Amphiphiles, aromatic

In the tris-pentafluorophenyl analog (TFPC), in contrast to other Co corroles, aromatic amines can substitute PPh3 to form six-coordinate trivalent bis(amine) complexes.788 Bis-chlorosulfon-ation of TFPC occurs regioselectively to give the 2,17-(pyrrole)-bis-chlorosulfonated derivative fully characterized as its triphenylphosphinecobalt(III) complex.789 The amphiphilic bis-sulfonic acid was also obtained. 

Thus, the question is whether such classes of molecules were present on the young Earth. The only witnesses capable of giving an answer to this question are meteorites (Deamer, 1988). The group of David Deamer studied Murchison material after extraction and hydropyrolysis (at 370-570 K, with reaction times of several hours or days). GC and MS analyses showed the presence of a series of organic compounds, including significant amounts of amphiphilic molecules such as octanoic (C ) and nonanoic acids (C9) as well as polar aromatic hydrocarbons. 

For systemic administration, the photosensitizer usually has to be delivered into the bloodstream by intravenous injection. Since the photosensitizer is a solid, this means that a solution or a stable suspension has to be provided. Metal complexes of the basic porphyrin and phthalocyanine nuclei are insoluble in water, so that some effort has to be made to render the system water soluble, or at least amphiphilic, by placing various substituents (e.g., S03H, C02H, OH, NR3+, polyether, aminoacid, sugar) on the periphery of the molecule. The aromatic character of the ligand offers a suitable opportunity for such substitutions to be made. Examples will appear frequently in the following sections. 

Scheme 2. Viologen amphiphiles having rigid aromatic segments.

In LB films [1], the arrangement of the various functional moieties is considered to be controlled spatially across the films at molecular dimensions as described above. As one of functional moieties, various polycyclic aromatic hydrocarbons were used [55,56]. Some of the compounds were mixed with arachidic acid to form stable monolayers [37], because the amphiphilc derivatives of aromatic hydrocarbons themselves often form unstable monolayers on the subphase [40], For preparation of stable monolayers of polycyclic aromatic amphiphiles, Steven et al. investigated the effects of the length of alkyl chain and the composition and pH of the subphase [57],... 

High asymmetric induction by amphiphilic dendrimers was reported by Rico-Lattes and co-workers [32]. These water-soluble but THF-insoluble dendrimers (e.g. 22, Scheme 23) consist of useful, readily available chiral auxiliaries and can be used in the homogeneous (when H20 is the solvent) or heterogeneous (in the case of THF as the reaction medium) catalyzed reduction of prochiral aromatic... 

Basu et al. (2004) reported a series of amphiphilic homopolymers in which the hydrophUic moiety is a carboxylic acid moiety and the hydrophobic moiety can be based on either an alkyl chain or an aromatic ring (Chart 2.7). These polymers self-assemble into either micelles or reverse micelles, depending on the solvent environment. Figure 2.7 represents the formation of a micellar assembly in a polar... 

Jang C-J, R)ti J-H, Lee J-D, Sohn D, Lee M. Synthesis and supramolecular nanostructure of amphiphilic rigid aromatic-flexible dendritic block molecules. Chem Mater 2004 16 4226-4231. 

Fig. 2 The structure of (a) 20 natural L amino acids and (b) aromatic residues that gives rise to (c) aromatic peptide amphiphiles, which form supramolecular polymers through hydrogen bonding and 71-stacking interactions...

Fig. 3 Mechanisms for enzymatic supramolecular polymerisation (a) Formation of supramolecular assembly via bond cleavage, (b) Formation of supramolecular assemblies via bond formation. Examples are shown of biocatalytic supramolecular polymerisation of aromatic peptide amphiphiles via (i) phosphate ester hydrolysis, (ri) alkyl ester hydrolysis, and (iii) amide condensation or reversed hydrolysis using protease...

The ability to controi mechanical properties enzymatically has been demonstrated in two recent examples based on phosphatase-triggered self-assembly of aromatic peptide amphiphiles [55, 56]. A very simple system based on Fmoc-Y... 

Attaching only one lateral chain to the rod-like core (T-shaped amphiphiles 181-183) gave rise to LC honeycomb phases where the cross-section of the honeycomb walls contains two rods arranged side-by-side, i.e., the honeycombs have double walls (Fig. 61a) [8]. However, attaching two lateral chains to opposite sides of the aromatic core (X-shaped polyphiles like compound 187) generates polygonal honeycombs with walls that are only one molecule thick (Fig. 61b) [319]. As a consequence of the thinner walls, effectively more space is left available for the lateral chains inside the cells. Hence, honeycombs with smaller cells could be achieved by using two short lateral chains instead of only one chain with the same total volume [330]. 

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