Spontaneous self-assembly reactions

Other Fe-S Clusters. Spontaneous self-assembly reactions using phosphines as terminal ligands have been reported to yield a variety of new Co-S (22) and Ni-S clusters (23). Extension to Fe-S clusters was initially effected by the following reaction in heterogeneous solution (2A). 

Polynuclear Fe-M-S Complexes from "spontaneous self assembly" reactions. Synthetic analog clusters for the Fe2S2 and Fe4S4 centers in the Fe/S proteins (ferredoxins) have been obtained by procedures that are based on the concept of "spontaneous self assembly". The latter (30) assumes that the cores of the Fe/S centers are thermodynamically stable units that should be accessible fiom appropriate reagents even in the absence of a protein environment. 

The reaction of the cyclic P3-ligand l,3,5-triphospha-2,4,6-trisilacyclohexane with AgOTf results in the synthesis of complex (101) with a cyclic P6 ligand.794 Optically pure (S,5)-(+)-(PPh2CH2CH2)2(PPhCH2CH2PPh) spontaneously self-assembles into left-handed double-stranded D2-double helix (102) and C2-side-by-side helix conformers of the disilver(I) cation.795... 

All cellular life today incorporates two processes we will refer to as self-assembly and directed assembly (Fig. 1). The latter involves the formation of covalent bonds by energy-dependent synthetic reactions and requires that a coded sequence in one type of polymer in some way direct the sequence of monomer addition in a second polymeric species. On the other hand, spontaneous self-assembly occurs when certain compounds associate through noncovalent hydrogen bonds, electrostatic forces, and nonpolar interactions that stabilize orderly arrangements of small and large molecules. Three well-known examples include the self-assembly of water molecules into ice, DNA... 

An example of a spontaneous self-assembling template reaction, in which small organic components are organized by the metal ion and undergo reaction to form a large cyclic organic product that includes the metal ion. 

Spontaneous self-assembly of larger molecules from smaller components can result from a metal acting as an organizer or director of components leading to reaction. 

Another strategy used vesicles constituted of catanionic surfactants resulting from the association of ionic surfactants of opposite charges. A triple-chained catanionic surfactant (TriCat) vras recently obtained via a spontaneaous acid-base reaction in water between AThexadecylamino-1-deoxylactitol and bis(hydro)g dodecyl)phosphinic acid, followed by pH measurements until stabilization (Fig. 16). A fluorescent double-chained catanionic amphiphile molecule (FluoCat) was also synthesized in order to label vesicles. In aqueous medium, TriCat-containing catanionic systems with or without the addition of FluoCat (TriCat and Tri-Cat/FluoCat 19/1) spontaneously self-assembled into stable vesicles, characterized by a narrow size distribution that did not exceed 200 nm in... 

The aqueous photochemistry of 2-oxooctanoic acid (a single-tailed surfactant) results in the synthesis of a double-tailed surfactant product followed by spontaneous self-assembly into vesicles. The photochemistry mechanism is detailed here, and the reaction products are identified using mass spectrometry. Then, the self-assembled vesicles are characterized using DLS, fluorescence microscopy, and NMR. ... 

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201). 

Many opportunities conversely are supported by reversible reactions of QM despite the noted complications. One example includes the synthesis and chiral resolution of binaphthol derivatives by two cycles of QM formation and alkylation.77 The reversibility of QM reaction may also be integrated in future design of self-assembling systems to provide covalent strength to the ultimate thermodynamic product. To date, QMs have already demonstrated great success in supporting the opposite process, spontaneous disassembly of dendrimers (Chapter 5). 

---