Supramolecular polymeric arrays

Self-assembly through secondary bonds results in the formation of discrete supermoiecules (dimers, trimers, tetramers) or supramolecular polymeric arrays, both in purely inorganic systemsand in organometallic compounds. They are frequently found in derivatives... 

G-QUARTET-BASED 2D SUPRAMOLECULAR POLYMERIC ARRAY and Dynamic SOL-GEL Interconversion... 

Fig. 3 Polyassociation of bis-guanine monomers (G-G) into a two-dimensional supramolecular polymeric array based on the formation of G-quartets, stabilized by potassium cations, and interconversion of the resulting hydrogel with the corresponding sol state through reversible cation binding and release by the [2.2.2] cryptand, modulated by acid-base alternation. The 2D array on the right is represented in an idealized fashion ignoring any defect...

Examples of supramolecular association as a result of intermolecular organolead-sulphur interactions are rare and compounds such as Me3PbSMe and Pl PbSPh are monomeric in the solid state463. In contrast, triphenyllead pyridine-4-thiolate, d-Pl PbSCsFLjN464, is a chain polymer as a result of intermolecular N—Pb interactions. The cyclic dithiolate 2,2-diphenyl-l,3,2-dithiaplumbolane 177465 self-assembles in the solid state via intermolecular tin-sulphur interactions into a one-dimensional polymeric array. The intramolecular Pb—S bond lengths amount to 2.52(2) and 2.49(1) A and the intermolecular Pb—S distances are 3.55(2) A. 

Some systems can be applied in the areas of ionic, electron, and energy transport studies (9) and in sensing technology. Finally, our results show a new way of embedding nucleobases self-assembly and supramolecular chirality of G-quadruplexes in hybrid materials, of interest for the development of a supramolecular approach to nanoscience (51). Likewise, the hybrid polymeric arrays with nucleobases functionalities represent an area where the best is surely best to came it unlocks the door to the new materials world paralleling that of biology. 

In the case of ordered mesoporous oxides, the templating relies on supramolecular arrays micellar systems formed by surfactants or block copolymers. Surfactants consist of a hydrophihc part, for example, ionic, nonionic, zwitterionic or polymeric groups, often called the head, and a hydrophobic part, the tail, for example, alkyl or polymeric chains. This amphiphiUc character enables surfactant molecules to associate in supramolecular micellar arrays. Single amphiphile molecules tend to associate into aggregates in aqueous solution due to hydrophobic effects. Above a given critical concentration of amphiphiles, called the critical micelle concentration (CMC), formation of an assembly, such as a spherical micelle, is favored. These micellar nanometric aggregates may be structured with different shapes (spherical or cylindrical micelles, layered structures, etc. Fig. 9.8 Reference 70). The formation of micelles. 

In fact, hardly any donor atoms other than nitrogen have been used to create multiporphyrin assemblies. Using hard Lewis acids as central metal opens the possibility to bind two axial ligands on either side of the porphyrins. With ditopic Ugands such as diols this can lead to polymerization. However, a few examples can be found in the Uterature, where the central metal of the porphyrin is axially coordinated by oxygen, sulfur or selenium to assemble porphyrins. The use of (non-porphyrinic) phosphine ligands apparently has so far not been successful in the construction of supramolecular multiporphyrin arrays. 

Innumerable possibilities exist based upon the cooperative use of classical dative-coordinate and secondary bonds for supramolecular synthesis. This strategy is only in its infancy but can serve for the controlled design of materials with predictable structures. In a first alternative, discrete supermolecular species formed through dative bonds are further associated into polymeric arrays through secondary bonds. This case can be illustrated by the... 

Supramolecular self-assembly is observed in diethyltin 3-(2-pyridyl)-2-thiolopropenoate, which forms linear, zigzag polymeric arrays with O — Sn bonds connecting the chelate C20SSn rings (intrachelate Sn-O 2.226 A and Sn-S 2.424 A, intermolecular Sn-O 2.219 A). The pyridine units do not participate in any coordination to tin [501a]. 

The biological self-assemblies inspired the chemists to design molecular recognition-directed supermolecules [3-6]. Multiple hydrogen-bonds between complementary molecular components and metal coordination interactions have been used to design small receptor-guest complexes [3], bulk supramolecular systems such as liquid crystals [7-10], and molecular cocrystals [11-18]. Supramolecular polymers are broadly defined as polymeric arrays of repeating molecular units which are assembled by reversible and directional noncovalent interactions [19,20]. This definition refers to their primary structures, and control on their secondary and ternary structures has not been a critical issue. 

The chemistry of supramolecular polymers has been extensively reviewed [5], In the past two decades, general overviews as well as more specific surveys have focused on individual classes of polymers or on the mechanisms and thermodynamics of supramolecular polymerization. The present chapter aims to retrace the genesis and the evolutiOTi of that subgroup of supramolecular polymers that share the calix[5]arene skeletmi as their common building block. To this end, relevant examples of dimeric capsules and/or encapsulation complexes key to the subsequent design of polycapsular AA/BB-type arrays, as well as discoveries pivotal to an effective self-assembly of AB-type architectures are surveyed in parallel. 

Finally, the complementary molecular affinity between a [60]fullerene component and a complementary host in organic solution has been used to construct supramolecular polymeric nano-arrays of [60]fullerene. Haino and coworkers have developed a supramolecular fullerene polymer through the iterative com-plexation of ditopic calix[5]arene 30 and dumbbell-shaped [60]fullerene 31 (Figure 9.33) [110]. Although pulsed-field gradient NMR studies indicate that the... 

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