chains (b) discrete macrocyclic structures (c) two-dimensional grid- and honeycomb-like networks (d) three-dimensional diamandoid open frameworks...

One of the targets in the formation of 2D porous nanostructures is to define and control the size of the cavities. The obvious approach is to extend the distance between the carboxylic acid groups and the center of the molecule, for instance by a phenyl group. 1,3,5-Benzenetribenzoic acid (BTB) is a rigid molecule and self-assembles also at the liquid-solid interface into honeycomb-type networks (Fig. 21 A) [55]. The circular cavities have a diameter of about 2.8 nm. In case of TMA, the cavity diameter is about 1 nm only. 

Kim and coworkers reported the application of breath figure method to a small photo-responsive molecule, i.e., a organogelator self-assembled into supramolecu-lar fibrillar networks and further ordered in a hierarchically honeycomb structure [194]. Recently, a new organogelator was synthesized and large-scale ordered honeycomb patterns were also observed [195]. Moreover, Babu et al. also reported the formation of hierarchical macroporous structures from an amino acid linked p-conjugated organogelator [196]. 

Macrocyclic ligands, mac, are usually coordinated into the equatorial plane of the metal ions, the axial positions being occupied by weakly bonded ligands, which can be replaced by the cyano bridges. The self-assembly process involving ro 5-[M (wac)(H20)2] and [M(CN)6] ions yields 2D [M 3M2] networks. Within a layer, each mac)f moiety is linked to two [M (CN)6] ions in trans positions, and each [M(CN)6] ion is surrounded by three [M(wac)f units. If the three M. mac) units adopt a facial configuration around the M ion, then layers with a stair-shaped honeycomb architecture are formed mac stands for cyclam, 1,4,8,11-tetraazacyclotetradecane) (Fig. 36). A meridial arrangement of the three M mac)f moieties leads to flat brick-wall-like layers mac = 3,10-diethyl-l,3,5,8,10,12-hexaazacyclotetradecane (Fig. 37). ... 

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